Power And Industrial Plant Engineering Reviewer Jas Tordillo.pdf

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Power and Industrial Plant Engineering Reviewer REVISED EDITION I by: Jose Arvin S. Tordillo Mechanical Engineer Review Director of Tordillo Engineering Review Center Former Reviewer DERC, Cebu City (1995-2000) Reviewer RLB CDTC, Espana St., Manila (1995-present) Graduate BSME, Leyte Institute of Technology, 1994 Graduate BSEE, Unioereitu of Cebu, 2000 BSCE, with academic subjects at UC Eleventh Place, ME Board, October 1994 Author of Various Engineering Reviewer Books and Textbooks

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;,~ ,:'\IEIi~; i"" ~"'."" . -, j l " ; 0:'

POWER AND INDUSTRIAL PLANT ENGINEERING REVIEWER Revised Edition

POWER AND INDUSTRIAL PLANT ENGINEERING REVIEWER is one of three board subjects of Mechanical Engineering and weighs 35 percent in the hoard exam. This book has been prepared to help both the student and graduate of mechanical engineering in preparation for the board examination. 1111'

Copyright © 1998 By Jose Arvin S. Tordillo

All rights reserved. No part of this book may be Reproduced or transmitted in any form or by any means, electronic or mechanical including photocopying, recording, mimeographing, or by any information and retrieval system, without written permission from the copyright holder.

This book is a compilation of formulas and principles of Power and ludustrial Plant Engineering. Typical illustration problems with complete solutions .1Ie found at the end of each topic and 99 percent of the problems were taken from p.ist board exams. And with the addition of practice problems to let the students t rain in solving problems. The board examination of mechanical engineering was .i lrcudy computerized or in multiple-choice type of questions which includes the .k-tinition of terms and elements of mechanical engineering. The other part of this IH10k is a multiple-choice question of some common terms of Power and Industrial I 'l.uit Engineering. Comments and suggestions for improvement of this book will be I h.inkfully welcome and accepted. It is hopefully expected that this book will be III-.ed by teachers and students alike.

I \,HUS

My special thanks to Engr. Diego Inocencio T. Gillesania, Engr. Rey L. and Engr. Donato M. Busa who have contributed to the success of this book.

I wish to dedicate this work to my loving wife Rusyl for her support and to Almighty God for giving me this gift; to my mother, Lilia; to my sister Menchie ,lIld her husband Am-Am, to my sister Fe who is now in Jefferson City, USA; to my I" ,,111('r Bonnette and to his wife Sheryl; to my youngest brother, BonBon; to my ", 'I 'hews, Cybil, Bhep-Bhep, En-En, Baby Bliss and Dave; to my uncles and unties; I" .dl my cousins; to lola, Enriqua for her continuous prayer; and to all my friends i, 'I l heir assistance and moral support. Other people, as well, contributed to this I"" II-. ill their own special ways. My omission of their names should not be taken as 1.1, I-. of appreciation. It wouldn't have been possible without all of you. Thank lIlt'

ISBN 971-91931-8-2

I

Printed by: DMC Busa Printers Sanciangco St. Cebu City Tel No. (032) 416-8016

,'>II,

,lg,lill'

JOSE ARVIN SECO TORDILLO CEBU CITY, PHILIPPINES

Table of Contents

Table of Contents Conversions. _

To my wife, Rusyl

My late father, Bonifacio Sr.

My mother, Lilia

My sisters, Menchie and Fe Florabel

My brothers, Bonnette and BonBon

My brother-in-law, Am-Am

My sister-in-law, Sheryl

My Nephews, Cybil, Bhep-Bhep, En-En,

Baby Bliss and Christian Dave

And to all of you.

.

Thermodynamics

Definitions Properties of a Working Substance Work, Heat and Power First Law of Thermodynamics Second Law of Thermodynamics Third Law of Thermodynamics Zeroth Law of Thermodynamics Ideal Gases Pure Substance The Carnot Cycle Sample Problems in Thermodynamics

. . . .. .. .. . .. . .. ..

Fuels and Combustion

Classification of fuels Solid Fuels Liquid Fuels Gaseous Fuels Properties of Fuels and Lubricants Combustion Sample Problems in Fuels and Combustion Diesel Power Plant

Basic Classification of Common Internal

Combustion Engines Cycle Analysis of 4-stroke Gasoline Engine Cycle Analysis of 2-stroke Gasoline Engine Cycle Analysis of 4-stroke Diesel Engine Cycle Analysis of 2-stroke Diesel Engine Performance of Diesel Generating Set... Typical Heat Balance of Diesel Engine Five Auxiliary Systems of Diesel Engine Waste Heat Recovery Boiler Utilizing the

Diesel Engine Exhaust. Power Developed at an Altitude Sample Problems in Diesel Power Plant... Steam Power Plant

Steam Cycles..... Steam Generators (Boilers)........................................... Steam Turbines....................................................... Steam Condensers.......

F-1

F-1

F-4

F-5

F-5

F-5

F-5

F-6

F-10

F-13

F-14

. F-19

F-19

F-21

. F-22

. F-22

. F-25

.. F-26

. . .

.. . . . .. .. .. . :

. .. ..

F-29

F-30

F-31

F-31

F-32

F-32

F-35

F-36

F-37

F-37

F-37

F-44

F 47

f' ~):l

r

r,4

Table of Contents

Table of Contents

------------

Feedwater Pumps Steam E n g i n e s . . Sample Problums 111 Steam Power Plant..

. ..

F-56 F-57 F-59

. .. . .

F-65 F-65 F-67 F-68

,········· ..

Geothermal Power PI;Hlt Defiruuons.. .

Types of Geothermal Plants

Perforn l;1l1ce of Flashed-Steam Geothermal Plant.

Sample IJrolJlem in Geothermal Power Plant..

Gas Turbine POW(~I Plant Air St;III(f;lId, Ideal (Brayton) Cycle Perfo' 111; ince of Actual Cycle

Idf:;11 GdS Turbine Cycle with Regenerator.

S;II11ple Problems in Gas Turbine Power Plant..

F-70 F-71 F-73 F-74

.. . .. ·

Hydro-Electric Power Plant Basic Parts of High-Head Hydro-Electric Power Plant.. .........

Pumped Storage Hydro-Electric Power or Hydraulrc Accumulator Classification of Hydraulic Turbines Performance of Hydro-Electric Power Plant.. Sample Problems in Hydro-Electric Power Plant... Nuclear Power Plant Typical Nuclear Power Plant... : Commercial Types of Nuclear Power Reactors

F-77 F-78 F-79 F-80 F-82

···· ..· ·. ..

..

·..· ·..

F-85 F-86

Non-Conventional Power Sources Solar Power , , ,· ·..· ··..·..·..······ . Wind Power , ·· · ··..·..·..·· ·..·· . Tidal Power ·..·· ····..·,· ·..· . Low Thermal Head Plant... .. Magneto Hydro Dynamic Plant... · · ·.. Therrnoionic Converter ·..····..··..· ······ ..····· .., .. Fuel Cell,

F-87 F-87 F-88 F-88 F-88 F-88 F-88

Instr umo: itat 1011 1 yp(~S of Instruments [)f:fI111tI0I1S

·

.

F-89 F-91

.....................................................................

F-95

·..·..·..····..····

" .. ' .. ,

··· .

Variablo Load Problem

Formulas ..

Chimney Calculation of Chimney Diameter and Height... Sample Problems III Chimney

. .

F-96 F-97

MClchine Foundation Functions of Machine Foundation Design Procedure in Machine Foundation Machine Foundation General Requirements Sample Problems in Machine Foundation Ileat Transfer and Heat Exchangers Modes of Heat Transfer Conduction Through a Plane Wall Conduction Through Composite Plane Wall. Conduction from Fluid to Fluid Conduction Through Pipes r Conduction Through Composite Pipes Conduction from Fluid to Fluid through Pipe Convection Radiation , Sample Problems in Heat Transfer , " IS

. .. . .

F-100 F-101 F-102 F-103

.. .. ..

. . .

F-106 F-106 F-107 F-107 F-108 F-108 F-109 F-110 F-111 F-112

.. ..

F-116 F-116

. . .. . . ..

F-117 F-119 'F-120 F-121 F-122 F-122 F-123

.. , •• , •••••

. .

(Air) Compressors Uses of Compressed Air Classification of Air Compressors Performance of Single-Stage, Single-Acting, Reciprocating Compressor DOUble-Acting, Single-Stage Reciprocating Compressor Two-stage Reciprocating Compressor Three-Stage Reciprocating Compressor Multi-Stage Reciprocating Compressor Performance of Centrifugal and Rotary Compressors Sample Problems in Gas (Air) Compressors

.

, '1111pS

. . ..

Definitions Typical Pumping Installations Basic Classification of Pumps Head and Power Calculations Calculating the Friction Head Characteristics of Reciprocating Pumps Characteristics of Centrifugal Pumps Cavitation Sample Problems in Pumps IllS

and Blowers

Types of Fans

Head and Power Calculations

Fan Laws

Sample Problems in Fans and Blowers

. .. .. . . ..

. . . .

F-125 F-127 F-128 F-130 F-131 F-132 F-133 F-134 F-134

F-138 F-139 F-141 F 141

---

Table of Contents ------------Refrigeration Ice Refriqer auon . Mechanical R(~fllq(~riltion . The COIllPI(~SSI(HI Cycle . Reversed Curnot Cycle in Refrigeration . Rdrlcwr ,111011 Cycle with Subcooling and/or Superheating .. Refrlgcl .itron System with Heat Exchanger .. f~cfrl~lcr;ltJ()1I Compressors . Perf on lldllc(~ of Reciprocating Compressors .. RefrIU(~I, 1111 Condensers · ·..···· ..····· Exp,~I)SI()1I Uevices . R(~frl<J(~1 ,liltS

.

Cak.: IIdt 111\1 the Cooling Load from Products

.. .. .. .

MlIltl 1)1(~ssure Refrigeration System low 1 (~Ill perature Refrigeration O!lWI MctrlOds of Refrigeration S;mlpl(~ Problems in Refrigeration Air Conditioninq Air Conditioning Properties of Air The Psychrometric Chart Processes in the Psychrometric Chart... Air Mixing Air Conditioner Cooling Tower · Dryer Air Conditioning Calculations Sample Problems in Air Conditioning

F-145 F-145 F-146 F-148 F-149 F-149 F-149 F-150 F-151 F-152 F-152 F-154 F-154 F-156 F-157 F-158

·

Table of Contents

Conversions

I Linear

= 5280 feet = 1760 yards 1 nautical mile = 6080 feet 1 league = 3 nautical miles = 18240 feet 1 yard = 3 feet = 0.9144 m 1 meter = 100 cm = 1000 mm = 3.28 feet = 1.093 yard 1 foot = 12 inches 1 inch = 2.54 cm = 25.4 mm 1 rod = 5.5 yards = 16.5 feet 1 furlong = 40 rods

= 220 yards

1 cable length = 720 feet

1 fathom = 6 feet

1 span = 9 inches

1 vara = 33.33 inches

1 mil = 0.001 inch

1 statute mile

F-161 F-161 . F-163 .. F-164 F-164 . F-165 . ······· ..· F-166 . F-167

F-168 ··..··..·

F-170 .. . ..

·..·..· ·

·..· ··

lndustna: Processes

Some Industries in the Philippines Imillslr till Equipment

Dryers .. .. Evaporators Conveyors Cr nnes FOllmJry E.quipment. Fir o PI otcctiOll Systems

Scope.... .. General Safety Requirements Commodity Classification Definitions. . Practice Problems Power and Industrial Plant Engineering Elements and Terms . . Compilation of Pels! ME Board Exam

F-176

.

F-176

F-177

F-178

F-178 F-179

I

F-180

F-180 F-180 F-181

I I

F-184 ET-1 PB-1

I

. . .

. .. . ··..··· .. . . .

I

..

Area 1 hectare = 10,000 sq. m = 11,960 sq. yards 1 acre = 43560 sq. ft = 4046.8 sq. m = 0.4047 hectare 1 square meter = 10.76 sq. ft = 1.195 sq. yard

Volume 1 quart = 2 pints 1 US gallon = 231 cu. inches = 3.7854 liters = 4 quarts

Table of Contents

Table of Contents ---------------

1 British qallon = 277.42 cu. inches 1 cu. m = 1000 liters = 35.31 cu. ft = 264.2 US gallon 1 cu. ft = 7.48 US gallon = 28.32 liters = 1728 cu. inch 1 ganta = 3 liters = 8 chupas 1 cavan = 25 gantas

1 erg

= 10- Joule 1 Joule = 1 N-m 1 kJ = 1000 Joule

Power 1 horsepower = 550 ft-Ib/sec = 33,000 ft-Ib/min = 2545 Btu/hr = 42.4 Btu/min = 0.746 kw = 746 watts = 1.014 MHp 1 kw = 3413 Btu/hr = kJ/sec 1 watt = J/sec 1 MHp = 0.736 kw 1 Boiler Hp = 33,480 Btu/hr = 35,322 kJ/hr

Angle 60 degrees = = = = 90 deg = 1 deg = 1 min =

27t radians 400 grads 6400 mils 1 rev 100 grad 60 min 60 sec

Temperature

Mass & Weight

°C

1 ton = 2000 pounds (Ibs.) 1 longton = 2240lbs 1 metric ton = 1000 kg = 2200lbs 1 pound = 16 ounces 1 kip = 1000lbs 1 kg = 2.22 Ibs 1 kgf = 9.80665 Newtons 1 Newton= 0.1019 kg = 0.04591b 1 pound (Ib) = 0.453592 kg = 0.138255 N

Work/Energy 1 Btu = 778 ft-lb = 252 cal = 0.252 kcal = 1.055 kJ 1 kcal = 4.187 kJ 1 cal = 4.187 Joule

= 1 dine-em

= ~(oF - 32) 9

OF =

2- °C 5

OK oR

= °C = OF

+ 32

+ 273 + 460

L1°C = ~ (L1°F) 9

L1°F

=

2- (L1°C) 5

= L1°K L1°F = L1°R

L1°C

Pressure 1

atmospheric pressure (atm) = 101.325 kPa = 14.7 psi = 760 mm Hg = 29.92 in Hg = 1.033 kq/crn"

-

iv

-- - - - - - - - - - - - - - - - - - - - - -

Table of Contents

Table of Contents

---

Properties of Air

1 bar = 100 kPa 1 Pa = 1 N/m 2 1 kPa 1 kN/m 2 = 1000 Pa

Btu

=

0.24

C p = 0.24---

lb- 0

Fluids 1 poise = 1 dyne-sec/em" = 0.1 Pa-s 1 stoke = 1 cm 2/s 0.001 m2/s 1 lb-sec/tf = 478.7 poises 2/s 1 ff/s = 929 cm 1 fe/s = 0.646 million gallons per day (mgd) 448.8 gal/min (gpm) 3/s 1m = 1000 litis = 35.31 fe/s

=

Cv

F

0.171~

kJ

kcal kg _0 C

0.171~

lb _0 F

/~I.L~'

1.0-­ kg- 0 C

m-"

0.716~ kg

kg-O C

_0

C

0.287~

R = 53.3 ft - lb lb-o R

kg _0 K

k=1.4

=

Cp =

Fundamental Constants acceleration of free fall (g) . Avogadro constant (L, NA ) .. Boltzmann constant (k = R/N A ) .. electric constant (Eo) · ···· · electronic charge(e) .. · .. electronic rest mass (me) . Faraday constant (F) gas constant (R) . .. gravitational constant (8) Loschmidt's constant (Nd · magnetic constant (uo) . neutron rest mass (m n ) .. Planck constant (h) . proton rest mass (m p ) . speed of light (c) .. Stefan-Boltzmann constant (o ) ..

Properties of Water

9.80665 m/s 23

6.02252 x 10 mol' 1.380622 x 10-23 J/K 12 8.854 x 10- F/m 1.602192 x 10-19 C 31 9.109558 x 10- kg 4 9.648670 x 10 C/mol 8.31434 J/kg mol-oK 2 11 2 6.664 x 10- N m /kg 3 2.68719 x 10 25 m7 4n x 10- Him 1.67492 x 10-27kg 34 6.626196 x 10- Js 1.672614 X 10-27 kg 8 2.99792458 x 10 rn/s 8 2 5.6697 x 10- m- K-4

kJ

4.187-kg- 0 C

1.0~

lb-O F

CfiL{ ~SD'IDJ;J.­

K~~

L = latent heat of fusion, =

335

~

144 Btu lb

kg

Specific (sensible) heat of ice

= 2.093 = 0.5

~O kg_

c

Btu

lb-O F

Latent heat of vaporization (from and at 100°C)

= 2257 ~ kg

970.3 Btu lb

Latent heat of water vapor in air and flue gases (average)

=

2442 ~ kg

1050 Btu lb

To my wife, Rusyl My late father, Bonifacio Sr. My mother, Lilia My sisters, Menchie and Fe Florabel My brothers, Bonnette and BonBon My brother-in-law, Am-Am My sister-in-law, Sheryl My Nephews, Cybil, Bhep-Bhep, En-En, Baby Bliss and Christian Dave And to all of you.

.......

Formulas and Principles

Formulas and Principles - THERMODYNAMICS

THERMODYNAMICS DEFINITIONS: Ihermodynamlcs - is the study of heat and work and those properties of .ubstance that-bear a relation to heat and work, Working Substance - a substance to which heat can be stored and from .vluch heat can be extracted. ,I.

Pure Substance - a working substance whose chemical composition remains the same even if there is a change in phase; Ex. Water, ammonia, Freon-12.

11, Ideal Gas - a working substance which remains in gaseous state during its operating cycle and whose equation of state is PV mRT ; Ex. Air, O2 , N 2 , CO 2 •

=

PROPERTIES OF A WORKING SUBSTANCE Mass and Weight Mass - a property of matter that constitutes one of the fundamental physical measurements or the amount of matter a body contains, Units of mass are in Ibm, slugs, kgm, or in kg. Weight - the force acting on a body in a gravitational field, equal to the product of its mass and the gravitational acceleration of the field. Units

of weight are in Ibf , kg f , N or kN.

Volume

,llld ,110

Volume - the amount of space occupied by, or contained in a body is measured by the no. of cubes a body contains. Units of volume In fe, Gallons, liters, ern", or rn".

Pressure = force per unit area. Units of pressure are measure in psi, 2 2 kg/cm , kN/m or kPa. 1\1 )';olule

Pressure kPaa Psia

........

J

= Gauge Pressure + Absolute Atmospheric Press = kPag = Psig

+ 101.325 + 14.7

Form~/as and P~i-;;~iPle~~-THE-R~ODYNAM ICS ----_. ---- - - ------- ---- -------------­

Formulas and Principles - THERMODYNAMICS

F-2

__ .

= 0 kPag, 0 psig

=101.325 kPa 2

=1.033 kg/cm =29.92 in Hg

=760 mm Hg

=14.7 psia

1 bar =100 kPa

'i

1 Atm Pressure

Pressure of Perfect Vacuum

Specific Weight,

Density of water

=

3

3

Density of Liquid Density of Water

= 1000 kg/m 3 =

9.81 KN/m 3

Density of a

Specific Gravity of a Gas (Relative Density)

Relations of Temperature Scales,

kN/m

r

= 62.4 Ib/ft 3

absolute zero pressure

Temperature - the degree of hotness or coldness of a substance.

of

Weight _ --= --_ ..

(I)

Specific Gravity of a liquid (Relative Density)

4. Temperature

0C

-

Volume

= - 101.325 kPag

=

-

0

C and

0

F:

GIS

Denslt.y of :\ 11

Density of air =! 2 kg/me, at 101.325 kPa and 21 1 "C. Internal Energy, tr, kJ/kg

= 2-

=

(oF - 32)

9

-9 oC + 32 5

Internal enerqy - herit energy due to the movement of the molecules within the substance brought aboi.t Its temperature Internal energy is zero if temperature is constant.

Temperature at which molecules stop moving

-273°C -460°F

=

=

Flow Work, W, kJ/kg Flow work

Absolute Temperatures:

-K = oC + 273


=

W

Temperature Change or Temperature Difference:

~oC = 2- ~oF

~oK

=

~oC

- work due to the change in volume.

=

F x L

where:

P v

PA x L.

= Pv

= pressure, kPa = specific volume,

m 3/kg

Enthalpy, h, kJ/kg

9

~oF

= ~ s-c

~oR

=

Enthalpy sum of the internal energy of a body and the product of pressure and specific volume.

~oF

5

5. Specific Volume, Density, and Specific Weight Density, p

=

Mass

kg/m

Enthalpy

=

Internal Energy

h

=

u

3

Entropy,s.

Volume

+

+ Flow Work

Pv

k,T

~---~~

kg-OK

Specific Volume, v

=

Volume Mass

=

1 P

m

3/kg

Entropy - measure of randomness of the molecules of a substance - measures the fraction of the total energy of a system th. It available for doing work

I'. II'
Formulas and Principles - THERMODYNAMICS

F-5

Formulas and Principles - THERMODYNAMICS

F-4

FIRST LAW OF THERMODYNAMICS

WORK, HEAT, POWER and EFFICIENCY

Total Energy Entering a System = Total Energy Leaving a System

= Force x distance, ft-Ib, kN-m or kJ

Work

1

W=FxL=Pv

-.&+----t/

Heat _ form of energy due to temperature difference.

_ units of heat are in Btu, cal, kcal, kJ

Q

= mCtlT

W

then C = Cp or C, H1 + KE 1 + PE 1 = H2 + KE2 + PE2 + q + W

Specific Heat, C = the heat required to change the temperature of 1 kg of a substance 1-c.

from which:

C = specific heat at constant pressure, p

C = specific heat at constant volume, v

~ kg- C

~ kg- C

kJ

or

or

--0

­

. fd . k P ower = ume rate 0 olng wor

550 ft-Ib/sec 33, 000 ft-Ib/min 2545 Btu/hr 42.4 Btu/min 0.746 kw

I

SECOND LAW OF THERMODYNAMICS

hp, watts or kw

Kelvin Planck statement applied to the heat engine: "It is impossible to construct a heat engine which operates in a cycle .uid receives a given amount of heat from a high temperature body and does If1 equal amount of work." Clausius statement applied to the heat pump: "It is impossible to construct a heat pump that operates without an »iput work." The most efficient operating cycle is the Carnot Cycle.

Conversion units of power:

1 hp = = = = =

neglecting KE PE and q

kg_OK

1kca\ = 4.187kJ 1N-m= 1J 1000 J = 1 kJ

Work = Time -­

2)

= m(h 1-h2) + }'2 m(V/-V2 + m(z1-z2) - q

W = m(h 1-h2)

kJ

Conversion units of heat: 1 Btu = 778 ft - Ib = 252 cal ( 0.252 kcal) = 1.055 kJ

W

kg- K

1 MHp 1.014 MHp 1 Boiler Hp 1 watt

= 0.736 kw Hp = 33, 480 Btu/hr = 35,322 kJ/hr = J/sec

=

fHIRD LAW OF THERMODYNAMICS "The entropy of a substance of absolute zero temperature is zero"

!EROTH's LAW III(~

...

~

"If two bodies has the same temperature as a third body they have sarne temperature with each other."

Formulas and Principles - THERMODYNAMICS

F·6

Formulas and Principles - THERMODYNAMICS

Processes Involving Ideal Gases

IDEAL GASES An ideal gas is a substance that has the equation of state:

Any Process:

PV = mRT

==

PlY)

1;

= absolute pressure, kPa 3/sec 3 = volume, m or m

where: P V m

= mass,

kg or kg/sec kJ R = gas constant, - - 0 ­

kg- K

T == absolute temperature, oK

P2Y2

R

Cp

cp

==

-

kJ

M

kg-OK

U2

-

U 1 = mC y(T rT 1 )

H2

-

H 1 == mC p (T r T 1 )

82

-

8 1 == mC p In

P mR In ---.Z P1

-xdiabatic Throttling Process: constant enthalpy or isenthalpic process, 'itat is, h 2 == h, and t 2 = t 1 r .onstant Pressure or Isobaric Process: P 1 == P 2 .onstant Volume or Isovolumic Process: V 1 == V 2 , .onstant Temperature or Isothermal Process: T 1 == T 2 onstant Entropy or Isentropic Process: adiabatic and reversible, 8 1 == 8 2

'olytropic Process: non-adiabatic process

k

Cy where:

-

Process: No friction loss /\diabatic Process: No heat loss, no heat gain, that is completely insulated .ystern

Cv == R ==

T~ _4

Tj

ft-1b 1b-OR

M

mR

I <eversible

8.3143

1545

==

T2

Basic Properties of an Ideal Gas: R ==

-7

R == gas constant M == molecular weight C p == specific heat at constant pressure C, == specific heat at constant volume k == specific heat ratio

PROCESSES: I

onstant Pressure

P 1 == P 2

~ = Y2 Tj

T2

, .harles Law)

Properties of Air:

Work Done == P 1(V2 - V 1 )

k == 1.4

M == 28.97 kg air/mole of air

R == 53.3

Cp == 0.24

Cy == 0.171

ft -1b 1b-oR Btu lb-OF Btu lb-OF

== 0.287

== 0.24

T~

Entropy Change == mCp In ---=-­ T)

kg-OK

kca1

kg-OC == 0.171

Heat Added == mC p(T rT 1 )

kJ

kcal

kg-OC

== 1.0

kJ

kg-OC

== 0.716

~ kg-OC

onstant Volume

V 1 ==V 2

~

==

T1

u.u lr», Law)

Work Done = 0

P2

T2

F-8

Formulas and Principles - THERMODYNAMlc~;

Formulas and Principles - THERMODYNAMICS

Heat Added

= mCv(Tz-T 1) Entropy Change = mCv In

Heat Added

=

me, (n -

k)(T2 - 'II) I

11 --

T

---.2 T1

Entropy Change

=

mC,(n - k) In T2 n-l

Constant Temperature (Boyle's Law)

T1

= T2

T1

= P2V 2

PN1

Work Done

F -9

= PN1 In ­

MIXTURES INVOLVING IDEAL GASES

V2 VI

onsider a mixture of three gases, a, b, and c, at a pressure P

'Icl a temperature T, and having a volume V.

=

Heat Added

mRT 11n V 2 VI

Entropy Change

=

Mass or Gravimetric Analysis: 111T = m a

V2 VI

mRln

J = m a + mb +~c 111'1

Constant Entropy

PV

k

= C,

PN/

=

(~~

JT

Work Done

=

=

TI

Heat Added

PV

n

= C,

v = Va

(V 2 J

+ Vb + V c

Va

j

=

= volume that gas a would OCCUPy at pressure P and Temperatur-e T

PIVI -P2V2 k -1

PN1

Work Done

k- I

VI

1 = Va + Vb + Ve

V

V

V

Vb = volume that gas b would OCCUpy at pressure P and Temperatur-e T

= 0

T2 = ( P2 1----;PI

=

TI

=0 n

=

V c = volume that gas c would OCCUpy at pressure P and Temperature T P2V2

n-I

T1

mT

Volumetric or Molal Analysis:

T2

Entropy Change

Polytropic Process

mT

P2V/

k-I

T2

+ 111b + 111 e

T2 TI

=

n

(I ~

rJalton's Law of Partial Pressure:

n- I

P = Pa + Pb + Pc

V2

PIVI -P2V2 n-1

Pa . "II

= partial

pressure of gas a, that is, the pressure that gas a will

If It alone occupies the volume occupied by the mixture, etc.

1',1

V~(l»)

v

Vb Ph = -(P) V

Vc Pc =-(P) V

....

F -10

Formulas and Principles - THERMODYNAMICS

4. Specific Heat of the Mixture: Cp

Cv

~

Formulas and Principles - THERMODYNAMICS

Saturated liquid and Saturated Vapor

ma mb me -Cpa + -Cpb + -Cpe

mT mT mT

Examples of saturation temperature at various pressures for three common pure substances: Saturation Temperature

rna mb me --Cva + --Cvb + -Cve

mT mT mT

Pressure 50 kpa 101.325kpa 500 kpa

Water

81.33°C 100°C

151.86°C

PURE SUBSTANCE Pure Substance - is a working substarice that has a homogenous and invariable chemical composition even though there is a change of phase. Saturation Temperature - the temperature at which vaporization takes place at a given pressure, this pressure being called the saturation pressure for the given temperature.

Temp Press

Specific Volume Y..c JLg Vfg

Ufg

actual temperature and

suococted Liquid - liquid whose temperature is lower than the saturation temperature at the given pressure.

Compressed liquid - liquid whose pressure is higher than the saturation pressure at the given temperature. - if the temperature is held constant and the pressure is increased beyond the saturation pressure.

Freon-12 -45.19°C

-29.79°C

15.59°C

Internal Energy

Enthalpy

.!de .!dfg .!dg

Entropy

hf b.fg !J.g

~e ~fg

~g

= vg

-

Vf

hfg

= hg

- hf

= ug

-

Uf

Sfg

= Sg

- Sf

Mixture x = quality or dryness factor

= ratio of mass of saturated vapor to the total mass of the mixture,

expressed in decimal or percent.

1-x

= wetness

Properties of Mixture:

Degrees Subcooling - difference between saturation temperature and actual temperature. Critical Point - is the condition of pressure and temperature at which a liquid and its vapor are indistinguishable.

Ammonia -46.73°C -33.52°C 4.08°C

Properties of saturated liquid and saturated vapor at various temperatures and pressures are found in tables (Table 1 and Table 2 for steam) with the following typical construction:

Superheated Vapor - vapor whose temperature is higher than the saturation temperature at the given pressure. Degrees Superheat - difference between saturation temperature.

F - 11

v

= v,

U

Uf

=

+ +

X Vfg X Ufg

h = hf + x hfg

s:;:sr+XSrg

The T . S diagram of a Pure Substance T I

I

Mixture - substance made up of liquid and vapor portion. Subcooled Liquid Region Saturated Liquid Line

-----+---. I

.1

~

Critical Point

Super heated Vapor - - - - . Region Saturated Vapor -----1,I---1.~Mixture Region

I

S

~.

F ·12

Formulas and Principles - THERMODYNAMICS

Formulas and Principles - THERMODYNAMICS

--- -'--~---~---'---~._._~--~._-_ _----~~ ..

The Mollier Diagram (h-s) of steam is usually useful in determining the final enthalpy of steam after an isentropic process.

THE CARNOT CYCLE

Processes Involving Pure Substances:

T

1. Isobaric or constant pressure process: P1 = Pz

'1"1

2. Isothermal or constant temperature process:

'1"2

'1'-1

=

I

4

11

Work Net

T1 = T2 Evaporation and condensation processes occur at constant pressure and constant temperature.

=

T,

3

I

I

2

•

3. Isovolumic or constant volume process: V 1 = V 2 For constant mass: V1 = V2 If the final state is a mixture: V1 = (VI + x VIg)z

4. Isentropic or constant entropy process: S1 = S2

S,

=

= h2

If the final state is a mixture: h1 = (hi + x hlg)z

=

T 1-T2 =

OA

Heat Added or Rejected

Constant Pressure Heating or Cooling of Liquid

Q

Evaporation or condensation C and T C) (P

=

=

Q

=

w = kJ

Cp = 4.187 - - 0 ­ kg- K

= m(h fg) = m(h g - hi) hlg = latent heat

Q

= m(u2 - U1)

Constant Entropy ( S = C ) (Isentropic)

Q

= m(h z - h

Constant Enthalpy (h = c) (Throttlinq)

Q = 0

S1- S4

S2- S3

T 1(S1 - S4)

I1r

llr

= T 1(S1 - S4)

- Tz(S,- S4)

W

Q A -QR

'1'1 (S: - S4) - T 2 (Sj - S4)

QA

QA

T1(Sl - S4)

OA - OR

T] -T2

or

where: nT 1)

and

T 4-T3

'1']

Constant Volume (V = C )

QR

OR = T 2(Sr S3) = T Z(S1 - S4)

= mCp (T 2- T1) For water:

\V

Wp

If the initial state is a mixture, such as in steam calorimeter: (hi + x h(9 ) 1 h2

Process

SI = S2

QAB~

Isentropic process is reversible (no friction loss) and adiabatic (no heat loss, that is. completely insulated system).

5. Throttling or isenthalpic (constant enthalpy) process: h1

S S-,

I1T

=

TH -'1'1 TH

Carnot Cycle efficiency highest absolute temperature lowest absolute temperature

T1 = T H Tz = TL

= =

F - 13

F -14

Formulas and Principles - THERMODYNAMICS

Formulas and Principles - THERMODYNAMIC,

Basic Working cycles for various applications:

=

Efficiency Application

Basic Working Cycle

Steam Power Plant Gasoline Engine (Spark-Ignition) Diesel Engine (Combustion-Ignition) Gas Turbine Refrigeration System

Rankine Cycle Otto Cycle Diesel Cycle Brayton Cycle Refrigeration Cycle

T11-TI

1660 - 685

'IJ[

1660

1"

= 58.73%

An ideal gas at 45 psig and 80 cF is heated in a closed container to 130'f­ What is the final pressure? (Apr 97) A. 54 psia C. 75 psia B. 65 psia 0.43 psia Solution:

=

=

45 + 14.7 59.7 psia P 1 T 1 = 80 + 460 = 540 T 2 = 130 + 460 = 590 0R

SAMPLE PROBLEMS:

0R

1. A Carnot engine receives 130 Btu of heat from a hot reservoir at 700°F and rejects 49 Btu of heat. reservoir. (Bd. Prob Apr. 97) A. -21.9°F B. -24.2°F

Calculate the temperature of the cold C. -20.8°F D. -22.7°F

PI

Pc

TI

'1'2

59.7

Po

540

590

--0=-­

Solution: TH

= 700 + 460 = 1160

P2 = 65.23 psia 0R

Carnot Engine Efficiency = Q A -QR

TH -TL

QA

130- 49

1160-TL 1160

130

TL TL

TH

~437.23°R

A Carnot engine requires 35 kJ/sec from the hot source. The engine produces 15 kw of power and the temperature of the sink is 26°C. What is the temperature of the hot source in °C? (Apr 97) A. 245.57 C.250.18 B. 210.10 0.260.68 Solution:

=-22.77°F

T c

2. The maximum thermal efficiency possible for a power cycle operating between 1200°F and 225°F is: (Apr. 97) A. 58% C. 57.54% B. 58.73% D. 57.40%

-~)

TH TL

= 1200

= 225

+ 460

+ 460

= 1660

=

+ 273

Efficiency

I~

Solution:

= 26

Tl j

0=

-

=

W Q-;

299°K 'I'll -

TL

Tf!

299

Til

0R

685 oR

Til

= 52325 cK

T" = 52325 - 273 = 250.25 °C

F -16

formulas and Principles - THERMODYNAMICS

Formulas and Principles - THERMODYNAMICS

5. An air bubble rises from the bottom of a well where the temperature is 25'oC, to the surface where the temperature is 27°C. Find the percent increase in the volume of the bubble if the depth of the well is 5 m. Affnospheric pressure is 101,528 Pascals. (Apr 96) A. 49.3 C. 56.7 B. 41.3 0.38.6

fear Throttling Process: 1.03 MPa

h, = h z (hf + x hfg)1 = hz 768.55 + x(2010.7) = 2726.6 x = 0.9738 = 97.38% Percentage Moisture = 100 - 97.38

Solution:

0.100 MPa

1

125°C

2 ~

----....

....•...

0

~

- -...

= 2.62%

P2V2

PIVI T1

F -17

T2

where: P 1 = = T1 Pz

= =

Tz

=

5(9.81) + 101.528 150.578 kPa 25 + 273 298 oK 101.528 kPa 27 + 273 300 oK

A water temperature rise of 18°F in the water cooled condenser is equivalent in °C to: (Oct 94) A. 7.78°C C.263.56°K B. 10°C D. -9.44°C

27°C

101.528 kPa

=

2

=

Solution: 5m

150.578VI 298

Vz

= 1.493 V

% Increase

101.528V2

5 0F Temperature Change, L'l oC = -L'l

1

300

9 25°C

1

= V2 -

VI

VI

1.493VI - VI VI

= 0.493 = 49.3%

=

5 -(18) = 100 C

9

Steam flows into a turbine at the rate of 10 kg/s and 10 kw of heat are lost from the turbine. Ignoring elevation and kinetic energy effects, calculate the power output from the turbine. (Oct 94) Given: h, = 2739.0 kJ/kg and hz = 2300.5 kJ/kg A. 4605 kw C. 4375 kw B. 4973 kw 0.4000 kw

6. Steam enters a throttling calorimeter at a pressure of 1.03 MPa. The calorimeter downstream pressure and temperature are respectively 0.100 MPa and 125°C. What is the percentage moisture of the supply steam? (Oct 95) Properties of steam:

P, MPa hf hfg hg

1.3 2010.7 2779.25

2726.6 kJ/kg

Note: at 0.100 MPa and 125°C, h

=

A. 2.62 B. 5.21 Solution:

.......

hf 1 = 2779.25 - 2010.7

= 768.55

C.3.15 D. 1.98

Solution: First law of Thermodynamics Energy In = Energy Out rnh, = mh z + W + q W = m(h 1-hz) - q = 10(2739 - 2300.5) - 10 = 4375 kw Ihe enthalpy of air is increased by 139.586 kJ/kg in a compressor. The 'CIte of air flow is 16.42 kg/min. The power input is 48.2 kw. Which of the following values most nearly equals the heat loss from the compressor in kw? (Apr 95) A. -10.0 C. +10.0 I~. -995 D. +9.95

Formulas and Principles - FUELS AND COMBUSTION F - 1

Formulas and Principles - THERMODYNAMICS

F -18

FUELS AND COMBUSTION

Solution: By first law of thermodynamics mh 2 + (-q) q = m(h 2 - h.) - W 16.42

q = q

-

CLASSIFICATION OF FUELS:

=

mn, + W

a. Solid Fuels (Principal component: Carbon, C) Coal, coke, wood, charcoal, bagasse, coconut shells and husks, briquetted fuels)

(139.586) - 48.2

60

= -10

b. liquid Fuels (Principal component: Hydrocarbon, CnHm )

kw

Gasoline, alcohol, kerosene, diesel, bunker, other fuel oils

10. An iron block weighs·5 N and has a volume of 200 ern". What is the density of the block? (Apr 96) A. 988 kg/cu.m B. 1255 kg/cu. m

C. 2550 kg/cu. m D. 800 kg/ cu. m

C.

Gaseous Fuels (Principal component: Hydrocarbon, CnHm) Natural gas, producer gas, blast furnace gas, liquified petroleum gas (LPG), methane, ethane, acetylene, propane

SOLID FUELS

Solution:

=

Density

kg (1 00)3 crn3 = x -- x 3 200cm3 9.81~ rn Volume

= 2548 kg/m

Density

5~

Mass

Three methods of classifying coals (adopted in US since 1927):

1. Classification by Rank - degree of metamorphism, or progressive alteration, in the natural series from lignite to anthracite - probably the most universally applicable method of classification, in which coals are arranged according to fixed carbon content and calorific value, in BTU, calculated on the mineral-matter-free basis.

3

11. A volume of 400 cc of air is measured at a pressure of 740 mm Hg abs and a temperature of 18°C. What will be the volume at 760 mm Hg abs and

o-cz C. 356 cc

A. 376 cc B. 326 cc

Classification of coals by rank: I. Anthracite II. Bituminous

III. Sub-bituminous IV. Lignite

D. 366 cc

Solution:

PIVl

P2V2

TI

T2

740(400)

760V2

1R + 273

0+273

V2

=

365.4 cc

2.

Classification by Grade - quality determined by size designation, calorific value, ash, ash-softening temperature, and sulfur.

3.

Classification by Type or Variety determined by the nature of the original plant material and subsequent alteration thereof.

Three varieties of coal in the high-volatile C bituminous group: 1. agglomerating and nonweathering 2. agglomerating and weathering ~ nonagglomerating and nonweathering

~

F - 20

Formulas and Principles - FUELS AND COMBUSTION F - 21

Formulas and Principles - FUELS AND COMBUSTION Moist BTU - refers to coal containing its natural bed moisture but not including visible water on the surface of the coal. Burners for Pulverized Coal: - although an early method, still is used 1. Vertical firing extensively, but with all the secondary air admitted around the burner nozzle so that it mixes quickly with the coal primarily air mixture from the burner nozzle. - a form of vertical firing, consists of burners 2. Impact firing located in an arch low in the furnace or in the side walls and directed toward the furnace door, with high velocities of both primary and secondary air. This type of firing is used extensively in wet-bottom or slagging-type furnace. 3. Horizontal firing - employs a turbulent burner, which consists of a circular nozzle within a housing provided with adjustable valves, the unit being located in front or rear wall. This type of burner is suited to high capacity and dry bottom furnaces. - is characterized by burners 4. Corner or Tangential firing located in each corner of the furnace and directed tangent to a horizontal, imaginary circle in the middle of the furnace. This type of firing is suited to either wet or dry bottom furnace operation and medium or high-volatile coals, and it is capable of extremely high capacities.

Note: Wet-bottom construction generally is chosen for low grade coals that have low fusion characteristics, whereas dry bottom construction often is selected for high-fusion coals. Coke _ is the solid, infusible, cellular residue left after fusible bituminous coals are heated, in the absence of air, above temperatures at which active thermal decomposition of the coals occurs. High temperature ranges from 815 to 1093 DC (average practice, 926 to 1037 DC). Low temperature coke is DC. formed at temperatures below 704 The residue, if made from a noncooking coal, is known as char. Wood Fuel - may come to the boiler plant in the form of cordwood, slabs, edging, bark, sawdust, or shavings. The major variable in wood is moisture content; air dried wood seldom contains less than 12% water, whereas kiln dried usually contains from 1 to 7%. There are three general methods in burning wood fuels (1.) in moving bed on an inclined grate, (2). In suspension, as in spreader stokers, or (3). in piles on flat grates. Charcoal _ the only carbon for steel making and other metal smelting from prehistoric times up to eighteenth century. Charcoal is produced by partial combustion of wood at about 400DC and with limited air. Hardwood charcoal weighs about 31 kgs. per m 3 and softwood charcoal about 28 kgs. per rn".

II(~

maximum of 14% volatile and 2% moisture is customarily established.

. lie heating value of charcoal ranges from 25,531 to 32,495 kJ/kg.

';traw, Paper, and Miscellaneous Waste Fuels - also classified as solid . ,,~Is.

I

(QUID FUELS

Oils - any liquid or liquefiable petroleum products burned for the

'neration of heat in a furnace firebox, or for the generation of power in an

, 'I(jlne, exclusive of oils with a flash point below 37.7 DC by the Tag closed

,·,ter. Fuel oils in common use fall into into four classes: (1). Residuals

.uls: which are topped crude petroleums or viscous residuums obtained in

,.tlilery operations; (2). Distillate fuel oils, which are distillates derived

:" octly or indirectly from crude petroleum; (3). Crude petroleums and

weathered crude petroleums of relatively low commercial value; and (4) I iionded fuels, which are mixture of two or more of the preceding classes. I llel ;1

(;asoline - as a refined petroleum naptha which by its composition is .:utable for use as. a carburetant in internal combustion engines. Motor ; .soline for automotive use, is mixture of hydrocarbons distilling in the range DC DC to 204.4 by the standard method of test. The hydrocarbons , 37.7 "Iong chemically to four principal classes: paraffins, olefins, naphtenes, , ,(J aromatics. Gasoline ordinarily graded by volatility and antiknock value, or " tane number. K(~rosene - a petroleum distillate having a flash point not below 22.8 DC as ,Iurmined by the Abel tester.

I\lcohol - the alcohol most frequently used considered as fuel for internal .nbustion engines is ethly alcohol, sometimes called grain alcohol. Its ·,rlern chemical name is ethanol (CzHsOH). Two other alcohols that have "(;n used as fuel are methanol and isopropanol, which are also called methly , ohol and isoprohyl alcohol.

is a product of the destructive distillation of I .o al Tar and Tar Oil 'uminous coal carried out at high temperature. liquefied Petroleum Gases (LPG) - are mixtures of hydrocarbons .uefied under pressure for efficient transportation, storage and use. Illesel fuel oils - refiners grade fuels broadly according to methods of 'oduction: (1). Distillate fuels are produced by distillation of crudes, (2). I':esidual fuels, are those left after the distillation process, (3) blended fuels, Ire mixtures of straight distillate fuels with cracked fuel stacks.

F·22

-._.

Formulas and Principles - FUELS AND COMBUSTION

GASEOUS FUELS - gaseous fuels commonly used in industry, whether distributed by public utilities or produced in isolated plants, are composed of one or more simple gases in varying proportions. Diesel LUbricating Oils - crude oils are frequently described as "paraffinic", "naphthenic", or "mixed based". Two broad types of oils are in use: 1. Straight oils - are produced entirely from the crudes chosen through elimination of undesired constituents by suitable refining processes. 2. Additive oils - are produced by adding to straight mineral oils certain oil-soluble compounds that enhance the lubricating oil properties for use in a diesel engine. SAE three types of lubricating oils; 1. Regular type - suitable for moderate operating conditions. 2. Premium type - having oxidation stability and bearing corrosive­ preventive properties making it generally suitable for more severe service than regular-duty type. 3. Heavy duty type - has oxidition stability, bearing corrosion­ preventive properties, and detergent-dispersant characteristics for use under heavy-duty service conditions.

Properties of Fuels and LUbricants:

- - - - ---'-----

-

---

----

-

--

-._----­

Formulas and Principles - FUELS AND COMBUSTION F - 23 Instruments used for measuring specific gravity:

Hydrometer, pycnometer, westphal balance

API and Baume Gravity Units: °API

141.5

=

SG at 15.6°C °Baume

140

= SG at 15.60C

- 131.5

(for petroleum products)

- 130 (for brine)

Specific gravity at temperature t, applying correction factor: SG t = SG 15 6, C [1 - 0.0007(t - 15.6)]

Heating value or Calorific value, kJ/kg a. Higher heating value (gross calorific value) - the heating value obtained when the water in the products of combustion is in the liquid state.

b. Lower heating value (net calorofic value) - the heating value obtained when the water in the products of combustion is in the vapor state.

Instruments used in measuring the heating value of fuels: a. Oxygen bomb calorimeter: for solid And liquid fuels b. Gas calorimeter: for gaseous fuels Calculating heating value by formulas:

1. Analysis of composition: a. Proximate analysis - analysis of the composition of fuel which gives, on mass basis, the relative amounts of moisture content, volatile matter, fixed carbon and ash.

b. Ultimate (chemical) analysis - analysis of the composition of fuel which gives, on mass basis, the relative amounts of carbon,' hydrogen, oxygen, nitrogen, sulfur, ash and moisture.

2. Specific Gravity; Density

Density of Liquid

Specific Gravity

= Density of Water =

Density of Gas Densitv of Air

a. DUlong's formula, used for solid fuels of known ultimate analysis:

Q h = 33,820 + 144,212(H - 0 ) + 9,304 S 8

b. ASME formula, for petroleum products:

Q h = 41,130 + 139.6 (OAPI)

kJ/kg

c. Bureau of Standards Formula: Q h = 51,716 - 8,793.8 (SGf

kJ/kg

kJ/kg

----_.~

F - 24

.-- - - - - - - -

---­

----------

Formulas and Principles - FUELS AND COMBUSTION I- - 25

Formulas and Principles - FUELS AND COMBUSTION

Fire Point - the temperature at which oil gives off vapor thilt burns continuously when ignited

Difference between higher and lower heating value: Qh

-

QL

where:

= H2

9(H 2)(2442)

= 26

Pour point - the temperature at which oil will no longer pou .... freely or the temperature at which oil will solidify

- 15(SG), %

Dropping Point - the temperature at which grease melts

4. Viscosity of Lubricants Viscosity - resistance to flow or the property which resists shearing of the lubricant.

Cloud Point - temperature at which the paraffin elements separate from oil

Absolute viscosity - viscosity measurement of shear resistance

Conradson number (carbon residue) - the percentage by weight of the carbonaceous residue remaining after destructive distillation

which

is

determined

by

direct

Octane number - the ignition quality rating of gasoline, wh ich is the percentage by volume of iso-octane in a mixture if iso-octane and heptane that matches the gasoline in anti-knock quality.

Kinematic viscosity - absolute viscosity divided by the density Viscosity index - the rate at which viscosity changes with temperature

Cetane number - the ignition quality rating of diesel, which is the percent of cetane in the standard fuel.

Units of Viscosity

Absolute viscosity:

lb - sec 1 reyn = --:-z­

_

1 poise

m

Kinematic Viscosity: cm Z 1 stoke 1 -sec

=

=

Dyne -sec cm z

=

0.1 Pa-sec

COMBustiON Combustion - chemical reaction, between fuel and oxygen, which is accompanied by heat and light.

2

0.0001 m /sec

Theoretical air-fuel ratio - the exact theoretical amount, as determined from the combustion reaction, of air needed to burn a unit amount of fuel, kg air per kg fuel.

Viscosimeter - an instrument , consisting of standard orifice, used for measuring viscosity (in SSU and SSF)

Actual air-fuel ratio - theoretical air-fuel ratio plus excess air

SSU (Saybolt Second Universal) - number of seconds required for 60 ml of oil (at 37.5°C) to pass through a standard orifice SSF (Saybolt Second Furol) - unit used for very viscous liquids using a relatively larger orifice 1 centistoke 62 SSF

= 0.308(SSU - 26)

= 660 SSU

5. Other properties of fuels and lubricants: Flash Point - the temperature at which oil gives off vapor that burns temporarily when ignited

'1'0 excess air

I

=

Actual A/F - Theoretical A/F

Theoretical A/F

vpical combustion reaction of a fuel with known chemical formula: Fuel + Air

CnH m+

X

= Products of Combustion O2 + x(3.76) N2

= YCO2

+

Z

H20 + x (3.76) N2

where: x, y and z represents the number of moles

~~

---~._~--

Formulas and Principles - FUELS AND COMBUSTION F - 27

Formulas and Principles - FUELS AND COMBUSTION

F - 26

% Excess air

Molal analysis is volumetric analysis. Air by volume consists of 21% oxygen and 79% nitrogen, thus there are 3.76 mols of N2 per mol of O 2,

= _ -

Actual A IF - Theo A I F Theo A/F 19-15 -1-5 x 100%

x 100%

= 26.67%

O 2 is only 23.2% by mass of air.

A fuel has the following volumetric analysis:

Molecular weight of air, M = 28.97 kg air per mol of air.

CH 4

= 68%

C 2H6 = 32%

Combustion of solid fuel with known ultimate analysis: Theo AlF

=

o

11.5 C + 34.5(H - - ) + 4.3 S 8

kgair kgfuel

Molecular Weights:

C 12 N2 28

H2 = 2 S = 32

O2 = 32

=

=

Solution: Combustion reaction with theoretical air:

0.68 CH 4 + 0.32 C 2H e + 2.48 O2 + 2.48(3.76) N2

SAMPLE PROBLEMS 1. There are 20 kg of flue gases formed per kg of fuel oil burned in the combustion of a fuel oil C 12H26. What is the excess air in percent? (Oct 96)

C.26.67 D.8.21

A. 20.17 B. 16.56

Assume complete combustion with 15% excess air at 101.325 kPa, 21°C wet bulb and 27°C dry bulb. What is the partial pressure of the water vapor in kPa? C.17.28 A. 9.62 D.15.94 B. 12.81

= 1.32 CO 2 + 2.32 H20 + 2.48(3.76) N2 Combustion reaction with 15% excess air:

0.68 CH 4 + 0.32 C2 He + 1.15(2.48) O 2 + 1.15(2.48)(3.76) N2

=1.32C02

+ 2.32 H20 + 1.15(2.48)(3.76) N2 + 0.15(2.48) O 2

Solution: Total mols in products of combusticn: Solving for the theoretical air-fuel ratio: C

+ 18.5 O + 18.5(3.76)N 2 2 12H 26 Theo AlF

= =

= 12C02

+ 13 H20 + 18.5(3.76)N 2

=

18.5 + 18.5(3.76) 88.06 1 15 kgair 88.06(28.97) kgfuel 12(12) + 26(1)

molsair molfuel

=

Actual AlF = 20 kg flue gases - 1 kg fuel

= 19 kgair kgfuel

= 1.32

+ 2~32 + 10.723 +

0.372

= 14.735 mols ~artial

=

pressure of water vapor, Pw

=

Vw (P) V

~(101.325)

.. 14.735 = 15.95 kPa

--_ - - - - - - - - - - - - ­ ..

F " 28

3. A diesel electric plant supplies energy for Meralco. W(

W' WI

During a 24-hour period, the plant consumed 200 gallons of fuel at 28°C and produced 3930 kw-hr. Industrial fuel used is 28 °API and was purchased at P5.50 per liter at 15. 6°C. What should be the cost of fuel to produce one kwhr?

,

I,'·

"':'

B. P1.10

,}

Solution: ·1 ,,,

Solving for density at 15.6°C:

·1"1,1

141.5

=

°API ~

141.5

28 =

SG 15 6

Basic Classification of common Internal Combustion Engines:

- 131.5

Gasoline Engine

Gasoline

Spark

Otto

Kerosene Engine

Kerosene

Spark

Otto

Gas Engine

Gaseous Fuel

Spark

Otto

Diesel Engine

Diesel

Oil-Diesel Engine

Fuel Oils

SG t =

Number of strokes per cycle: Two-stroke Four-stroke

Z8 C

SG 15 6[1 - 0.0007(t - 15.6)1

=

0.887[1 - 0.0007(28 - 15.6)1

Density at 28°C

Price per kg

-

=

0.879(1)

P5.50 ­ 0.887

=

=

=

0.879

0.879 kg/Ii

P6.20 per kg

Cost Per kw-hr

jll3

Heat of Compression

Diesel

Heat of compression

Diesel

Other Classifications

= 0.887

Solving for density at 28°C:

apiA

Operating Cycle

SG 15 6

Density at 15.6°C = 0.887(1) = 0.887 kglli

SG

Method of Ignition

Fuel Used

- 131.5

SG I 5 6

~11!cld!l1

INTERNAL COMBUSTION ENGINES (I C E)

Type of Engine

C. P1.069 D. P1.00

A. P1.05

~'1

F·29

Formulas and Principles - DIESEL POWER PLANT

Formulas and Principles - FUELS AND COMB"USTION

=

200 gal

x

3.7854 Ii

3930 kw - hr

= P1.05 per kw-hr

gal

x

P6.20 0.879 kg x-­ kg Ii

Number of Cylinders: Single-cylinder Two-cylinder Three-cylinder, etc. Position of cylinders: Vertical Horizontal Incline Arrangement of cylinders: In-line Radial Opposed cylinder Opposed piston V-type Method of cooling: Air cooled Water cooled

Method of starting: Manual: crank, rope, kick Electric: battery Compressed Air Using other engine Application: Automotive Marine Industrial Stationary Power Locomotive Aircraft Number of piston sides working: Single-acting Double-acting Intake pressure: Naturally aspirated Supercharged

..

F - 30

Formulas and Principles - DIESEL POWER PLANT

Formulas and Principles - DIESEL POWER PLANT

Cycle Analysis of two stroke Gasoline Engine:

Cycle analysis of 4-stroke Gasoline Engine: Carburetor

P

Products of Combustion

3

P

@JCompression Fuel

[i] Suction

4:>=-: '

~Exhaust -----"~

Heat Added, Q A

:=

=

mC v(T 4-T 1)

=

QA

-

Cycle Efficiency

-

=

~

-----..

1

Intake Port

V

I

v

Cycle Analysis of 4-stroke Diesel Engine (Diesel Cycle)

QR

Fuel -----.. Injector .L

Cycle Efficiency

I

mCiT 3-T2 )

Heat Rejected, Q R Net Work, W net

Compression

4

_

Wnet -­ QA

QA -QR QA

1 ­ I

=

(T3-T2)-(T4-TI ) T3 -T2

2. Compression

k-I

Clearance Volume, V c = V3 = V2 Compression Ratio, rK

=

,---. Products of Combustion

~ V2

II

•

I I II

1. suction

I --

= .!..:.c c

4. Exhaust Clearance ratio, c

=

V2 o

V

=

V2

I

11~
=

= mC

Rejected,

QR

work, W net

=

, I, ';11

where: V D

Added, Q A

VI-V2

piston volume displacement

'11'1

1(;le

Efficiency

p(T3-T2 )

= mC QA

=

-

v(T 4-T 1 )

QR

W ll et

QA -QR

QA

QA

I[rc I] k

Ide Efficiency

=

1- I t I k(I --1)

.unpression Ratio, rK

c

=

VI V

­

2

l+c __ C

t ---- " 1V

>

F - 32

Formulas and Principles - DIESEL POWER PLANT

Cut-off Ratio, rc =

Formulas and Principles - DIESEL POWER PLANT

Y3 Y2

AlF =

=

Specific Heat Ratio, k

air-fuel ratio

1.4 for air standard

ma

Y2

Y2 Clearance Ratio, c = = YD

PYa

=

RT

V o = piston displacement, m 3/sec

Y j - Y2

=

Cycle Analysis of 2 stroke Diesel Engine:

(~J D LN C 2

= bore, rn. = length of stroke, m = speed, rev/sec (for 2-stroke) = speed/2, rev/sec (for 4-stroke) = number of cylinders

where: D L N N C

Fuel P

Exhaust Port

rna ". kgair mf kgfuel

=

~"

1. Compression I

Piston Speed = 2LN, m/sec 2L = distance traveled by piston in one revolution

Air

V

I

Indicated Power

Measuring instruments used: Engine indicator traces actual P-V diagram; Planimeter - measures area of P-V diagram Tachometer - measures speed

DIESEL POWER PLANT

~

- power developed inside the cylinder

PERFORMANCE OF DIESEL GENERATING SET: Indicated Power Air

~rna(kgfs)

Indicated Power Exhaust Gases (rna + mt)

Fuel

mf(kgls)

Qf(kJ/kg)

II

Generator

_Output

nJ

=

Pm; X V D

kw

Pm; = indicated mean effective pressure,

=

kPa

Area of diagram Length of diagram

X

spring scale

V D = piston volume displacement,

m3/sec

Generator Brake Power Diesel Engine Cooling Water In

Brake Power

Cooling Water Out

=

m, x Qh

rn.

=

Qh = ~--

= 2nTN,

kw

kw where:

where:

power developed by the engine

Measuring instruments used: Dynamometer measures the torque; Tachometer - measures the speed Brake Power

1. Heat Generated (Fuel)

-

fuel consumption, kg/sec heating value of fuel, kJ/kg

T = torque, kN-m N = speed, rev/sec

F - 33

.....

........

F - 34

Formulas and Principles - DIESEL POWER PLANT

Calculation of brake power using brake mean effective pressure: Brake Power

=

Pmb X V O,

where:

=

brake mean effective pressure, kPa

Pmb

b. m,

8. n m

=

Indicated Power

mechanical efficiency

Brake Power

9. n,

=

=

C.

-

=

Ind Power

= combined or overall

=

spec. fuel consumption

kg

kw - hr

mfx3600 GenOutput

Pmb Vo PmiV o

=

Pmb

a.

Indicated Heat Rate

Generator Output

=

kJ mrC3600)Qh --BrakePower kw-hr

Brake Power c. Engine-Generator Heat Rate

Generator Output = Brake Power x n,

= Ind Power

a.

nti

b. ntb

kJ

kw - hr

14. Generator Speed

= indicated thermal efficiency = = brake thermal efficiency

= illf(3600)Qh OenOutput

x n m x n,

10. Thermal efficiency of

kJ kw-hr

mf(3600)Qh IndPower

==

Pmi

b. Engine Heat Rate

efficiency

kg kw-hr

13. Heat Rate

Friction Power

Brake Power

=

m,

==

Ind Power x nm

= electrical or generator

ill fx3600 BrakePower

=

== brake spec. fuel consumption

kw

7. Friction Power = Indicated Power - Brake Power Brake Power

-------._-­

-

Formulas and Principles ­ DIESEL POWER PLANT

Ind Power

N =

m.Q,

l20f P

Brake Power ==

where: N f

m.Q,

=

speed, rpm

p

= frequency (usually 60 hz)

=

no. of poles (even)

Oen Output C.

ntc == combined or overall thermal efficiency ==

m.Q,

Useful Output (Brake Power) Cooling Loss Exhaust Loss Friction, Radiation, Etc

11. Volumetric Efficiency (air only) Actual volume of air entering

= Va

Piston Displacement ==

=

Va V

o

maRT P

Heat Inputby Fuel...

rn, == indo spec. fuel consumption

.. . . .. .

34%

30%

26%

10%

100%

Supercharging:

12. Specific Fuel Consumption a.

Typical Heat Balance of Diesel Engine:

mfx3600 ==

IndPower

kg kw-hr

Supercharging - admittance into the cylinder of an air charge with

density higher than that of the surrounding air.

F - 35

F·36

---------

Formulas and Principles - DIESEL POWER PLANT

F . 37

Reasons for supercharging: 1. to reduce the weight-to-power ratio 2. to compensate for power loss due to high altitude

Waste Heat Recovery Boiler Utilizing Diesel Engine Exhaust:

Types of superchargers: 1. Engine-driven compressor 2. Exhaust-driven compressor (turbo-charger) 3. Separately-driven compressor

............

~

•

Exhaust Gases

Air

I

Diesel Engine

LJkw I- Generator

f­

I

1

Lub oil tank, lub oil pump, oil filter, oil cooler, lubricators

Steam

... .. . . . . . . . . . '/


raw By Heat Balance in Boiler:

mgCpg(t 1 - t2 )

= ms(hs - hr)

where:

=

Cpg

4. Intake and Exhaust System:

..

I

ms

Feedwater ---. . . . . h ..........) . . . .

r

2. Cooling system:

3. Lubrication System:

= rna + mr hs

'-­

Five Auxiliary Systems of Diesel Engine: 1. Fuel system: Fuel storage tank, fuel filter. transfer pump, day tank, fuel pump

Cooling water pump, heat exchanger, surge tank, cooling tower, water side

m g t1

.-­

r-

tz

specific heat of exhaust gas

Air filter, intake pipe, exhaust pipe, silencer

5. Starting System: Air compressor, air storage tank Advantages of Diesel Engine over other I.C.E. engines:

1. 2. 3. 4.

Low fuel cost 5. Simple plant layout High Efficiency Needs no large water supply No longer warm-up period

Power Developed at an altitude:

Bg

P=B---­ s 29.92 520

where:

Ps = standard power or power at sea level B = new pressure or actual barometric pressure, in Hg (decrease in pressure, approx. 1 in Hg per 1000 ft) T = new temperature or actual absolute temperature, oR (decrease in temperature approx. 3.6°F per 1000 ft) 29.92 in Hg = standard atmospheric pressure 520 = temperature at sea level 0R

SAMPLE PROBLEMS: I. A six cylinder, four stroke diesel engine with 76mm bore x 89mm stroke was run in the laboratory at 200 rpm, when it was found that the engine torque was 153.5 N-m with all cylinders firing but 123 N-m when one cylinder was out. The engine consumed 12.2 kg of fuel per hour with ;J

Formulas and Principles - DIESEL POWER PLANT

Formulas and Principles - DIESEL POWER PLANT

F - 38

heating value of 54,120 kJ/kg and 252.2 kg of air at 15.6°C per hour. Determine the indicated power. (Apr 97) A. 32.1 kw C. 23.3 kw B. 38.4 kw D. 48.3kw Solution:

=

Brake Power

2nTN

Friction Power Per Cylinder

Friction Power (Total) Indicated Power

= 2n(0.1535)( w)1 = 2000

= 32.1{~-j = 1.031kw

= 1.031(6) =

-

3. A single-acting, four cylinder, 4-stroke cycle diesel engine with a bore to stroke of 21.59 x 27.94 ern, operating at 275 rpm, consumes 8.189 kg/hr of fuel whose heating value is 43,961.4 kJ/kg. The indicated mean effective pressure is 475.7 kPa. The load on the brake arm, which is 93.98 cm is 113.4 kg. What is the brake arm mean effective pressure in kPa? (Apr 96) A. 415.20 C.319.95 B. 124.17 D.645.53

32.15 kw

Solution:

2n(0.123{2~~Oj

T

Solution:

= m w(h 1-h2 )

45(42.4) = m w(168.07 - 158.03)'

Q

rn;

Vw

= 190.04Ib/min

= (i2.4

v; =

...........

190.04

= 3.0455 fe/min

=

P mb

~.

0.09376 m

3/sec

=

=

2nTN

BrakePower Yo

=

=

2n(1.045) ( -27 5) 60

=

30 kw -

30

0.09376 = 319.97 kPa

A 2000 kw diesel engine unit uses 1 bbl oil per 525 kw-hr produced. Oil is 25°API. Efficiency of generator is 93%, mechanical efficiency of engine is 80%. What is the thermal efficiency of the engine based on indicated power (%)? (Oct 95) C. 39.6 A. 31.69 O. 35.6 B. 29.47 Solution: 1 bbl

= 42 Gallons

Solving for the density:

°API 3.0455(7.481) = 22.8 Gal/min

= (~) 02LNC

Torque = 113.4(0.00981 )(0.9394) = 1.045 KN-m

Brake Power

engine on test, 45 Hp are absorbed by the cooling water that is pumped through the water jacket and the radiator. The water enters the top of the radiator at 200°F. At that temperature, enthalpy of the water is 168.07 Btu/lbm. Water leaves the bottom of the radiator at 190°F and with an enthalpy of 158.03 Btu/Ibm. What is the water flow rate for a steady-state C. 23 Gal/min D. 24 Gal/min

piston volume displacement

(0.2159)2(0.2794)( 275 ) (4) = = ( ~) 4 2x60

6.19 kw

= Brake Power + Friction Power = 32.15 + 6.19 = 38.34 kw

condition? (Apr 97) A. 25 Gal/min B. 20 Gal/min

=

V o

2. In a test laboratory, it was found out that of the 80 Bhp developed by an

•

F - 39

=

141.5 SG . 15 6

-131.5

F:40

(l.

_ 131.5

141.5

25 =

SG 15 .6

SG 15 6 = 0.904 Density, P

=

Qh

=

0.904(1)

rn, = fuel consumed

0.904 kg/Ii

139.6(OAPI)

= 41,130 +

139.6(25)

=

=

143.724 kg

525

44,620 kJ/kg

TI

(~:Jk-I Tz

P 1V/ = P 2V/

20+ 273

(6r- 1

= 705.645 kw-hr

0.93(0.80)

=

705.645(3600)

Indicated Thermal Efficiency

Tz

= 6

VI rk = V

z

=

F - 41

The compression ratio of an ideal Otto cycle is 6:1. Initial conditions are 101.3 kPa and 20 deg C. Find the pressure and temperature at the end of adiabatic compression. (Oct 94) A. 1244.5 kPa, 599.96 oK C. 1244.5 kPa, gage, 60°C B. 1244.5 kPa, 60°C D. 1244.5 kPa, 599.96°C Solution:

= 42(3.7854)(0.904) =

= 41,130 +

Indicated Work

•

Formulas and Principles - DIESEL POWER PLANT

Formulas and Principles - DIESEL POWER PLANT

=

Pz = 2,540,323

2,540,323 143.724(44620)

kw-s or kJ

= 39.6%

5. A supercharged six-cylinder four-stroke cycle Diesel engine of 10.48 cm bore and 12.7 ern stroke has a compression ratio of 15. When it is tested on a dynamometer with a 53.34 cm arm at 2500 rpm, the scale reads 81.65 kg, 2.86 kg of fuel of 45,822.20 kJ/kg heating value are burned during a 6 min test, and air metered to the cylinders at the rate of 0.182 kg/sec. Find the brake thermal efficiency. (Apr 95) A. 0.327 C. 0.307 B. 0.367 D. 0.357

PI

(~Jk

T2 = 599.96 oK

v.

~ = (6) 1.4 = (6)1.4 101.3

P2 = 1244.5 kPa In an air standard Otto cycle, the clearance volume is 18% of the displacement volume. Find the compression ratio and thermal efficiency. (Oct 93) C. 0.53 A. 0.52 D.0.60 B. 0.55 Solution:

Solution:

T

=

81.65(0.00981 )(0.5334)

=

Brake Power

2nTN

=

0.42725 kN-m

2500 J = 2n(0.42725) ( ~

= 111.854 kw

.......

mr

=

nib

=

2.86 6(60)

=

BrakePower ITl

rQh

0.00794 kg/sec

=

111.854 (0.00794)( 45,822.20)

= 0.307

VI rk = Vz

l+c = c

Eff =

-

1

=

1+ 0.18 0.18

-'-=1k-l rk

= 6.556

1 = 053 (6.556)1.4-1 •

A certain diesel engine with the following specifications, 8 cylinder, 400 mm x 600 mm, four stroke cycle has a fuel consumption of 0.6 Ibs/hp-hr based on 19,100 Btu/lb. Engine speed is 280 RPM with an indicated mean effective pressure of 130 psi. If the jacket water carries away an estimated 25% of the heat supplied, find its capacity (GPM) required if the allowable rise is 40°F. (Oct 92)

I

F -42

---

Formulas and Principles - DIESEL POWER PLANT

A. 241.9 B. 236.5

-

Formulas and Principles - DIESEL POWER PLANT

43

Solution:

C. 249.1 O. 268.7

a. the pressure change alone

Solution:

VD

=

piston volume displacement

=

(~J (0.4)2(0.6)( 280 (8) 4 2x60'

The decrease in pressure due to elevation is approximately 1 in Hg per 1000 ft, therefore

= (~) 02LNC

J

B = 29.92

..

rn,

=

= Pm; V D

P

= PS(29~92J~5~0

= 130(101.325)(1.407433509) 14.7

= 2.5 (23.42) (1) 29.92

= 1,261.16 kw = 1,690.56 hp

= 1.957 MW

fuel consumption

HeatSupplied

= mfQ h

= 0.6(1,690.56) = 1,014.336 = 1,014.336(19,100)

= 23.42 in Hg

Power developed at an altitude:

= 1.407433509 m 3/sec Indicated Power

- 1 (1981.2X3.28) 1000

Ibs/hr

b.

pressure and temperature change The decrease in temperature with elevation is approximately 3.6 0 F per 1000 ft, therefore:

= 19,373,819.6 Btu/hr

Heat carried by jacket water

= 0.25(19,373,817.6)

T = 520 -

3.6(1981.2X3.28) 1000

::. 4,843,454.4 Btu/hr = 80,724.24 Btu/min Power developed at an altitude: Q =

mCp(~T)

80,724.24 = m(1.0)(40) m = 2,018.106 Ib/min

v

= (2,018.106/62.4.) x 7.482

=

241.9 Gal/min

9. Find the power which a 2.5 MW natural gas engine can develop at an

~

altitude of 1981.2 meters taking into consideration:

a. the pressure change alone b. pressure and temperature change

(Bd. Problem Apr 92)

P

= 2.5(23.42)~496.6 = \. 29.92

520

1.912 MW

= 496.6 0 R

~

..........

F -44

Formulas and Principles - STEAM POWER PLANT

STEAM

POWER

Formulas and Principles - STEAM POWER PLANT

PLANT

F - 45

=

Heat Added in Boiler

h 1 - h4 kJ/kg = m(h 1-h4) kw

STEAM CYCLES

m(h l -h 4 )

=

Heat added in Boiler

nb

1. RANKINE CYCLE - ideal steam power cycle. m kg/s

Rankine Cycle Efficiency or Thermal Cycle Efficiency:

=

Net Turbine Work Heat Added

Boiler

=

(hi - h z )

-

(h 4 - h 3 )

hi -h 4 4

CARNOT CYCLE applied to steam power. Pump Carnot cycle - the most efficient thermodynamic cycle. The T -5 Diagram

.

Q A = heat added in boiler = T 1(S1-S4)

T

Q R = heat rejected in condenser = T2(SZ-S3) = T 2(S1- S4)

W = work = Q A - Q R = T1(S1-S4) - T 2(S1- S4 )

4

, Turbine Work

nT = carnot cycle efficiency

3

8

= h1 - h2

nT

kJ/kg

Turbine Work = m(h 1-h2) x n, kw where: n, = turbine efficiency

Pump Work

mV3(P4 -P3) n p

QA

QA

=

h2 - h 3 kJ/kg = m(hz-h3) kw

kw

TI(SI -S4)-Tz(SI -S4) Tj(SI - S4)

=

=

40

T] =T 4 T 2 =T 3

3

1

2 8

I

where:

n,

= pump efficiency

T1 -Tz

T H -TL

T1

TH

highest absolute temperature T1 TH T 2 = T L = lowest absolute temperature

T

= h4 - h3 kJ/kg = m(h h3) kw

= V3(P 4-P 3) kJ/kg

=

Q A -QR

The T-5 Diagram:

4 -

Pump Work

W

where:

= m(h 1-h2) kw

Heat Rejected in condenser

=

83

=8

4

8 1 == 8 2

F -46

Formulas and Principles - STEAM POWER PLANT

3.. REHEAT CYCLE - to increase turbine power, low cycle efficiency.

Formulas and Principles - STEAM POWER PLANT

F - 47

Heat Balance in regenerative heater: m,h 2 + (m - m,)h 5 = m h6

3

5. REHEAT· REGENERATIVE CYCLE

Generator m-ml

Generator Power

Boiler II

m ---. 1

'"

Generator

6 Pump

Turbine Work = (h, - h2 ) + (h, - h4)

= (h. - h6 )

Heat Added

= he -

hs

=

=

Boiler

m\

+ (h3 - h2 )

Heat Rejected in condenser Pump Work

kJ/kg

kJ/kg

h4- hs

Air

vs(P6 - P5)

Pump

2

4. REGENERATIVE CYCLE - to improve the cycle efficiency, decrease •

turbine power, decrease heat addition.

1 m

Generator Boiler

The four major components of a steam power plant: 1. Steam Generators (Boilers) 2. Steam Turbines 3. Steam Condensers 4. Feedwater Pumps

STEAM GENERATORS (BOILERS)

W""IL..r\W. Pump 2

Heater

Primary classification of boilers (based on relative position of heated water and hot gases):

Pump 1

Turbine work = m(h, - h2 ) + (m - m, )(h2 - h3 )

= (m - m, )(h h4)

= (m-m,)(h 5-h4) = (m-m,)v4(P S-P4)

Heat Rejected in condenser Pump Work 1

3-

Pump work 2 = m(hr - h6 ) = mVe(Pr - P6 )

Heat Added in boiler

.-.

=

m(h, - hr)

1. Water Tube (Tubulous) Boiler - type of boiler in which the water is inside the tubes while the hot gases surround the tubes. 2. Fire Tube (Tubular) Boiler - type of boiler in which the hot gases pass inside the tubes while the water is outside the tubes.

F - 48

Formulas and Principles - STEAM POWER PLANT

Formutes: and Princtptes . --- ------

Boiler Auxiliaries and Accessories: i

Stoker - combustion equipment for firing solid fuels (used in water tube boilers)

I'i

,,.,

j'l

.\lowdown valve - valve throuqh wh«;n the imp~~(itles Uldl ::..(;Ill" " d. nud drum are remove Sometimes called blow off valve

Breeching - the duct that connects (he boiler and the chimney

Burner - combustion equipment for firing liquid and gaseous fuels (used in fire-tube boilers)

i~ir Preheater - heat exchanger wtuch utilizes the heat of the flue gases [() preheat the air needed for combustion

Feedwater pump - delivers water into the boiler

'Iitions:

Feedwater heater - pre-heating device which utilizes steam mixed with the feed water.

E Boiler Construction Code shall mea.: UD f3c;:icr Ccnstn iction ,ode of the PSfv!E with amendments and Interpr(;!;;dlons thereto made ind approved by the Councn of the Society.

Economizer - feedwater pre-heating device which utilizes the heat of the flue gases

Boiler or Unfired Pressure Vessel lnstallatrons InciLde all boilers ,nd unfired pressure vessels constructeo inc,tollt:;,; ;.':d;'ed Ir, operation or instructed for

Pressure Gauge - indicates the pressure of the steam in the boiler Safety Valve - a safety device which automatically releases the steam in case of over-pressure.

dng lnstallations '. any 1)1)!I,:!r ',J( uih,E';'J ,'i(;:~,s;m~ :U:, "C': cc.rst.uctoo, ',stailed, placed in operation but subject to annual mspection

Temperature Gauge - indicates the temperature of the steam in the boiler.

•

:>. Lf\.M hJIt'L; (

or Steam Generator - a closed vessel mrendec for use in healinn ate, or for application of heat to generate steam or other vapor to be .seo externally to itself.

,J

Fusible Plug - a metal plug with a definite melting point through which the steam is released in case of excessive temperature which is usually caused by low water level.

»d Pressure Vessel - a vessel In which press ire in obtained from an '((ernal source, or from all indirect application of heat

Water Walls - water tubes installed in the furnace to protect the furnace against high temperature and also serve as extension of heat transfer area for the feedwater.

.r Boiler - a closed vessel in which stearn or other vapor (to be used .;,':ternally to itself) is generated at a pressure of more than 1055 kg/cln 2 Jage by the direct application of heat.

Gage Glass (Water Column) - indicates the water level existing in the boiler. Baffles - direct the flow of the hot gases to effect efficient heat transfei between the hot gases and the heated water. ! Furnace - encloses the combustion equipment so that the heat generated will be utilized effectively. Soot Blower - device which uses steam or compressed air to remove the' soot that has accumulated in the boiler tubes and drums. Draft fans (forced draft and induced draft fans) - supply air needed for combustion and create the draft required for the flow of gases in the boiler.

,,:-native Boiler - a boiler mounted all a self-propelied track locomotive rnd usee! to furnish motivating power for travelling on rails ,.iDle Boiler an internaily fired boiler . .vhich is self-contained and 'irncirily intended for temporary location and li .e construction ann usage :, ooviouory portable. ,..dire Boiler- as used in this Code herein shall mean any boiler which

loes .iot exceed any of the toliowing limits: 405 mm inside diameter,

! 065 rn"'l overall length of outside to outside of heads at center, 1.85 n/

,f watei fieatlng surface, 1.03 kq/cm" maximum ailowable working

l

Jrf;S::jL.;f e.

\ Pr es sur o Heating Boiler - a boiler operated at pressure not exceeding i (I',:! hI,: III.' <J
F - 50

Formulas and Principles - STEAM POWER PLANT

Hot Water Supply Boiler externally to itself.

a boiler furnishing hot water to be used

F - 51

Condemned Boiler or Unfired Pressure Vessel - a boiler or unfired pressure vessel that has been inspected and declared unsafe to operate or disqualified stamped and marked indicating its rejection by qualified inspecting authority.

- a steel catwalk or platform at least 455 mm wide and provided Willi standard handrails and toe board on either side should be installed across the tops of adjacent boilers. - the lowest factor of safety permissible on existing installation shall be 4.5 excepting for horizontal return tubular boilers having continuous lap seems more than 3650 mm in length where the factor of safety shall be 9. Reinstalled or secondhand boilers shall have a minimum factor of safety of 6 when the lonqltudinal seams are of lap riveted construction, and a minimum factor of safety of 5 when the longitudinal seams are of butt and double strap construction. - the age limit of a horizontal return tubular, flue or cylinder boiler havinq a longitUdinal lap joint and operating at a pressure in excess of 0.345 MPa 'or 3.45 Bar gage shall be thirty years (30 years). A reasonable time for replacement shall be given at the discretion of the Inspection not to exceed one {1} year.

Internal Inspection - an inspection made when a boiler or unfired pressure vessel is shut down and handholes, manholes, or other inspection openings are opened or removed for inspection of the interior.

- the maximum allowable working pressure on a water tube boiler shall not exceed 1.10 MPa or 11.0 Bars. The maximum allowable working pressure for any cast iron boiler except hot water boilers, shall be 1.0 Bar gage.

Reinstalled Boiler or Unfired Pressure Vessel - a boiler or unfired pressure vessel removed from its original setting and re-erected at the same location or erected at a location without change of ownership. Second Hand Boiler or Unfired Pressure Vessel - as used herein shall mean a boiler or unfired pressure vessel of which both the location and ownership have been changed after primary use.

..

Formulas and Principles - STEAM POWER PLANT

External Inspection an inspection made on the external parts accessories and/or component even when a boiler or unfired pressure vessel is in operation . Steam Generators - situated not less than 3 m distance from bUildings not forming part of factory. - no part of the steam generator should be closer than one from any wall. - steam generators should be mounted over a suitable foundation or concrete pad of not less than 305 mm thick and with sufficient area at base to be supported by the bearing capacity of the soil with a factor of safety of not less than four {4}. - when boilers are replaced or new boilers are installed in either existing or new buildings, a minimum height of at least 2130 mm shall be provided between the top of the boiler proper and the ceiling except in single installation of self-contained boilers where a minimum height of at least 915 mm shall be provided between the highest point of any valve steam or fitti~g and the ceiling. - no smokestack should be closer than 305 mm from any exposed woodwork or framing. - smokestack should be sufficient to withstand a wind load 160 kph and rise at least 5000 mm above the eaves of any building within a radius of 50 meters. - when feeding hot water, feed pump should at least be 1220 mm below hot well to prevent vapor lock. - two check valves should be provided between any feed pump and boiler.

PERFORMANCE OF BOILERS:

Boiler

Fuel m, kg/hr kJ/kg

o,

I

mL-,

A'

....

~ .

-=

l ......

r----lUlI

Feedwater, h(

Furnace

1.

rn,

2.

HS = heating surface, m 2 = total surface area through which the heated water and hot gases exchange heat.

= rate of evaporation of steam or mass flow rate of steam

= kg/hr

3. Os = heat supplied or heat generated by fuel

= mfOh

r-­ Formulas and Principles - STEAM POWER PLANT F -52

Formulas and Principles - STEAM POWER PLANT

STEAM TURBINES

4. Rated Boiler Horsepower

= _HS

(for water tube)

=

(for fire tube)

PERFORMANCE OF STEAM TURBINES:

0.91 HS

Steam

1.1

Generator Output

i

ms hi

(1 boiler hp _

Generator

= IDs(hs-h f )

5. Developed Boiler Horsepower

35,322

L...-. Turbine Output

(3)com(Brake Power)

Developed Boiler HP

6. Percent Rating

+

reo",

h2

= 35,322 kJ/hr)

Rated Boiler HP

hl'2

7. ASME Evaporation Units (rate at which heat is transformed)

= ms(hs - hi)

8. Factor of Evaporation (FE)

... • •

1. Ideal Turbine work

kJ/hr

=

9. Boiler Thermal Efficiency

hs - h f

=

where: h 1 h2

2257

IDrQh

=

10. Actual Specific Evaporation

IDf'

entering

= enthalpy after ideal (isentropic) expansion

where: h 2a nst

= enthalpy after actual expansion = stage efficiency =

m S(h 1-h2) nT

=

mS(h1-h2)(nst)nm

4. n, = electrical or generator efficiency = Generator Output

=

Turbine Output rn, x FE

12. Equivalent Specific Evaporation

=

kg/hr from and at 100 o C IDS x FE IDf

kgsteaID kgfuel

frdm .

and at 100°C

Generator Output

= =

Turbine Output x n, m S(h 1-h2) nT ne

5. Thermal Efficiency a. nIb

.......

kw

where: nT = turbine efficiency = nst x nm n m = mechanical efficiency

kgsteaID kgfuel

(Boiler Economy)

11. Equivalent Evaporation

= enthalpy of steam

3. Turbine Power Output

mtOh IDS

m S(h 1-h2)

2. Actual Turbine work = m S(h 1-h2a) = mS(h 1-h2) nst

IDs(hs - h f )

ms(h s - hi) - energy consumed by accessories

Net Boiler Eff.

=

= brake thermal efficiency

_

Turbine Output IDs(hj

-

hf2)

F - 53

F - 54

Formulas and Principles - STEAM POWER PLANT Formulas ----- - and Principles -

b. nte = combined or overall thermal efficiency =

nR

Generator Output

= Ideal Rankine thermal efficiency

=

h] - h 2 h] - hf2

1. SUrface Condenser - type of condenser in which the steam and cooling water do not mix; commonly used design is the shell-and­ tube

6. Engine Efficiency of Turbine Cooling Water In

a. neb = brake engine efficiency

=

tl,

Brake Power

ffiw

ll1s(h] -h 2) _ ~) ..

~

b. nee = combined or overall engine efficiency

-_.-­

p

.......

. Water Out

Cooling tz

_ Generator Output ffiS(h] - h 2 )

7. Willan's Line:

... ••

Willan's line is a straight line which shows the relation between the steam consumption (m s • kg/hr) and the load (L, kw) of a steam turbine generator unit.

Heat Balance in Condenser:

= ms(hs-hf)E

mwCp(trt 1 )

IDS

Cp = 4.187 ~ kg _0 C

kg/hr

E = heat extraction factor

b L,KW

I

No load

F - 55

Classifications of Steam Condensers:

ll1s(hj -hf2)

C.

STEAM POWER PLANT

Full Load

Vacuum Efficiency, Nv

Nv

STEAM CONDENSERS Functions of Steam Condensers: a. To create vacuum at turbine exhaust and to increase the turbin power. b. To convert steam to liquid so that it can be pumped back to the boiler.

=

Patm Patm

-

Pcond

-

Psat

Palm - atmospheric pressure

Peond - absolute condenser pressure

Psat - saturation pressure

..

Formulas and Principles - STEAM POWER PLANT

F - 56

2. Contact (Jet) condensers - type of condenser in which the steam

Formulas and Principles - STEAM POWER PLANT

.. ),

STEAM ENGINES

and cooling water are mixed. Steam Engines are double-acting and the process is isentropic.

Steam

{;t,,:}

Cooling Water In

Condensate Brake Power

II

FEEDWATER PUMP 2 - - -__ lahz

..

1. Ideal P-V Oiagram

p

m kg/s

, •

hI PI

Pump Work

1 _

-

..

= m(h 2-h1) = mV1(P2-P1) = mgh

•..-­

kw kw

where: m = mass flow rate, kg/sec 3/kg V1 = specific volume, m P1 = entrance pressure, kpa P2 = exit pressure, kPa h = head, meters Pump Input Power (Brake Power of the pump)

Pump Work

=

....-- V D

watt

Pump Efficiency

2. VD

==:r--

=

piston volume displacement

=

2

=

(~J 02LN,

(~)

m

3/s

02 LN + (:

V

(piston rod neglected)

J (02-d2)LN, m

3/s

(piston rod considered)

F - 58

Formulas and Principles - STEAM POWER PLANT

3. Indicated Power

Formulas and Principles - STEAM POWER PLANT

8.

Engine Efficiency

Measuring instruments used: Engine Indicator traces the actual P-V diagram; Planimeter measures area of P-V diagram; Tachometer measures speed.

a. nei

Indicated Power = Pm; V o, kw

b. neb = brake engine efficiency =

Pm; = indicated mean effective pressure,

','J

=

indicated engine efficiency

=

Indicated Power ms(h[ - h 2 )

Brake Power ms(h l -h 2 )

kPa 9. Efficiency of Equivalent Rankine cycle:

=

..

Area Of Diagram Length Of Diagram

X

spring scale

=

=

WT

QA

hi -h 2

hi - hf2

4. Brake Power Measuring instruments used: Dynamometer measures the torque; Tachometer measures the speed. Brake Power

= 21lTN,

I. A steam boiler on a test generates 885,000 Ib of steam in a 4-hour period. The average steam pressure is 400 psla, the average steam temperature is 700°F, and the average temperature of the feedwater supplied to the boiler is 280°F. If the boiler efficiency for the period is 82.5%, and if the coal has a heating value of 13,850 Btu per Ib as fired, find the average amount of coal burned in short tons per hour. (Apr 97)

kw

=

torque, kN-m

where: T N = speed, rev/s

•

Calculation of brake power using brake mean effective pressure:

••

Brake Power

=

P mb V o ,

SAMPLE PROBLEMS:

kw

A. 9.84 short tons per hour C. 12.05 short tons per hour B. 10.75 short tons per hour D. 11.45 short tons per hour

Solution:

P rnb = brake mean effective pressure,

kPa

5. Friction Power = Indicated Power - Brake Power

6.

nm

=

Brake Power

mechanical efficiency

Brake Power

=

=Indicated .' P ower

The following enthalpies should have been given in the problem.

From steam table:

At 400 psia and 700°F, At 280°F,

h,

=:

hz

=:

1362.7 Btu/lb

249.1 Btu/lb

Indicated Power x nm

m, =

885,000/4

= 221,250 Ib/hr

7. Thermal Efficiency a. nIl = indicated thermal efficiency =

Indicated Power

=

Boiler Efficiency

ms(h z - hI)

mrQ h

ms(h l -hf2 )

0.825 = 221,250(1,362.7-249.1)

b. nIb

=:

brake thermal efficiency

=

m r (13,850)

Brake Power mS(h] - hf2 )

rn,

=

21,563 Ib/hr

F - 60

Formulas and Principles - STEAM POWER PLANT FormUlas and Principles - STEAM POWER PI AN r

_

21,563

- --

'.,

Solution:

2000

= 10.78 short tons per hr

2.

Steam is admitted to the cylinder of an engine in such a manner that the average pressure is 120 psi. The diameter of the piston is 10 in and the length of the stroke is 12 in, What is the hp of the engine when it is making 300 rpm? (Apr 97) A. 171.5 C. 173.2 B. 175 D. 174.4

VD

= piston

=

..

~

volume displacement

-2)(300)(2) (-10)12(1 12

4 12

=

=

(~) D 2LN x 2

h2 = (h, + hfgh

h2 = 670.56 + 1.00(2086.3)

= 2756.9

h, = h, == 670.56

3

(120)(144)327.25 33,000

= 171.4

HP

3. In a cogeneration plant, steam enters the turbine at 4 MPa and 400°C. One fourth of the steam is extracted from the turbine at 600 kPa pressure for process heating. The remaining steam continues to expand to 10 kPa. The extracted steam is then condensed and mixed with feedwater at constant pressure and the mixture is pumped to the boiler pressure of 4 MPa. The mass flow rate of steam through the boiler is 30 kg/so Disregarding any pressure drops and heat losses in the piping, and assuming the turbine and pump to be isentropic, how much process heat is required in kw? (Apr 96)

h

At 600 kPa: hf = 670.56 h fg = 2086.3

A, 15,646.8 B,2,4GB'2

=

15,647.5 kw

generator. The feedwater enters the economizer at 145°C and leaves at 205°C. The steam leaves the boiler drum with a quality of 98%. The unit consumes 2.75 kg of coal per second as received having a heating value of 25,102 kJ/kg. What would be the overall efficiency of the unit in percent? (Apr 96) Steam Properties: At 5 MPa and 400°C; h == 3195.7 kJ/kg

At 5 MPa: h, = 1154.23 hfg == 1640.1

At 205°C: h, = 875.04

At 145°C: hf = 610.63

A. 65

C, 88 D. 78

B. 95

I

I

23.5 ke/.s ------.. Steam S Mpa, 400°C

..,

Solution:

Steam Properties: At 4 MPa and 400°C:

(2756.9 - 670,56)

4. 23.5 kg of steam per second at 5 MPa and 400°C is produced by a steam

Indicated Power = Pmi VD

=

30

= -4

327.25 fe/min

,I

••

30 kg/s

Q == m 1 (hr h 3 )

Solution: It

S1 = S2

S1 = (Sf + Sfgh

6.7690 == 1.9312 + x(4.8288)

x = 1.00 (saturated vapor)

= 3213.6 kJ/kg,

Boiler s = 6.7690 kJ/kg-OK

Sf = 1.9312 Sfg 4.8288

=

C, 3,578.5 D. 1,026.9

Heat Absorbed Overall Efficiency Heat Supplied ffis(h s -h r) = ffirQ h ==

F1

Feedwater Fuel

V"-

2.75 kg/s

1_

20S oC

Qh = 25,102 kJ/kg 145°C

Overall Efficiency _ 23.5(3195.7-610.63) 2.75(25,102) , 88 %

=

F·62

Formulas and Principles - STEAM POWER PLANT

Formulas and Principles - STEAM POWER PLANT

5. A steam plant operates with initial pressure of 1.7 MPa and 370°C The temperature and exhaust to a heating system at 0.17 MPa. condensate from the heating system is returned to the boiler at 65.5°C and the heating system utilizes from its intended purpose 90% of the energy transferred from the steam it receives. The nt is 70%. If the boiler efficiency is 80%. what is the cogeneration efficiency of the system in percent. Neglect pump work. (Oct 95)

OR

= (3187.1 - 2670.6)(0.70) = 0.90(hz-h 3 )

= 0.90(2670.6 - 274.14) OA

=

At 0.170 MPa:

=3187.1 kJ/kg

h f = 483.20 htg =2216.0

Sf = 1.4752 Stg 5.7062

=

ill

At 65.5°C: hf = 274.14 A. 78 B. 102.10

..

S:;: 7.1081 kJ/kg-OK

C. 91.24 0.69

3187.1- 27~ 0.80

:;: 3641.2 kJ/kg

Cogeneration Efficiency:

=

WT + Q R

=

361.55 + 2156.81 3641.2

QA

QA ~\

h1 = 3187.1 kJ/kg

~

~

QR

Solution:

V3 (P4 -P3 )

=

Wp

TIp

where:

Solving for h2:

=

=

h2 = (h f + xhfg)

:;: 483.20 + 0.9871(2216.0)

2670.6

=

:;:

= 1/1000

:;: 0.001 m 3/kg

P4 17.5 + 1.5

19 MPa

= 19,000 kPa

P3 = 0.007 MPa

= 7 kPa

np = 0.70

V3

S1 S2 (Sf + XSfg)z

7.1081 1.4752 + x2(5.7062)

X2 = 0.9871

h a = h 4

:;:

69.16 %

MPa and 530°C expand in a turbine to 0.007 MPa. The turbine and pump polytropic efficiencies are 0.9 and 0.7, respectively, pressure losses between the pump and the turbine inlet are 1.5 MPa. What should be the pump work in kJ/kg? (Oct 95) A. 17.3 C. 37.3 B. 27.3 0.47.3

, ·f

=

kJ/kg

6. A superheat steam Rankine Cycle has turbine inlet conditions of 17.5

Solution:

••

= 2156.81

lib

Steam Properties: At 1.70 MPa and 370°C: h

= 361.55 kJ/kg

hI -h 4

=

-

F • 63

274.14

W T = (h 1-h 2 )n,

= =

Wp =

0.001(19,000 - 7)

= 27.1

0.70 kJ/kg

Formulas and Principles - STEAM POWER PLANT

F - 64

7. Determine the vacuum efficiency of a surface condenser which operates at a vacuum of 635 mm Hg and exhaust steam enters the condenser at 45.81 cC. The barometric pressure is 760 mm Hg. A. 80.4% C.92.7% B. 85.2% D. 98.3% Solution: From steam table at 45.81 cC:

(760-635)0.1013 760 P bar - Pcond Vacuum Efficiency = P bar ­ Psat

Pcond

..

P sat

=

_

=

=

0.010 MPa

0.01666 MPa

0.1013-0.01666 0.1013-0.010

Formulas and Principles - GEOTHERMAL POWER PLANT F - 65

GEOTHERMAL POWER PLANT Definitions: 1. Magma - molten metal within the earth which is basically nickel-iron in composition whose stored energy heats the surrounding water thereby producing steam or hot water. 2. Well-bore product - the effluent coming out from the geothermal well as produced after drilling. This can be purely steam or hot water, or a mixture of both. 3. Steam-dominated geothermal field - refers to a geothermal plant with its well producing all steam as the well-bore product.

=

92.7%

4. Liquid-dominated geothermal field - the well-bore product for this type of field is practically all hot water, pressurized. 5. Sources of geothermal energy: a. hot spring b. Steam vent c. geyser

'.

6. Fumarole - a crack in the earth through which the geothermal substances passes.

Types of Geothermal Plants: 1. Dry or superheated Geothermal Power Plant -

kw

.:t=: Dry

,: ~ : ::

Superheated

Steam

To Reinjection Wells

Formulas and Principles - GEOTHERMAL POWER PLANT F - 67

Formulas and Principles - GEOTHERMAL POWER PLANT

F -66

PERFORMANCE OF FLASHED-STEAM GEOTHERMAL PLANT

2. Separated Steam or Single flash Geothermal Plant

rnS Generator

I

Generator Output

rn g 1

-2 .,.L.:.::::::::::-- ~ Turbine Output

Mixture

J.

To Reinjection Wells To Reinjection Wells

.

f"i

ffiw

The T-S Diagram:

3. Separated Steam/Hot-Water-Flash or Double Flash

T

Geothermal Plant

Mixture . ·t

I

I

4. Single Flash Plant with Pumped Well

..

•

Flasher

:

To Reinjection Wells

s mg = mass flow rate of ground water

rn, = mass flow rate of steam entering turbine

Throttling process (1-2)

h 1 = h 2 = (hf + x hfgh

where: x :::: quality after throttling

Mass flow rate of steam entering the turbine:

rn, = x (mg )

5. Binary Geothermal Plant

Turbine Output = m s(h 3-h 4)nT

where: nT = turbine efficiency

Generator Output = m s(h 3-h 4)nT x n,

n, = generator efficiency

where:

\

Heat Rejected in Condenser = m s(h 4-h s )

~o:te~llI\ To Reinjection Wells

Overall Plant Efficiency

_ Turb ineOutput rngh J

F - 68

Formulas and Principles - GEOTHERMAL POWER PLANT

SAMPLE PROBLEMS:

h3 = hg at 1.04 MPa = 2779.6 kJ/kg

1. A liquid dominated geothermal plant with a single flash separator receives water at 204°C. The separator pressure is 1.04 MPa. A direct-contact condenser operates at 0.034 MPa. The turbine has a polytropic efficiency of 0.75. For a cycle output of 50 MW, what is the mass flow rate of the well-water in kg/s? (Oct 95) Steam Properties: At 204°C: hi = 870.51 kJ/kg At 1.04 MPa: hi = 770.38

.

hlg = 2009.2

At 0.034 MPa: hi = 301.40 SI = 0.9793

hlg Sig

hg = 2779.6 Sg = 6.5729

C. 186

B. 2100

D. 2444

.

3

~

1.04 MPa . . .

fig

.-L 1

IDs

I

T_._L'_~

2

204°C

row

T-S Diagram:

T

,

S

S3

=

S4

=

(SI +

X

Slg)4

6.5729 = 0.9793 + x4(6.7463)

= 0.829

h4 = (hi + xh lg)4

= 301.4 + 0.829(2328.8) = 2232.3

X4

Solving for the mass flow rate to the turbine. m s : W T = m s (h3 - h4)nT

50,000 m s(2779.6 - 2232.3)0.75

m, = 121.8kg/s

Solving for the quality X2 (after throttling): h 1 = h 2 = (hi + x high 870.51 = 770.38 + X2 (2009.2)

X2 = 0.049836

Solution:

.'•'"

Solving for h4:

=

= 2328.8

= 6.7463

A. 2871

·It

Formulas and Principles - GEOTHERMAL POWER PLAN I I

--I+-. 50 MW

Solving for the mass flow rate of the well water: rn, = X2 (m g ) 121.8 = 0.049836 (m g)

mg 2,444 kg Is

=

f.'1

.

F -70

Formulas and Principles - GAS TURBINE POWER PLANT

Formulas and Principles - GAS TURBINE POWER PLANT

GAS TURBINE POWER PLANT

Turbine Expansion (Isentropic) Process 3-4:

83

8 4

::

PN/ :: P 4V4 k

Air Standard, Ideal (Brayton) Cycle: T!

T4

2~1: / I

1/.... /

..

Air

P

T3 T4

I==P4

WT

S

I

Exhaust

::

P4

=( V4 J k l V3

turbine work

= mCp(T 3-T4 )

W N = net turbine work Cycle Efficiency

"'.'.

k-\

=

WT

-

We

Ideal T -8 Diagram

Open Cycle Gas Turbine

1

JT

T =(P3 3

::

WN

::

WT-Wc

QA

QA

Compression (Isentropic) Process (1-2):

81

=8

PN/ = PzV2k

2

Closed Cycle Gas Turbine:

k-I

-

T2 _(P2

2~

T

Ik

T;-I\I\j

It

2=(~)k--I

T TI

•

I

I

V2

S

We = compressor work = mCp(Tz- T 1) for air where: Cp :: 1.0 ~ kg_ O C

PERFORMANCE OF ACTUAL CYCLE: Fuel, mf == r.m,

Qh kJ/kg Pressure Ratio

:: P3

P4

_

P 2

-

PI

Generator Output 'Combustor

Heat Added in Combustor (Process 2-3):

QA

~Yhl'm:t

= mCp(T \ T.,)

Air

rna + mr == ma(l

+ rr)

rr == fuel-air ratio

F - 71

F·72

Formulas and Principles - GAS TURBINE POWER PLAN I

Formulas and Principles - GAS TURBINE POWER PLANT

The T-5 Diagram:

=

Overall Thermal Efficiency

/1

~

T

2

)4' ..' '

.,/ '/4

~ 2.. .'

i

.... :

Combustor Efficiency

..':

Heat Absorbed By Air Heat Supplied By Fuel

Ideal Gas Turbine Cycle with Regenerator:

1 .... I

=

Generator Output Qf

S Regenerator

y~... ,

We :: ideal compressor work :: m aCpa(T 2-T1)

.

~

We'

=

actual compressor work

=

m aCPa(T 2'-T1 ) where:

Cpa

=

::

ID a C pa (T2

IdealCompressorWork CompressorEfficiency

•

III •

i

LNV'[-., X

We

.

I

i

l1e

-Tj )

l1e

=

specific heat of air = 1.0

~O

kg_ C

T

·It ..

4

:

3 W T = ideal turbine work

= (m a + mt)Cpg(T3-T4)

= m a(1 + rt)Cpg(T W T' = actual turbine work =

4

3-T4 )

=

m a(1 + rf)Cpg(T3-T4' ) where:

2,c.· ideal turbine work x turbine efficiency

=

1

.

m a(1 + rt)Cpg(T3-T4) x nT

S

rf = fuel-air ratio nT = turbine efficiency CPg specific heat of gas

=

Of = heat generated by fuel

=

(rn, rf)Qh

=

rn. Q h

where: Q h = heating value of fuel kJ/kg Actual Net Work, WN'

Thermal Efficiency (Gas Turbine)

c/

=

=

W T' - Wc'

QA

Heat Balance in Regenerator: mCp(Tx-T 2 )

- W aux

=

mCp(T4-T y )

Tx-T2 = T4-T y

WT ' - We' - Wau x

Qr

= heat added in combustor = mCp(T3-Tx)

f

ffectiveness of Regenerator

=

Actual amount of heat transferred Amount of heat that could be transferred reversibly

"

\

F -74

Formulas and Principles - GAS TURBINE POWER PLANT

Formulas and Principles - GAS TURBINE POWER PLANT

SAMPLE PROBLEMS:

Solution:

1. In a gas turbine unit, air enters the combustion chamber at 550 kPa, 22rC and 43 m/s. The products of combustion leave the combustor at 511 kPa, 1004°C and 140 m/s. Liquid fuel enters with a heating value of 43,000 kJ/kg. For fuel-air ratio of 0.0229, what is the combustor efficiency of the unit in percent? (Apr 96) C. 78 A. 64 D. 102 B. 92

T

w.,.' 100 kPa

300 0K

5 m 3/s

Fuel 1

1

I

550 kPa 227°C 43 mls

rf = 0.0229 Combustion

Chamber

PV ::: mRT

(100)(5) ::: m(0.287)(300)

m ::: 5.81 kg/s

2 511 kPa 1004°C 140 m1s

Solving for T 2: k-I

i =(~:)T

'11

....

:: ..

Heat Supplied by fuel ::: mf Q h ::: 0.0229(43,000) ::: 984.7 kJ/kg air

T2 300

Heat Absorbed ::: Cp(T 2-T 1) + 1;2 (V/ - V/) ::: 1.0(1004 _227) + 1;2

lI

Solving for T 4 : k-l

::: 785.9 kJ/kg air " Com b us tor Eff IClency

1.4-1

= (loH

T 2 = 579 oK

(140)2 - (43)2] 1000

785.9 ::: - - ::: 79.8 % 984.7

2. Air enters the compressor of a gas turbine at 100 kPa and 300 0K with a 3/s. volume flow rate of 5 m The compressor pressure ratio is 10 and its isentropic efficiency is 85%. At the inlet to the turbine, the pressure is 950 kPa and the temperature is 1400oK. The turbine has an isentropic efficiency of 88% and the exit pressure is 100 kPa. On the basis of an air standard analysis, what is the thermal efficiency of the cycle in percent? A. 42.06 C. 31.89 8. 60.20 D. 25.15

T3

=( P3JT

T4

4

lP

1.4-]

1400 = ( 950 J~

T4 1000

T4 We

W' c

=

736 oK

::: mCp(TrTd ::: 5.81 (1.0)(579-300) ::: --

W - c_ 11c

/

2/ / ' I

Solving for the mass flow rate:

t

~

3

1;

Solution:

..

F- - 75

1621 0.85

-

1621 kw

::: 1907 kw

S

Formulas and Principles - GAS TURBINE POWER PLANT

F -76 W T

= =

mCp(T 3-T4 )

5.81 (1.0)(1400 - 736)

W T'

=

3858(0.88)

WN'

=

W/ - We'

QA

P~~t>lJ F--'" 77

HYDRO-ELECTRIC POWER PLANT

3858 kw

3395 kw

Basic Parts of High-Head Hydro-Electric Plant:

= 3395 - 1907 = 1488 kw

= mCp(T 3-T 2)

= 5.81(1.0)(1400-579) = 4770kw

Cycle Efficiency

. \

=

=

Formulas and Principles - HYDRO-ELECTRIC POWER

_ -

WN ' QA

-

1488 4770

--

=

31.19%

·11

....

.• •

Reservoir - stores the water coming from the upper river or water falls .

Headwater - the water in the reservoir.

Spillway - a weir in the reservoir which discharges excess water so that the

head of the plant will be maintained.

Dam - the concrete structure that encloses the reservoir.

Silt Sluice - a chamber which collects the mud and through which the mud is

discharged.

Trash Rack - a screen which prevents the leaves, branches and other water

contaminants to enter into the penstock.

Valve - opens or closes the entrance of the water into the penstock.

Surge chamber - a standpipe connected to the atmosphere and attached to

the penstock so that the water will be at atmospheric pressure.

,

Penstock - the channel that leads the water from the reservoir to the turbine

~i, 'i lj

l

F -78

Formulas and Principles - HYDRO·ELECTRIC POWER PLANT

Turbine - converts the energy of the water into mechanical energy, Generator - converts the mechanical energy of the turbine into electrical energy output. Draft Tube - connects the turbine outlet to the tailwater so that the turbine can be set above the tailwater level.

Formulas and Principles - HYDRO-ELECTRIC POWER PLANT F - 79

Classification of Hydraulic Turbines: 1. Impulse (Pelton) Turbine - high head and low flow. ....-:::;;

][

,;;;;;;:=;";;.;.,~-:::,,.n~ r

Nozzle

~

RUl'kpt

Runner

Tailrace - a channel which leads the water from the turbine to the tailwater.

..-Casing

Tailwater - the water that is discharged from the turbine.

Run-of-the-River (Low Head) Hydro-electric Power Plant:

...

I'.

.....

..

•

Pondage .:~:~~~~~:::~~:'~:::::::~::~::::~::::~~~~:::~::~:~-:

2. Reaction Turbine a. Francis Turbine - low head and high efficiency.

caS ing

Pondage - the water behind the dam of a run-of-the-river hydro-electric plant.

~~

\ \"

~ Wicket Gate

T

Runner

b. Propeller (Kaplan) Turbine - very low head and efficiency is lower than Francis.

Pumped Storage Hydro-Electric Plant or Hydraulic

Accumulator: Pumped storage plant - is a hydro-electric plant which involves the use of off-peak energy to store water and to use the stored water to generate extra energy to cope with the peak load.

n

Storage

Selection of Turbine Type based on head: Net Head Up to 70 ft 70 ft to 110ft 110ft to 800 ft 800 ft to 1300 ft 1300 ft and above

Type of Turbine Propeller Type Propeller Type or Francis Francis Type Francis or Impulse Impulse

F·-SO

Formulas and Principles - HYDRO-ELECTRIC POWER PLANT

PERFORMANCE OF HYDRO-ELECTRIC PLANT: 1. hg

Formulas and Principles - HYDRO-ELECTRIC POWER PLANT

120f 9. Generator Speed, N = __

p

= gross head = difference between headwater and tailwater

where:

elevation

N ::: speed, rpm

f ::: frequency (usually 60 hz)

p ::: number of poles (even number)

2

2. hi

fLY = friction head loss = -

2gD

2fLy

(Darcyeq.), meters

10. hw

= - - (Morse eq.), meters gD

I II

...

I.... '

.­

..

= total length of pipe, in meters

= velocity, m/sec

V g

D

= 9.81 m/sec"

= inside diameter,

where:

h :::

=

net head or effective head

= hg

-

hi

2

V = velocity of jet

P = inlet gage pressure

g = 9.81 rn/sec"

12. Head of Reaction (Francis and Kaplan) Turbine P h=-+Z+

s

h g

Q

V

meters

4. Penstock efficiency = ~

5. General Flow equation:

h (nh)

nh = hydraulic efficiency

P

where:

3. h

:::

8"+ ­ 2g

(Friction head loss is usually expressed as a percentage of the gross head).

2 2 VA -VB

2g

= AV

=

•

3/sec

volume flow rate, m where: Q 2 A = cross-sectional area, m V velocity, m/sec

=

6.

7.

= Q8h

Water Power where:

8

kw

=

specific weight of water or density 3 = 9.81 kN/m = 1000 kg/m 3

Turbine Output = Q 8 h (nt) where:

n, = turbine efficiency

8. Generator Output = Q 8 h nt n,

....

utilized head

11. Head of Pelton (trnpulse) Turbine:

= coefficient of friction

where: f L

I

:::

2

where:

n, = electrical or generator efficiency

13. Peripheral coefficient, 8 =

PeripheralVelocity VelocityOfJet

(Relative Speed) where:

D = diameter of runner, meters

N = speed of runner, rev/sec

g ::: 9.81 m/sec"

h = net head, meters

_

7tDN

-

J2gh

F ~81

-

Formulas and Principles - HYDRO-ELECTRIC POWER PLANT F - 83

'Formulas and Principles - HYDRO-ELECTRIC POWER PLANT

F·82

=

Volume

Area x Height

14. Specific speed of hydraulic turbine:

=

66,055,050

=

N

s

NM 5 4 h

where:

rpm

/

N h

= speed, rpm = head, feet

)leight,

h

=

(50 x 10

6

)

h

1.32 m

tl"~in" working under an available head of 40 meters, The energy transferred from the water to the runner is 350 J, Assuming a mechanical efficiency of 95%, what is the discharge through the turbine in cu. m/s? (Apr 96) A. 0,0345 C, 1.511 B. 0.135 0.1,234

2. 45 kw of the shaft power is developed by a In Metric Units:

Ns

=

O.2623N~ h

rpm

5/4

where:

N

=speed,

h

= head, meters

rpm

Solution: II

~

\..... .

If

•

15. et

=

eh em e y

Since the given power of 45 kw is a shaft power, a hydraulic efficiency of, say, 87% will be assumed.

where: et = total efficiency of turbine eh = hydraulic efficiency em = mechanical efficiecny e y = volumetric efficiency

Shaft Power

Q

1. A hydro-electric plant having 50 sq. km reservoir area and 100 m head is

used to generate power. The energy utilized by the consumers whose

load is connected to the power plant during a five-hour period is 13.5 x 10'

to the 6th power kw-hr. The overall generation efficiency is 75%. Find the fall in the height of water in the reservoir after 5-hour period. (Apr 97) I A. 2.13 m C. 3.21 m "

B. 1.32 m

D. 0.53 m

Solution:

o

= volume flow rate in m

Energy Output

13.5 x 106

o =

=

=

3/sec

V

the center of the spiral casing at the inlet is 38 meters and velocity of water at the inlet is 5 m/s. The discharge is 2.1 cu. m/s. The hydraulic efficiency is 0.87 and overall efficiency is 0.84. The velocities at the inlet and exit of the draft tube are 5 mls and 1.5 m/s, respectively. The top of the draft is 1 m below the center line of the spiral casing while the tailrace(water) level is 3 meters from the top of the draft tube. There is no velocity of whirl at either top or bottom of the draft tube and leakage losses are negligible. What is the power output of the turbine in kw? (Apr 96) C. 901.3 A. 748.8 D. 832.6 B. 632.9 38 m

Solution:

0(9.81)(100)(0.75)(5)

3669.725 m

= 0.139 m 3/sec

3, A vertical draft tube is installed on a Francis turbine and the total head to

0 is h nt x Time h

=

total head

3/sec

=

In 5 hours, the volume of water consumed:

,,1

= Q(9,81 )(40)(0.95)(0.87)

45

SAMPLE PROBLEMS:

= Q is h n m nh

= 3669.725(5 x 3600) =

p

8

+

Z

y2 + y2 +

38 +

(1 + 3)

2g +

'

~m

---=:{ \

3m

(5)2 _ (1.5)2 2(<).~

3/s

i

B

A.

3

66,055,050 m

2.1 m

1)

li'illili"l"nr','ib.

H

H

_____

F·84

Formulas and Principles - NUCLEAR POWER PLANT

Formulas and Principles - HYDRO-ELECTRIC Ji'OWER PLANT

Volume

= 43.16

m

F - 85

= Area x Height

134,914 = (2.5 x 106 ) H

Turbine Output = Q 8 h nt

H

= 2.1(9.81)(43.16)(0.84)

=

0.0539 m

=

5.39 em

= 746.9 kw

4. A Pelton Wheel is to be designed to run at 300 rpm under an effective

head of 150 m. The ratio of the nozzzle ,diameter to the diameter of the

pitch circle is 1/12. Assuming e~iciency of 84%, what is the size of the

wheel in meters? Assume speed ratio of 0.45. (oct 95)

A. 1.05 C. 1.55 B. 2.00 D. 2.86

;;1

~

, ....'. ..

•

Typical Nuclear Power Plant: Reactor Drum

Solution:

e =

Control Rods

.figh 0.45

o

Containment

r~1

Biological Shield

7tDN

=

Control Cubicle

(300 \

7tD 60)

Thermal Shield

fi(9.8 1)(1 50)

Reflector

= 1.55 m

'\

Feedwater

Pump

6,000,000 m3 at the head of 170 m. Assume hydraulic efficiency of 80%

and electrical efficiency of 90%. The fall in the reservoir level after a load

of 15 MW has been supplied for 3 hours, if the area of the reservoir is 2.5 sq. km is closest to: A. 5.39 em B. 4.32 cm

=

power Output Q 8 h nh n, 15,000 Q(9.81 )(170)(0.80)(0.90)

3/s Q = 12.492 m

=

In 3 hours, volume of water consumed: = 12.492(3)(3600) 3 134,914 m

=

Steam

Generator

' C. 5.98 em D. 4.83 cm

I

k?1l

I I

5. A hydroelectric generating station is supplied from a reservoir of capacity)

Solution:

1.,

NUCLEAR POWER PLANT

Fuel Core - radioactive material, U energy.

235

238

with U

,

which is the source of

Moderator - slows down the neutrons to thermal energy, made of carbon and beryllium.

Controls Rods - Boron coated steel rods used to control the reactor. Reflector - made of lead or carbon which surrounds the core to bounce back any leakage of neutrons. Thermal Shield - prevents escape of radiation from reactor vessel.

F -_ 86_ _ _ _F,_o"--~_'__m..:..:u_'_"_as~an_'__d'_'_'_Princie~~- NUCLEAR POWER PLANT _ Formulas and Principles - NON-CONVENTIONAL POWER

Reactor Drum - encloses the fuel core and components.

4.

Biological Shield - concrete or lead which absorbs any leakage of radiation and protects operators from exposure to radioactivity.

NON - CONVENTIONAL POWER SOURCES

Containment Vessel - prevents spread of radiation in case of a major explosion; made of concrete.

~

I....•

Gas-cooled Power Reactor (GCPR) The gas coolant used in this type of reactor is carbon dioxide.

Control cubicle - contains the meters that show the operating quantities in the reactor.

,~

SOLAR POWER Types,f Solar collectors: 1. Flat Plate 2. Concentrating 3. Focusing

Coolant - absorbs the heat from the fuel core and then release the heat to the water in the steam generator. Coolant Pump - circulates the coolant. Turbine-Generator - generates the electric power.

Photovoltaic Cell - a device which converts solar energy to energy.

electrical

Condenser - converts steam coming from the turbine into liquid. Solar Energy received at earth's surface Feedwater Pump - delivers the feedwater to the steam generator. where: Qs

Commercial Types of Nuclear Power Reactors:

:

1. Pressurized Water Reactor (PWR) This type of reactor uses high pressure light or heavy water as both moderator and coolant. This is the type which is constructed in Morong, Bataan with capacity of 620 MW and intended to supply power to the Luzon area. In 1986 the Philippine government decided to stop the completion of the plant because of the controversy regarding its safety and economic features.

II·

2. Boiling Water Reactor (BWR) This is the simplest form of nuclear reactor. The feedwater from the rower turbine goes directly into the reactor and picks up the heat from the fuel core. Thus the feedwater also serves as the coolant. The first (~x:p(~r unental reactor installed in diliman, Quezon City is of this type. It II"~," r.;1I1;lClty of 1MW. \

Heavy Water Roar:tor (HWR) rIll', tYI'" of lI·oIr.tC 1I

11';(

~'i

heavy water or Deuterium, 0 20 as coolant.

F - 87

, ,i

= Qs (1-i)A

kcallhr

= solar energy without atmospheric interference = 1200 kcal/hr-m 2

i

= atmospheric interference, usually expressed in

A

= surface area of solar collector, m 2

percent

WIND POWER Typical uses of wind power: 1. to drive water pumps 2. to drive rice and corn mills 3. to charge batteries 4. to generate power Types of windmills: 1. Turbine type 2. Rotor type 3. Propeller type 4. Dutch sail type 5. Panemone type

F·88

Formulas and Principles -

~ON·CONVENTIONAL

POWER Formulas and Principles - NON-CONVENTIONAL POWER

--'=-:-lrg

TIDAL POWER Tidal Power is basically hydro-electric power utilizing the difference in elevation between high and low tide to produce energy. A basin is required to catch the sea water during high tide while the water drives a turbine.

INSTRUMENTATION PHYSICAL QUANTITY MEASURED

INSTRUrtiENTS USED

Pressure Bourdon pressure gauge Compound gauge Vacuum gauge Manometer

Draft gauge

Barometer

LOW THERMAL HEAD PLANT

,I

:'.'

~

I.....

~

:: ...

low thermal head plant, otherwise known as Ocean Thermal Energy Conversion, makes use of the temperature difference between the ocean surface water and the water at the sea bottom. Surface water which is at relatively high temperature is pumped to an evaporator where the water evaporates into saturated steam. This steam drives a single stage turbine thereby producing electricity, and exhaust to a jet condenser maintained at the saturation pressure of the subsurface water temperature pumped from the sea bottom.

Temperature Mercurial thermometer Bi-metallic thermometer Thermocouple Radiation pyrometer Optical pyrometer Weight Platform balance

Spring balance

Analytical balance

Beam balance

Pendulum scale

MAGNETO HYDRO DYNAMIC PLANT In a magneto hydrodynamic generator, combustion gases produced in a combustion chamber at high pressure and temperature and seeded with metal vapor to increase its electrical conductivity, is passed through an expansion tube lined with a strong magnetic field. This induces an electric voltage in the gas conductor and effects the flow of electrons through the electrodes along the magnetic field, thereby generating electricity.

THERMOIONIC CONVERTER

Density; Specific Gravity

Heating value of fuel

Hydrometer, pycnometer, Westphal balance Bomb calorimeter Gas calorimeter

Viscosity Viscosimeter

Thermoionic converter is a device which converts heat energy directly to electrical energy.

Area of irregular plane figures Rotational speed

FUEL CELL Fuel cell is a device which converts chemical energy to electrical energy. Vibration intensity and frequency. linear speed Distance travelled by a vehicle Velocity of flow

Planimeter Tachometer

centrifugal, vibration,

electric

Stroboscope

Vibrometer Speedometer Odometer Velometer

..

_-----------------------=~.....-.---

F·90

Formulas and Principles - NON-CONVENTIONAL POWER

Flow (rate)

Indicated Power Brake Power

I~

Ilil

~

Analysis of flue gas

I

..

i

.'"

Rotameter, anemometer, Flowmeter Engine Indicator Dynamometer a. absorption dynamometer(prony brake, water brake) b. transmission dynamometer(electric dynamometer, electric cradle dynamometer) Orsat apparatus (Gas analyzer)

Formulas and Principles - NON·CONVENTIONAL POWER

F - 91

DEFIN ITIONS:

Accessible - a term applied to a device of function that can be used or be seen by an operator for the purpose of performing control actions, set point changes, auto-manual transfer, or on-off actions. Alarm - a device of function that signals the existence of an abnormal condition by means of an audible or visible discrete change, or both, intended to attract attention. Assignable - a term applied to a feature permitting the channelling (or direction) of a signal from one device to another without the need for switching, patching, or changes in wiring. Auto-Manual station - synonym for control station. Balloon - synonym for bubble.

Steam calorimeter throttling, separating, condensing barrel, electric

Behind the panel - a term applied to a location that is within an area that contains (1) the instrument panel, (2) its associated rack-mounted hardware, or (3) is enclosed with the panel.

Dry bulb and Wet bulb temperature of air

Psychrometer sling, aspiration

Binary - a term applied to a signal or device that has only two discrete positions or states.

Moisture Content (humidity) of air

Hygrometer

Board - synonym for panel.

Relative humidity of air

Humeter

Bubble - the circular symbol used to denote and identify the purpose of an instrument or function. It may contain a tag number.

Quality of steam

\.

-

Hardness of steel

•

Surface roughness Angle Linear distance (thickness, depth, etc.)

Inaccuracy in alignments, eccentricities Spacu cloarance, gap

Brinell Hardness tester Rockwell hardness tester Vickers hardness tester Profilometer Protractor" Rule, depth gauge, vernier caliper, micrometer caliper Dial indicator Feeler gauge

Computing device - a device or function that performs one or more calculations or logic operations, or both, and transmits one or more resultant output signals. (or called computing relay). Configurable - a term applied to a device or system whose functional characteristics can be selected or rearranged through programming or other methods. Controller - a device having an output that varies to regulate a controlled variable in a specified manner. Control station - a manual loading station that also provides switching between manual and automatic control modes of a control loop. (or called auto-manual station).

r-----­

F - 92

Control valve - a device, other than a common, hand actuated ON-OFF valve or self-actuated check valve, that directly manipulates the flow of one or more fluid process streams. Converter - a device that receives information in one form of an instrument signal and transmits an output signal in another form. Digital a term applied to a signal or device that uses binary digits to represent continuous values or discrete states.

l~

J

I....• •" •

Formulas and Principles - NON-CONVENTIONAL POWER

Formulas and Principles - NON-CONVENTIONAL POWER

Distributed Control System - a system which, while being functionally integrated, consist of subsystems which may be physically separate and remotely located from one another. Final control Element - the device that directly controls the value of teh manipulated variable of a control loop.

F -

93­

Monitor light - synonym for pilot light. Panel - a structure that has a group of instruments mounted on it, houses

the operator-process interface, and is chosen to have a unique designation. (

or called board).

Panel-mounted - a term applied to an instrument that is mounted on a panel

or console and is accessible for an operators normal use.

Pilot light - a light that indicates which of a number of normal conditions of a system or device exists. (or called monitor light). Primary element - synonym for sensor. Process - any operation or sequence of operations involving a change of energy ,state, composition, dimension, or other properties that may be defined with respect to a datum.

Function - the purpose of, or an action performed by, a device.

Process variable - any variable property of a process.

Identification - the sequence of letters of digits, or both, used to designate

Program - a repeated sequence of actions that defines the status of outputs as a fixed relationships to a set of inputs.

an individual instrument or loop. Instrument - a device used directly or indirectly to measure and/or control a variable .

Programmable Logic Controller - a controller, usually with multiple inputs and outputs, that contains an alterable program.

Instrumentation - a collection of instruments or their application for the purpose of observation, measurement, control, or any combination of these.

Relay - a device whose function is to pass an information in an unchanged torm or in some modified form.

Local _ the location of an instrument that is neither in nor on a panel or console, nor is it mounted in a control room .

Scan - to sample, in a predetermined manner, each of a number of variables intermittently.

Local Panel - a panel that is not a central or main panel.

Sensor - that part of the loop or instrument that first senses the value of a process variable, and that assumes a corresponding, predetermined, and ,! itell igible state or output.

Loop - a combination of two or more instruments or control functions arranged so that signals pass from one to another for the purpose of " measurement and/or control of a process variable. Manual Loading System a device or function having a manually adjustable output that is used to actuate one or more remote devices.

Set Point - an input variable that sets the desired value of the controlled . .sriable.

Shared Controller • a controller, containing preprogrammed algorithms that e usually accessible, configurable, and assignable.

. II

Measurement _ the determination of the existence or the magnitude of a variable. Monitor - a general term for an instrument or an instrument system used to measure or sense the status or magnitude of one or more variables for the purpose of deriving useful information.

Shared display - the operator interface device (usually a video screen) used ") display process control information from a number of sources at the .unmano of the operator. '>witch - a device that connects, disconnects, selects, or transfers one or 1111 P Circuits, and is not designed as a controller, a relay, or a control valve.

i

F -94

Formulas and Principles - NON-CONVENTIONAL POWER:-:

_ 1=nr...... ''''r-

Test Point - a process connection to which no instrument is permanently

connected, but which is intended for the temporary or intermittent connection

of an instrument.

VARIABLE LOAD

Transducer - a general term for a device that receives information in the form of one or more physical quantities, modifies the information and/or its form, if required, and produces a resultant output signal.

:: plant capacity

Reserve over peak Average Load

Transmitter - a device that senses a process variable through the medium of

a sensor and has an output whose steady-state value varies only as a

predetermined function of the process variable.

::

- peak load

kw-brs energy h

no. of ours

1. Load factor ::

J

Average Load

Peak Load

Actual energy produced 2. Capacity factor ::

Maximum possible energy

that might have been produced during the same period

I•

Annual kw-hrs Annual capacity factor :: kw plant capacity x 8760

.....

3.

annual kw-hrs _

Use factor ::

kw plant capacity x no. ofhrs operation

;

...

"'nd Principles- VARIABLE LOAD

4.

Demand factor::

5. Diversity factor ::

Actual maximum demand Connected Load Sum of individual maximum demands Maximum simultaneous demand

6. Plant factor

A verage Load

::

Rating of equipment supplying the load

7. Utilization factor ::

Maximum demandof system Rated capacity of system

8.

Operation factor ::

Duration of actual service Total duration of the period of time considered

F -96

Formulas and Principles - CHIMNEY

CHIMNEY

Formulas and Principles - CHIMNEY dg == density of flue gases

j !

I

...

.

T2

---+---. I t t

Air IDa kg/s

;

D

tT

Furnace

Fuel m, kg/s

T g

Og

:::

Og

::::

d,

(Ifnl'.lly of dll

H(da-dg)

Area x Vel

kPa

:::: .!!.- 0 4

2

Vel

volume flow of flue gases::::

1

HEIGHT

P = -­ Ra'I;,

average temperature of flue gases

mRT g g g

m3/s

V :::: theoretical velocity of flue gas in chimney

: : J2 g hd

T1

:::

:::

Vel ::: actual velocity of the flue gases mls

H

D ::: internal diameter of chimney, meters (for a tapering chimney, D is the internal diameter at thetop) H ::: height of chimney, meters T a ::: temperature of air, oK T g ::: average temperature of flue gases, oK R a ::: gas constant of air R g ::: gas constant of flue gases P ::: barometric pressure, kPa 101.325 kPa

!l1;lft pressure

~ 2

p

w

g

Actual velocity of flue gases in chimney is only 30% to 50% of theoretical velocity, thus to get the actual velocity, multiply the theoretical velocity by a velocity coefficient of 0.30 to 0.50 .

Flue Gases Il1g = mr+ rna

h',',

T T

::::

DIAMETER

Calculation of Chimney Diameter and Height using basic gas laws:

II •

P

::::

RgTg

Functions of Chimney: 1. To dispose the exhaust gases at suitable height so that no pollution will occur in the vicinity. 2. To produce the necessary draft required for thr flow of the gases. Stack - name given to steel chimney.

F - 97

Vel (actual)

:::: (theo vel) x C v

C v :::: velocity coefficient :::: 0.40 (usual assumption)

SAMPLE PROBLEMS: J.lf the actuaJ draft required for a furnace is 6.239 cm of water and the frictional losses in the stack are 15% of theoretical draft, calculate the required stack height in meters. Assume that the flue gas have a!> average temperature of 149°C and molecular weight of 30, Assume air temperature of 21°C. (Oct 95)

A. 215 B. 230

C.220

D. 210

r

Formulas and Principles - CHIMNEY

Formulas and Principles - CHIMNEY

F -98

d 9

Solution:

hw hw hw hw

::= ::= ::=

::=

total draft 6.239 + 0.15 hw 7.34 ern water 0.0734 (9.81) ::= 0.72 kPa

d, ::=

J

=

__ P_ RaTa

R = 8.3143

I

I,•

C

•

­

M

d g

hw

P :::

:::

RgTg

RgTg

Draft

101.325 0.287(21 + 273) ::: 1.2 kg/m

8.3143 30 101.325 0.277(149 + 273)

101.3 0.277(260 + 273)

= 0.02286(

3

0.686 kg/m

1 ) 0.00100

=

22.746 kg/m

2

Solving for the velocity of the flue gases considering a velocity coefficient of vAO:

.

=

Vel (actual)

= 0.277

= 0.867

=

3

Solving for the density of the flue gas:

!

= density of flue gases = ~ :::

Solving for the density of air:

F - 99

kg/m

= OAOx./2(9.81) 22.746 _ 0.686 - 10.2 m/s

3

= H(d a - d g)

0.72::= H(1.2 - 0.867)0.00981

Pi

OAOx 2g~ dg

Og ::: Area x Vel 46.72 0.686

= ~

o =

2.916 m

4

0 2 ( 10 .2)

H ::= 220 m 2.52 kg of coal per second are consumed by a steam boiler plant and The air temperature outside is 32 0 C , the average temperature of the flue gases entering the chimney is 343°C and the average temperature of the flue ,. gases in the chimney is 260 0 C . The gage fluid specific volume is 1.005 x 10-3 m 3/kg and a theoretical draft of 2.286 cm of water at the chimney; base is needed when the barometric pressure is 101.3 kPa. Find the

2. produced 18.54 kg of dry flue gas per kg of coal fired.

diameter of the chimney in meters. (Apr 95) Solution: m g

::: mass flow of flue gases ::: 18.54(2.52) ::: 46.72 kg/s

Flow gases have higher molecular weight than air; assume M ::= 30, so that:

R g ::= 8.3143/30 ::: 0.277

A steam generator with economizer and air heater has an overall draft loss of 21.78 cm water. If the stack gases are at nrc and if the atmosphere is at 101.3 kPa and 26°C, what theoretical height of stack in meters is needed when no draft fans are used? Assume that the gas constant for the flue gases is the same as that for air. (Apr 95) A. 565 C. 545 B. 535 O. 550 Solution:

da = density of air = _PRaTa

= 1.180 kg/m 3

=

101.3 -

0.287(26 + 273)

_.

-Formulas and Principles

F -100 d g

=

density of flue gas

= 0.784 kgfm Pressure

=

\j.'

RgTg

=

101.3 0.287(177 + 273)

3

=

Draft Pressure, hw

=

P

DESIGN PROCEDURE IN MACHINE FOUNDATION: Manufacturer's manual supplies foundation drawings, but in the absence of such drawings, the following guide can be used. Refer: PSME Code, pp 9-11; Morse, pp 108-113

Height x Density

Draft Pressure

217.8

=

Formulas and Principles - MACHINE FOUNDATION F -101

MACHINE FOUNDATION

0.2178(1000)

=

WM

= 217.8

kg/m

2

H(da - dg)

H(1.180 - 0.784)

~WF

H = 550 m

II I

,I

...• =: •

I~ •

1.

MACHINE FOUNDATION

.1

L

Knowing the bedplate dimensions of the machine, determine the upper dimensions of the foundation "a" and "L". Allow a clearance from the edge of about one foot or about 10% of the length of the bedplate .

2. Knowing the weight of the machine, W M, determine the required weight of the foundation, WF, by any of the following methods:

Functions of Machine Foundation:

a.

1. To support the weight of the machine, and to distribute U-Ie weight of , the machine and its own over a safe sub-soil area.

WF = 3 to 5 times the WM

b. WF

2. To absorb the vibrations produced by the machine.

3. To maintain the a\\gnmer.t of the machine.

exWex where:

Monolithic Foundation _ concrete foundation which is formed by pouring the entire concrete mixture continuously at one time and allowing the structure to harden as a whole unit. small clearance between machine and Grouting - process of filling a and levelled, by using a special . foundation, after the machine is aligned hardening mixture.

3.

(Sec. 2.4.1.2, PSME Code)

IN

WF = weight of the foundation, kg We weight of the engine, kg N = engine speed, rpm e = an empirical coefficient, [Table 2.4.2.3(4), PSME Code]

=

C.

Volume of foundation can be computed based on HP of the engine, [Table 2.4.2.3(4), PSME Code]

d.

Weight of foundation can be computed based on the HP of the engine, [Morse, Table 4-5, p. 108]

Knowing the bearing capacity of the soil, solve for the base width "b". For machine foundation use only Y2 of the given safe soil bearing capacity. The safe bearing capacity is computed using a factor of safety of 5.

F - 102

Formulas and Principles

MACHINE FOUNDATION

Formulas and Principles - MACHINE FOUNDATION

s.. W 2

bL

where: Sb

==

safe soil bearing capacity

Note: If "b" will come out less than "a", then make b foundation has a rectangular cross-section.

==

a,

that is, the

4. Using a density of 2406 kg/m3 for concrete, determine the volume of the foundation.

J

I•

VF =

5.

WF 2406

m3

Compute the depth of the foundation "h": VF

=

(a;

b) h L

6. Finalize the design; make adjustments in the dimensions jf necessary provided the required volume is maintained and without reducing the required base area. .

I ......

Other data and information:

=: 'II

1() I

M +WF

7. Use Class A (1 : 2: 4) mixture, that is, 1 part cement, 2 parts sand and 4 parts stone.

8. Determine the quantity of cement, sand and stone using the following data: To produce 1 cu yd of concrete using 1:2:4 mixture, the following are needed: 6 sacks cement, 0.44 cu yd sand and 0.88 cu yd stone.

9. Weight of steel bar reinforcements needed should be about )1;,% to 1% of the weight of the foundation.

10. Anchor bolts should be imbedded in the concrete at least 30 times the bolt diameter.

Machine Foundation General Requirements: all heavy machinery shall be supported on solid foundations of sutfiCIC/11 mass and base area to prevent or minimize the transmission of ObjectIOlld!>I!: vllJr;lllon to the building and occupied space and to maintain the supported Pldc;)1IIW ;11 Its proper elevation and alignment.

- foundation mass should be from 3 to 5 times the weigh t of III,' machinery it is sUPPosed to SUpport. If the unbalanced inertial for Ct,s produced by the machine shall be calculated, a mass of weight equal to 10 to 20 times the forces should be used to dampen Vibration. For stability, the total combined engine, driven equipment, and foundation center of gravity must be kept below the foundation's top. - the weight of the machine plus the weight of the foundation should be distributed over a sufficient soil area which is large enough to cause a bearingof stress safety five (5)within the safe bearing capacity of the soil with a factor of - foundation should be isolated from floor slabs or bUilding footings by at least 25 mm around its perimeter to eliminate transmission of vibration. - foundations are preferably built of concrete in the proportion of 1 : 2 : 4. The machine should not be placed on the foundation until seven (7) days have elapsed or operated until another seven (7) days have passed. • concrete foundations should have steel bar reinforcements placed both vertically and horizontally, to avoid thermal cracking. Weight of reinforced steel should be from Y2 % to 1% of the weight of foundation. - foundation bolts of specified size should be used and surrounded by a pipe sleeve With an inside diameter of at least (3) times the diameter of the anchor bolt and a length 1 times the diameter of the bolt. NO foundation bolts shall be less than 12 rnrn diameter.

a.

Machine should be leveled by driVing wedges between the machine's base and concrete foundation and with the aid of a spirit level. Grout all spaces under the machine bed with a thin mixture of one part cement and one part sand. The level wedges should be removed after grout has thoroughly set and fill wedges holes with grout.

SAMPLE PROBLEMS: I. What is the required base area of the foundation to support an engine with specified speed of 1200 rpm and weight of 9,000 kg. bearing capacity of soil as 47.867 kPa. Use e == 0.11. (Oct 95) 2 A. 5.57 m C. 7.75 m2 2 B. 8.87 m D. 10.5 m2 Solution: WF

:::

weight of foundation

::: ex W M x

IN

== 0.11(9,000) ../1200 == 34,295 kg

s, :::

W F + WM Area

Assume

Formulas and Principles - MACHINE FOUNDATION

F ·104

b

_ (34,295 + 9,000)0.00981

47.867 Area

8.87 m

=

w

width,

-10~

= 0.905 m = 905 mm

Therefore, the value for W of 2030 mm earlier calculated is very safe

Area =

Formulas and Principles - MACHINE FOUNDATION F

2

Solving for the depth 0: density of concrete is 2406 kg/m

3

2. If you get employed by an industrial plant which experiences brownouts nowadays and operations had to stop during the power outages, it become necessary for management to procure a stand-by diesel generating set with a capacity of 500 kw, as recommended by the Chief Engineer of the company. The diesel gens et procured has 6 cylinders running at 1500 rpm with piston bore and stroke of 98)( 98 rnrn. The unit weighs 4540 kg and has a base dimensions of3725 mm L by 1430 mm W. Height of the unit is

! ,. '1

P 1;1

~

"'-i

1760 mm. a. Determine the size (L x W x D) of the foundation required if the soil bearing capacity of the site of the genset is 12,200 kg per square meter.

b. Find the volume of each foundation materials in 1:2:4 mixture and

= 19,342 2406

=

8.039 m

3

2.03(0)(4.325) = 8.039

0= 0.916m= 916mm

Therefore:

W = 2030 mm

L = 4325 mm

D = 916 mm

= 8.039 m3

b. Volume of foundation

size and number of reinforcement bars.

3

For 1:2:4 mixture, 1 m of concrete requires 7.8 sacks (7.8 fe) of 3 3 cement, 0.44 m of sand and 0.88 m of stone, therefore:

Solution:

a. Consider a clearance from the edges of about 1 foot, say 300 mm

Quantity of cement

WF = exW e where: e

=

WF

=

)(

.IN

0.11

[from table 2.4.2.3(4)]

0.11(4540)"1500

=

19,342 kg

Solving for the required value of the width W: for machine foundation, the given bearing capacity of the soil is divided by 2, thus:

S" \,\,I~L~ ) I

hI.

1

'ill)

\

~.\() ~ 19,342

----1>(.U25)

= 7.8(8.039) = = 63 ft3 =

L = 3725 + 2(300) = 4325 mm W = 1430 + 2(300) = 2030 mrn The width W however, will be checked against the given soil bearing capacity. A suitable equation for calculating the weight of the foundation, W F , is that from the PSME Code, page 11:

tai

Volume of foundation

Quantity of sand

= 0.44(8.039)

Quantity of stone

=

63 sacks

1.78 m3 3

= 3.54 m

3

0.88(8.039) = 7.07 m

Weight of steel bars should be about ;1;,% to 1% of the weight of the foundation, say, %%. From Kent's Design Handbook, weight of % in steel bars is 0.668 Ib/ft, therefore, weight of 20 ft long bar is 0.668 x 20 = 13.36 Ibs = 6.06 kg, thus: 1/' t Ib 0.0075(19,342) No. 0 f /2 In S ee ars = 6.06

= 24 pes,

F -106

Formulas and Principles - HEAT TRANSFER

Fn,,..,,,,I,,,, .. ~_.4 Qrinciples - HEAT TRANSFER

HEAT TRANSFER

Conduction through Composite Plane Wall

Heat Exchanger • any device which effects a transfer of heat from one substance to another. Examples: condenser, superheater, evaporator, economizer, etc.

Q

=

k]A(t a - t b )

where:

k1

Xl

k 2A(t b

Modes of Heat Transfer:

-

= thermal conductivity of first layer

k2 = thermal conductivity of second layer

te )

x2

1. Conduction - mode of heat transfer by molecular communication through

A heat transfer area which is both layers

solid materials or stagnant fluids.

J

I......'

... .'

"I ' I,'

2.

= Convection - mode of heat transfer in which the heat is carried from one point to another by actual movement of the substance. a. Free convection - the substance moves because of the decrease in its density which is caused by increase in temperature. b. Forced convection - the substance moves because of the application of mechanical power such as that of a fan.

ACta-t e )

~

:

xI

x2

kj

k2

-+-­

Conduction from Fluid to Fluid

t2 h z

,/'

Q = h 1A(trt a ) = h2A(teJ-t 2 )

where: Q = heat transmitted, W

2

A = heat transfer area, m ta = surface temperature on hot side, ° C (0 K)

tb = surface temperature on cold side, ° C (0 K)

k = thermal conductivity, W/m-oC

where: h 1 = surface film conductance on the hot side, W/m 2 _ oC surface film conductance on the cold side, W/m 2_ oC h2

=

Q.

k

Plane Wall

td

I~

x

I~I

/' t,

tb

kA(ta - t b )

ti}t:

..-- Fluid

Q

Conduction through a Plane Wall =

k]

kz

hI t l

waves are passed from one body to another through a space.

Q

kJ

Fluid ----.

3. Radiation - mode of heat transfer in which invisible electromagnetic

.....

common to

.> a

~~

t

Composite Plane Wall

Q =

A(t, -(2) I

xl

x2

x3

I

hJ

kl

k2

k3

h2

-+-+-+-+­

Let U = I hi

xl

x2

x3

k1

k2

k3

I h2

--+-+-+-+­

-

-Formulas and Principles - HEAT TRANSFER

Formulas and Principles - HEAT TRANSFER

F -108

Conduction from Fluid to Fluid through Pipe

= UMT

Q

where:

U = overall conductance or overall coefficient of heat

transfer, W/mz-oC

Conduction through Pipe

=

Q

2n:kL(t a - tb)

=

2nkL(t a -tb)

In I2

II

D DI

I n ­2

t.

tb

tb t,

where: L = length of pipe

,

Conduction through Composite Pipe

Q

=

Q

= h iAi (t 1-ta ) = hoAc(tc-tz) where:

2rrk lL( t a - t b ) I2

.....

hi = surface conductance on inside surface ho = surface conductance on outside surface

1nIl

ta

' ~

Q =

2rrk 2L(tb - tc)

I3

Q

1n ­

••

I2

Q ­

Ajh j

2nL(ta - t c)

-

(t 1 - t 2 )

=

In(I2/ II) + In(I3/ I2)

k1 k 2

= =

where: k 1 thermal conductivity of inner pipe k thermal conductivity of outer pipe z L = common length of the pipe

In(I2/ Ij) In(I3 / I2) + ----- + + 2rrk 1L

2rrk 2L

1

Aoh o

Simplified Equation: Q

= UiAitlt = UoActlt where:

Ui = overall conductance based on inside area overall conductance based on outside area Uo

=

F -109

.

F -110

Formulas and Principles - HEAT TRANSFER

Formulas and Principles - HEAT TRANSFER

where:

Mean Temperature Difference a. Parallel Flow Heat Transfer t,

tl

_

T t,

tl I

Lit I

i~

I

~ ~

t,

m = mass flow, kg/sec

Cp = specific heat, J/kg_oC

t 2-t 1 = temperature change, °C

b. Surface Convection:

At A

tl

F - 111

Oc

~tB

= hcA(t1 - t2 )

where:

he A t1 t2

Length AtA = t x-t 1 At B ty-tz

=

J/sec

= surface coefficient associated with 2_oc =

= =

convection, J/sec-m heat transfer area, m 2 (A = nDol for pipe) temperature of hot surface, °C temperature of fluid, °C

Radiation b. Counter Flow Heat Transfer

a+r+t=1

T

It,

.-----~';L JL.­ .

.......

.'

.-tz

t] - .

l~,

\

t, tl

t,

A~~'

ty

Length

... ~

=

=

absorptance the fraction of radiant heat that is absorbed. where: a r = reflectance = the fraction of radiant heat that is reflected. t = transmittance = the fraction of radiant heat that is transmitted. "black body" - a body which absorbs (and emits) all the impinging radiant heat. "gray body" - actual body that radiates less heat than a black body.

1. Arithmetic Mean Temperature Difference

tI· Anth et

=

Ath,. + At s 2

_

AtA-M B

In M A

Convection a. Convection heat transfer of a fluid with known specific heat: 111C:p(\ .:

tl )

OR

=

4 20, 4 08.4 x 10-8 Fe(T4 1 ­ T2 )

J/sec

J/m 2-hr

where: Fe = emissivity factor T 1 = absolute temperature of surface radiating the heat, oK T2 absolute temperature of surface receiving the heat, oK

=

At B

U

=

Heat transmitted by radiation:

2. logarithmic (True) Mean Temperature Difference log ,i\.t

=

e ratio of radiation from an actual body to Emittance (emissivity) the radiation from a black body.

-

---

Formulas and Pr;nc;~es - HEA! TRANSFER

F -112

Formulas and Principles - HEA"i-TRANSFER

F -113

temperature of 22°e, what is the quality of the steam which arises at its destination if the mass flow rate is 0.125 kg steam/sec? (Oct 95)

SAMPLE PROBLEMS: 1. At an average temperature of 100°C, hot air flows through a 2.5 m long tube with an inside diameter of 50 mm. The temperature of the tube is 2 200C along its entire length. Convective film coefficient is 20.1 W /m _oK. Determine the convective heat transfer from air to the tube. (Apr 97) A. 900W C.624W B. 909 W D. 632 W

Properties of steam:

Pressure Temperature

2.5 MPa

hI 914.52

213.67°e

Enthalpy hlg 1885.5

hg 2800.0

k for 85% magnesia = 0.069 W/mz_oK

I!!il

'.'11

Solution:

IJ

A = heat transfer area = nDL

I .""-I'

"

""1

ho for still air = 9.36 W/m 2-oK

= n(0.050)(2.5) = 0.3927 m

A.93%

e.84% D.76%

B. 98%

2

Solution:

Q c = h cA(trt 1)

Q

= 20.1 (0.3927)( 100-20) = 631.5 W 2 used as a source for solar collectors. 2. The sun generates 1 kw/m when A collector with an area of 1 m 2 heat water. The' flow rate is 3.0 liters/min. What is the temperature rise in the water? The specific heat of water is 4,200 J/kg_oC. (Apr 97) e. 0.50 oe A. 4.8°C D. 0.84°e B. 0.48°e

5.08 em

.>

rl

Still Air

l1li

-

5.08 em

Still Air

m

I~i;>=""'="'"''=''''''''='''.= .... Ao

~t

:: 4.76°C

3. Steam, initially saturated at 2.05 MPa, passes through a 10.10 cm standard steel pipe for a total distance of 152 m. The steam line is insulated with a 5.08 cm thickness of 85% magnesia. For an ambient

Q

h

2

152m

rnopxt

1000 = 0.05(4,200)~t

= 5.50 + 5.08 = 10.13 cm

2

= . . .: .: .: ;.=. . . .= . . .= . . .=. . .=. . . .=. . .=. . . . ~')Jtr:r 2( 0

2

= 0.05 kg/sec m =3 -Iix -1.kg - x min min 11 60 sec Q =

rz

10.10 - -- 505 . cm

0.125 kg/s

1 kw 2 - - (1 m) = 1 kw = 1000 W

=

=

110.10 em

Solution: Q

r1

= nD 2L = 2nr2L = 2n(0.1013)152 =

96.746 m Z

Heat transferred (conduction) = Heat transferred (Enthalpy) Q

= heat transferred by conduction t, - to

=

In(f 2 /f,)

--+ 2nkL

Aoh o

--------------~---.....- ~

­ Formulas and Principles - HEAT r--RANSFER

Formulas and Principles - HEAT TRANSFER

F -114

Heat Transmitted by conduction

= Total heat transr radiation in the

In(0.101310.0505)

= hc(t 1 - t z)

96.746(9.36)

= 20(100-25) = 1500W/m z

= 16,427.4 W

= heat transmitted by radiation = 20,408.4 x 10.8 E (T 4 - T/)

qR

= 16.4274 kw Q = heat transferred due to change in enthalpy =

= heat transmitted by convection

qc +

2n(O.069)(152)

J/hr-m~ = 20,408.4 x 10. (0.8)[(100 + 273)4 - (~5 + 273)4 J z

1,872,793 J/hr-m = 1,872,793/3600 = 520 W/m z 8

=

ms(h 1 - hz)

= 0.125(2800-h z) = 2668.6

Q

= (h. + x hIgh 2668.6 = 914.52 + x(1885.5) x ::: 93%

Q

= total heat transmitted ::: heat transmit~ed by conduction o = 1500 + 520 = 2020 W/m z

hz

k(t. -t b )

=

x

=

2020

air and its surrounding, which are at 25°C. by a brick wall 0.15 m thick.

o The brick has a thermal conductivity of 1.2 W1m- K and a surface

emissivity of O.B. Under steady state conditions and outer surface

temperature of 100°C is measured. Free convection heat transfer to the

air adjoining this surface is characterized by a convection coefficient of 20 W/m 2_0 K. What is the brick inner surface temperature in DC? (oct 95)

II

A. 637.7 B. 352.5

C. 461.4 D. 256.3

II

= 352.5 DC

ta

5. Calculate the energy transfer rate across 6 _

n wall of firebrick with a temperature difference across the wall of 50°C_ The thermal conductivity of the firebrick is 0.65 Btu/hr-ft-rf at the temper~ture interest. (Oct 94) A. 285W/m z C.112W/_ 11 2 2 B. 369 W/m D. 429 W/- ,,2 Solution:

Solution:

K = 1.2 W/m-oK

qR , qc A m bilent air

.

I

Gases /

Q = qc + qR

l200°CJ outer \...

,lreCi,

zs'c

)"1...

t.inner

per unrt

1

Q

Hot

COnSI(jl!1

1111,

1.2(t. -100) 0.15

4. The hot combustion gases of a furnace are separated from the ambient

'.

11., 111

1

16.4274

..

nitted by convection and surface

o~tside

213.967 - 22

=

hz

F - 115

= 6 in = 0.50 ft

ta - t b Q

c

Qc

~I

that is, A

x

2

= 1 m

=

= 50(9/5) =

90 of

kA(t. - t b ) = 0.65(1)(90)

x 0.50

= 117

Btu/hr-fe

=

117

1055 J hr x -- x x hr - ft2 Btu 3600sec

=

369W/m

Btu

2

(3.28)2ft2

m2

1II I1

F -114

Formulas and Principles - HEAT TRANSFER

_

-t-

2n(0.069)(l52)

= 16,427.4

= 16.4274

Q

IJ

ii, ,.,""

."

'II,l

"

.....

Heat Transmitted by conduction

213.967-22 In(O.lO 131 0.0505)

= =

Formulas and Principles - HEAT TRANSFER

h2

= =

1

~'--

qc

96.746(9.36)

qR

heat transferred due to change in enthalpy ms(h 1 - h 2 )

= 0.125(2800 - h2 ) 2668.6

=

Q

= heat transmitted by radiation = 20,408.4 x 10-88 E (T 14 - T2 4) J/hr-m 2 = 20,408.4 x 10- (0.8)[(100 + 273)4 - (25 + 273)4] = 1,872,793 J/hr-m 2

= 1,872,793/3600 = 520 W/m 2

= total heat transmitted = heat transmitted

Q = 1500 + 520 = 2020 W/m 2

(h. + x hfgh

2668.6 = 914.52 + x(1885.5)

x = 93 %

air and its surrounding, which are at 25°C, by a brick wall 0.15 m thick. The brick has a thermal conductivity of 1.2 W/m-oK and a surface emissivity of 0.8. Under steady state conditions and outer surface temperature of 100°C is measured. Free convection heat transfer to the :

air adjoining this surface is characterized by a convection coefficient of 20 W/m 2-oK. What is the brick inner surface temperature in DC? (Oct 95) A. 637.7 C. 461.4 B. 352.5 D. 256.3 Solution:

2020

Hot Gases /

qc A m bilent air ,

I...

temperature difference across the wall of 50°C. The thermal conductivity of the firebrick is 0.65 Btu/hr-ft-oF at the temperature interest. (Oct 94) 2 A. 285 W/m C. 112 W/m 2 2 B. 369 W/m D. 429 W/m 2

x

= 6 in = 0.50 ft

25°C

t, - tb Q = qc + qR

Q

c

Q c

­

=

5. Calculate the energy transfer rate across 6 in wall of firebrick with a

100°C - outer

I...

keto -t b )

x

1.2( t. -100)

0.15

Solution:

qR

1

=

= 50(9/5) = kAna - t b ) x

.l.

= 1 m2

90 OF

=

0.65(1)(90) 0.50

= 117 Btu/hr-ft" J = 117 Btu X1055 --x hr - ft2

Consider per unit area, that is, A

by conduction

= 352.5°C

ta

,

I

=

Q

4. The hot combustion gases of a furnace are separated from the ambient

t. inner

= heat transmitted by convection

hc(t 1 - t2 )

= 20(100 -25) = 1500 W/m 2

W kw

K = 1.2 W/m-oK

,11111

radiation in the outside surface

16.4274 h2

= Total heat transmitted by convection

11 ~

= 369 W/m 2

Btu

hr 3600sec

(3.28)2ft2 X --:;--­

m2

F -116

Formulas and Principles - GAS COMPRESSORS

Formutn«

•• :1","1

------

GAS

~I~

COMPRESSORS

Principtes - GAS COMPRESSORS

• • Ij

Centrifugal Compressor (low pressure, high capacity)

2.

Compressor - a machine which is used to increase the pressure of a gas by decreasing its volume.

Uses of compressed air:

I, I! 1 '.,.

1. to drive pneumatic tools such as pneumatic hammer, air hoists, etc. 2. sand blasting 3. industrial cleaning 4. spray painting 5. starting diesel engines 6. to supply air in mine tunnels 7. manufacture of plastics and other industrial products

t

P, 3.

Rotary Compressor (medium pressure, low capacity) a. Vane (sliding blade) Compressor

Classification of Air compressors: 1. Reciprocating Compressor (high pressure, low capacity)

Pz

••

Free Air Lrnloader

~

b.

Screw Compressor

Discharge Valve

PI

---lK~L

=';V/7/ZlF

P

z

Automatic Pressure Switch Drive Motor

Service Valve

/

Performance of Single-stage, Single-acting Reciprocating Compressor P

PI~P2 V,'

P z = P3

P, =P4

, 3

I

I

I

I

~" 1

..

I

I

VI'

Vc

Vo

V

•

-~----

F -118

Formulas and Principles - GAS COMPRESSORS

Formulas and Principles - GAS COMPRESSORS 5.

1. Compression Process (1 - 2)

Compressor Work (Power)

= PzV2n

PNt

= n -I

T z ==

where:

I'

=

6. Brake Power = power required to drive the compressor

2

= -1t4

D LN

Compressor Efficiency m

3/sec

Compressor Power = Brake Power x Comp Efficiency 7.

where: D = bore, m

L = stroke, m

N = speed, rev/sec

=

= volume flow at suction = PI

Isentropic Wark

9. Ideal Indicated Power = PmNo where: Pm; =

VI' V

-

indicated mean effective pressure

Double acting, Single-stage Reciprocating Compressor

D

I~

Conventional volumetric efficiency:

= 1 +

m/sec

Actual Fluid Work

rnRTI

4. Volumetric Efficiency, nv

n,

Piston Speed = 2LN,

8. Adiabatic Compressor Efficiency

3. Capacity of Compressor, V 1

nv --

Compressor Power

=

2. Piston Displacement, Vo

V 1'

= nmRTlr(PzJn;1 - 11 n-1 PI

n-1

where: P 1 = suction pressure, kP'a P 2 = discharge pressure, kPa

= polytropic exponent

n

= k for isentropic process (k = 1.4 for air) 1 for isothermal process n

Vo

nPIVI'r(P2J~~ - 11· PI

(PZI----;;­

TI PI)

J I.."

F -119

c-c( ~

t

PI

_

where: c = clearance -

Vc V

D

P

P2

\v v

Formulas and Principles - GAS COMPRESSORS

Formulas and Principles - GAS COMPRESSORS

F -120

2:~~I'l(:~ t~ -II

Piston Displacement a.

Compressor Work =

Piston rod neglected:

VD

= 2 (~j DZLN

F -121

To solve for heat rejected in intercooler:

b. Piston rod considered:

Solve for mass flow:

m

PV'

_1_'

=

RT j

n

~ (Dz_dz)LN 4

Z

V D = - D LN + 4

J

I,.'.

Solve for T x:

(:~

1'x

1']

Two-stage Reciprocating Compressor P2

P2

C

14 If

= mCp(TX-T1)

Px I PI

't

I.

(

,

I

nmR1']

J

\I(PX 1n:1 _

n-1lp]) Px

~

1'\

Px

J

or Px =

nmR1']

Three-stage Reciprocating Compressor t y Pv ­

..-.--.

t

P

I

Pz P2

VI'

Py Pv--tl-­

1

ll(!2'I n:] -11

n- 1lpx)

~p]PZ

1.0 kJ/kg-OK

tl

= Work in 2 nd stage

=

=

V PI

1. No pressure drop in intercooler 2. Perfect intercooling 3. Work in 151 stage

where: Cp for air

'41..

'"

I

Ideal (Optimum) Conditions:

ta·t

= heat rejected in intercooler

Q

P

Px

r'

n-]

J

2

3

PI.l...I---­ I

W1 = W 2 = W 3 For ideal conditions, pressure ratios are equal:

Px 1',

Py

Pz

Px

Py

Compressor Work

=

from which: Px

3:J~~' 'l(~; f -II

=

(p/P Z) 1/3

V

F -122

Formulas and Principles - GAS COMPRESSORS

Heat rejected in intercoolers

=

Formulas and Principles - GAS COMPRESSORS

F·123

2 m Cp (T x - T 1)

P

2

Summary of Multi-stage Reciprocating compressor

No. of stages

Px = interstage pressure after first stage

_ 1/2 P X - (P 1P2 )

2

1

1

.·f

P x = (p,2P 2 ) 1/3

3

W

Compressor Work

(Power)

=

..... .....

~I

PI

r ~, 1

l

2nP]v] 'I ( Px ) n-1 P1

n

_

VI

•

1

Compressor work:

W= 3oP' V,'l(P' I";, - lj n-1 \P

W

""

nP1V r( P2Jn:l j

n -1

II

PI

-1 1

1)

Px =(P 13P 2 ) 1/4

4

w

4oP'V,{(P' 1"" -11

=

0-1

It

....1.

P,I

l

Pl)

j

General Formula Px

S

=(P 1S -1P2 ) lIS

W

=

SuP,V,' r(P, )n:1 _ 1j n-1

• •11

l\P

1

Performance of Centrifugal and Rotary Compressors

SAMPLE PROBLEMS: 1. A single stage air compressor handles 0.454 m 3/sec of atmospheric pressure, 27°C air, and delivers it to a receiver at 652.75 kPa. Its volumetric efficiency is 0.72, its compression efficiency on an isothermal basis is 0.85 and its mechanical efficiency is 0.90. If it rotates at 350 rpm, what power in kw is required to drive it? (Apr 95) A. 95 C. 120 B. 112 D. 100 Solution: Wi

PI 3/s ~ VI m

t

r

\'\

\'\ 111'/\

P '

= isothermal power = P N1 In = 101.3 (0.454) In = 85.685 kw

Drive Power

=

P2 PI

652.75 101.3

85.685 0.85(0.90)

= 112 kw

An air compressor is to compress 8.5 m 3/min from 98.56 kPa to 985.6 kPa. Assuming conditions ideal, and with n = 1.3, what will be the saving In work due to two staging? (Apr 95)

,.

Solution:

_ nP1V

Work of Single Stage

1..

-

l

n-I

2

\. PI

-

1.30 -1

Definitions:

-n

J

'I

Hydraulics - or hydrodynamics, is the mechanics of water or other liquid whether at rest, or in motion.

..J

1.30-1

98.56

l

'j

=

For Two-Stage: Px

=

JPl

2

= ~(98.56)(985.6) =

Work of Two-Stage

=

n-1

=

II

~ ~60)

2(1.3)(98.56l 1.30 -1

= Saving

311.67 kPa

l

PI)

(311.67) 98.56

1.3-1 U

_

42.43 kw

Hydrostatics - is the science of water at rest. Hydrokinetics - is a science of water in motion. Hydrodynamics - is a general term, and is generally associated with the science of the force exerted by water in motion, such as driving a turbine connected to an generator.

JJ

Atmospheric Pressure earth.

1

Gauge Pressure - is just the term implies the pressure on a gauge on open air, the gauge being connected to a closed pipe.

2nPIVI,rl(~In~1 _

~t ..

.,.

Pump - a machine which is used to add energy to a liquid in order to transfer the liquid from one point to another point of higher energy level.

J (985.6)~

8.5 (1.30)(98.56) ( 60

~

... ,tl

(p

n -1

_

.'fj

...,.

'

j

l

F -125

PUMPS

C. 5.6 kw D. 3.5 kw

A. zero B. 4.6 kw

{

Formulas and Principles - PUMPS

Formulas and Principles - GAS COMPRESSORS

F -124

1

Vacuum solids.

-

is due to the weight of the atmosphere on the

- a perfect vacuum is a space entirely devoid of gas, liquids, or

Absolute Pressure - is the sum of the atmospheric pressure and the gauge pressure.

36.83 kw = 42.43 - 36.83

= 5.6 kw

Bourdon Gauge - consists essentially of a curved tube, fixed at the open end, with the other (closed) end free and attached to a lever which is geared to the indicator needle. Manometer - is a gauge in a form of a glass U-tube one leg of which of open to the atmosphere, or a straight tube one end of which is open to the atmosphere. Pitot Tube - is used to measure the pressure of water discharging from a nozzle or flowing in a pipe by having its open end in the water and the other end connected to a gauge or manometer.

~

Piezometer - is a device set in a pipe to enable a Bourdon Gauge or a manometer attached to the piezometer to show the net or normal pressure.

F ·126

Formulas and Principles - PUMPS

Submersible Pump - a vertical turbine pump with the pump and motor closed coupled and designed to be installed underground, as in the case of a deepwell pump.

Suction lift - exist when the total suction is below atmospheric pressure.

Aquifer - an underground formation that contains sufficient saturated permeable materialto yield significant quantities of water.

- exists when the total suction head is above atmospheric

Velocity head - is figured from the average velocity obtained by dividing the discharge in cubic feet per second or cubic meter per second by the actual area of the pipe cross section in square feet or square meter.

~

...

i.'....­ '

......

~

F -127

Capacity - is the rate of flow of liquid measure per unit of time. usually gallons per minute (gpm) or liters per minute (Ipm).

Suction head pressure.

1 l•.

Formulas and Principles - PUMPS

Total discharge head - is the reading of a pressure gage at the discharge of the pump, converted to feet of liquid and referred to datum, plus velocity head at the point of gage attachment. Total head - is the measure of the energy increase per pound imparted to the liquid by the pump and is therefore the algebraic difference between the total discharge head and the total suction lift exists. Net Positive Suction Head (NPSH) - is the total suction head in feet or in . meter of liquid absolute determined at the suction flange and referred to datum, less the vapor pressure of the liquid in feet or meter absolte.

AqUifer Performance Analysis - a test designed to determine the amount of underground water available in a given field and proper well spacing to avoid interference in that field. Wet Pit - a timber, concrete, or masonry enclosure having a screened inlet to keep partiallyfilled with water by an open body of water such as pond, lake or streams. Ground Water - that water which is available from a well, driven into water-bearing subsurface strata (aquifer). Static Water level - the level with respect to the pump of the body of water from which it takes suction when the pump is not in operanon. Pumping Water level • the level, with respect to the pump of the body of water from which it takes suction when the pup is in operation. DraW-down - the vertical difference between the pumping water level and the static water level.

Typical Pumping Installations:

Centrifugal Pump - a pump in which the pressure is developed" principally by the action of centrifugal force. . .. - ..,~

End Suction Pump - a single suction pump having its suction nozzle on the' opposite side of the casing from the stuffing box and having the face of the suction nozzle perpendicular to the longitudinal axis of the shaft .

Discharge Pipe

• '41

In Line Pump - a centrifugal pump whose drive unit is supported by the: pump having its suction and discharge flanges on approximately the same center. Horizontal Pump - a pump with the shaft normally in a horizontal position.

Pressure Gauge Pump.

Vertical Shaft Turbine Pump - a centrifugal pump with one or more impellers discharging into one or more bowls and a vertical eductor or column pipe used to connect the bowls to the discharge head on which the pump driver is mounted. Horizontal Split-Case Pump - a centrifugal pump characterized by a nousinq which is split parallel to the shaft. IS a pump that takes suction from a public service main or private Booster Pump use water ~;y"t"l11 1m tho purpose of increasing the effectivewater pressure.

,

1/

I

Foot Valve/Strainer Lower Reservoir

Check Valve

Upper Reservoir

Formulas and Principles - PUMPS

F -128

Basic Classification of Pumps: 1. Reciprocating Pump

(low discharge, high head, low speed, self­

Formulas and Principles - PUMPS 5. Jet Pump (Injector) (for pumping boiler feedwater; pump)

F -129

used as accessory of centrifugal

priming)

Jet

f t. i... .,.

Piston Rod Cylinder

BASIC PARTS OF CENTRIFUGAL PUMPS: 2. Centrifugal Pump

(high discharge, low head, high speed, not self- ,

priming)

•

Impeller - imparts velocity to the liquid, resulting from centrifugal force as the impeller is rotated. Casing - gives direction to the flow from the impeller and converts this velocity energy into pressure energy which is usually which is usually measured in feet of head .

••••

Shaft - transmit power from the driver to the impeller.

••

Vane or Blade

I•

"

~I-

... ,.

3. Rotary Pump

(low discharge, low head, used for pumping viscous

liquids like oil) a. Gear Pump b. Screw Pump c. Vane Pump 4. Turbine Pump (for pumping water with high suction lift; for pumping

Stuffing box - this is a means of throttling the leakage which would otherwise occur at the point of entry of the shaft into the casing . 1. Packing - this is the most common means of throttling the leakage between the inside and outside of the casing. 2. Gland - to position and adjust the packing pressure. 3. Seal Gage (also called water-seal of lantern ring) - provides passage to distribute the sealing medium uniformly around the portion of the shaft that passes through the stuffing box. 4. Mechanical Seal - provides a mechanical sealing arrangement that takes the place of the packing.

condensate) Shaft Sleeve - protects the shaft where it passes through the stuffing box. Wearing Rings - keeps internal recirculation down to a minimum. Wearing Plates - with open type impellers or end clearance wearing fits, this perform the same purpose as wearing rings do with radial clearances. Bearings - accurately locate shaft and carry radial and trust loads.

-~

F - 133

Formulas and Principles - PUMPS

Formulas and Principles - PUMPS

F -132

Characteristics of Centrifugal Pumps: hI

=

2fLY

z

1. Specific Speed - the speed at which a geometrically similar impeller

(Morse Equation)

of a pump would run to discharge 1 gpm at 1 foot head.

gD

where: hI f

= friction head loss, m = coefficient of friction (should be taken from Morse

Ns

table if Morse equation is used) m (including equivalent lengths of the fittings)

v g D

= velocity, m/sec = 9.81 m/sec z = inside diameter,

2. Similar Pumps:

a.

If piston rod neglected: V 0

= 2 (~)

b.

DZLN

N]JQ; _ NzJQ; H]3/4

Hl/ 4

-

2

11:

V o :: - D LN + 4

.1"

where: d

2. Q

-

4

= Vo-Q

% Slip

=

Yo-Q

YD

2

Z

(D - d )LN

= diameter of piston rod

= actual discharge = Av

3. Slip

Qz 3

N 20 2

= impeller diameter

3. Same Pump:

b. If piston rod considered: 11:

~ N]O] 3

where: D

'11

.......

a.

1. Piston Displacement

.• ·f'

.,......

H 3/ 4

m

Characteristics of Reciprocating Pumps:

I.

N.JQ where: N s = specific speed, rpm N = speed, rpm Q = discharge, gpm H = head, ft

= total length,

L

=

x 100

a. Constant impeller diameter (D 1

Q]

Nl

Q2

N2

-!!L H2

=

=D2 ) ,

(~J2 N 2

variable speed

.!l

=

P2

(~J3 N 2

b. Constant Speed (N 1 = N z), variable impeller diameter

Q]

0]

Q2

°2

.!!.L Hz

=

(ELJ2 O2

.!l = P2

(ELJ3 02

4. Centrifugal Pumps in Parallel or Series Operations 4. Volumetric Efficiency =

Q

YD

For Pumps in parallel, performance is obtained by adding the capacities at the same head. For Pumps in series, performance is obtained by adding the heads at the same capacity.

F ·134

Formulas and Principles - PUMPS

Special Classification of Pumps Based on Suction Lift:

Formulas and Principles - PUMPS Solution:

1. Shallow Well Pump ( ordinary centrifugal pump, for suction lift up to 25 feet) 2. Deepwell Pump (centrifugal pump with injector, for suction lift up to 120 ft) 3. Turbine Pump (multi-stage pump, for suction lift up to 300 ft) 4. Submersible Pump (multi-stage pump, driven by submersible motor)

,1. .,~.

......

,

.'.'

.,'1

.... •..1

tll~

Bad Effects of Cavitation: 1. drop in capacity and efficiency 2. noise and vibration 3. corrosion and pitting

Q = 15li/s = 0.015

Vs :::

~= As

whose free surface is 60 m below ground level. The water is to be raise," 5 m above the ground by a pump. The diameter of the pipe is 10 cm the inlet and 15 em at the exit. Neglecting any heat interaction with th surroundin ts and frictional heating effects, what is the necessary power input to the pump for a steady flow of water at the rate of 15 Iitersls in kw? (Apr 96) A. 9.54 C. 7.82 B. 5.34 D. 11.23

i

m%

0.015

:::

~(0.1 0)2

1.91 m/s

4

Vd

:::

~= Ad

0.015

~(0.15)2

::: 0.85 mls

4

H ::: (Zd - Zs)

+

y2_ y 2 d

s

2g

::: [5 - (-60)]

I. Water in the rural areas is often extracted from underground water sourc

15 IiIs

"11~10 em

NPSH (Net Positive Suction Head) - difference between actual suctio pressure and saturation vapor pressure of the liquid.

SAMPLE PROBLEMS:

..

60m

Cavitation - the formation of cavities of water vapor in the suction side

of a pump due to low suction pressure.

Causes of cavitation: 1. low suction pressure 2. low atmospheric pressure 3. high liquid temperaturee 4. high velocity 5. rough surfaces and edges

6. sharp bends

~If-

~ "'-15 em

5m

Cavitation; NPSH

1.

F ·135

+

(0.85)2 - (1.91)2

2(9.81)

::: 64.85 m Water Power ::: Q w H

::: 0.015(9.81 )(64.85)

::: 9.54 kw

(Note: 9.5.4 kw is the water power; the power input to the pump cannot be solved because no efficiency is given.) 2. The rate of flow of water in a pump installation is 60.6 kg/sec. The intake static gage is located 1.22 m below the pump centerline and reads 68.95 kPa gage; the discharge static gage is 0.61 m below the pump centerline and reads 344.75 kPa gage. The gages are located close to the pump as

lit" F • 134

Formulas and Principlee- PUMPS

Form/lias and Principles. PUMPS

Special Classification of Pumps Based on Suction Lift:

Solution:

1. Shallow Well Pump ( ordinary centrifugal pump, for suction lift up to 25

~~ ~ 15li/s 1s em

:t

feet) 2. Deepwell Pump (centrifugal pump with injector, for suction lift up to 120 ft) 3. Turbine Pump (multi-stage pump, for suction lift up to 300 ft) 4. Submersible Pump (multi-stage pump, driven by submersible motor)

d..-

5m

60m

Cavitation; NPSH

.1 1.-10 em

I

~'

I

,

I

ii, ..... . , I'

.'fll

'

"'" ''."1 "lIIf

Cavitation - the formation of cavities of water vapor in the suction side of a pump due to low suction pressure.

Causes of cavitation:

1. low suction pressure 2. low atmospheric pressure 3. high liquid temperaturee 4. high velocity 5. rough surfaces and edges

6. sharp bends

Q

Vs

= 151i/s = 0.015 m 3/s = !l= As

0.015

=

~(0.10)2

1.91 m/s

4

Vd Bad Effects of Cavitation: 1. drop in capacity and efficiency 2. noise and vibration 3. corrosion and pitting

= ~= Ad

0.015

= 0.85 m/s

~(0.15)2 4

H

= (Zd - Zs)

+

y2_ y2

d

s

2g

NPSH (Net Positive Suction Head) - difference between actual suction pressure and saturation vapor pressure of the liquid.

= [5-(-60)]

+

(0.85)2 - (1.91)2 2(9.81)

= 64.85 m

SAMPLE PROBLEMS:

Water Power

I. Water in the rural areas is often extracted from underground water source whose free surface is 60 m below ground level. The water is to be raised 5 m above the ground by a pump. The diameter of the pipe is 10 em at the inlet and 15 em at the exit. Neglecting any heat interaction with the surroundtrrts and frictional heating effects, what is the necessary power input to the pump for a steady flow of water at the rate of 15 liters/s in kw? (Apr 96) A. 9.54 C. 7.82 8. 5.34 D. 11.23

= = =

Q w H

0.015(9.81 )(64.85)

9.54 kw

(Note: 9.5.4 kw is the water power; the power input to the pump cannot be solved because no efficiency is given.)

2. The rate of flow of water in a pump installation is 60.6 kg/sec. The intak .. static gage is located 1.22 m below the pump centerline and reads 6R !I',

~

kPa gage; the discharge static gage is 0.61 m below the pump centortu«­ and reads 344.75 kPa gage. The gages are located close to the pump ,I',

-- --

F -136

Formulas and Principles - PUMPS

Formulas and Principles - PUMPS

much as possible. The area of the intake and discharge pipes are 0.093 2 m 2 and 0.069 m ,respectively. The pump efficiency is 70%. Take 3 density of water equals 1000 kg/m . What is the hydraulic power in kw? (Apr 96) C. 31.9 A. 17.0 D. 15.2 B. 24.5

Solution:

2!L=(~r H2 N2 -150 -

Solution:

360

N2

1('

;JJ,I

!t

... I

, .,PI

"

",'1

MI"1

""1

.,.

I I

I

1.22 m

\.!...)!

= 2711

r

rpm

operating at 1770 rpm. Changes have increased the total head to 375 ft. At what rpm should the pump be operated to achieve the new head at the same efficiency? (Apr 97) C. 3434 rpm A. 2800 rpm D. 2424 rpm B. 3600 rpm

3/s

Solution:

Vs Vd

Q - 0.0606

=

Q - 0.0606

= 0.878

= As -

= ~ -

0.093

0.652 m/s HI

0.069

2

H2

m/s

-

2

=

344.75 - 68.95 + (-0.61 + 1.22) + (0.878) - (0.652) 2(9.81) 9.81

2

28.742 m

Hydraulic Power (Water Power)

QwH

0.0606(9.81 )(28.742)

= =

= 17.1

(~~r

200 _- (1770J2

-375 N 2

2

Z Vd - Vs - P - P, +-----"--...;;. H - -d - + W 2g

=

kw

3. A pump operating at 1750 rpm delivering 500 gal/min against a total head of 150 ft. Changes in the piping system have increased the total head to 360 ft. At what rpm should the pump be operated to achieve this new head at the same efficiency? (Apr 97) A. 2730 rpm C. 2711 rpm B. 2740 rpm D. 2600 rpm

.l

750 N2

4. A pump delivers 500 gpm of water against a total head of 200 ft and

344.75 kPag

= 0.0606 m

C -­

0.61 m

68.95 kPag Q = 60.6/1000

F - 137

N 2 = 2424 rpm

F~

Formulas and Principles - FANS AND BLOWERS

Formulas and Principles - FANS AND BLOWERS

FANS AND BLOWERS

Head and Power Calculations:

Fan - a machine which is used to apply power to a gas in order to cause

movement of the gas.

Blower - a fan which is used to force air under pressure, that is, the

resistance to gas flow is imposed primarily upon the discharge.

'. . . l...! _I'

II

• Q m3/s

Exhauster - a fan which is used to withdraw air under suction, that is, the

resistance to gas flow is imposed primarily upon the inlet.

l: I..

Common Uses of Fans:

Ventilation, air conditioning, forced and induced draft service for

boilers, dust collection, drying and cooling of materials, cooling towers,

heating, mine and tunnel ventilation, pneumatic conveying and other industrial

process work.

Basic Assumptions:

1. constant temperature

2. negligible inlet velocity (Vs = 0) Capacity of Fan, Q = volume flow rate measured at outlet (m 3/s) Area x velocity

=

Types of Fans

Static Pressure Head:

, ...,

l

.'hl

hs =

.'••••.,

where: hs = static pressure head, meters of air hw = manometer reading, meters of water dw = density of water 3 = 9.81 kN/m or 1000 kg/m 3 da = density of air, kN/m 3 3 1.2 kg/m at 101.325 kPa and 21.1°C

~I",

ta'tat

Propeller Fan

Tubeaxial Fan

hwd w da

Vaneaxial Fan

=

Centrifugal Fan:

Velocity Head:

Housing Motor

~

•

hv =

• Rotor

2

Vo 2g

Where: hv = velocity head, meters of air Vo = outlet velocity, m/s 9 = 9.81 rn/s"

i

F -139

Formulas a'1d Principles - FANS AND BLOWERS F - 141

Formulas and Principles - FANS AND BLOWERS

F· f40

Fans Laws:

Total head:

a. Variable Speed (constant fan size, constant density)

h = hs + hv

=

Air Power where:

Q d, h, Q

kw

= fan capacity, = density of air,

da h :: head, m

I:

l.

, .• ......, ,

• .411.

"I.' ~I", ta....

=

Brake (Input) Power

3/s

m 3 kN/m

Nz

Q1

Fan Efficiency

=

p]

P2

(~~r

~ hz

= O 2

d]

Pj

d2

Pz

d] dz

SAMPLE PROBLEMS:

1. What hp is supplied to air moving at 20 fpm through a 2 x 3 ft duct under a pressure of 3 in water gage? (Apr 97) A. 0.786 hp C. 0.642 hp

B. 0.741 hp D. 0.0566 hp

Basic Assumptions:

1. considering inlet and discharge static pressure 2. considering inlet and discharge velocities 3. constant temporature

Solution:

o

Total head :: static pressure head + velocity head

(h W2 -hwl)w a

= fan capacity = A x v = (2 x 3)(20/60) 2 fe/s

=

=

h :: head

Pz - Pj + V/ - VIZ w 2g

W

hwd w da

_ _.4_) = --'-8{....o.1=2X_62

h = 15.6

ft of air da Air Power = 0 da h

Z

+ V/ - Vj

2g

=

P 1 and hW1 is negative if below atmospheric pressure.

~

:~ l~~r

where: d = density

P = power

Bernoullis Equation Applied to Fan:

=

Qz

Air Power

Pressure: 29.92 in Hg (101.325 kPa)

Temperature: 70°F (21.110c)

h

NI

b. Variable density (constant fan size, constant speed)

Standard Air:

h =

-2L

where: P 1 and hW 1 = inlet static pressure reading P2 and hW 2 = discharge pressure reading 3 3 w = density of water (1000 kg/m or 9.81 kN/m ) 3 w a :: density of air (1.2 kg/m at 101.325 kPa and 21.11°C) V1 = inlet velocity, m/s V 2 = discharge velocity, m/s

where: d,

2(da)(15~a) 550

~

da

= density of air in

Ib/ft 3

= 0.0567 hp

2. A fan whose static efficiency is 40% has a capacity of 60,000 fe/hr at 60°F and barometer of 30 in Hg and gives a static pressure of 2 in of water column on full delivery. What size electric motor should be used to drive this fan? (Apr 97) A. 1/2 HP C. 2 HP B. 1 HP D. 1 1/2 HP

~

F ·14~

Formulas and Principles - FANS AND BLOWERS

Formulas and Principles - FANS AND BLOWERS

Solution: hs

h ::: = static pressure head

_ hwd w d

:::

a

C :::

2 2 } 62.4) d a

where: d a

1:

::: 9.45(1.20 ::: 9.874 kw Fan Efficiency :::

:::

:::

'.. .....

:::

Static Air Power

0.315

Use 1-hp motor.

3.

9:~74

3/s

at a static pressure of 5.08 cm of water when 4. A fan delivers 4.7 m operating 3/s at a speed of 400 rpm. The power input required is 2.963 kw. If 7.05 m are desired in the same fan and installation, find the pressure in cm of water. (Apr 95) A. 7.62 cm C. 11.43 em B. 17.14 cm D. 5.08 cm Solution:

Air enters a fan through a duct at a velocity of 6.3 mls and an inlet static pressure of 2.5 em of water less than atmospheric pressure. The air leaves the fan through a duct at a velocity of 11.25 mls and a discharge static pressure of 7.62 cm of water above the atmospheric pressure. If 3/s, 3 the specific weight of the air is 1.20 kg/m and the fan delivers 9.45 m what is the fan efficiency when the power input to the fan is 13.75 kw at the coupling? (Oct 94) C. 75.6% A. 71.80% D. 95.3% B. 86.3% Solution:

Air Power

13.75 ::: 71.81%

0.40 ::: 0.79 hp

I~' ••

x 0.00981 )(88.761)

Input Power

Static Fan Efficiency

'.,

2(9.81)

Air Power ::: Q d, h

550 = 0.315hp

.'fi'

~

3

60,OOO(d )(10~'~) 3600 a da

Brake (Input) Power

2g

1.20 ::: 88.761 meters of air

density of air in Ib!ft

velocity head

-[0.0762 -{-0.025j1 000 + (11.25)2 _ (6.3)2

Static Air Power ::: Q da h

l. tt,-.

:::

ft of air

+

1.1

--+ w

::

10.4 da

total head ::: static pressure head P2 -PI V/ - v j 2

,

- -f+7.62 em water

-2L=~

N2

Q2

4.7 7.05

400 N2

-=-

N2

:::

600 rpm

-.!:!L

=

H2

(~~r

5.08 =(400)2 H2 600 H2

:::

11.43 cm of water

5. A fan described in a manufacturer's table is rated to deliver 500 m 3/min at a static pressure gage of 254 em of water when running at 250 rpm and requiring 3.6 kw. If the fan speed is changed to 305 rpm and the air handled were at 65°C instead of standard 21"C, find the power in kw. (Apr 95)

A. 3.82 kw

B. 5.08 kw

e. 4.66 kw D. 5.68 kw

i

............---­ Formulas and Principles - REFRIGERATION

'j:: -145

Formulas and Principles - FANS AND BLOWERS

F -144

REFRIGERATION Solution: Solving for the power required at 305 rpm and 21°C:

.!l (~J3

Methods of Refrigeration: 1. Ice Refrigeration 2. Mechanical Refrigeration 3. Absorption Refrigeration 4. Steam Jet Refrigeration 5. Air Cycle Refrigeration

='

P2

N2)

~

='

P2

!I. l.

.'Wlt

••••

..

.• Q: '

tl

.....".

(

250

Refrigeration - maintaining a space cooler than the surrounding .

3

1

\ 305)

P z = 6.5 kw Solving for the power required at 305 rpm and 65°C:

Ice Refrigeration

p

= density = -RT

d

P

2

d;-

='

='

P2'

P z'

='

~T2

T 2

='

T;

U--ISOlid ttu;t-IUqUldI t, DC

tr

65 + 273

6.5 -

l~·T]

d]

p]

4J

21 + 273

= 5.68 kw

°c

t 2 DC

Amount of cooling provided by the ice

= m[C1(trt 1) + L + cz(tz-tf ) ] , kJ

where: m = mass of ice, kg

C1 :::l: specific heat of ice

= 2.093 kJ/kg-OC = 0.5 Btu/lb-OF Cz = specific heat of water = 4.187 kJ/kg-OC = 1.0 Btu/lb-OF latent heat of fusion 335 kJ/Kg L melting temperature O°C tf

= =

= =

= 144

Btu/lb

Mechanical Refrigeration Basic Components: 1. Compressor - compresses refrigerant vapor and causes it tp flow in the system.

2. Condenser - the refrigerant condenses while rejecting heat to the cooling medium which is either air or water.

!

Formulas and Principles - REFRIGERATION

Formulas and Principles - REFRIGERATION

F -146

j'I'I'

I:

Compressor Work (Power), We = hz - h, kJ/kg = m(h z - h1) kw

3. Expansion Valve - reduces the pressure of the refrigerant so that low temperature will be attained; regulates the flow of the refrigerant

F -147

I,

I'

11,1

illl

to the evaporator.

', , '

I!~~

1

Heat Rejected in Condenser, Q R = hz - h3 kJ/kg = m(h z - h3 ) kw

4. Evaporator - the liquid portion of the refrigerant evaporates while absorbing heat from the surrounding.

Il!1 :1

To find the cooling water requirement of condenser, mw:

mwCp6 T = m(h z - h3 )

@] Liquid I

:z::::::::;:

Superheated ~vapor

E;.pansion Valve

where:

Vapor

(

Cp 6T

= specific heat of water = 4.187 kJ/kg-OC = temperature rise of the cooling water

Expansion Valve (Process) h3 = h4 h3 = (h, + X hlg )4

l......

Evaporator Coils

I,

1"1

Iii II!, "',,1,

I

\',II I 1II1 I

~

(i)

i,

II""'I

Motor

where: x = quality or weight of flash gas per unit weight of refrigerant

I ,II

1,,1,'i,

1 ! I!

Refrigerated Space

I

Refrigerating Effect, Q A = h1 - h4 kJ/kg = m(h 1 - h4 ) kw

Compressor

,

........1

.... .... ~..... ,

.. .... '

=

The Compression Cycle P

m kg/s ~

2

P

2

:=

(1 ton of refrigeration

p 3 -l

-1

:

7

= 3.516 kw = 200 Btu/min)

2

=

/

I We

I

I

I

n, = h 4

h,

h2

QA

hI -h 4

Compressor Work

We

h z -hI

Compressor Power Tons of Refrigeration '

//

Superheat horn

Volume Flow at Suction, V 1 ' , = m V1 m 3/s ,

S

= S2

III: "1'

:1: 1[1

Power Per Ton

=

S~

III 1IIIII

Re frigerating Effect

h

T

~

'1111

Coefficient of Performance (COP)

P 4=P,1

QA

m(hl - h 4 ) Tons of Refrigeration 3.516

J

I,

1'1

:1

kw/ton

Ii'

Net Work

F ·150

Formulas and Principles - REFRIGERATION

Fnrrn,d""",

3. Rotary Compressor a. Vane type b. Screw type

3. V1'

= volume flow at suction where:

Classification of refrigeration compressors, based on enclosure:

----~-"~~

"",.,..J Principles - REFRIGERATION

V1

= m

= specific volume at suction,

2. Hermetically sealed Compressor

type in which the

compressor and the motor are enclosed in the same housing.

{

,l.

I, ....

= volumetric efficiency = l

V'

o

I~"'f 'c'I....·",..

I.....

l

Conventional (clearance) volumetric efficiency:

ny = 1 + c - c ( where:

3. Semi-Hermetic Compressor - hermetically sealed compressor

Performance of Reciprocating Compressor

0

V2

3

I

,

VD

1. Compressor work (Power)

= h 2 - h, kJ/kg

= m(h 2 - h 1 )

V

specific volume at suction, m 3/kg specific volume at discharge, m 3/kg

2. Water-cooled a. Shell-and-tube b. Shell-and-coil Shell·and·tube (Vertical) Condenser Cooling Water In

kw

I

2. V D = piston displacement

= =

Types of condensers used in refrigeration: 1. Air-cooler a. Bare tube b. Finned tube

~1

l~vl Vc

~~ J

Refrigerant Condensers

0

PI I

= 1 + c - c(

VD V1

P P2 I

,:~ Jlln

V c = clearance = _c

in which the cylinder head can be removed for servicing of the

valves and pistons.

(!Jill

=

2:0 2LNC, 4

m 3/sec

'

~ IillW kg~S Refrigerant Vapor

where:

m 3/kg

" 4. ny

1. Open-type compressor

compressor whose crankshaft extends through the compressor housing so that a motor can be externally coupled to the shaft.

V1

m kg/s

0 = bore, m L stroke, m speed, rev/s

N number of cylinders C

= = =

Refrigerant Liquid

Cooling Water Out

r

Formulas and Principles - REFRIGERATION

F -152

= m(h,-h 2)E where: 6t = temperature rise of cooling water E = heat extraction factor

m wCp6t

Expansion Devices

l. .'....

Functions of the Expansion Device: 1. to reduce the pressure of the liquid refrigerant from the condenser in order to attain low temperature 2. to control the flow of the refrigerant to the evaporator Types of Expansion Devices: 1. Capillary Tube Inside diameter: 0.50 mm to 2 mm Length: 1 m to 6 m Capacity: up to 10 kw

2. Expansion Valves a. Gate Valve b. Constant Pressure Expansion Valve c. Thermostatic Expansion Valve d. Thermostatic Expansion Valve with External Equalizer e. Float Valve (used with flooded evaporator)

.... ,

....

~I'" lilt..

-'...

II.

Halocarbon Refrigerants R-12 CCI2F 2 Dichlorodifluoromethane R-22 CHClF 2 Monochlorodifluoromethane R-40 CH 3CI Methyl Chloride Inorganic Refrigrants R-717 NH3 Ammonia R-718 HP Water R-729 Air R-744 CO 2 Carbon Dioxide

III. Hydrocarbon Refrigerants R-50 R-170 R-290

An azeotropes is a mixture of two substances in whlcll ttll' components cannot be separated by distillation. (R-502 is a mixture of 48.8% R-22 and 51.2% R-115).

Desirable Properties of a Refrigerant: Thermodynamic Properties: l . low freezing point 2. low condensing pressure 3. low evaporating pressure 4. low power per ton 5. low volume flow per ton 6. high COP Chemical Properties: 7. non-toxic 8. non-flammable 9. non-corrosive

] O. not destructive to refrigerated products

Physical Properties: ] l. low viscosity

]2. high thermal conductivity

] 3. easy leak detection

14. miscible with oil

] 5. reasonable cost

Leak Detection:

Refrigerants 1.

CH 4 C2H 6 C3H s

I', I

IV. Azeotropes

By heat balance:

(

Formulas and Principles - REFRIGERATION

Methane Ethane Propane

R-12 and other systems using halocarbon refrigerants: Detection: loss of cooling capacity Location: a. soap sud b. prestolite or alcohol torch c. electronic leak detector

Ammonia Systems: Detection: toxic odor Location: a. soap sud b. sulfur candle c. litmus paper

F -154

---

Formulas and Principles - REFRIGERATION

Formulas and Principles - REFRIGERATION

Calculating the Cooling Load from Products 1. Without Freezing: Cooling Load m Cp £\t,

=

2. Refrigeration System with One Compressor Serving Two (or Evaporators kw

m

where: m = mass of the product, kg/s Cp = specific heat of the product, M temperature change, °C

P

3 kJ/kg-OC

2

=

I

ff 2. With Freezing:

r~

I.,

t.'

.....,

'tI1f;

'""1 ."1 -:""i

......

Cooling Load

7

2

m/

= m[c1(t 1-tl } + L + C2(trt 2}],

where: m C1 L C2 t1 tl t2

kw

= mass of the product, kg/s

= specific heat above freezing, = latent heat of fusion, kJ/kg = specific heat below freezing, = initial temperature, °C = freezing temperature, °C = final temperature, °C

,

= =

h

kJ/kg-OC

By heat balance at junction: rn.h, + (rn-rn.jh, = rnh,

kJ/kg-OC

3.

Refrigeration System with Flash Tank

....--m

For Water: C1 4.187 kJ/kg-OC 1.0 Btu/lb-oF L 335 kJ/kg = 144 Btu/lb

Cz = 2.093 kJ/kg-OC = 0.50 Btu/lb

=

3

2

p

,( Total Refrigeration Load

=

(1 Ton of Refrigeration

J

"7 2

Cooling load from products + Heat gain from external sources'

= 3.516 kw = 12,000 Btu/hr) I

Multi-Pressure Refrigeration System 1. Refrigeration System with Two-Stage Compressor

Px

P

Pz

"1

I

1

7'

By heat balance in Flash Tank:

mh, rn.h, + (rn-rn.jh,

=

2

1

Px I PI I / I

Compressor Work

1II'"!!)

= (h x-h 1) +

(hz-hy)

/

I

By' heat balance at junction: rn.h, + (rn-m.jn, = rnh,

,

L-¥

h

h

'/

Formulas and Principles - REFRIGERATION

Formulas and Principles - REFRIGERATION

F -156

F - 157

By heat balance in the cascade condenser

Low Temperature Refrigeration

m 1(h rh 3 )

::

mz(hs-hB)

Cryogenics • the science of low temperature

Total Compressor Work (Power) = m 1 (h rh 1 ) + m Z(h 6-h s)

Cascade Refrigeration System:

PI;£t 7

R

Other Methods of Refrigeration:

6

1. Absorption Refrigeration System (Ex. NHrHzO System)

!=i

I

"I

h

i

( "1

NH,

Condenser

P

f

72

4 Evaporator

I

h

I

[vaporator

I

..

I

I

By heat balance in the cascade condenser:

m1(hz-h3 )

_"1

::

mz(hs-h8)

2.

Steam Jet Refrigeration:

Compressor Work :: m1(hz-h1) + mz(h6-h s)

Steam

-

. -'=:-:::=1

1

Refrigerating Effect:: m1(h1-h4 )

Cascade Refrigeration system with Direct Contact Cascade Condenser: Coolin/(

Load

P

.....

P6

P2

1 If l------21 Iv

6

I 7 -y }2

3. Air Cycle Refrigeration

PI I" Stage

I

Evaporator

P :: P

::

z

3

z ::

~P1P6

P

P

s::

P8

h

Expander :::

Compressor

pressure at the cascade condenser :II!

II

i

._~

- -

-- -Formulas and Principles - REFRIGERATION

F -158

Refrigerating Effect = m(h 1 - h4 )

5(3.516) = m(353.6 - 238.5)

m = 0.153 kg/s

1. A refrigeration system operates on an ideal vapor compression using R­ 12 with an evaporator temperature of minus 30°C and a condenser exit temperature of 49.30C and requires a 74.6 kw motor to drive the compressor: What IS the capacity of the refrigerator in tons of

By heat balance in condenser: m(h 2 - h 3 ) = mwCpL'it

0.153(377.0 - 238.5) = mw(4.187)(7)

m; = 0.723 kg/s

refrigeration?

=

{

.,

382 kJ/kg, exit c: 248.15 kJ/kg; Enthalpy at condenser entrance at evaporator entrance:: 248.15, exit = 338.14. (Apr 96) A. 43.1 C. 21.3

B. 34.5 D. 18.2

v; = V w

QR

'-'''1

--..

0.723(60) 1 43.38 3.7854

= 43.38 =

Ii/min

11.46 GPM

3. An ideal vapor compression refrigeration cycle requires 2.5 kw to power the compressor. You have found the following data for the cycle: the enthalpy at the condenser entrance = 203 kJ/kg, exit = 55; evaporator entrance = 55 kJ/kg, exit = 178. If the mass flow rate of the refrigerant is 0.10 kg/s, then the coefficient of performance of this refrigeration cycle is most nearly: (Oct 94) A. 592 C. 5.92 D. 4.92 B. 59.2

.'t'ltll

I. '"

=

Solution:

l.,

---"'' 1 ~.,..,

159

Formulas and Principles - REFRtGERATION

SAMPLE PROBLEMS:

ft,

f" -

QA

Solution: W = m(h z-h1) 74.6 = m(382 - 338.14)

m = 1.7 kg/s

Q A

Ref. Effect

= m(h 1 - h4)

= QA

= 1.7(338.14-248.15)

COP

= 153 kw

~ 3.516

or COP

=

=

= m(h 1-h 4 ) = 0.10(178-55)

= 12.3 kw

12.3 2.5

W

43.5 tons of refrigeration

= hI -h

4

h 2 -hI

=

4.92

178-55 203 -178

= 4.92

2. A Freon 12 waste water system operating at a 5°C suction temperature and a 400C condensing temperature has an evaporator load of 5 tons. If the condenser is selected for a t-c water temperature rise, how many GPM must be circulated through the condenser?

The following enthalpies have been found: condenser entrance = 377.0

kJ/kg, exit = 238.5; evaporator entrance = 238.5 kJ/kg, exit =353.6.

(Oct 94)

A. 11.46 GPM

B. 9.05 GPM

Solution:

C. 12.56 GPM D. 14.36 GPM

f

A reverse Carnot cycle requires 3 hp and extracts energy from a lake to heat a house. If the house is kept at 70°F and requires 2000 Btu per minute, what is the temperature of the lake? (Oct 93) A. 35°F C. 39°F B. 36°F D. 40°F

Solution:

I

, ,

I

5'

--=

--.

-.­

Formulas and Principles - AIR CONDITIONING

Formulas and Principles - REFRIGERATION

F -160

F -161

AIR CONDITIONING w

= T2 = QR = Q = R 2000

8

·r

3 hp = 3(42.4) = 127.2 Btu/min 0R 70 + 460 = 530 2000 Btu/min T2(82-83 ) = T2(81-84 ) = 530(8 1-84)

1-8 4

Q

A

= 2000 530

=

T 1(8 1-8 4 )

0 = T 1(200 I 530 )

ill

..

~

IN'

• 'tlm ....u

, ~'...... '

=

QR

127.2

=

W

-

1

2000 _ T1(2000 530 )

t 1 = 496 - 460 = 36°F

Functions of Air Conditioning: 1. control the temperature 2. control the humidity 3. control the purity, that is, removal of dust and other impurities 4. control of air movement or circulation Psychrometry - study of the properties of air and its water vapor content. Psychrometer - the instrument used in the study of the properties of air.

QA

T 1 = 496°R

Air Conditioning - controlling the properties of air so that the air will be suitable for its intended use. .

Saturated Air - air whose condition is such that any decrease in temperature will result in condensation of the water vapor into liquid.

Moist air - is a binary mixture of dry air and water vapor.

Dry Air . oxygen .

non-condensing components of a mixture mainly nitrogen and

Vapor - condensable components of the mixture.

Unsaturated Air - air containing superheated vapor.

Properties of Air:

-......

DBoe

\ p

n -wa'c

(.;)~~:.. ~'\ ..........•.......

.........~~J.}

Wrl Cloth

1. Temperature, DC Dry bulb temperature (DB) - the actual temperature of the air or the temperature of air as registered by an ordinary thermometer.

.Formulas and Principles - AIR CONDITIONING

F -163

Formulas and Principles - AIR CONDITIONING

F -162

Wet bulb temperature (WB) - temperature of air if it is saturated or temperature of air as registered in a wetted wick thermometer.

6.

Relative Humidity, RH, %

_

Actual partial pressure of water vapor Saturation pressure of pure water vapor at same temperature

Wet bulb deprJ!ssion - difference between wet bulb and dry bulb

thermometers.

_

Py Psat

Pv

= RH

psychrometer - is an instrument consisting of two thermometers, one to measure the dry bOlb and the other to measure the wet bulb temperature of the air.

(Psat - saturation pressure can be found at the steam table at dry bulb temperature)

2. Pressure, kPaa

·{Jill

(Dalton's Law) P = P a + Pv P ) v or (P a = P

••

.'..... ,.

IONI ....

~' I

..

x P sat

7. Dew Point -

where: P = total pressure of air-water vapor mixture Pa = partial pressure of dry air Pv = partial pressure of water vapor

the temperature at which the water vapor in the air condenses when the air is cooled at constant pressure. Dew Point the temperature which the air becomes saturated at constant pressure.

8. Percent Saturation, %

3. Specific Volume _

Actual humidity ratio

From PV = mRT

= Va m

v

Density,p =

Humidity ratio of saturated air at the dry bulb temp

RaT Pa

RaT P-Pa

1

3

kg/m

m3/kg dry air

=

dry air

W

W sat

v

.

-.....

The Psychrometric Chart

4. Humidity Ratio, W, kg water vapor kg dry air W

= 0.622

where: P P

=

y

P

Pa

0.622

Humidity Ratio

~ P-P y

w.,

= total pressure, kPa

Dew point"

= partial pressure of water vapor,

v

kPa

~ "."."~""""'-

···W

5. Enthalpy, h, kJ/kg dry air h

= Cp t

+ W hg

where: Cp t W h g

= specific heat of dry air =

WB

1.0 kJ/kg-OC

= temperature (dry bulb), °C = humidity ratio, kg water vapor/kg dry air = enthalpy of saturated water vapor at the air temperature.- kJ/kg

DB

Temperature F'C

F -164

Formulas and Principles - AIR CONDITIONING

Formulas and Principles - AIR CONDITIONING

Processes in the Psychrometric Chart

F - 165

By heat balance: rn.h, + m 2h2 = (rn, + m2)h 3

W

By moisture balance: m1 W 1 + mzWz = (rn, + mz)W 3

7,t/ 6 1

By temperature balance (dry bulb):

rn, T 1

1-4-0--'2

"all

/1~

5

...,

T

t.

0-2 0-3

......

0-4 0-5

.'tI'lll

.....

1,.. .....

11

.....

0-1

0-6 0-7 0-8

' 4

+ mzTz =

(rn,

+ mz)T 3

Applications of Psychrometry:

8

1. Air Conditioner 2. Cooling Tower 3. Dryer

I

Cooling

Heating (Dryer)

Humidifying (Isothermal Dryer)

Dehumidifying

Cooling and Dehumidifying (Air Conditioner) Heating and Humidifying (Cooling Tower) Cooling and Humidifying (Adiabatic Dryer) Heating and Dehumidifying (Chemical Dehumidification)

1. Air Conditioner

hj hz

2

Air Mixing

V m 3/s

'----1~~

1

3 (m, + m2)

/

• /3 2

Refrigerating Capacity

------;-1

= m(h 1-hz) = ~ Vj

Rate of Moisture Removal

kw

(h 1-h z)

kw

= m(W 1-WZ) v

= -

vI

kg/s

(W 1-WZ) kg/s

w.

----- =­

F -166

Formulas and Principles - AIR CONDITIONING

Formulas and Principles - AIR CONDITIONING ms

where: m = mass flow rate of air, kg/s \/1 = specific volume at 1

F -167

= m3 - m4 = m1(WrW 1)

% make-up water

=

Amount of Make - up Water Mass of water flowing

ms m3

2. Cooling Tower where: 2

~Al'O", Hot Water In

r~.M

l~.'...,.

In, - - . . 3 t,

!

i

~

+"--­ i

JC

t"b

VI ... 1

1

ml Air Inlet

Energy Balance: rn.h, + m3h3 + mshs = m1h2 + rn.h,

Cool Water Out

Make-up Water

where:

rn, = m3 - rn,

5 rn.h, + m3h3 + (m3-m4)hs = m1 h2 + m4h4

ms Heat Balance

.....,

/2

Heat absorbed by air = Heat rejected by water

1

where: rn, = mass flow rate of water flowing, kg/s Cp specific heat of water 4.187 kJ/kg-OC

...... ......

'

'-'"

......

t db

1\

rn, = make-up water requirement rn, = mass flow of air entering W 1 = humidity ratio of air entering, kg/kg W 2 = humidity ratio of air leaving, kg/kg rn, = mass flow of water entering rn, = mass flow of water leaving

m1(h2-h 1) = m3Cp(t a-t b )

=

=

Range = t a - t b

3. Dryer

Approach = tb - tWb

Efficiency of Cooling Tower

=

=

Actual Range Theoretical Range

t a - t b

t a - twb

Make-up Water Requirement By mass balance: m1 W1 + rn, = m1W2 + rn,

Hygroscopic materials the moisture content.

- substances which are particularly variable in

Bone-dry weight (Bdw) - final constant weight reached by a hygroscopic substance after being dried out. Moisture content =

Weigth of moisture Gross Weight

F -168

Formulas and Principles - AIR CONDITIONING

Gross Weight

=

Formulas and Principles - AIR CONDITIONING

Bone-dry weight + weight of moisture

@]

F ·169

m,

Outside Air

rn, (Ventilation) Recirculated Air

Humid Air #

3

Fresh Air

m, kg/s

1

..

4

Drying Chamber

2

"11

-

IDs ~ m"

..-

0

Conditioned Space

......

"4 Wet Fced

Heated Air

.....-- m r

8 ms I

f Replacec Air

~

Bdw4

f

Conditioner

I

0

Supply Air

1--.

QL

r1l

IDs

g/s

ms'*::/'5

-'-

- Qs

Dried Product

Bdw,

"4I

1111

l.

1~~

Isothermal Dryertbest drier) Adiabatic Dryer

"..

~

I

I

Non-adiabatic Dryer(actual drier)

Process (4 -1) - Cooling and dehumidifying

.'''t." Moisture removed from materials = Moisture absorbed by air = ma (W 3 - W z) kg/s = m4 - ms kg/s

.....

4

Bone dry weight of wet feed Bdw, Heat supplied in heater Efficiency of dryer

==

=

Os = Sensible Heat Load

msCp(tz - t-) kw

=

where:

= bone dry weight of dried product = Bdw, ma(h z - h 1)

kw

OL

Heat absorbed by materials Heat Supplied

ms(W z-W 1)h v

kw

hv = 2442

kJ/kg (average) + OL

= Total Heat Load = Os = ms(hz - h kw 1)

Air Conditioning Calculations

SHR

= Sensible Heat Ratio (or Factor)

=

Air Conditioning Equipment:

1. Cooling and dehumidifying coils of a refrigerating system 2. Water chiller 3. Spray Equipment

°C

= Latent Heat Load

=

where:

Or

Cp = 1.0 kJ/kg_oC

t1 , tz = dry bulb temperatures,

Qs Qs +QL

If recirculated air and outside air are mixed before entering conditioner: m Oh3 + (ms-mo)h z

= msh 4

Air Conditioner Capacity

= ms(h

4

-

h1 )

kw

F ·170

Formulas and Principles - AIR CONDITIONING

Formulas and Principles - AIR CONDITIONING h = Cp t + W hg 1.0(34) + 0.022(2563.6) 90.4 kJ/kg

If recirculated air and outside air separately enter the conditioner: Air conditioner Capacity Ventilation Load

= mo(h 3 -

= mo(h 3-h1) h1)

= =

+ (ms-mo)(h 2-h1 ) kw

3. A mechanical draft dry cooling tower cools the cooling water from 600C to

kw

25°C at the rate of some 149.4 giga grams per hour. Atmospheric air enters the tower at 20°C and leaves at 35°C. The fan is driven by a 7460 kw motor. What is the mass flow rate of the air into the cooling tower in kg per second? (Apr 96)

SAMPLE PROBLEMS:

A. 105,628 B. 541,752

1. A room being air conditioned is being held at 25°C dry bulb and 50% "'Ill

Mill

t.

• •It''11

3/s

relative humidity. A flow rate of 5 m of supply air at 15°C dry bulb and

80% relative humidity is being delivered to the room to maintain that

steady condition, What is the sensible heat absorbed from the room air in kw? (Oct 96) A. 508 C.40.5 B. 60.8 D. 70.9

Solution: 9

I

l

=

mw

149.4x10 1000(3600)

Heat loss by water

(mCp~t)water

=

mRT

PV 100(5) = m(0.287)(15 +273)

m 6.049 kg/s

rna

=

sensible heat

= mCp(tTt 1)

6.049(1.003)(25-15) = 60.8 kw

= =

= Heat gain by air

= (mCpM)air

= 403,023

kg Is

4. 3287 kg of moisture per hour is being removed from a material by a drier

2. What is the enthalpy of the air-vapor mixture at 65% relative humidity and 34°C when the barometric pressure is 101.3 kPa. Given: P Sot at 34°C 5.318kPa hg at 34°C 2563.6 kJ/kg C. 95.5 kJ/kg A. 90.4 kJ/kg B. 86.7 kJ/kg D. 87.3 kJ/kg

= 41,500 kg/s

41,500(4.187)(60-25) = m a(1.006)(35-20)

=

=

.....

C. 254,168

D. 413,919

Solution:

Qs

'f

and the air leaving it has a humidity ratio of 0.02343 kg moisture per kg of dry air. The outside air is initially at 15°C dry bulb and has a relative humidity of 50%. The air is heated to a temperature of 69.1 °C by steam coils and between the heater and the drier air inlet a drop of 9.1 °C occurs in the air temperature. How much steam is required in kg/s if the steam supplied is at 135 kPa and 0.98 quality? (Oct 96) A. 1.55 C. 1.26 B. 1.02 D. 1.66

o{)

Solution:

Solution:

Pv

= RH

Steaam(135 kPa) 0.98 quality

P SDt

X

= 0.65

x 5.318

W = 0.622

= 0.022

~ P-Py

kg/kg

F·171

m,

= 3.4567 kPa 3.4567 = 0.622 101.3-3.4567

Outside Air I

is'c db

o

(!]:>s 1= m.

I

I

I hs HeatedAir

Drying Chamber

'~====::==r~~ ~69.10C 60°C

SO%RH

hr

Humid Air

w, ~ 0.02343 kglkg

@ Dried Product

o

Wet Feed

Formulas and Principles - AIR CONDITIONING

F -172

F -173

Formulas and Principles - AIR CONDITIONING

b. pound of final product c.

pound of bone-dry material

Solution:

a. Consider 1 Ib of original product or wet feed

----t W 1

3

~2 --l--w 1 =W 2

(The values of the air and steam properties should have been given in the problem)

~"1I1

l~

.'.""1 .....

From psychrometric Chart, at 15°C db and 50% RH: W 1 = W z = 0.0054 kg/kg h 1 = 28.5 kJ/kg dry air From steam table, at 69.1°C: hg = 2625.3 kJ/kg

where: hz = Cp t + W h g = 1.0(69.1) + 0.0054(2625.3) = 83.3 kJ/kg From steam table, at 135 kPa:

hfg :: 2235.0 hg :: 2688.8

hf = 453.83 fg where: h s = h f + X h = 453.83 + 0.98(2235) = 2644.1 kJ/kg Solving for the mass flow rate of air, rna: Moisture removed from materials :: Moisture absorbed by air :: ma(W 3-W Z) 3287 :: m a(0.02343 - 0.0054) rn, = 182,307 kg/hr = 50.64 kg/s By heat balance in the heater: heat absorbed by air :: heat rejected by steam

ma(hz-h,) = ms(hs-hf)

50.64(83.3 - 28.5) :: ms(2644.1 - 453.83)

ms = 1.267 kg/s

5. Copra enters a dryer containing 60% water and 40% of solids and leaves with 5% water and 95% solids. Find the weight of water removed based on each: a. pound of original product

Bone-dry weight(Bdw) :: Bdw

=

Bdw,

= Bdwz

GW

x (1 - MC)

Gross weight x (1 - Moisture Content) ::

GW

x (Solid Part)

= mz(0.95)

m z :: 0.421 Ib (gross weight of drie9 product)

(1) 0.40

Weight of water removed = rn , - mz

:: 1 - 0.421 = 0.579 Ib of water removed

b. Weight of water removed per Ib of final product Bdw1 = Bdw z m1(OAO) = (1)0.95 m, :: 2.375 Ib (gross weight of original product) Weight of water removed :: m 1 - m2

= 2.375 - 1 = 1.375 Ib of water removed

c. Weight of water removed per Ib of bone-dry material

=

Bdw, = Bdwz 1 Ib m1(OAO) 1 rn, :: 2.5 Ib (gross weight of original product)

=

Bdw, = Bdw z 1 = m2(0.95) mz = 1.053 Ib (gross weight of final product) Weight of water removed :: rn, - m z

= 2.5 - 1.053 = 1.447 Ib of water removed

,.

F .174

Formulas and Principles - FIRE PROTECTION SYSTEMS

INDUSTRIAL PROCESSES Flow Diagram or Flow Sheet _ a diagram showing the flow of the materials through the various equipment or processes involved in the manufacture of a certain product. a. Process flow diagram - indicates only the processes involved, drawn in block diagrams b. Equipment flow diagram - shows the various equipment used in the processing c. Equipment-process flow diagram - combines the equipment and processes in the diagram. Some Industries in the Philippinos:

•"1

l.., . '••'111

.....

1. Sugar Manufacturing (Raw and Refined sugar) 2. Cement Manufacture (Wet and Dry Process) 3. Rice and Corn Milling 4. Pulp and Paper Manufacture 5. Plywood Manufacture 6. Glass Manufacture 7. Beer Manufacture 8. Copper Milling 9. Steel Manufacture 10. Coconut oil milling 11. Fertilizer Manufacture 12. Flour Milling

INDUSTRIAL EQUIPMENT A. DRYERS Three methods of drying system based on heat transfer: 1. Direct or convection drying 2. Indirect drying 3. Infrared or radiant heat drying

Formulas and Principles - FIRE PROTECTION SYSTEMS

F - 175

Types of dryers, based on heat source: 1. steam heated 2. oil fired, coal fired 3. electric Classification of dryers: 1. Rotary Dryer - most commonly used dryer which consists of a rotating cylinder inside which the materials flow while getting in contact with the hot gases; the cylinder is tilted at a slight angle and fitted with lifting flights; used for copra, sand. wood chips. 2. Tower Dryer - consists of a vertical shaft in which the wet feed is .introduced at the top and falls downward over baffles while coming in contact with the hot air which rises and exhausts at the top; used for palay, wheat, grains . 3. Hearth Dryer - type of dryer in which the material to be dried is supported on a floor through which the hot gases pass; used for copra, coal, enamel wares. 4. Centrifugal Dryer - consists of centrifuge revolvinq at high speeds causing the separation, by centrifugal force, of the water from the material; used for dryir'\::l fertilizer, salt, sugar. 5. Tray Dryer - consists of trays, carrying the materials to be dried, placed in compartment or moving conveyor; used for ipil-ipil leaves, grains. 6. Infrared Ray Dryer - consists of infrared lamps in which the rays are directed to the articles to be dried; used for drying painted articles like cars. B. Evaporators Evaporators are used either to remove the water from a liquid substance, like sugar juice, or to produce distilled water by condensing the steam. Three principal types of evaporator according to construction:

Types of dryers, based on movement of materials: 1. Continuous dryer 2. Batch dryer

1. Horizontal tube evaporator - consists of vertical horizontal cylindrical body; two rectangular steam chests in the lower section contain tube sheets; primarily suitable for non-viscous liquids that do not deposit salt or scale during evaporation.

I'"

-­

F - 176

Formulas and Principles - INDUSTRIAL PROCESSES

INDUSTRIAL PROCESSES Flow Diagram or Flow Sheet _ a diagram showing the flow of the materials through the various equipment or processes involved in the manufacture of a certain product a. Process flow diagram - indicates only the processes involved, drawn in block diagrams b. Equipment flow diagram - shows the various equipment used in the processing c. Equipment-process flow diagram - combines the equipment and processes in the diagram. Some Industries in the Phllippines:

....1\

-..,

1. Sugar Manufacturing (Raw and Refined sugar) 2. Cement Manufacture (Wet and Dry Process) 3. Rice and Corn Milling 4. Pulp and Paper Manufacture 5. Plywood Manufacture 6. Glass Manufacture 7. Beer Manufacture 8. Copper Milling 9. Steel Manufacture 10. Coconut oil milling 11. Fertilizer Manufacture 12. Flour Milling

INDUSTRIAL EQUIPMENT A. DRYERS Three methods of drying system based on heat transfer: 1. Direct or convection drying 2. Indirect drying 3. Infrared or radiant heat drying

Formulas and Principles -INDUSTRIAL PROCESSES

F - 177

Types of dryers, based on heat source: 1. steam heated 2. oil fired, coal fired 3. electric Classification of dryers: 1. Rotary Dryer - most commonly used dryer which consists of a rotating cylinder inside which the materials flow while getting in contact with the hot gases; the cylinder is tilted at a slight angle and fitted with lifting flights; used for copra, sand, wood chips. 2. Tower Dryer - consists of a vertical shaft in which the wet feed is introduced at the top and falls downward over baffles while coming in contact with the hot air which rises and exhausts at the top; used for palay, wheat, grains, 3. Hearth Dryer - type of dryer in which the material to be dried is supported on a floor through which the hot gases pass; used for copra, coal, enamel wares, consists of centrifuge revolving at high 4, Centrifugal Dryer speeds causing the separation, by centrifugal force, of the water from the material; used for dryiny fertilizer, salt, sugar. 5, Tray Dryer - consists of trays, carrying the materials to be dried, placed in compartment or moving conveyor; used for ipil-ipil leaves, grains, 6. Infrared Ray Dryer - consists of infrared lamps in which the rays are directed to the articles to be dried; used for drying painted articles like cars. B. Evaporators Evaporators are used either to remove the water from a liquid substance, like sugar juice, or to produce distilled water by condensing the steam. ' Three principal types of evaporator according to construction:

Types of dryers, based on movement of materials: 1. Continuous dryer 2. Batch dryer

1. Horizontal tube evaporator - consists of vertical horizontal cylindrical body; two rectangular steam chests in the lower section contain tube sheets; primarily suitable for non-viscous liquids that do not deposit salt or scale during evaporation

F -178

Formulas and Principles-INDUSTRIAL PROCESSES Formulas and Principles - INDUSTRIAL PROCESSES 2. Standard vertical tube evaporator - consists of vertical cylindrical shell with flat, dished or conical bottom; most widely

used type; can be used for liquids that deposit salt or scale

during evaporation. 3. Long-tube, natural-circulation vertical evaporator - consists of long tubes so that the liquor passes through the evaporator

but once; used with non-salting or non-scaling liquids; can be

used with high viscosities; one of the cheapest types.

1'1 1111

_lilt

...m

Multiple Effect Evaporator - series of evaporators so connected

that the vapor from one body is used as the heating steam in the

next. Types of Multiple Effect (multi-stage) Evaporator: 1. Parallel feed 2. Backward feed 3. Forward feed 4. Mixed feed

C. Conveyors

t'MII

~".Il

.r::

11 "",'1 .11

.....,

Common types of conveyors and the materials suitable for each:

1. 2. 3. 4. 5. 6.

Flat belt conveyor - coal, copra, packages Troughed belt conveyor - coal, copra, ores

Screw conveyor - pulverized coal, flour, grains

Flight conveyor - packages, boxes, copra Bucket conveyor - copra, coal, grains Pneumatic conveyor - grains, linen, match sticks

D. Cranes Common types of cranes and their applications:

1. 2. 3. 4. 5.

Overhead travelling bridge crane - maintenance shops, ice plant Derrick crane - loading in ships, handling materials in piers Jib crane - construction work, maintenance shops Gantry crane - mining, piers Pillar crane - maintenance shops, piers

F -179

E. Foundry Equipment Melting furnaces used in foundry:

1. Crucible furnace - suitable for non-ferrous metals; the metal is melted inside a crucible heated by an oil-fired burner. 2. Cupola furnace - for melting iron; the heat comes from coke burning inside the cupola itself. 3.

Induction furnace - for ferrous and non-ferrous metals, uses electric current for melting the scraps or ingots.

Methods of casting used in foundry:

1. sand casting 2. 3. 4. 5.

pressure die casting metal mold casting centrifugal casting plaster mold casting

Formulas and Principles - FIRE PROTECTION SYSTEMS

F -180

FIRE PROTECTION SYSTEMS Scope The provision of the Fire Protection shall apply to and govern the

"'1111

'UIII

F - 181

Formulas and Principles - FIRE PROTECTION SYSTEMS

following: a. . All private or public buildings, facilities, structures and their premises, constructed, existing and proposed. b. Storage, handling or use of combustible, flammable, toxic, explosives and other hazardous materials. c. Applications of Fire Safety construction, automatic fire suppressions and fire protective equipment or systems. General Safety Requirements The owner of any building, structure, facility shall install, provide" incorporate, adopt and maintain under operable and usable conditions the automatic fire protection devices equipment, fire safety construction, and'

are metal products such as electrical coil, electrical devices. Dry cell batteries,

stoves, metal cabinets, washers, dryers, including foods in non-combustible

containers.

Class II.

is defined as class I products in slatted wooden crates, solid wooden boxes, or equivalent combustible packaging materials on wood pallets. Class III. - is defined as wood, paper, natural fiber cloth, plastic products on wood pallets. products may contain a limited amount of plastics. Examples of class III are wood dressers with plastic drawer glides, handles, and trim. Class IV - is defined as class I, II, III products containing an appreciable amount of plastics in paper board cartons on wood pallets. Examples of class IV products are small appliances, typewriters, and cameras with plastic parts. "Sprinkler System Design Curves for Solid pile, Palletized and Bin box over 12 ft (3.7 m), and shelf storage 12 ft (3.7 m) to 15 ft (4.6 m) high."

warning system. Purpose The purpose of these standard is to provide a reasonable degree of: protection for life and property from fire through the installation of the appropriate type of fire protection for the different buildings, structures or i facilities. Application and Scope This standard applies to storage. 6.40 m or less in height, of commodities which with their packaging and storage aids would classify as ordinary combustibles. This standard also applies to storage of commodities which with their packaging and storage aids would classify as non­ combustibles regardless of storage height. This standard does not cover unpacked bulk storage such as grain, coal or similar commodities. ' Rack storage of Materials over 12 ft (3.66 m) in height in racks, and storage up to and including 25 feet (7.62 m) in height and storage over 25 feet

Definitions Available height for storage - the maximum height at which commodities, packaging or storage can be stored above the floor and still maintain adequate clearance from structural members and the required clearance below sprinklers. Ordinary combustibles- this term designates commodities, packaging or storage aids which have heats of combustion kJ per kg similar to wood, cloth or paper and which produce fires that may normally be extinguished by the quenching and cooling effect of water. Exposure - the exterior presence of combustibles which, if ignited, could cause damage to the storage building or its contents.

(7.62 m) in height. Water density for fire protection for these particular hazard varies' , from 0.24 gpm/sq. ft or (9.779 Ipm/sq. m) to 0.68 gpm/sq. ft (27.7 Ipm/sq. m).

Fire Wall - a wall designed to prevent the spread of fire having a fire resistance rating of not less than four hours and having sufficient structural stability under fire conditions to allow collapse of construction on either side without collapse of wall.

Commodity Classification:

Horizontal Channel - any uninterrupted space in excess of 1524 m in length between horizontal layers of stored commodities.

Class I.

_ is defined as essential non-combustible product on wood pallets, or in ordinary corrugated cartons with or without single thickness dividers, or in ordinary paper wrappings, all on wood pallets. Examples of class I products

F -182

Formulas and Principles - FIRE PROTECTION SYSTEMS

Formulas and Principles - FIRE PROTECTION SYSTEMS

Non-combustibles this term designates commodities, packaging or storage aids which will not ignite, burn or liberate flammable gases when heated to a temperature of 7490 for five minutes.

Sprinkler System - for fire protection purpose, is an integrated system of one or more water supplies for fire use, underground and overhead piping designed in accordance with fire protection engineering standards.

Packaging container.

this term designates any commodity wrapping, cushioning or

II

=

r1.,111

this term designates commodity storage devices such as Storage Aids sheaves, pallets, dunnage, decks. Platforms, trays, bins, separators and skids. Warehouse - any building or area within a building used principally for the storage of commodities. Extra combustible - materials, which, either by themselves or in combination with their packaging, are highly susceptible to ignition and will contribute to the intensity and rapid spread of fire.

l.." ~t"II'

Class A Fire - fire involving ordinary combustible materials such as wood, . cloth, paper, paper, rubber and plastics.

" r:: I •

.,,1111'

.

III

.....

~

Non-combustible - materials and their packaging which will neither ignite . nor support combustion. 1

Class B Fire - fire in flammable liquids and gases. Class C Fire - fire involving energized electrical equipment. Class 0 fire fire involving combustible metals, such as magnesium, sodium, potassium, titarsum and other similar metals. Dry stand pipe - a type of stand pipe system in which the pipes are not normally filled with water. Water is introduced into the system thru Fire Service connections when needed. Fire Service - an organization or a component of the Philippine National Police Fire Department personnel in-charge with the mission of fire prevention, fire protection. Means of egress - a continuous and unobstructed route of exit from any point in a building, structure or facility to a safe public way. Occupant load - the maximum number of persons that may be allowed to occupy a particular bUilding, structure or facility or point thereof.

-

Fire Code of the Philippines, which is Presidential

Halon 1301 - is a colorless, odorless, electrically non-conductive gas that is an effective medium for extinguishing fires. The chemical properties of the gas is bromotroflourromethane (CBrF3).

Moderate combustible - materials or their packaging, either of which will contribute fuel to fire.

" ,..,11

local Fire Code Decree No. 1185.

F -183

--

,

F -185

PRACTICE PROBLEMS PRACTICE PROBLEMS

F -184

7.

PRACTICE PROBLEMS

=

THERMODYNAMICS

A. B.

Thirty pounds of ice at 32°F is placed in 100 Ib of water at 100 oF. (The latent heat of ice may be taken as 144 Btu per lb.) If no heat is lost or added to the mixture, the

temperature when equilitJrium is reached is: C.50oF A. 51 oF

1.

·B. 2.

49°F

8.

D.52oF

B. C. D.

VH = 2,344 cu. ft and Vc = 7,031 cu. ft VH = 7,031 cu. ft and vc = 2,344 cu. ft VH = 2,443 cu. ft and Vc = 7,013 cu. ft

28.51bs

C. 32.4 Ibs

29.31bs

D.30.5Ibs

A. B.

D. 11.45 short tons per hour

C. 11.2 lb steam per lb coal D. 14.51b steam per lb coal

21.1 kw

C. 16.1 kw

14.2kw

D.11.85kw

10. Steam

is admitted to the cylinder of an engine in such manner that the average pressure is 120 psi. The diameter of the piston is 10 in and the length of stroke is 12 in. How much work can be done during one revolution, assuming that the steam is admitted to each side of the piston in succession?

~

4.

10.75 short tons per hour

A single cylinder, double acting, reciprocating steam engine has a 6 in bore, and 8 in stroke, and a piston rod diameter of 1 1/4 in. The average mean effective pressure found from the indicator cards is 62 psi for each end of the cylinder. The engine operates at 300 rpm and with a mechanical efficiency of 83%. If the engine is directly coupled to a generator having an efficiency of 92%, find the generator output in kilowatts.

A partly filled barrel contains 300 Ibs of water and 100 lbs of ice at 32° F. How many

pounds of steam at 212° F must be run into the barrel to bring its content up to 80°F?

A. B.

C. 12.05 short tons per hour

A. 12.1 Ib steam per lb coal B. 10.21b steam per lb coal

9.

=

9.84 short tons per hour

If coal having a heat of combustion of 14,000 Btu/lb is used in a heating plant of 50% efficiency, how many pounds of steam of 50% quality and 2120 F temperature can be made per pound of this coal from water whose initial temperature is 70° F? Note: at 70° F,.hf = 38 Btu/lb and at 2120 F, hf = 180 Btu/lb, hfg = 970 Btu/lb.

A small swimming pool 25 by 75 ft is to be filled with water at a temperature of 70° F to a depth of 5 ft. Hot water at 160 oF and cold water at 40 oF are available. How many cubic feet of each (neglecting the:hermal capacity of the tank itself) should be used in

filling the tank? A. VH = 2,433 cu. ft and Vc = 7,103 cu. ft

3.

A steam boiler on a test generates 885,000 lb of steam in a 4-hour period. The average steam pressure is 400 psia, the average steam temperature is 700°F, and the average temperature of the feedwater supplied to the boiler is 280° F. If the boiler efficiency for the period is 82.5 per cent, and if the coal has a heating value of 13,850 Btu per Ib as fired, find the average amount of coal burned in short tons per hour. Note: at 400 psia and 700 ° F, h 1362.7 Btu/lb and at 2800 F, hf 249.1 Btu/lb.

Air is compressed in a diesel engine from an initial pressure of 13 psia and a ,I temperature of 120oF to one-twelfth of its initial volume. Calculate the final temperature and pressure assuming the compression to be adiabatic.

.

A. B.

CO

18,085 ft-lb

C. 18,805 ft-lb

18,580 ft-lb

D. 18,850 ft-lb

A. P2=124psia;T2 =1010°F

B. C. D. 5.

P2=241psia;T2=1101oF

11. From

P2 = 421 psia; T2 = 1110°F

rpm?

An automobile tire is inflated to 32 psig pressure at 50°F. After being driven, the

temperature rises to 75° F. Assuming that the volume remains constant, the final

B. 6.

A. B.

P2 = 412 psia; T2 = 1011of

gage pressure is: A. 44.3 psig 34.4 psig

P2 = 2101 psia

=2210 psia

C. 117.5 hp

151.7 hp

D. 115.7 hp

volume' of 400 cc of air is measured at a pressure of 740 mm Hg abs and a temperature of 18°C. The volume at 760 mm Hg abs and O°C is:

A. 358 cc B. 366 cc

D. 37.4 psig

D. P2

171.5 hp

12. A

C. 43.4 psig

If 100 cu. ft of atmospheric air (pressure 14.7 psi) at zero Fahrenheit temperature are compressed to a volume of 1 cu. ft temperature 200°F, what will be the pressure of the compressed air in pounds per square inch?

A. P2 = 2110 psia C. P2 = 2011 psia

B.

problem No. 10, what is the horsepower of the engine when it is making 300

13.

C. 362 cc D. 369 cc

What is the temperature of 2 liters of water at 30°C after after 500 cal of heat have been added to it?

A. 25.3°C B. 35.2°C

C.30.25°C D.23.50°C

PRACTICE PROBLEMS

PRACTICE PROBLEMS

F -186

A. B.

A heat engine has its intake and exhaust temperature 157°C and 100°C, respectively.

14.

Its efficiency is:

A. 12.35%

B. 15.

15.25%

C.14.55%

16.

17.

0.65 hr per gal 0.75 hr per gal

A. B.

C. 1 cent

2 cents

D. 5 cents

By means of insulation, the loss in heat through a roof per square foot is reduced from 0.40 to 0.18 Btu per hr for each degree difference between inside and outside temperatures. The area of the roof is 10,000 sq. ft and the average difference between inside and outside temperatures is 35 0 during the heating season of 5000 hr. If the heating value of coal is 13,000 Btu per Ib and the efficiency of the heating plant is 60%, find the value of the coal saved per season at P15.00 per ton.

A. B.

A. B.

D. 0.45 hr per gal

3 cents

P317.00

C. P377.00

P371.00

D. P367.00

50.7 % 51.7 %

D. 17.9 hp

=

A. B. 24.

A. B.

D. 52.7 %

26.

C. 14,800 Btu/lb

16,700 Btu/lb

D. 17,600 Btu/lb

132 boiler hp

C. 123 boiler hp

128 boiler hp

D. 135 boiler hp

A fan whose static efficiency is 40% has a capacity of 60,000 cu. ft per hr at 60 0F and a barometer of 30 in Hg, and gives static pressure of 2 in of water column on full delivery. What size electric motor should be used to drive this fan?

A. B.

piston with an 18 in stroke. The piston rod diameter is 2 in. Indicator cards show a mean effective pressure of 70 psi for both the head end and the crank end. The engine operates at 350 rpm with an efficiency of 92 %. Determine the horsepower

=

18,400 Btu/lb

Calculate the horsepower of a boiler generating 4000 Ib of dry steam per hr, with a factor of evaporation of 1.06. The latent heat of steam at 212° F is 970 Btu per lb.

C. 57.1 %

19. A single cylinder, double acting, reciprocating steam engine has a 12 in diameter

C. 16.7 hp

15.6 hp

test of an oil fired boiler indicated 12.77 Ib of water evaporated per Ib of oil. The boiler pressure was 200 psia, superheat was 87°F, feedwater temperature 93°F, and the boiler and furnace efficiency 82.8%. What was the calorific value of the oil? Note: at 200 psia and 87°F, hs 1251.5 Btu/lb; at 93°F, hf 61 Btu/lb.

The quality of steam that gives up 475 Btu per Ib while condensing to water at a constant pressure of 20 psig is: (Note: at 34.7 psia, hfg = 939.5 Btu/lb)

A. B.

17.6 hp

23. A

25. 18.

D. 2301 hp

centrifugal pump draws water from a pit through a vertical 12 in pipe which extends below the water surface. It discharges into a 6 in horizontal pipe 15 ft above the water surface. While pumping 2 cu. ft per sec, a pressure gage on the discharge pipe reads 24 psi, and a gage on the suction pipe registers 5 psi below atmosphere. Both gages are close to the pump and are separated by the vertical distance of 5 ft. What is the horsepower output of the pump?

C. 0.56 hr per gal

In problem No. 15, what will be the cost at 5 cents a kilowatt-hour?

C. 2310 hp

2130hp

22. A

D.13.25%

A 300 watt water heater is attached to a water faucet. If the water runs at a rate that permits it to be heated from 60 to 120° F, how long will it take to obtain a gallon? Assume that 75% of the electrical energy will be utilized in heating the water.

A. B.

2013 hp

F -187

2 hp

C. 2.5 hp

1.75 hp

D.1 hp

What horsepower is supplied to air moving at 20 ft per min through a 2 by 3 ft duct under a pressure of 3 in water gage?

A. B.

0.0566 hp

C. 0.0665 hp

0.5660 hp

D. 0.0675 hp

output.

A. B.

228.5 hp

C. 225.8 hp

282.5 hp

D. 252.8 hp

27.

A refrigeration plant is rated at 20 ton capacity. How many pounds of air will it cool 90 to 70 0 F at constant pressure?

A. B.

20. A

300 hp engine is given a brake test. The brakes are water cooled. At what rate must water at 80 0 F flow through the brakes if the water must not rise above 180° F?

A. B.

13.5 gal per min

C. 12.3 gal per min

14.2 gal per min

D. 15.3 gal per min

21 .. Water from a reservoir is pumped through a hill through a pipe 3 ft in diameter, and a pressure of 30 psi is maintained at the summit, where the pipe is 300 ft above the reservoir. The quantity pumped is 49.5 cu. ft per sec, and by reason of friction in the pump and pipe there is 10 ft of head lost between the reservoir and summit. What amount of energy must be furnished the water each second by the pump?

50,000 Ib per hr

C. 60,000 Ib per hr

70,000 Ib per hr

D. 40,000 Ib per hr

28. A

refrigeration plant is rated at 20 ton capacity. What is the approximate engine horsepower required to operate the plant? Assume COP;: 4.

A. B.

23.4 hp

C. 24.3 hp

25.3 hp

D. 22.3 hp

29. A boiler installed where

the atmospheric pressure is 752 mm Hg has a pressure of 12 kg per sq. cm. What is the absolute pressure in MPa?

30.

A.

1.772 MPa

B.

1.727 MPa

38.

C. 1.277 MPa 0.1.327 MPa

A throttling calorimeter receives a sample of steam from a steam main in which the pressure is 1 MPa. After throttling, the steam is at 100 kPa and 120°C. What is the quality of steam in the steam main? Note: at 100 kPa and 120°C, h = 2716.6 kJ/kg; at 1 MPa, hf = 762.81 kJ/kg, hfg = 2015.3 kJ/kg.

A. B.

An oil storage tank contains oil with specific gravity of 0.88 and depth of 20 meters. What is the hydrostatic pressure at the bottom of the tank in kg per ern"?

A. 1.67 B. 1.ro

D.1.~

A. B.

C. 1210 kpa

1012kpa

0.1102 kpa

1201 kpa

32. Convert 36°F temperature A. 3°C

B. 32°C

A. B.

C.20°C

D.25°C

41.

5940F

D.625°F

II

outside is ­

42.

3

0.9.946

37. The

radiator of a heating system was filled with dry and saturated steam at 0.15 MPa after which the valves on the radiator were closed. As a result of heat transfer to the room, the pressure drops to 0.10 MPa. What percentage of steam has condensed? Note: at 0.15 MPa, hg 2693.6 kJ/kg; at 0.10 MPa, hf 417.46 kJ/kg, hfg" 2258.0

B. 32.56%

=

0.31.63%

0.27.51 kw

A. B.

0.0.0988

C.35.63%

C. 25.61 kw

B.

29.81 kw

C.4.79 0.4.37

the suction of an air compressor, in which the conditions are 97.9 kPa and 27°C, the air flow rate is 10.3 m 3/min. What is the volume flow rate at free air conditions of 100 kPa and 20°C?

C.0.0666

kJ/kg, hg " 2675.5 kJ/kg.

A. 33.61%

A. 28.511 kw

43. At

10,3 m3 /kg.

=

D. 14.56%

A. 4.97 B. 4.28

C.9.246

0.0766

12.63%

An air compressor delivers air to an air receiver having a volume of 2 m 3 . At the start, the air in the receiver is at atmospheric condition of 25°C and 100 kPa. After 5 minutes, the pressure of the air in the tank is 1500 kPa and the temperature is 60°C. What is the capacity of the compressor in m3/min of free air?

:

0.0566

C.13.16%

=

A boiler feed pump delivers 200,000 kg of water per hour at 10 MPa and 230°C. W hat is the volume rate of flow in m3/sec? Note: at 10 MPa and 230 o C, v = 1.1988 X

A. B.

11.36%

Steam at 5 MPa and 350°C enters a turbine and expands isentropically to 0.01 MPa. If the steam flow rate is 100,000 kg/hr, determine the turbine power? Note: at 5 MPa and 350°C, h 3068.4 kJ/kg; at 0.01 MPa, hf " 191.83 kJ/kg, hfg = 2392.8 kJ/kg.

100C. What is the temperature difference in of? C.495oF

C. 550 rn/sec 0.469 m/sec

at a pressure of 10 MPa and temperature of 230°C is throttled to a pressure of 1 MPa in an adiabatic process. What is the quality after throttling? Note: at 10 MPa and 230°C, h" 991.7 kJ/kg; at 1 MPa, hf =762.81 kJ/kg, hfg =2015.3 kJ/kg.

differen)e to ·C.

5490F

499 m/sec 459 m/sec .

40. Water

33. At what temperature are the two temperature scales o C and o F equal? A. -400 C. -30° B. -250 D. -35° 34. The temperature inside a furnace is 320°C and the temperature of the

36.

0.94.85%

at 2.5 MPa and 320°C expands through a nozzle to 1.5 MPa at the rate of 10,000 kg/hr. If the process occurs isentropically and the initial velocity is low, calculate the velocity leaving the nozzle.

the water is 2 meters deep?

35. Convert 60 Ib/tt3 to kN/m A. 9.426 B. 9.642

C. 95.96%

97.45%

39. Steam

pressure tank for a water pump system contains 2/3 water by volume when the

pressure is 10 kg/cm2 gage. What is the absolute pressure at the bottom of the tank if

A. B.

96.95%

C.1.56

31. A

A. B.

F -189

PRACTICE PROBLEMS

PRACTICE PROBLEMS

F ·188

44.

9.848 m

3/min

C. 8.984 m 3/min

9.484 m

3/min

0.7.854 m3/min

An iron block weighs 5 Newtons and has a volume of 200 cubic centimeters. What is the density of the block?

A.

800 kg/m 3

C. 1255 kg/m

3

B.

3

0.2550 kg/m

3

988 kg/m

F -190

45.

PRACTICE PROBLEMS

PRACTICE PROBLEMS

If the density of a gas is 0.003 slugs per cubic foot, what is the specific weight of the gas?

A.

9.04 N/m 3

B.

15.2 N/m

C. 76.3 N/m

3

54.

D. 98.2 N/m 3

55.

specific gravity Of mercury relative to water is 13.55. What is the specific weight of mercury? (The specific weight of water is 62.4 Ib per cubic foot.) 82.2 kN/m

3

102.3 kN/m 3

A. B.

C. 132.9 kN/m 3

D. 150.9 kN/m 3

47. If the specific weight of a liquid is 58.5 Ibf per cubic foot, what is the specific volume of

56.

48.

3/g

C. 0.9504 cm

3/g

0.6748 cm3;g

D. 1.0675 cm

3/g

0.5321 cm

Which of the following are not units of pressure?

A. B.

Pa

C. kg/m-s

57.

2

N/m 2

D. kg/m

2

50.

C. 63.2 kPa

25.8 kPa

D. 89.7 kPa

58.

9810 dyne/crn'' 9810N/m 2

59.

51. Water

is flowing in a pipe with a radius of 10 in at a velocity of 5 rn/s, At the end temperature in the pipe, the density and viscosity of the water are as follows: 3 p 997.9 kg/m fl 1.131 Pa-s What is the Reynold's number for this situation?

A. B.

52.

C.1140

88.2

D.2241

What is the flow rate through a pipe.4 inches in diameter carrying water at a velocity of 11 ft/sec?

A. B. 53.

44.1

3/s

590 cm3/s

C. 993 cm

726 cm3/s

D. 27,200 cm

A. B.

60.

61.

2/s2

N-m

C. kg_m

B.

erg

D. dyne

C. 369 W/m 2 D. 429 W/m 2

182 J 125 kJ

C. 655 kJ

D. 655 MJ

10.0

oC

2110C

C.44.1°C D. 88.2 °C

0.18 kJ/K

C. 0.34 kJ/K

0.25 kJ/K

D. 0.57 kJ/K

If a 1/3 horsepower pump runs for 20 minutes, what is the energy used?

A.

0.06 ergs

C. 0.30 MJ

B.

0.25 kW

D. 0 11 kW-h

A machine is capable of accelerating a 1 kg mass at 1 m/s" for 1 meter distance. The machine runs at 60 rpm. What is the power output of the machine?

A. B.

3/s

Which of the following is not a unit of work?

A.

112 W/m 2 285 W/m 2

In a constant temperature, closed system process, 100 Btu of heat is transferred to the working fluid at 100°F. What is the change in entropy of the working fluid?

= =

,11

C. 525 x 10. 5 m D. 765 x 10-5 m

A.

A. B.

C. 0.1 bar D.0.1atm

2.12 X 10'5 m

Air has a specific heat of 1 kJ/kg-K If 2 Btu of energy is added to 100 g of air, what is the change in air temperature?

What pressure is a column of water 100 centimeters high equivalent to?

A. B.

D. a rate of change of energy

3.22 x 10'5 m

B.

A. B.

cylinder stands vertically on one end, what pressure does the cylinder exert on the floor? 14.1 kPa

a newton-meter

A house has brick walls 15 millimeters thick. On a cold winter day. the temperatures of the inner and outer surfaces of the walls are measured and found to be 200C and _ 2 12'C, respectively. If there is 120 m of exterior wall space, and the thermal conductivity of brick is 0.711 J/m-s-oC, how much heat is lost through the walls per hour?

49. A cylinder weighs 150 Ibf. Its cross-sectional area is 40 square inches. When the

A, B.

C. a kg-m/s2

Calculate the energy transfer rate across a 6 in wall of firebrick with a temperature difference across the wall of 50 cC. The thermal conductivity of firebrick is 65 Btu/hr­ ft- of at the temperature of interest.

the liquid?

A. B.

a unit of power

A copper bar is 90 centimeters long at 86° F. What is the increase in its length when the bar is heated to 95 ° F? The linear expansion coefficient for copper, 0:, is 1.7 X 10.5 1/°C.

46. The

A. B.

Which of the following is the definition of a joule?

A. B.

3

F - 191

62. A

1 erg 1 cal

C. 1 J D. 1 W

power of 6 kW is supplied to the motor of the crane. The motor has an efficiency of 90%. With what constant speed does the crane lift an 800 Ibf weight?

A. B. 63.

PRACTICE PROBLEMS

PRACTICE PROBLEMS

F -192 0.09 m/s

C. 0.98 m/s

0.32 m/s

D. 1.52 rn/s

71. Which of the following A. h =u + p/T B. h = u + pV

A heat exchanger with an inlet enthalpy of 100 Btu/lb and outlet enthalpy of 200 Btu/lb. The mass flowing the system is 5 Ib/sec, what is the energy requirement for the

64.

500 kW

C. 561 kW

528 kW

D. 601 kW

An engine has an efficiency of 26%. It uses 2 gallons of gasoline per hour. Gasoline has a heating value of 20,500 Btu/lbm and a specific gravity of 0.8. What is the power

A. B.

0.33 kW

C 26.0 kW

20.8 kW

D.41.7kW

73.

of T: = 25°C and a pressure of P1 = U.101 MPa, are in a 10 cm diameter cylinder with a piston at one end. The piston is depressed, so that the cylinder is shortened by 10 centimeters. The temperature increase by 2°C. What is the change in pressure?

1111111

L.

A. B.

66.

. . . . . .1. .

.....

l

D. 0.327 MPa

output of this enigne?

A. B.

......11.

.........

C. 0251 MPa

0.167 MPA

An 8 cylinder engine has the following specifications at optimum speed: p = 283 kPa,

L = 14 ern, D = 12 em, N = 1500 strokes per minute. What is the average power

......1.11

~",I"

0.156 MPa

67.

89.5 N/s

3 C. 89.5 x 10 J-m/s

895 kW

D. 89.5 kJ

550 W

C. 30 MW

120 kW

D. 750 MW

68. Which of the following properties A. temperature B. mass

Internal energy is negative.

C. Specific volume is zero.

Entropy is non-zero

D. Vapor pressure is zero.

Mollier diagram plotted? •

C. h-s D. s-u

How is the quality, x, of a liquid-vapor mixture defined?

A. B. C. D.

the fraction of the total volume that is saturated vapor the fraction of the total volume that is saturated liquid the fraction of the total mass that is saturated vapor the fraction of the total mass that is saturated liquid

of vaporization? hg = enthalpy of the saturated vapor hf = enthalpy of the saturated liquid

A.

hg

C. hg - hf

B.

hf

D. hg

2

-

hr

78. The first law of thermodynamics is based on which of the following principles? A. conservation of mass C. action-reaction B. the enthalpy-entropy relationship D. conservation of energy 79. 0R,

D. 14.2 ft3/1bm

Which of the following is true for water at a referenre temperature where enthalpy is zero?

75. On what plane is the A. p-V B. p-T

are intensive properties? C. temperature and pressure D. temperature, pressure and

If air is at a pressure, p, of 3200 Ibf/ft2 , and at a temperature, T, of 800 what is the specific volume, v? (R = 53.3 ft-lbf/lbm-oR, and air can be modeled as an ideal gas) A. 9.8 fe/lbm C. 13.3 ft3/1bm 11.2 fe/lbm

D. 6900 Ibf-ftllbm

77. What is the expression for the heat

69. Which of the following thermodynamic relations is incorrect? A. TdS = dU + pdV C. U = Q - W B. TdS=dH-Vdp D.H=U-PV

B.

C. 5400 Ibf-ftllbm

3300 Ibf-ftil bm

Ibm of air are contained at 25 psia and 100°F. Given that Rair = 53.35 ft-Ibf/lbm­ of, what is the volume of the container? 3 A. 10.7ft3 C.15ft B. 14.7 ft3 D. 24.9 ft3

76.

composition

70.

2500 Ibf-ftil bm

B.

74. 3.0

If the average energy in a nuclear reaction is 200 MeV/fission, what is power output of 19 a reactor if there are 2.34 x 10 fissions per second?

A. B.

A.

A. B.

65. Two liters of an ideal gas, at a temperature

[

C. h = u + pN D. h = pV + T

at 1000 Ibf/ft 2 pressure and 300° R has a specific volume of 6.5 ft3/1bm and a specific enthalpy of 9800 Ibf-ftllbm. Find the internal energy per pound mass of steam.

output of the engine?

11 111111

relations defi nes defines enthalpy?

72. Steam

heating coil?

A. B.

F -193

What is the value of the work done for a closed, reversible, isometric system?

A. B.

zero

C. negative

positive

D. positive or negative

.. F - 195

PRACTICE PROBLEMS PRACTICE PROBLEMS

F -194

89. Find the change in internal energy of 5 Ibm of oxygen gas when the temperature changes from 100 oF to 120°F. Cv = 0.157 Btu/Ibm-oR.

80.

A.

14.7 Btu

C. 16.8 Btu

B. 15.7 Btu

D. 147 Btu

81. Water (specific heat, Cv = 4.2 kJ/kg_oK) is being

A.

heated by a 1500 W heater.

the rate of change in temperature of 1 kg of the water?

A. B.

0.043 Kls

C. 0.357 Kls

0.179 Kls

D. 1.50 Kls

=

82. One

kilogram .of water (Cv 4.2 kJ/kg-K) is heated by 300 Btu of energy.

change in temperature, in K?

A. 17.9.K C. 73.8 K B. 71.4K

83.

Gas is enclosed in a cylinder with a weighted piston as the top boundary. The gas I~, 3 heated and expands from a volume of 0.04 m to 010 m The pressure varies such that pV = constant, and the initial pressure is 200 kPa. Calculate the work done by the system.

B. adiabatic: heat transfer is not zero; isentropic: heat transfer is zero

C. D.

What is the

adiabatic: reversible; isentropic: not reversible both: heat transfer is zero; isentropic: reversible

91. What is true

A. B. 92.

C. -68.47 Btu/Ibm D. 63.78 Btu/Ibm

What is the resulting pressure , when one pound of air at 15 psia and 200° F is heated

n>0

C. n ---)

n<0

D. n

»

,yo

0

In an isentropic compression, p, " 100 psia, P2 = 200 psia, and V 1 = 10 in 1.4. Find V 2. 3.509 in

3

C. 5.00 in

B. 4.500 in

3

D. 6.095 in

A. 84.

about the polytropic exponent, n, for a perfect gas undergoing an isobaric

process?

=

B. -72.68 Btu/Ibm

D. 12.0 kJ

90. How does an adiabatic process compare to an isentropic process? A. adiabatic: heat transfer is zero; isentropic: heat transfer is not zero

D. 75.4 K

-74.49 Btu/Ibm

C. 9.59 kJ

What is

Determine the change in enthalpy per Ibm of nitrogen gas as its temperature changes from 500°F to 200 oF. (Cp 0.2483 Btu/lbrn-vft)

A.

6.80 kJ

B. 7.33 kJ

'

3

,

and y =

3 3

at constant volume to 800° F?

A.

15 psia

B. 28.6 psia

85.

C. 36.4 psla

93.

D. 52.1 psia

In an adiabatic, isentropic process, P1 T 2, using y 1.4. A. 576 0R

=

What horsepower is required to isothermally compress 800 fe of air per minute from

B. 590

0R

= 200 psi, P2 = 300 psi, and

T , = 700°R.

Find

G.6800k D.786°R

14.7 psia to 120 psia?

86.

A.

28 hp

C. 256 hp

B.

108hp

D. 13,900 hp

Helium (R = 0.4968 Btu/Ibm-oR) is compressed isothermally from 14.7 psia and 68 The compression ratio is 4. Calculate the work done by the gas.

A.

-1454 Btullbm

B. -364 Btullbm

87.

undergoes an isentropic compression from 14.7 psia to 180.6 psia. If the initial temperature is 68 ° F and the final temperature is 621.5° F, calculate the work done by the gas.

oF>

A.

.

8 kJ

B.10kJ

C. 0 Btu/Ibm D. 94.8 Btu/Ibm

C. -187 Btu/Ibm D. 46.7 Btu/Ibm

C. 12 kJ

D.14kJ

A piston-c~linder system contains a gas which expands under a constant pressure of 1200 Ibf/ft. If the piston is displaced 12 in during the process, and the piston diameter is 24 in, what is the work done by the gas on the piston?

A.

-138.2 Btu/Ibm

B. -94.8 Btu/Ibm

95.

1768 ft-Ibf

C. 2387 ft-Ibf

B. 1890 ft-Ibf

D. 3768 ft-Ibf

Nitrogen is expanded isentropically. Find the pressure ratio (pl/P2).

A.

Gas is enclosed in a cylinder with a weighted piston as the3 top boundary. The gas is 3 heated and expands from a volume of 0.04 m to 0.10 m at a constant pressure of 200 kPa. Calculate the work done by the system.

A.

88.

94. Air

96.

Its temperature changes from 620°F to 60°F.

0.08

C.26.2

B. 12.9

D.3547

Nitrogen is expanded isentropically. Its temperature changes from 620°F to 60°F. The volumetric ratio is V 2N 1 = 6.22, and the value of R for nitrogen is 0.0787 Btu/lbm­ oR. What is the work done by the gas?

A.

-1112.7 Btu/Ibm

B. -99.22 Btu/Ibm

C. 0 Btu/Ibm D. 99.22 Btu/Ibm

F -196

97.

PRACTICE PROBLEMS

During an adiabatic, internally reversible process, what is true about the change in entropy?

A. It is always zero. B. It is always less than zero. 98.

C. It is always greater than zero.

1.

D. It is temperature dependent.

dS = dOfT

C. dS > 0

dS = 0

D. dS < 0

99. For which type of process does A. irreversible B. isothermal 100.

the equation dO

2.

=TdS hold?

C. reversible D. isobaric

3. liSsurToundings

+ liSsyslem ~ 0

c. t.SsurToundings + liSsys,em os; 0

liSsurroundings

+ ,A,Ssystem < 0

D. ,A,SSurTOUndings

+ liSsystem >

0

Answer Key for Thermodynamics

,

I'

I

A diesel power plant utilizes diesel fuel with 28 ° API. The plant consumes 650 liters of diesel fuel at 26.6°C in 24 hours, while the power quarantee for the same period amounts to 1,980 kw-hrs. Determine the fuel rate in kg/kw-hr.

A. B.

Which of the following is true for any process?

A. B.

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20.

A B 0 C B A B C 0 0 A B C 0 A C B A A D

21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40.

B C A C 0 A A A C B D C A B A C 0 A A A

41, 42. 43. 44. 45. 46. 47. 48. 49. 50. 51. 52. 53. 54. 55. 56. 57. 58. 59. 60.

A A A D B C D D B B 0 0 0 B 0 C D B C C

61. 62. 63. 64. 65. 66. 67. 68 69. 70. 71. 72. 73. 74. 75. 76. 77. 78. 79. 80.

D D B B B B D D D C B B A D C C C 0 A B

81. C 82. D 83. A 84. B 85. B 86. B 87. C 88. D 89. B 90. D 91. D 92. D 93. D 94. B 95. B 96. D 97. A 98. C 99. C 100. A

F - 1!.l r

F U E L SAND COM BUS T ION

For an irreversible process, what is true about the total change in entropy of the system and surroundings?

A. B.

1111111

PRACTICE PROBLEMS

4.

6.

C 0.298 D.0.586

A steam generator burns fuel oil with 20 percent excess air. represented by C 14H 30. Calculate the actual air-fuel ratio.

The fuel oil may be

A.

14.97 kg air/kg fuel

C 17 97 kg air/kg fuel

B.

19.72 kg/ air/kg fuel

D. 2097 kg air/kg fuel

A certain coal has the following ullin li:llC 'lnCllySls C ::: 67%, H2 ::: 3%, 02 :::4%, N~ - 6%, S = 7%. Ash::: 5%. and Moisture e 8%. Find the air-fuel ratio if this coal is burned with 50% excess air A. 13.3 kg air/kg coal C 33.1 kg air/kg coal B. 14.6 kg air/kg coal D 16.7 kg air/kg coal A fuel consisting of 80% C 12H36 and 20% C 14H30 is burned with 30% excess air. The flue gases is at atmospheric pressure. Find the minimum exhaust temperature to avoid condensation.

A. B.

5.

0.289 0.357

55.5°C

C.60.5

0C

505°C

O.45.2

0C

A diesel power plant utilizes diesel fuel with 28 a API. The plant consumes 650 liters of diesel fuel at 26.6°C in 24 hours, while the power guarantee for the same period amounts to 1,980 kw-hrs. Determine the overall thermal efficiency of the plant.

A.

25.76%

C. 27.65%

B.

36.72%

0.39.27%

When one mol of carbon combines with 1 mol oxygen

A. B.

2 mots carbon dioxide 1 mol carbon dioxide

C. 1 mol carbon and 1 mol carbon dioxide D. 1 mol carbon monoxide

7. A diesel electric plant supplies energy for VECO. In one day operation, the plant

I

consumed 175 gallons of fuel at 30°C and produced 135.83 kw of electricity. Fuel used is 28 deg API and was purchased at 6.25 per liter at 15.6°C. What is the cost of fuel to be produced in one kw-hr?

A.

P1.25

C. P1.03

B.

P2.35

O. P3.33

8. A fuel gas has the following volumetric analysis:

=

=

C2H4 35% CH2 65% Assume complete combustion with 25% excess air at 101.325 kPa, partial pressure of the water vapor in kPa?

What is the

,

A. B.

9.

PRACTICE PROBLEMS

PRACTICE PROBLEMS

F -198 10.05 kPa

C. 11.35 kPa

9.85 kPa

0.12.97 kPa

5.

There are 22 kg of flue gases formed per kg of fuel oil burned in the combustion of fuel oil C'2H30. What is the excess air in percent? A. 28.67% C. 35.90%

B. 10. A

32.36%

6.

D. 32.50%

A 3000 kw diesel generating set which is using a 25°API fuel has the following data: fuel rate, 290 liters for 900 kw-hr; generator efficiency is 92%; and mechanical efficiency is 82%. Calculate the engine-generator fuel rate in kg/kw-hr.

A. 19.85

C.17.93

B.

0.14.20

11.14

7.

A. 0.2916

C.0.3567

B.

D. 0.9857

0.4587

In Problem No.5, Calculate the brake thermal efficiency.

steam generator burns fuel oil that has the following chemical analysis by mass in

percent: C = 85.3 H2 = 14.1 S = 0.5 N2 = 0.1 Combustion takes place in 125 percent in theoritical air. The flue gases leave the air preheater at 0.17 MPa. What is the partial pressure of the stack gases to avoid condensation in kPa? Take molecular weight of the flue gases as 28.80.

F -199

A. 30.14%

C.35.11%

B.

0.38.91%

28.12%

A 16-cylinder diesel engine is directly coupled to a 2400 volts, 3300 kw alternator. The engine consumes 1.252 drums of 25 c API diesel fuel with energy output of 990 kw-hrs. The mechanical efficiency of the engine is 83% and the alternator efficiency is 92%. Assume a drum of fuel contains 200 liters. Find the engine fuel rate in kg/bhp­ hr. A. 0.571

C.0157

B.

0.0.751

0.715

ANSWERS FOR FUELS AND COMBUSTION

I

1. 2.

I

A C

3. 4.

A B

\

5. 6.

C B

]

7. 8.

A A

\

9. C 10. C

I

8. ,

9.

DIE S E L (I. C. E.) POW E R P LAN T 1.

A 16-cylinder. V-type diesel engine, 4-stroke cycle, 514 rpm, 400 mm bore x 460 mm stroke is directly coupled to a 550 kw AC generator, 13,800 volts, 3 phase, 60 cycles and 93% efficiency. Calculate the BHP of the diesel engine.

A. B.

2.

....t. 3.

7,927.6 BHP

C. 2,475.4

B.

D. 4,785.2

3,876.3

An 8-cylinder, 450 mm x 600 mm, 4 stroke cycle diesel engine has an exhaust gas mass rate of 4.5 kg/kw-hr brake based on fuel having an air-fuel ratio of 20 to 1 and heating value of 10,540 kcal/kg. Engine speed is 260 rpm with brake mean effective pressure of 9.25 kg/cm 2. An estimated 22% energy loss is carried away by the jacket cooling water. Calculate the brake horsepower. A. 2110 BHP C. 2310 BHP 2011 BHP

B.

22.45 kg/sec

D. 24.84 kg/sec

0.26.71%

A. 1120.7

C.1720.1

B.

0.1270.1

1210.7

10. A six cylinder four-stroke

diesel engine, with 76 mm bore and 89 mm stroke was ran in the laboratory at 2000 rpm, when it was found that the brake torque was 15.6 kg-m with all cylinders firing but 12.5 kg-m when one cylinder was cut. The engine consumed 12.15 kg of fuel per hour witt a heating value of 45,130 kJ/kg and 137.4 kg of air at 15.5°C per hour. Determine the indicated power in kw. A.38.19kw

C.31.89kw

B.

0.32.05 kw

36.76 kw

11. In Problem

0.2910 BHP

In Problem No.3, Determine the mass flow rate of cooling water assuming water available at 25°C and allowed to rise 15°F. C. 32.45 kg/sec A. 28.44 kg/sec

C.32.15%

43.21%

0

0API

A. 2,747.2

A. 35.21%

B.

A 3500-Bhp turbocharged diesel engine, 16-cylinder, 400 mm x 500 mm, 360 rpm has a fuel consumption of 0.173 kg/Bhp-hr at full load using fuel with heating value of 10,900 kcal/kg. For this engine, heat carried by exhaust gases is 30% and heat carried by jacket water is 23%. A waste heat recovery boiler recovers 35% of the exhaust heat loss. Calculate the quantity of 136 kPa steam that can be produced in kg/hr if jacket water from engine at 70 C is used as boiler feed. Note: at 136 kPa, hg =2689.12 kJ/kg; at 70 ° C, hf = 292.98 kJ/kg.

9,347.5 BHP 0.6,756.9 BHP In problem No.1, if the unit uses bunker oil with 17 and the fuel economy is 4.0 kw-hr per liter of fuel oil, calculate the combined heat rate in kcal/kw-hr.

B. 4.

C. 8,267.5 BHP

In Problem No.7, Determine the overall thermal efficiency.

NO.1 0, determine the indicated mean effective pressure in kPa.

A. 945.89 kPa

C. 954.98 kPa

B.

0.998.54 kPa

989.45 kPa

12. The

compression ratio of an ideal Otto Cycle is 5:1. Initial conditions are 101.3 kPa and 22°C. Find the pressure and temperature at the end of adiabatic compression. A. 964.2 kPa, 288.6°K

C. 964.2 kPa, 561.6°C

B.

0.964.2 kPa, 561.6°F

964.2 kPa, 288.6 °C

~

F - 200

13.

PRACTICE PROBLEMS

PRACTICE PROBLEMS

An ideal Gasoline Engine(4-stroke} operates with an initial cycle temperature of 48°C and exhaust temperature of 150 a C. The change in temperature during combustion is

150 0K. Find the efficiency of the cycle.

A.

32%

C.26%

B. 28%

D.57%

STEAM POWER PLANT 1.

14. An

air-standard diesel cycle, compression starts at 101.3 kPa and 30°C. The compression ratio is 12 to 1. The maximum cycle temperature is 1600°C. Determine the thermal efficiency.

A. 51.19% B. 53.12% lllll~

D.55.12%

2.

34%

C.64%

58%

D.62%

16. A single-acting,

four cylinder, 4-stroke cycle diesel engine with a bore to stroke of 4 in x 7 in, operating at 1200 rpm, consumes 12.5 kg/hr of fuel. The load on the brake arm, which is 1DO cm length is 150 kg. What is the brake mean effective pressure in kPa? 2905 kPa

C. 300 kPa

3207 kPa

D. 307 kPa

3.

1 MW diesel power plant uses 2 bbl fuel at 26 0API per 75,000 watts of electricity in 24 hrs operation. Efficiency of generator is 92% and mechanical efficiency of 85%. What is the thermal efficiency of the engine based on indicated power in percent? 64.80%

C. 59.37%

56.90%

D. 35.80%

4.

18. A

waste heat recovery boiler produces 1 MPa dry saturated steam from 100°C feedwater. The boiler receives hot gases(C p = 1.0) at 4.2 kg per sec at a temperature of 9500 C. After passing through the waste heat boiler, the temperature of hot gases has been reduced to 250°C. How much steam in kg is produced per hour? Note: At 1 MPa dry saturated, h = 2778.1 kJ/kg

A B.

44878 kg

C. 47488 kg

4847.8 kg

D. 4887.4 kg

5.

1733.35 kw

C. 137335 kw

1483.75 kw

D 1256 78 kw

An open feedwater heater utilizes saturated steam at 150'C which is extracted from the turbine. The feedwater to be heated enters the heater at 60 c C. If the mixture leaves the heater as saturated liquid at the rate of 30,000 kg per hour, find the quantity of steam extracted from the turbine. Note: at 150°C, hf = 632.20 kJ/kg, hg = 2746.5 kJ/kg; at 60°C, hf:: 251.13 kJ/kg.

A B.

17. A

t.

4,775 kg/hr 4,577 kg/hr

2. 3

A C 8

4.

D

:';.

A

6

A

7. 8.

C A

9. 10 11. 12.

8 A A B

A

142,765,500 kJ/hr

C. 127,765,300 kJ/hr

B.

156,875,200 kJ/hr

D. 124,675,500 kJ/hr

In Problem No.4, calculate the equivalent specific evaporation.

A. B. 6.

C. 4,757 kg/hr D. 5,477 kg/hr

A boiler generates superheated steam at the rate of 50 tons per hour. Feedwater enters the boiler at 5 MPa and 120 0 C and leaves at 4.5 MPa and 320 °C. If the coal used has a heating value of 30,000 kJ/kg, and the coal is consumed at the rate of 5 tons per hour, calculate the ASME evaporation units in kJ/hr. Note: at 4.5 MPa and 320'C, h:: 3000.6 kJ/kg and s = 6.3815; at 5 MPa and 120°C, h = 507.09 kJ/kg.

11.048 13.012

ANSWERS FOR DIESEL POWER PLANT 1.

C. 34.89% D. 78.43%

A steam turbine receives 5,000 kg per hour of steam at 5 MPa and 4000C and velocity of 25 rn/sec. It leaves the turbine at 0006 MPa and 15% wetness and velocity of 20 m/sec. Radiation loss is 10.000 kJ/hr. Find the kw power developed. Note: at 5 MPa and 400°C, h :: 3195.7 kJ/kg and s = 66459; at 0.006 MPa, hf:: 151.53 kJ/kg, hfg :: 2415.9 kJ/kg.

A. B.

1111111

A. B.

39.48% 45.78%

Exhaust

C.54.97%

air-standard diesel cycle, operates with a compression ratio of 16 to 1. The ratio of the fuel by volume is 1.5. What is the cycle efficiency?

A. B.

An ideal Rankine cycle has throttle conditions of 6 MPa and 450 ° C. pressure is at 0.005 MPa. Determine the Rankine cycle efficiency. Note: at 6 MPa and 450°C, h:: 33018 kJ/kg ans s = 6.7193 hfg = 2423.7 at 0.005 MPa, hf:: 137.82 sf:: 0.4764 sfg = 7 9187

A. B.

15. An

A. B.

F - 201

C.14.084 D. 17.097

A Horizontal2 Return Tubular boiler has a steaming capacity of 4,546 kg/hr of steam at 11.4 kg/cm absolute saturated. Feedwater temperature is 80 0 C. It has an overall 2 effective heating surface of 186 m . Determine the developed boiler horsepower. A. 315.06 C.351.60

B.

342.09

D. 324.56

7. In Problem No.6, Determine the factor of evaporation. A. 1.~ ~1~

B.

1.08

D.1.65

8.

PRACTICE PROBLEMS

PRACTICE PROBLEMS

F·202

efficiency is 80%. If the boiler efficiency is 80%, what is the cogeneration efficiency of the system in percent? Neglect pump work.

A bunker-fired steam generating unit consumes 6 Metric Tons per hour of bunker having a heating value of 41.000 kJ/kg with a boiler efficiency of 80%. It is desired to convert this boiler to coal-fired using local coal having an average heating value of 29.000 kJ/kg. Using coal, however, the boiler efficiency is only 75%. What will be the coal consumption so that the boiler will maintain its steaming capacity?

A. 9.480 Mtons/hr B. 8.067 Mtons/hr

9.

A. B.

Steam Properties:

at 15 MPa and 600°C, h

D. 9.048 Mtons/hr

282 hours

C. 228 hours

296 hours

D. 248 hours

10. A

A. 69.50% B. 67.40% 15.

boner generates superheated steam at the rate of 20,000 kg per hour. Feedwater enters the boiler at 5 MPa and 200 C and steam leaves the boiler at 5 MPa 350 C. The coal used has a heating value of 32,000 kJ/kg and boiler efficiency is 78%. Determine the developed boiler horsepower. Note: at 5 MPa and 350 C, h = 3068.4 kJ/kg; at 5 MPa and 200 C, h = 853.9 kJ/kg. A. 1524 C.1254 0

0

1111111

1277 kg/hI'

steam power plant produces steam at a rate of 9,000 kg/hI' at 15 MPa and 600°C. Expands to the condenser with a pressure of 10 kPa. Calculate the power output of the turbine if the turbine efficiency of 90% is developed. Note: At 15 MPa and 600°C, h = 3582.3 kJ/kg, s = 6.6776 At 10 kPa, hf 191.83 kJ/kg, hg 2584.7 kJ/kg sf 0.6493, sg 8.1502 A. 3212.97 kw C. 3331.65 kw

tl

B.

3321.52 kw

=

=

cycle has turbine inlet conditions of 20 MPa and 600°C expand in a turbine to 0.01 MPa. The turbine and pump polytropic efficiencies are 90% and 65% respectively, pressure losses between pump and turbine inlet are 1.0 MPa. What should be the pump work in kJ/kg? A. 32.3 C. 34.5

14. The

33.2

D. 35.6

steam power plant operates with initial pressure of exhaust to a heating system at 0.01 MPa. The condensate returned to the boiler at 60°C and the heating system purpose 90% of the energy transferred from the steam

23,897.96 kw

D. 21,507.40 kw

Steam Properties:

at 6 MPa and 350°C, h = 3043.0 kJ/kg

at 205°C, hf = 875.04 kJ/kg

at 145°C, hf = 610.63 kJ/kg

A. B.

D. 3423.89 kw

13. A Rankine

B.

=

generator produces 18.5 kg/s of steam at 6 MPa and 350° C. The feedwater enters the economizer at 145°C and leaves at 205°C. The steam leaves the boiler drum with a quality of 98%. The unit consumes 11,520 kg/hI' coal with a heating value of 26,000 kJ per kg. What would be the overall efficiency of the unit in percent?

12. A

=

=

16. A steam

D. 1988 kg/hI'

=

In a cogeneration plant, steam enters the turbine at 5 MPa and 500°C. One-fourth of the steam is extracted from the turbine at 250 kPa pressure for process heating. The remaining steam continues to expand to 10 kPa. The extracted steam is then condensed and mixed with feedwater at constant pressure and the mixture is pumped

to the boiler pressure 5 MPa. The mass flow rate of steam through the boiler is 40

kg/sec. How much process heat is required in kw?

Steam Properties:

at 5 MPa and 500°C, h 3433.8 kJ/kg, s 6.9759

at 250 kPa, hf = 535.37 kJ/kg, hfg = 2181.5 kJ/kg

sf 1.6072, sfg 5.4455 A. 20,985.36 kw C. 22,756.45 kw

B.

D.1386

In Problem No. 10, determine the fuel consumption in kg/hr. A. 1774 kg/hI' C. 1477 kg/hI'

B.

D.64.80%

=

0

11.

C.68.44%

=

0

B. 1542

=3582.3 kJ/kg, s =6.6776

at 0.01 MPa, hf = 191.83 kJ/kg, hfg ." 2392.8 kJ/kg

sf = 0.6493, sfg = 7.5009

at 60°C,hf = 263.67 kJ/kg

C. 6.098 Mtons/hr

Two boilers are operating steadily on 136,500 kg of coal contained in a bunker. One boiler is producing 2,386 kg of steam per hour at 1.15 factor of evaporation and an 0 efficiency of 75%, and the other boiler produces 2,047 kg of steam per hour at 1.1 factor of evaporation and an efficiency of 70%. How many hours will the coal in the bunker run the boilers if the heating value of the coal is 32,000 kJ/kg?

WIII~

F - 203

15 MPa and 600°C and from the heating system is utilizes from its intended it receives. The turbine

17.

54.10%

C.68.97%

43.21%

D.95.20%

A boiler produces superheated steam at the rate of 5.56 kg/sec. Feedwater enters the boiler at 5 MPa and 200°C and steam leaves the boiler at 5 MPa and 350°C. The coal used has a heating value of 32,000 kJ/kg and boiler efficiency is 78%. Determine the developed boiler HP.

Steam Properties:

at 5 MPa and 350°C, h = 3068.4 kJ/kg

at 5 MPa and 200°C, h = 853.9 kJ/kg

A. B.

1254

C.1524

1425

D.1495

!

I

r 18.

A coal fired power plant has a turbine-generator rated at 1000 MW gross. The plant required about 9% of this power for its internal operations. It uses 9800 tons of coal per day. The coal has a heating value of 6,388.9 kcal/kg and the steam generator efficiency is 86%. What is the net station efficiency of the plant in percent?

A. B:

33%

C.36%

34%

0.45%

F - 205

PRACTICE PROBLEMS

PRACTICE PROBLEMS

F - 204

A. B.

685.97

C.395.48

591.34

0.521.98

ANSWERS FOR GEOTHERNMAL POWER PLANT

11. A

13. B

12.0

~

ANSWERS FOR STEAM POWER PLANT 1. 2. 3. 4.

5. 6. 7. 8.

A C

B 0

9. 10. 11. 12.

A A B 0

13. 14. 15. 16.

A C A B

17. A 18. A

A C 0 A

GAS TURBINE POWER PLANT 1.

1I111~

In a gas turbine operating on the air standard cycle, the air enters the compressor at 100 kPa and 30· C at the rate of 20 m 3/sec and is compressed to 500 kPa. The maximum temperature is 780· C and the exit pressure of the turbine is 100 kPa. Determine the net turbine power.

A. B.

GEOTHERMAL POWER PLANT 1111111

.".111

1.

2.

III

A flashed-stearn geothermal power plant is located where underground hot water is available at 15 MPa and 300·C. To produce a steam-water mixture in the separator where the unflashed water is removed, this water is throttled to a pressure of 1 MPa. The flashed steam which is dry and saturated passes through the steam collector and enters the turbine at 1 MPa and expands to 1 atm. The turbine efficiency is 80% and the generator efficiency is 95%. For a generator output of 12 MW, calculate the ground water flow rate in kg per hour required for continuous operation. Note: at 15MPa and 300· C, h = 1337.3 kJ/kg, s = 3.2260; at 1 MPa, hf = 762.81, hfg = 2015.3, hg = 2778.1, sg = 6.5865; at 1 atm, hf = A. 512,870 kg/hr C. 623,870 kg/hr R. 712,456 kg/hr 0.845,734 kg/hr A liquid dominated geothermal power plant with a single flash separator receives water at 204· C. The separator pressure is 1.04 MPa. A direct contact condenser

operates at 0.034 MPa. The turbine has a polytropic efficiency of 0.75. For a cycle output of 50 MW, what is the mass flow rate of the well-water in kg/s? Note: at

204.C, hf = 870.51 kJ/kg; at 1.04 MPa, hf = 770.38, hfg = 2009.2, hg = 2779.6, sg =

6.5729; at 0.034 MPa, hf 301.40, hfg 2328.8, sf 09793, sfg 6.7463.

=

II

A. B. 3.

=

2871 2100

=

=

2.

Steam Properties:

at 250°C, h = 1085.36 kJ/kg

at 1.2 MPa, hf = 798.65 kJikg, hfg = 1986.2 kJ/kg, hg = 2784.8

sf 2.2166, sfg 4.3067

at 0.030 MPa, hf = 289.23 kJ/kg, hfg = 2336.1 kJ/kg

sf = 0.9439, sfg = 6.8247

=

=

0.4538 kw

2496 kw, 18.94%

C. 2496 kw, 19.85%

2469 kw, 14.67%

0.2469 kw, 16.98%

Air enters the compressor of a gas turbine at 100 kPa and 25°C with a volume flow rate of 4 m 3/sec. The compressor pressure ratio is 8 and its isentropic efficiency is 90%. At the inlet to the turbine, the pressure is 900 kPa and 1127°C temperature. The turbine has an isentropic efficiency of 85% and the exit pressure is 100 kPa. On the basis of an air-standard analysis, what is the thermal efficiency of the cycle in percent?

A. B. 4.

33.26%

C.38.97%

36.34%

0.42.34%

In a gas turbine unit, air enters the combustion chamber at 500 kPa, 240°C and 45 m/s. The products of combustion leave- the combustor at 500 kPa, 1020°C and 150 m/s. Liquid fuel enters with a heating value of 43,000 kK/kg. For fuel-air ratio of 0.023, what is the combustor efficiency of the unit in percent?

C.186 0.2444

A liquid dominated geothermal plant with a single flash separator receives water at 2500C. The separator pressure is 1.2 MPa. The condenser operates at 0.030 MPa. The turbine has a polytropic efficiency of 80%. For a cycle output of 40 MW, what is the mass flow rate of the well-water in kg per sec?

C. 4583 kw

4358 kw

Air enters the compressor of a gas turbine at 100 kPa and 30· C at the rate of 20 3/sec m and is compressed to 500 kPa. The maximum temperature is 780· C and the exit pressure of the turbine is 100 kPa. What is the net turbine power and cycle efficiency if the compressor efficiency is 80% and the turbine efficiency is 85%?

A. B. 3.

4853 kw

A. B.

79.9%

C.80.09%

78.9%

O. 77.21%

ANSWERS FOR GAS TURBINE POWER PLANT

I 1.

A

I,

?- ..r:..,

II -J.

A

I 4.

A

I

7.

H Y 0 R O-E L E C T RIC POWER PLANT A Mini-hydro plant is to be constructed has an average annual rainfall of 139 cm. The catchment area is 206 sq. km with an available head of 23 meters. Only 82% of the rainfall can be collected and 75% of the impounded water is available for power. Hydraulic friction loss is 6%, turbine efficiency is 78% and generator efficiency is 93%. Determine the average kw power that could be generated for continuous operation.

1.

A. B. 2.

Mill.

885.5 kw

C. 858.5 kw

835.3 kw

D. 895.8 kw

B. 3.

8.

6.

D. 72,050,704 kw-hr

2000 kw, 1000 kw

D. 4.83 m

A pelton wheel is to be designed to run at 300 rpm under an effective head of 150 m. The ratio of the nozzle diameter to the diameter of the pitch circle is 1/12. Assuming efficiency of 84%, what is the size of the wheel in meters. Assume a speed ratio of 0.45. C 1.55 A. 1.05

A francis turbine is installed with a vertical draft tube. The total head to the center of the spiral casing at the inlet is 38 m and velocity of water at the inlet is 5 m/s. The discharge is 2.1 m 3/s. The hydraulic efficiency is 087 and overall efficiency is 0.84. The velocities at the inlet and exit of the draft tube is 1 meter(water) below the centerline of the spiral casing while the tailrace(water) level is 3 meters from the top of the draft tube. Neglect velocities of whirl and leakage losses. What is the total head on the turbine in meters?

A. 27,927 Bhp B. 29,856 Bhp

C.57.3%

B.

59.4%

D. 51.2%

A hydro-electric generating station is supplied from a reservoir of capacity 6,000,000 m 3 at a head of 170 m. Assume hydraulic efficiency of 80% and electrical efficiency of 90%. The fall in the reservoir level after a load of 15 MW has been supplied for 3 hours, if the area of the reservoir is 2.5 sq. km is closest to: 5.39 cm

C. 5.98 cm

4.32 cm

D. 4.83 cm

C. 30,135 Bhp D. 31,097 Bhp

ANSWERS FOR HYDRO-ELECTRIC POWER PLANT [

55.1%

C.55.20 D.48.12

hydro-electric plant has a 20 MW generator with an efficiency of 96%. The generator is directly coupled to a vertical francis type hydraulic turbine having an efficiency of 80%. The total gross head on the turbine is 150 m while the loss of head due to friction at the penstock up to the turbine inlet flange is 4% of the gross head. Determine the Brake Horsepower rating of the turbine.

D. 4000 kw, 2000 kw

A.

D.2.86

10. A

D. 33.079 m

A hydro-electric pumped storage plant has a generator-motor efficiency of 95%, turbine efficiency of 81% and pump efficiency of 76%. Average elevation between upper and lower poools is 31 m. Assume a 2% loss of head in pipe friction. This unit was installed to carry a daily peak load of 1500 kw-hrs. There is a daily evaporation loss of 1000 metric tons. Calculate the over-all efficiency of conversion.

A. B.

C. 5.98 m

A. 34.72 B. 43.27

The flow of a river is 21.25 m3/sec and the head of the site is 30.47 m. It is proposed to develop the maximum capacity at the site with the installation of two turbines, one of which is twice the capacity of the other. The efficiency of both units is asssumed to be 85%. Francis turbines will be used with specific speed of 65. Determine the kw output of each unit. A. 3600 kw, 1800 kw C. 3000 kw, 1500 kw

B. 5.

9.

3/sec

30.039 m

5.39 m

B. 4.32 m

B. 2.00

A hydro-electric plant discharging water at the rate of 0.75 m and entering the turbine at 0.35 m/sec with pressure of 275 kPag has a runner of 55 cm intemal diameter. Speed is 514 rpm at 260 brake horsepower. The casing is 2 meters above the tailwater level. Calculate the effective head. A. 39.045 m C. 34.059 m

B. 4.

74,005,740 kw-hr

A hydroelectric generating station is supplied from a reservoir of capacity 6,000,000 m 3 at a head of 170 m. Assume hydraulic efficiency of 80% and electrical efficiency of 90%. The fall in the reservoir level after a load of 15 MW has been supplied for 3 hours, if the area of the reservoir is 2.5 sq. km is closest to:

A.

A proposed hydro-electric plant, the headwater elevation is 700 meters and the tailwater elevation is 580 meters. Average annual water flow is determined to be equal to that volume flowing through a rectangular channel 4 meters wide and 0.5 meter deep and average velocity of 5.5 meters per second. Assuming that the plant will operate 360 days per year, find the annual energy in kw-hr that the power site can develop if the hydraulic turbine that will be used has an efficiency of 92%. Consider a headwork loss of 4% of the available head. A. 79,050,704 kw-hr C. 76,500.740 kw-hr

1111111

F - 207

PRACTICE PROBLEMS

PRACTICE PROBLEMS

F - 206

1. 2.

C A

I

3. 4.

B A

5. 6.

D A

l

7. 8.

A C

D

9. 10. A

CHIMNEY 1.

A boiler needs a smoke stack to produce 25 mm water draft at sea level. Other data as follows: Average air temperature: 25°C Barometer reading: 760 mm Hg Boiler flue gas temperature entering stack: 260 °C Flue gas flow rate: 45 kg/sec 3 Flue gas density: 0.72 kg/m Determine the required height of the stack.

I

F ·208

PRACTICE PROBLEMS

A. B.

2.

3.

.UI~I

4. 11111111

'r

53.76 m

C. 56.73 m

51.25 m

D. 59.84 m

PRACTICE PROBLEMS

3.

In Problem No.1, Determine the required diameter of the stack.

A.

1.05m

C.1.50m

B.

1.75 m

D. 2.35 m

The inlet temperature to the stack of the flue gases is 220°C and exit temperature to the atmosphere is 150°C. The molecular weight of the gases is 30. The draft pressure required for a furnace is 8.347 cm of water. Determine the required stack height in meters, if the air temperature is 300 0K. A. 221 m

C. 230 m

B.

D.210m

225m

C. 2.52 m

B.

D. 3.10 m

2.0 m

1'11111

11. A

12.

B-----J

3-:-A- - - -

- I 4.

~"I'WI .''1 1

~III.".

5.

Brine enters a circulating brine cooler at the rate of 5.7 m 3/hr at -100C and leaves at­ oC. 16 The specific heat of the brine is 1.072 kJ/kg_oC and the specific gravity is 1.10. The refrigerant evaporates at -25°C. What is the required heat transfer area if the overall coefficient of heat transfer is 0.454 kw/m2_oC? 2 A.1.4m C.1.8m 2 2 B. 2.1 m D. 3.2 m 2

6.

A 12 in thick furnace wall with a dimension of 5 m by 2 m has a temperature difference of 60°C. The wall has a thermal conductivity of 0.75 Btu/hr-tt-oF. Calculate the heat transmitted across the wall.

1111111 1

HEAT TRANSFER AND HEAT EXCHANGERS 1.

~I.'

~

A counterflow heat exchanqor is designed to heat fuel oil from 280C to 900C while the heating fluid enters at 138°C and leaves at 105°C. The fuel oil has a specific gravity of 21 °API, a specific heat of 0.5 kcal/kg-oK and enters the heat exchan~er at the rate 3,000 liters per hour. Determine the required heating surface area in m if the overall coefficient of heat transfer for this heat exchanger is 400 kcal/hr-rn ",» K. 2 A. 3.486 m C. 4985 m 2

2

B. 4.268 m D. 5.892 m 2

I

C

A. B.

2.

A. B.

Determine the thermal conductivity of a wood that is used in a 1.5 meter square test panel, 25 mm thick, if during a 4-hour test period there are conducted 190,000 Joules through the panel with a temperature differential of 6°C between the surfaces. Express answer in W/m-oC. 0.0244 W/m-oC

C. 0.0422 W/m-'C

0.0322 W/m-oC

D. 0.0933 W/m-'C

7.

=

The walls of a cold storage plant are composed of an insulating material (k 0.2336 kJ per hr-rn-v C) 10.16 cm thick held between two layers of concrete (k = 3.7382 kJ per hr-rn-v C) each 10.16 cm thick. The film coefficients are 81.76 kJ/hr-m 2-,C on the outside and 40.88 kJ/hr-m 2- o C on the inside. Cold storage temperature is -6.67'C and the ambient temperature is 32.22'C. Determine the heat transmitted in kw through an area of 55.74 m2.

A. B.

1.948 kw

C. 1.1448 kw

1.736kw

D. 1.8144 kw

D.548 0C

485°C

4.

ANSWERS FOR CHIMNEY

1,""1

A heat exchanger is designed for the following specifications:

Hot gas temperature, 11450C

Cold gas temperature, 45° C

Unit surface conductance on the hot side, 230 W/m2.oK

Unit surface conductance on the cold side, 290 W/m2.0 K

Thermal conductivity of the metal wall, 115 W/m-o K Find the maximum wall surface temperature if the wall thickness is 25 mm. A. 584°C C.458 0C

B.

The exhaust of a power plant produced 252,000 m 3/hr of flue gases. The air temperature outside is 30°C and the average temperature of the flue gases in the chimney is 220°C. The required draft pressure of water vapor is 4.568 em with a molecular weight of 30 for the flue gases. Find the diameter of the chimney in meters. A. 2.9 m

F - 209

2545 W

C. 2455 W

2445 W

D. 2554 W

The heat exchanger is to be designed for the follOWing specifications:

Hot gas temperature, 1145 ° C

Cold gas temperature, 450 C

Unit surface conductance on the hot side, 230 W/m 2•0K

Unit surface conductance on the cold side, 290 W/m 2_ 0K Find the maximum thickness of metal wall between the hot gas and the cold gas, so that the maximum temperature of the wall does not exceed 5450C. A. 20 mm

C 30 mm

B.

D. 40 mm

25 mm

ANSWERS FOR HEAT TRANSFER

r

~: ~ ~

~: ~

I~: g

I

7. A

I

mechanical efficiency of the compressor is 80%. Assuming perfect intercooling with optimum interstage pressures, determine the fuel consumption in kg/hr of the diesel engine if the brake thermal efficiency is 30% and the fuel used has a heating value of 10,700 kcal/kg.

~R(GA~COMPRESSORS 1.

A single-acting air compressor operates at 450 rpm with an initial condition of air at 97.9 kPa and 270C and discharges the air at 379 kPa to a cylindrical tank. The bore and stroke are 355 mm and 381 mm respectively with a 5% clearance. If the surrounding air is at 100 kPa and 20°C while the compression and re-expansion processes are py 1 3 = C, determine the power of the compressor.

A. B. 2.

39.9 kw

C. 45.6 kw

43.2 kw

D. 49.6 kw

In problem No.1, determine the free air capacity in m

A. B.

WI.I~I

A. B. 7.

C. 0.2455

0.4552

D. 0.8539

A. B. 8. 3/min

3.

A single-stage, single cylinder air compressor is rated at 4.25 m of air. Suction cond1tions are 1 atm and 27°C and discharge pressure is 1034 kPa. The compression process follows the equation py135 C. If the compressor is to run two­ stage at optimum intercooler pressure with perfect intercooling, what will be the percentage of power saved? A. 10% C.20%

'r

B. 4.

5.

6.

C. 2.722 m

3.275 m3/min

D. 4.374 m

15 Bhp 20 Bhp

C.15.46%

16.69%

D. 14.35%

23.36 kw

C. 29.63 kw

32.85 kw

D. 26.63 kw

In Problem No.8, determine the free air capacity in m

A. B.

3/sec.

0.01712

C.0.1885

0.1712

D.0.1637

ANSWERS FOR GAS COMPRESSORS

1. 2.

A C

[ _

3. 4.

B

D

05. ~.

A A

1=

7. A L--=8.'-----=-D

3/min

3.744 m 3/min

3/min

A two-stage reciprocating single-acting air compressor has a rated capacity of 80 m 3/hr of free air at 2loC and 1.033 k~cm2 abs when running at 600 rpm. The absolute discharge pressure is 30 kg/cm and the air is discharged to an air receiver of 1,250 liters capacity. The compressor haS two low-pressure cylinders each 127 mm diameter and one high-pressure cylinder of 69.85 mm diameter, piston stroke is 101.6 mm. The compressor is driven by a 1750 rpm, 3-phase, 60 hertz, 460 volts motor thru v-betts with transmission efficiency of 95%. Determine the Bhp at an efficiency of 85% if the polytropic exponent n = 1.35.

A. B.

16.96%

A single-acting air compressor operates at 300 rpm with an initial conditions of air at 97.9 kPa and 27°C and discharges the air at 379 kPa to a cylindrical. The bore and stroke are 355 mm and 381 mm, respectively with a percentage clearance of 5%. If the surrounding air is at 100 kPa and 20 ° C while the compression and expansion 13 C. Determine the compressor power. processes are Py

A. B.

9.

D.30%

A two-cylinder single-acting air compressor is directly coupled to an electric motor running at 1000 rpm. Other data are as follows:

Size of each cylinder: 150 mm x 200 mm

Clearance volume: 10% of displacement

Polytropic exponent n: 1.36

Air molecular mass: 29 Calculate the volume rate of air delivery in terms of standard air for a delivery 0K pressure 8 times ambient pressure under ambient conditions of 300 and 1 bar.

A. B. 'II'

15%

C. 7.39 kg/hr D. 8.95 kg/hr

=

=

11111111

6.55 kg/hr 7.24 kg/hr

The piston displacement of a double-acting compressor is 0.358 m 3/sec, delivers gas from 101.325 kPa and 300 0K to 675 kPa at the rate of 0.166 m 3/sec at 150 rpm. Find the compressor percent clearance if n = 1.33.

3/sec.

0.5542

F - 211

PRACTICE PROBLEMS

PRACTICE PROBLEMS

F·210

C. 25 Bhp D. 30 Bhp

A three-stage, single-acting:i diesel engine-driven reciprocating air compressor is 2 guaranteed to deliver 170 m /hr free air at suction conditions of 1.03 kg/cm abs and 2 270C and discharge pressure of 35 kg/cm abs. Test results show that the polytropic exponent for both compression and re-expansion processes is 1.34 and the

PUMPS 1.

A centrifugal pump delivers 227 m 3/hr of water from a source 4 meters below the pump to a pressure tank whose pressure is 2.8 kg/cm 2. Friction loss estimates are 2 meters in the suction line and 1 meter In the discharge line. The diameter of the suction pipe is 250 mm and the discharge pipe is 200 mm. Find the kw rating of the driving motor if the pump efficiency is 70%.

A. B. 2.

31 kw

C. 35 kw

kW

D. 45 kw

42

A pump is to deliver 80 GPM of water at 60°C with a discharge pressure of 1000 kPag. Suction pressure indicates 50 mm of mercury vacuum. The diameter of the suction and discharge pipes are 5 inches and 4 inches, respectively. If the pump has an efficiency of 70%, determine the brake horsepower of the pump.

A. B.

13.9 hp

C. 9.732 hp

11.34 hp

D. 7.58 hp

I.

,.

2~.4 An acceptance test was conducted on a centrifugal pump having a suction pipe3/hr cm in diameter and a discharge pipe 12.7 cm in diameter. Flow was 186 m of clear cold water. Pressure at suction was 114.3 mm Hg vac and discharge pressure was 107 kPag at a point 91 cm above the point where the suction pressure gage was measured. Input to the pump was 15 hp. If the pump runs at 1750 rpm, what new hp brake hp would be developed and required if the pump speed were increased to 3500 rpm? Assume constant efficiency. C. 130 bhp A. 110bhp

3.

B.

1I1llU

1liliU

5.

A.

9.51 kw

C. 11.25 kw

B.

10.50 kw

0.15.50 kw

In problem No.4, determine the reading of the pressure gages installed just at the outlet and inlet of the pump. A. Po = 654,45 kPag, Pi = 32.67 kPag

B. C. D.

Po = 732.34 kPag, PI = 38.76 kPag Po

9.

Po = 985.35 kPag, Pi = 48.95 kPag

846.78

C.848.67

486.87

D. 884.34

10. Water from a reservoir is pumped over a hill through a pipe 450 mm in diameter and a pressure of 1.0 kg/cm 2 is maintained at the summit. Water discharge is 30 m above the reservoir. The quantity pumped is 0.5 m 3/sec. Frictional losses in the discharge and suction pipe of the pump is equivalent to 1.5 m head loss. The speed of the pump is 800 rpm, what amount of energy must be furnished by the pump in kw?

A. B.

206 kw

C. 236 kw

260 kw

D. 250 kw

11. Determine the mechanical efficiency of a centrifugal water pumped which has an input of 3.5 HP if the pump has an 8-in nominal size suction and 6-in nominal size discharge, if it handles 150 gpm of water at 150 oF. The suction line gage shows 4 in Hg vacuum and discharge gage shows 26 psi. The discharge gage is located 2 ft above the center of the discharge pipe line and the pump inlet and discharge line are at the same elevation. Take density of steam at 150° F equal to 61.2 lb/ft:',

A. B.

72%

C.70%

74%

0.77%

ANSWERS FOR PUMPS

1

=867.25 kPag, Pi =43.25 kPag

A boiler feed pump receives 45 liters per second of water at 90°C and enthalpy of 839.33 kJ/kg. It operates against a head of 952 m with an efficiency of 70%. Calculate the enthalpy leaving the pump in kJ/kg.

A. B.

0.140 bhp

A motor driven pump draws water from an open reservoir A and lifts to an open reservoir B. Suction and discharge pipes are 150 mm and 100 mm in inside diameter, respectively. The loss of head in the suction line is 3 times the velocity head in the 150 mm pipe and the loss of head in the discharge line is 20 times the velocity head in the 100 mm pipeline. Water level at reservoir A is at elevation 6 m and that of reservoir B at elevation 75 m. Pump centerline is at elevation 2 m. Overall efficiency of the system is 73%. Determine the power input of the motor.

4.

Of

120 bhp

F - 213

PRACTICE PROBLEMS

PRACTICE PROBLEMS

F·212

1. 2. 3.

A C B

I

4. 5. 6.

A B B

I

7. 8. 9.

A B C

QO'

A 11. A

3/hr

6.

lib

.1.

A plant has installed a single suction centrifugal pump with a discharge of 68 m under 60 m head and running at 1200 rpm. It is proposed to install another pump 3/hr. with double suction but of the same type to operate at 30 m head and deliver 90 m What must be the impeller diameter of the proposed pump if the diameter of the existing pump is 150 mm? C. 130 mm A. 120 mm

B.

7.

8.

145 mm

A.

30.75 Ii

C. 39.50 Ii

B.

45.20 Ii

0.37.30 Ii

The power output is 30 HP to a centrifugal pump that is discharging 900 GPM and which operates at 1800 rpm against a head, H = 120 ft, 220 volt, 3-phase, 60 hertz. If the pump is modified to operate 1200 rpm, assuming its efficiency remains constant, determine the theoretical head. C. 51.34 ft A. 49.01 ft 53.33 ft

3/sec of air through a 1. Find the air horsepower of an industrial fan that delivers 25.98 m

0.915 m x 1.22 m outlet. Static pressure is 127 mm of water. Air temperature is 21°C and the barometric pressure is 700 mm of mercury.

0.165 mm

A 4 m 3/hr pump delivers water to a pressure tank. At the start, the gage reads 138 kPa until it reads 276 kPa and then the pump was shut off. The volume of the tank is 160 liters. At 276 kPa the water occupied 2/3 of the tank volume. Determine the volume of water that can be taken out until the gage reads 138 kPa.

B.

FANS AND BLOWERS

0.62.45 ft

A. B.

2.

53.82 HP

C. 59.65 HP

62.56 HP

D. 65.75 HP

A forced draft fan is used to provide the combustion air requirements for a boiler that burns coal at the rate of 10 metric tons per hour. The air requirements are 100,000 m 3/hr, air is being provided under 150 mm water gage by a fan which has a mechanical efficiency of 60%. Assu me fan to deliver at a total pressure of 150 mm water gauge. Find the size of the driving motor in kw.

A. B.

61.8 kw

C. 68.1 kw

72.5 kw

0.79.3 kw

I

F -214 3.

PRACTICE PROBLEMS'

PRACTICE PROBLEMS Enthalpy at condenser entrance :: 1650 kJ/kg, condenser exit evaporator entrance:: 410.4 kJ/kg, evaporator exit e 1471.6 kJ/kg.

At 101.325·kPa and 21°C. an industrial fan develops a brake power of 100 kwand head of 120 mm water gage. What will be the power if this fan is operated at 98 kPa and 32°C at the same speed?

A. B. 4.

93.17 kw 87.61 kw

4.

Air enters through a duct of a fan with a velocity of 4 rn/s and an inlet pressure of 2 cm of water less than atmospheric pressure. The air leaves the fan through a duct at a velocity of 12 rn/s and a discharge static pressure of 8 cm of water above atmospheric pressure. If the specific weight of air is 1.2 kg/m3 and the fan delivers 12 m3/sec, what is the fan input power to the motor if the fan has a mechanical efficiency of 70% and motor efficiency of 80%.

A. 23 kw B. 26 kw

111'1.'

A. B.

C. 91.3 kw D. 85.24 kw

5.

A fan delivers 5 m3/s at a static pressure of 6 cm of water when operating at a speed of 300 rpm. The power input required is 3.5 kw. If 9 m3/s are desired in the same fal' and installation, find the pressure in cm of water.

5.

A. B.

'r

11.49

C.14.19

14.91

D.19.44

ANSWERS FOR FANS AND BLOWERS

I 1.

I 2.

A

C

I 3.

A

I 4.

A

I 5.

D

J

REFRIGERATION 1.

•• 2.

A simple saturated refrigeration cycle for R-12 system operates at an evaporating temperature of -5°C and a condensing temperature of 40°C. For a refrigerating capacity of 1 kw, determine the work of the compressor. At 40°C, hf:: 238.5 kJ/kg; at -5°C, hg :: 349.3 kJ/kg; Enthalpy entrance to the condenser, h :: 372 kJ/kg.

A.

0.205 kw

C. 0.502 kw

B.

0.350 kw

D. 0.906 kw

8.

B.

12.34 kw 17.35 kw

C. 15.44 kw D. 19.85 kw

A refrigeration system is to be used to cool 45,000 kg of water from 29°C to 18°C in 5 hours. The refrigerant is ammonia and the operating conditions are 616 kPa evaporating pressure and 1737 kPa liquefaction pressure. Determine the quantity of cooling water in the condenser for an increase in temperature of 7°C.

9.

3215kw

D.37.50kw

92.3 kw

D. 95.4 kw

An ammonia compressor operates at an evaporator pressure of 316 kPa and a condenser pressure of 1514.2 kPa. The refrigerant is subcooled by 5oC and is superheated by 8°C. For an evaporator load of 87.5 kw, determine the quantity of cooling water in the condenser if the increase in temperature of water is 7 0 C . Enthalpy entering the condenser:: 1715 kJ/kg, exit:: 361.2 kJ/kg, entering the evaporator e 361.2 kJ/kg, exlt e 1472 kJ/kg. A. 11,350 kg/hr C. 13,100 kg/hr B. 12,845 kg/hr D. 13,400 kg/hr Fish weighing 11,000 kg with a temperature of 20°C is brought to a cold storage and which shall be cooled to -10° C in 11 hours. Find the required plant refrigerating capacity in tons of refrigeration if the specific heat of fish is 0.7 kcal/kg-oC above freezing and 0.3 kcal/kg-oC below freezing point which is -30C. The latent heat of freezing is 55.5 kcal/kg.

A. B.

A refrigeration system using refrigerant 22 is to have a refrigerating capacity of 60 kw. The evaporating temperature is -10°C and the condensing temperature is 42°C. Determine the power required by the compressor. Enthalpy Condenser entrance:: 440 kJ/kg. Condenser exit:: 252.4 kJ/kg, Evaporator exit « 401.6 kJ/kg, evaporator entrance > 252.4 kJ/kg.

A.

3.

7.

C. 5.94 kg/s D. 8.54 kg/s

A vapor compression cycle is designed to have a capacity of 100 tons of refrigeration. It produces chilled water from 22°C to 2°C. Its coefficient of performance is 5.86 and 35% of the power supplied to the compressor is lost Determine the size of electric motor required to drive the compressor in kw. A. 60,5 kw C, 100.5 kw

B. 6.

410.4 kJ/kg,

A refrigeration system operates on the reversed Carnot cycle. The minimum and maximum temperatures are -25°C and plus 72°C respectively. If the heat rejected to the condenser is 6000 kJ per min. Find the power input required. A. 28.12 kw C. 34.0 kw

B.

C. 30 kw D. 36 kw

4.59 kg/s 3.02 kg/s

F - 215

20.4

C.22.2

20.2

D.24.4

It is desired to design a Freon-12 ice makinq unit to produce 5 metric tons of ire at _ 9.5°C from raw water at 26.7 oC in 20-hour operation. The condenser temperature for the system is 35°C and the evaporator temperature is -16°C. Find the tons of refrigeration capacity.

A.

9.2 tons ref

C. 10.8 tons ref

B.

11.5 tons ref

D. 12.8 tons ref

A vapor compression refrigeration system is designed to cool 9,500 liters of milk received each day from an initial temperature of 27°C to a final temperature of 3.33 0C in 5 hours. The density of milk is 1.03 kg/liter, and the specific heat is 0.94 kcallkg­ DC. Determine the refrigerating capacity in tons of refrigeration.

A. B.

14.4 TR 15.2TR

C. 15.6 TR D.17.8TR

,

F - 216

PRACTICE PROBLEMS

--------

ANSWERS FOR REFRIGERATION

I

1. 2.

I'

A

C

3. 4.

A A

I

5. 6.

B

I

C

7. 8.

0 A

I

AIR CONDITIONING 1.

In an air-conditioning unit 3.5 m 3/s of air at 27°C dry-bulb temperature, 50 percent

relative humidity, and standard atmospheric pressure enters the unit. The leaving

condition of the air is 13° C dry-bulb temperature and 90 percent relative humidity.

Using properties from the psychrometric chart, calculate the refrigerating capacity in

kilowatts.

A. B. II~~

2.

'~

88 kw

C. 95 kw

93 kw

0.34 kw

In a cooling tower, 28.34 m 3/min of air at 32°C db and 24°C wb enter the tower and leave saturated at 29°C. How many kg per hour of make-up water is needed if a spray of water enters at 38° C with a flow of 34 kg/min?

A. B.

3.

15.45 kg/hr 21.19 kg/hr

C. 19.21 kg/hr 0 25.36 kg/hr

A rotary dryer is to deliver 1.5 Mtons per hour of copra with moisture content not to

exceed 3%. The wet feed contains 40% moisture. The air enters the dryer with a

humidity ratio of 0.016 kg/kg dry air and leaves at 60°C and 100% relative humidity. If

the dryer operates at atmospheric pressure. determine the amount of wet feed in

Mtons per hour. .

A. B. 4.

4.542 Mtons/hr 2.425 Mtons/hr

C. 5.125 Mtons/hr D. 3.534 Mtons/hr

The cooling load calculations on a theater show that at design conditions the sensible

heat load is 200 kw and the latent heat load is 70 kw. The indoor design conditions

are 26°C dry bulb and 50% relative humidity. Air is to be supplied to the theater at

16° C while the outside air is at 30°C dry bulb and 60% relative humidity. Take

ventilating air as 25% of the supply air. Calculate the tons of refrigeration required by

the conditioner. A. 102.4 TR C. 124.3 TR

It

B.

110.5TR

D.114.8TR

ANSWERS FOR AIR-CONDITIONING

I 1.

A

I 2.

C

I 3.

B

-

J ~-- -- - ]

Elements and Terms in

Power and Industrial Plant Engineering

II'"

Elements and Terms- MODULE 1

ET -1

MODULE 1 1.

Which of the following is the basis of Bernoulli's law for fluid flow?

A. B. C. D.

2.

3.

4.

S.

viscosity of fluid surface tension

tackiness density flash point viscosity

none of the above vapor unsaturated air ice

Specific heat Btu latent heat" relative heat

What is the study of condition of air and moisture in the atmosphere?

A. B. C. D. 7.

gravity air resistance

The amount of heat needed to raise the temperature of one Ib of that substance one degree Fahrenheit is:

A. B. C. D. h.

Fourier's law

The heat transfer process in a cooling tower consists of a transfer of heat from water to:

A. B. C. D.

I.

The principle of conservation of mass

The measure of the fluid resistance when acted upon by an extel nal force is called:

A. B. C. D.

'~

The principle of conservation of energy

A leak from a faucet comes out in separate drops. Which of the following is the main cause of this phenomenon?

A. B. C. D. 111111

The continuity equation

Atmospherics Psychrometries Thermodynamics Gas dynamics

What is the gage used to measure 0.001 to 1 atm pressure?

A.

Bourdon

B.

Water manometer

ET - 2

Elements and Terms- MODULE 1

C. D. 8.

9.

Elements and Terms- MODULE 1

C. D.

Mercury manometer Metallic diaphragm

transmulation radiation

D.

betatron radiation

A. B. C. D.

Walton radiation gamma radiation

Which engine is suitable in the power plant to generate power of 100 hp to 5000 hp?

A. B. C. D.

IIU~

-41.04°F 4060°F ·38.40°F ·31.40°F

pressure when applied to valves and fittings, implies they are suitable for a working pressure of from:

A. B. C. D.

Diesel engine Motor Steam engine

862 to 1200 kPa 758 to 1000 kPa 500 to 1000 kPa 658 to 1050 kPa

10. In

an Internal combustion engine, the stroke that discharges gas inside the engine's cylinders:

A. B. C. D.

compression power

the apparent power in any circuit is known

A. B.

Measured Power

C.

Power Factor

D.

KVAR

I ~. In process of pair formation, a pair cannot be formed unless the quantum has an energy greater than:

A. B. C. D.

Capacity

A. B.

Carbon dioxide and water

C. D.

Carbon monoxide, water and ammonia

A. B. C. D.

Water, carbon monoxide and carbon dioxide

valve piston connecting rod

The odorless refrigerant; its boilingpoint varies over a wide range of temperatures:

A. B.

Freon 22 Freon 12

1/2 mV 2 05MeV hv/C

color scale at 2200 0f is roughly:

Carbon monoxide

wrist pin

2 moC 2

I (i. The temperature of hot metals can be estimated by their color. For steel iron, the

The part that directs the flow of the refrigerant through the compressor:

A. B. C. D. 14.

a_

of that circuit.

12. The product of complete combustion of gaseous hydrocarbons

13.

general term for a device that receives information in the form of one or more physical guantities, modifies the information and/or its form, if required, and produces a resultant output signal: A. Converter B. Transducer C. Sensor D. Scanner

exhaust

the

1111

I 7. A

inlet

11. The ratio between the actual power and

'1

Ammonia

16. Medium

Gasoline engine

111111

'~

Freon refrigerants

J 5. The boiling point of freon 22 is:

One of the two types of non-material nuclear radiation is:

A. B. C.

ET - 3

'I J

white orange dark red yellow

Mathematically, a thermodynamic property is which of the follOWing? A. a point function

B. C. D.

discontinuous a path function exact differential

,. - - - -

21. A

device whose function is to pass an information in an un hanged form or in some modified form:

A. B. C.

sensor

D.

transducer

A. B. C. D.

is to meter the flow of refrigerant to the evaporator:

,

A. B. C. D.

equalizers thermostatic expansion valve crossover valves of the compression stroke:

30.

air cell

thermal treatment lime soda treatment demineralization process ion exchange treatment

Engines using heavy fuels require heating of the fuel so that the viscosity at the injector is:

sniffer valve

A. B. C. D.

24.

A. B. C. D.

29.

ET - 5

A chemical method of feedwater treatment which uses calcium hydroxide and sodium carbonate as reagents:

transmitter

23. The volume remaining when the piston reaches the end 1111111

28.

relay

22. A device whose primary function

II~I~

Elements and Terms- MODULE 1

Elements and Terms- MODULE 1

ET - 4

around 200 SSU

100 SSU or less 200 SSU ± 50

150 SSU or slightly higher

The temperature of a fluid flowing under pressure through a pipe is usually measured by:

A. B. C. D.

combustion chamber turbulence chamber pre-combustion chamber

glass thermometer electric-resistance thermometer thermocouple all of the above

Specific heat capacity is an SI derived unit described as:

A. B. C. D. 25.

J/kg

J 1. An

increase in the deposition of slag and ash on the surface for heating of oil-fired boilers in both marine and stationary service has affected boiler efficiency. The following are the causes except:

W/m-oK

J/m

3

A. B. C. D.

J/kg-OK

The fundamental difference between pipe and tubing is:

A. B. C. D.

II..

•• 26.

Compression Joints The smoothness of the surface

\2.

Roots type blower Pulse turbocharger Constant pressure turbocharger Turbo compressor

Crankshaft of reciprocating type compressor is basically made of:

A. B. C. D.

semi-steel aluminum alloy cast iron steel forging

Siagging of high temperature superheater surfaces High temperature corrosion of steel Increase of heat transfer in the boiler

The type of filter where the filtering element is replaceable:

A. B. C. D.

Bell and spigot joint

One of the most popular types of compressor is basically made of:

A. B. C. D. 27.

The dimensional standard to which each is manufactured

Low temperature corrosion of the cold section of air heaters and duct works

paper edge filter metal edge filter pressure filter filter with element

\3. Which does not belong to the group? A. air injection system B. mechanical injection system C. time injection system D. gas admission system q.

Cooling water system consists of equipment to dissipate heat absorbed by the engine jacket water, lub oil and the heat to be removed from air intercooler in measurable to keep the engine outlet water temperature constant and the differential of the cooling water at a minimum preferably not to exceed:

1\. 10 to 30°F

B. C. D. 35.

Elements and Terms- MODULE 1

Elements and Terms- MODULE 1

ET -6

~

10 to 50°F

I, What

is the process whereby a fissionable species is utilized as a source of neutrons to produce more nuclei of its own kind than are used up?

10 to 20°F

A. B. C. D.

10 to 40°F

There are two broad types in the classification of lubricating oils, they are:

straight

and

11.1~

36.

,­

37.

C. D.

crooked

+2.

inactive additives

A. B. C.

does not change

D.

indeterminate

38.

Developing Culturing Multiplying Breeding

A process of heat transfer due to motion of matter caused by a change in density:

A. B.

Absorption

C.

Conduction

D.

Convection

Radiation

~ 3. Ii. 'rat is the most efficient thermodynamic cycle?

greater

A. B.

lesser

What is the function of the compression joint of pipes or tubes?

A.

it is used to connect two pipes by welding

B.

it is used to connect two pipes by pressing both ends

C.

when tightened, compress tapered sleeves so that they form a tight joint 01 the periphery of the tubings they connect

D.

it connects two pipes with the use of threaded couplings

Carnot Diesel

C,

Rankine

D.

Brayton

~ ..:j.. The diagonal lines in the Psychrometric Chart represent:

A. B. C. D.

Effective temperature Dry-bulb temperature Wet-bulb temperature Dew-point temperature

The component of a rotary pump

11lI"

'"

••

active

Amount of air required in the low by-pass factor

'II~III

]

A. B.

ET -7

39.

40.

A.

gears

B.

piston

C. D.

impeller

15.

screw

An instrument commonly used in most Research and Engineering Laboratorl because it is small and fast among the other thermometers:

How do you treat a statement that is considered a scientific law?

A. B.

We postulate to be true

C.

We generally observed to be true

D.

Believe to be derived from mathematical theorem

Accept as a summary of experimental observation

i 11. The transmission of heat from one place to another by fluid circulation between tile

A. B.

mercury thermometer Iiquid-in-glass thermometer

A.

Convection

C.

gas thermometer

B.

Radiation

D.

thermocouple

C. D.

Conservation

What is the term used to express the ratio of specific humidities, actual vers saturated?

spots of different temperatures is called:

Conduction

, What is referred by control volume?

;\. Relative humidity

I ~,

Absolute humidity

('

[ I, ''I'' 't'

I ),

Pur cunt saturation

of saturation

A. B. C.

An isolated system Closed system Fixed region in space

I). Reversible process only

48.

A. B. C. D.

Which of the following types of flow meters is most accurate?

A. B. C. D.

Venturi tube Pitot tube Flow nozzle

A. B. C. D.

II". 50.

steam water natural gas

[Tl11111111/('

friction losses

dlr(~cIIOll

a pipe expander fitting a large radius bend in a pipe line to absorb longitudinal expansion in the pipe line due to heat

56. What is the color code of steam A. silver gray B. green C. red D. yellow

pipe lines?

air

'i 7, What is absorb by sulphites in boiler water treatment? A graphical representation between discharge and time is known as:

A. B. C. D.

111111

51.

a double long radius elbow to

a pipe bent to a loop to chanqe

ET ­

Foam type

49. Pneumatic tools are powered by:

.~

Elements and Terms- MODULE 1

Elements and Terms- MODULE 1

ET - 8

monograph

A. B. C.

hydrograph

I) carbon dioxide and oxygen

hectograph

'\8.

A. B.

water and ash content

C.

high cetane number

D.

sulphur and asphaltene content

high octane number

;;; 9.

53. The

54.

boiler pressure furnace temperature boiler drum pressure

A.

relative humidity

B. C. D.

percent saturation degree of saturation specific humidity

Highest pressure drop in refrigeration cyle:

I ,

a restriction In flow area occurs

a valve designed to allow a fluid to pass through in one direction only a valve designed to release the excess pressure a valve which allows flow of fluid in either direction a valve used for checking the pressure of fluid

Expansion valve Evaporator '1,1.

lubricating oil pre-heater in an emergency

to keep the !ub oil viscosity down under cold condition and enhance the starting of the cold engine

B. C. D.

to avoid moisture condensation in the engine to avoid corrosion to engine parts to see to it that the lubrication system is functioning properly

of the following refrigerants is most highly toxic?

A. B. C. D.

Condenser


A.

I , Which

Compressor

What is an expansion loop?

shock waves always occur a valve is closed in a line

110. What is the prime purpose of providing stand-by diesel genset?

specific measurement of moisture content of air:

A. B. C. D. 55.

boiler water weight

the specified mass flow rate cannot occur

What is a check valve?

A. B. C. D.

52. What is the function of a radiation pyrometer? A. B. C. D.

What is meant by choking in pipe flow?

A. B. C. D.

difficult?

••

impurities settled in mud drums

topograph

In a diesel engine, what elements in the fuel that make the work of the lubricant more

I.

oxygen carbon dioxide

Ammonia Freon 12 Sulfur dioxide Methyl chloride

Wilter turbine converts:

r

A. B. C. D. 63.

B. C. D.

mechanical energy into electrical energy hydraulic energy into electrical energy mechanical energy into hydraulic energy hydraulic energy into mechanical energy

70.

A. B. C. D.

Time for a pressure to traverse the pipe The pressure reservoir at the end of the pipe Rate of deceleration of flow Relative compressibility of liquid expansion

71.

A. B. C. D.

is:

II~lIIi

65.

reversible adiabatic process constant entropy process irreversible adiabatic process isometric process

must be calculated equal to zero negative positive

What characterizes a reaction turbine?

-­

•• 67.

A. B.

steam losses velocity as it leaves the diaphragm

C.

steam will react with a force in the diaphragm

D.

steam is deflected

steam strikes the blades at right angles

The work done in an adiabatic process in a system:

A. B. C. D. 68.

is equal to the net heat transfer plus the entropy change is equal to the change in total energy of closed system plus entropy change is equal to the change in total energy of closed system plus net transfer

How do you increase the output of a centrifugal pump?

A. B. C. D. 69.

is equal to the change in total energy in a closed system

speed up rotation install recirculation line increase the suction pipe area increase the discharge pipe area

Based on the first law of thermodynamics, which of the following is wrong?

A. The heat transfer equals the work piUS energy change

The net heat transfer equals the net work of the cycle The net heat transfer equals the energy change if no work is done

sulfur dioxide silicon dioxide hydrogen dioxide nitrogen dioxide

turbo blower in exhaust header to create vacuum in cylinders air reversing direction in cylinders uses two blowers to purge cylinders air travelling in one direction

One .Ioule of work is done by a force of one Newton acting through a distance of:

Assuming real process, the net entropy change in the universe is:

A. B. C. D.

66.

72.

The heat transfer cannot exceed the work done

What takes place in a uniflow scavenging?

Throttling of the refrigerant through the expans'on valve in a vapor refrigeration cycle

A. B. C. D.

ET - 11

The main cause of air pollution as a result of burning fuel oil is:

How do you differentiate surge from water hammer?

A. B. C. D.

64.

Elements and Terms- MODULE 1

Elements and Terms- MODULE 1

ET -10

A.

one meter

B. C. D.

one inch a foot one cm

73. In

a centrifugal pump, if the impeller is kept the same and the speed varied, the pump output shall change in accordance to the equation:

A. B. C. D.

=N = O2

0,/0 2 0,

2/N

,

0, + N, = O 2 + N2 O 2/0,

=N

2/N,

74. In an Imhoff Tank: A. the effluent contains very little dissolved oxygen B. there are no settling compartments C. the sludge and raw sewage are not mixed D. the sludge and fresh sewage are well mixed to give complete digestion 75. A thermodynamic

system which undergoes a cyclic process during a positive amount of work os done by the system:

A. B. C. D.

reversed rankine cycle heat pump reversible-irreversible process heat engine

7(). The transmission of heat from hot body to cold body by electromagnetic wav" .. called: ;\. conduction

I ..

If

---------

B. C. D. 77.

Elements and Terms- MODULE 1

Elements and Terms- MODULE 1

ET -12

B. C. D.

absorption convection radiation

The boiling point of Freon 12 CCI,F,:

A. B. C.

84.

78.

A. B. C. D.

-416'C -40'C -29.6"C

With regards to corrosion of metals, passivation is the process that:

111111

79.

intensifies deterioration temporarily

B. C. D.

changes the composition of the metal

••

alters the grain size of the metal

A. B.

flow energy

C. D.

enthalpy

81.

A. B. C. D.

internal energy

A. B. C. D.

isobaric polytropic

A. I ~.

A. B. C. D.

quadruples remains constant halves

increase in enthalpy of a substance when it undergoes some phase change at constant pressure and temperature

A. B. C. D.

heat of fusion

heat of vaporization

1'1';11 of cyrstallization

tim ;IflI,It ''''l(~
l('\. If

.'\.

It JlJlllOlI" ... 1

liquid until the temperature drops to a certain point

temperature of 50% RH wet bulb temperature

4570 to 7620 mm/min 7800 to 9200 mmlmin 8500 to 10,000 mmlmin 8.00 to 10.0 mlmin

integral-grate boiler none of the above integral-furnace boiler integral-cogeneration boiler

To provide alert security To provide machines with appropriate guards To maintain a fire brigade To train delivery personnel

Class D Fire· fire caused by LPC:; Class B Fire - fire caused by oil and other hydrocarbons Class C Fire - electrical fire Class A Fire - fire caused by light combustible materials like paper and wood

,,(). All heavy machinery should be supported on solid foundations of sufficient mass and base area to prevent or minimize transmission of:

( .. heat of transformation

I).

temperature of grains of moisture per lb of bone dry air

~ R. Which of the four does not belong to the group?

doubles

S2. The

adiabatic saturation temperature

of the best known safety practices in industrial plant is:

A. B. C. D.

throttling

If an initial volume of an ideal gas is compressed to one-half its original volume and to twice its original temperature, the pressure

A. B. C. D.

:.; 7. One

isometric

its stoppage in cooling will result in water and ice mixture

A type of boiler which incorporates furnace water cooling in the circulatory system is otherwise known as:

shaft work

An adiabatic process with no work done is:

••

A. B. C. D.

S6.

it freezes out most of water into ice]

Air used for comfort cooling shall maintain a movement of from:

inhibits further deterioration

(u + pv) is a quantity called:

.1 80.

;\.

S5.

cooling the solution below the limit liquifies the entire mixture

Dew point is which of the following?

D.41 8 C 'Il~

ET -13

'I().

objectionable vibration to the building and occupied space objectionable vibration or forces from nearby machine better control of the drainage system objectionable sound coming from the exhaust

On existing installation boiler, to lowest factor of safety permissible shall be:

A.

7

B. 6

Elements and Terms- MODULE 2 ET -14

C. D.

C. 5 D. 4.5 91.

"'II

••

.

99.

20 years

tensor

100.

tangent

B. C. D.

It is elastic. It has a high modulus of elasticity . It is plastic It is ductile.

A type of water turbine where a jet of water is made to fall on the blades or buckets and due to the impulse of water, the turbine starts to move:

A. B. C. D. 96.

hot water cold water

A. B.

fermenters

C. D.

cooler

brew kettle starting tubs

resultant

A.

95.

vapor heavy water

Yeast as raw material for beer making is added to the equipment called:

represents the sum of two vectors?

A specimen is subjected to a load. When the load is removed, the strain disappears. From this information, which of the following can be deduced about this material?

••

water

30 years

93. Which of the process where work done is zero? A. isentropic B. polytropic C. isometric D. isobaric

...."

A. B. C. D.

35 years

B. C. D.

94.

air

Which is used as a moderator in certain types of nuclear reactors?

18years

92. What is the name for a vector that A. scalar

l1li11

.J

1)8.

The age limit of a horizontal return tubular flue or cylinder boiler having a longitudinal lap joint and operating at a pressure in excess of 0.345 MPa or 3.45 Bar gage shall be

A. B. C. D. "l~

ET -15

Elements and Terms- MODULE 1

Pelton wheel steam turbine Francis turbine reaction turbine

What keeps the moisture from passing through the system?

A. B. C. D.

dehydrator aerator trap humidifier

MODULE 2 What are the main components in a combined cycle power plant?

A. B. C. D.

diesel engine and air compressor gas engines and waste heat boiler steam boiler and turbine nuclear reactor and steam boiler

What do you call the changing of an atom of an element into an atom of a different element with a different atomic mass?

A. B. C. D.

atomization atomic transmulation atomic pile atomic energy

What condition exists in an adiabatic throttling process?

A.

enthalpy is variable

ll.

enthalpy is constant

( . . entropy is constant

I ).

',P"l:lfic volume is constant

In. Tho IIpoelfl<: ur'1vlty of a substance is the ratio of its density to the density of: /\.

Illl'!l

H.

1).0',

urv

What do you call the weight of the column of air above the earth's surface?

A. B. C.

air pressure aerostatic pressure wind pressure

f). atmospheric pressure

Combined process of cooling and humidifying is also known as:

5.

Elements and Terms- MODULE 2

Elements and Terms- MODULE 2

ET -16

1 1. What

do you call the passing of heat energy from molecule to molecule through a substance?

A. B.

heating and humidifying evaporative cooling process

A. B.

conduction

C. D.

moisture removal process

C.

conservation

D.

convection

cooling tower

What is the force required to accelerate a mass of 1 gram at a rate of 1 cm/sec/sec?

is the lowest temperature to which water could possibly be cooled in a cooling tower?

A. B C, D.

What type of turbine has low head and high discharge?

;\ . Pelton wheel

111M

7.

8.

H.

Francis turbine

C. D.

Jonval turbine

13. The

What is a Bull Head Tee? A. a pipe tee with head shaped like a bull

B.

a welded built-up tee

C.

a pipe tee with its run larger than its branch

D.

a pipe tee the branch of which is larger than the run

14-. Dew

What is the main power generating plant that produces the most electricity per un. thermal energy in the fuel input and has the greatest surplus of electricity for motlj cogeneration systems? steam engine

9.

the temperature of adiabatic saturation

the wet bulb depression

the dew point temperature of the air

Aniline point Cetane No, Octane No. Diesellndex

point is defined as:

A.

the temperature to which the air must be cooled at constant pressure to produce saturation

B. C. D.

the point where the pressure and temperature lines meet the temperature which dew is formed in the air the pressure which dew is formed in the air

.

:, 5.

steam turbine

What type of lubricating oils are produced entirely from the crudes chosen through

elimination of undesired constituents by suitable refining processes?

A. B. C. D.

gas turbine

D.

the effective temperature

indicator used to determine the anti-knock characteristics of gasoline:

A. B. C. D.

Kaplan turbine

A. B. C.

radiation

12. What

A. dyne B. poundal C. slug D. kg force 6.

ET -17

diesel engine

What is the term as the ratio of the volume at the end of heat addition to the volume

additives inert straight premium

the start of heat addition?

A. compression ratio B. air-fuel ratio C. volumetric ratio D. cut-off ratio

I n.

What is the ideal cycle for gas turbine work?

. (1.

In a liquid-dominated geothermal plant, what process occurs when the saturated

steam passes through the turbine?

A. B. C. D.

isobaric . polytropic isometric isentropic

1\ , Brayton cycle

I~

:~I;lq combined cycle

(

11,,11')1" «vcte

I ).

I

III ',' ,"

'yl,­

Gas being heated at constant volume is undergoing the process of:

A. B.

isotropic adiabatic

III

III

II

C. D.

,~

'l

isobaric

"

A. B. C. D.

1:2:5

A. B. C. D.

20. How does the

values for work per unit mass flow of air in the compressor and turbine' influenced by the addition of a regenerator? '

L.l ".1­

......

.­

C. D.

greatly decreased

unchanged

D.

27.

A. B.

C. D.

21. The work done by

a force of R newtons moving in a distance of L meters is converted' entirely into kinetic energy is expressed by the equation:

22. In

A. B. C.

RL = 2MV

D.

RL = 1/2 MV

RL = RL N-m

250°F

3

evaporator combustion chamber regenerator heater

normally flowing from a high temperature body to a low temperature body wherein it is impossible to convert heat without other effects Is called the:

= 1/2 MV 2

B.

air temperature entering air heater increases

C. D.

furnace pressure is approximately constant

:2 9.

does not indicate qualities qualities viscosity

design stability, the center of gravity of the total combined engine. equipment and foundation should be kept:

second law of thermodynamics

B. C.

first law of thermodynamics third law of thermodynamics

What are the immediate undesirable products from the petroleum-based lubricating oil when subjected to high pressure and temperature?

A. B. C. D.

economizer gas outlet temperature decreases

does not indicate contamination

A.

D. zeroth law of thermodynamics

The color of lubricating oil indicates:

24. For

300°F

28. Heat

a steam generator with good combustion control, what occurs if the load

A. B. C. D.

150°F 200°F

2

increased? A. air temperature leaving air heater decreases

23.

below the foundation top

Heat exchanger used to provide heat transfer between the exhaust gases and the air prior to its entrance to the combustor:

greatly increased

RL

in line with the surface of the foundation

A.1 B. 5 C. 1/2

1:2:4

slightly increased

above the foundation top

What is the suggested maximum permissible dose (MPD) of gamma ray exposure for general individuals not working in a nuclear setting, by choice, in rem/year?

2:3:5

A. B.

anywhere

commercially available petroleum lubricating oil deteriorates starting from operating temperature of:

26.

2:4:6

ET -19

25. Most

Foundations are preferably built of concrete in the proportion of what measures of portland cement: sand: crushed stones?

r-III~

~.. ,..

A. B. C. D.

I,;

isometric

18. A receiver in an air compression system is used to: A. avoid cooling air before using B. increase the air discharge pressure C. collect water and grease suspended in the air D. reduce the work needed during compression 19.

Elements and Terms- MODULE 2

Elements and Terms- MODULE 2

ET -18

'0.

gums, resins, and acids sulfur soots and ashes carbon residue

The intake pipe to a hydraulic turbine from a dam is:

A. B.

spiral casing

C.

surge tank

tailrace

D. penstock

ET·20

31.

When 1 mol of carbon combines with 1 mol of oxygen:

A. B. C. D.

32.

A. B. C. D.

1 mol carbon and 1 mol carbon dioxide 1 mol carbon monoxide

D. 33.

aneroid

39.

anemometer

A. B. C. D.

anemograph

Air standard efficiency of a diesel engine depends on

34.

35.

compression ratio

36.

x

= number of ions

produced per mass of air + coulombs per kg

120°F 180°F 150°F 130°F

W. What is the

process that has no heat transfer?

A.

reversible

torque

B.

isothermal

Heavy water is:

+1. The

polytropic

D.

adiabatic

0 2 0 (2 is written as subscript)

demand factor diversity factor power factor utilization factor

the deficiency air supplied the actually air supplied none of these the theoretically air supplied

Mechanism designed to lower the temperature of air passing through it:

internal combustion engine never work on

A. B. C. D.

W 20 (2 is written as subscript)

Percent excess air IS the difference between the air actually supplied and the theoretical divided by:

A. B. C. D.

C. 8 20 (2 is written as subscript) H 20 (2 is written as subscript)

The ratio of the sum of individual maximum demands of the system to the overall maximum demand of the whole system:

A. B. C. D.

37.

x = mass of air over surface area of an exposed object

fuel

A. B. C. D.

~

x = mass of air x surface area of an exposed object

speed

A. B. C. D.

~lll"

x = number of ions produced per mass of air x coulombs per kg

The viscosity of most commercially available petroleum lubricating oil changes rapidly above:

anemoscope

A. B. C. D.

ET·21

The term "exposure" in radiological effects is used as a measure of a Gamma ray or an X-ray field in the surface of an exposed object. Since this radiation produces lonizatlon of the air surrounding the object, the exposure is obtained as:

1 mol carbon dioxide

A. B. C.

11-111l1li

....·..

F

'"..

.\8.

2 rnols carbon dioxide

A device for measuring the velocity of wind

"I~~

~.1

_I..

Elements and Terms- MODULE 2

Elements and Terms- MODULE 2

-\- 2.

cycle:

Rankine Diesel Dual combustion Otto

The dividing point between the high-pre~ure and refrigeration cycle occurs at the:

A. B. C. D.

low-pressure sides of the

expansion valve compressor condenser cooling oil

·13. What

is the force which tends to draw a body toward the center about which it is rotating?

A. B.

centrifugal force

C. D.

centrifugal advance

centrifugal in motion centripetal force

air cooler air defense air spillover air cycle

I-\-. The simultaneous generation of electricity and steam (or heat) in a single power plant:

A.

steam turbine-gas turbine

ET -22

B. C.

cogeneration

D.

waste heat recovery

excess air is the difference between the air actually supplied and the theoretically required divided by:

A. B. C. D.

"'11l1li

.J

1Irat...

.....

....·..

e

II­

..

~

52.

A. B. C. D.

the deficiency air supplied the actually air supplied none of these

A. B. C. D.

53.

A. B. C. D.

lesser indeterminate does not change

A.

equipotential surface

B. C. D.

potential at a point

54.

A. B. C. D.

potential difference

A.

1000 dynes/sq. cm

B.

1000 cm of Hg

B.

nuclear

C.

conduction

D.

radiation

A. B. C. D.

D.

cyclic process

quasi-static process isometric process

51. The

ratio of the average load to the peak load over a designated period of time Is called:

A.

load factor

plant use factor

hetrograph hygrometer hygrodeik hygrograph

calorimeter differential calorimeter gas calorimetry calorimeter

turbulent critical dynamic laminar

Q -W

= Uz - U 1

Q +

V dP = Hz - H1

Q -

V dP = Hz- Hj

Q - P dV

= Hz - H

1

')6. Is

one whose pressure Is higher than the saturation pressure corresponding to its temperature:

A. B. C. D.

a system deviates infinitisimally from equilibrium at every instant of its state, It is undergoing: isobaric process

diversity factor

equation applies in the first law of thermodynamics for an ideal gas in a reversible open steady-state system?

50. When

A. B. C.

reactive factor

55. What

C. 1000 psi D. 1000 kg! sq. cm.

49. Heat transfer due to density differential: A. convection

2

If the fluid travels parallel to the Adjacent layers and the paths of individual particles do not cross, the flow is said to be:

electrostatic unit

48. A pressure of 1 millibar is equivalent to to:

MODUL~

What is an apparatus used in the analysis of combustible gases?

greater

done per unit charge when charge Is moved from one point to another:

and Terms-

What is the clockwork-operated device which records continously the humidity of the atmosphere?

the theoretically air supplied

46. What amount of air is required in a low bypass factor?

47. Work

B. C. D.

gas turbine plant

45. Percent

,...~

I=/arnants

Elements and Terms- MODULE 2

"7.

saturated liquid compressed liquid saturated liquid compressed gas

The locus of elevations to which water will rise in the piezometer tube is termed:

A. B. C. D.

energy gradient friction head hydraulic g~adient critical path

58.

I

The total energy in a compressible or incompressible fluid flowing across any section in a pipeline is a function of:

A. B. C. D.

pressure and velocity

II"

A. B. C. D.

density of some standard substance is

'"

62.

relative gravity

uniform flow turbulent flow

A. B. C.

quantity of discharge through an orifice

D.

friction factor of a pipe

velocity of flow in a closed conduit length of pipe in a closed network

A. B. C. D.

A. B. C. D.

internal energy

liquid: absolute humidity calorimeter

evaporization vaporization

sublimation condensation

steady flow uniform flow

discharge continuous flow

"0.

pounds

Newton kilograms dyne

When a substance in gaseous state is below the critical temperature, It is called:

A. B. C. D.

vapor cloud moisture steam

boiling point thermal energy

. I . Is the condition of pressure and temperature at which a liquid and its vapor ant indistinguishable:

64.

A.

critical point dew point

gas turbine

B. C.

impulse turbine

I).

relative humidity

Type of turbine that has high pressure and low pressure is called:

A. B. C.

as:

h9. S. I. unit offorce:

potential energy

The temperature at which its vapor pressure is equal to the pressure exerted on the

affects the distribution of air'

h8. Weight per unit volume is termed A. specific gravity B. density C. weight density D. specific gravity

kinetic energy

frictional energy

lowers the temperature of the air does not affect the distribution of air

The volume of a fluid passing a cross section of a stream In unit time is called:

A. B. C. D.

continuous flow

A. B. C. D.

63.

67.

steady flow

The sum of the energies of all molecules in a system, energies appear in sever, complex forms, is the:

••

A. B. C. D.

specific density

The hvtiraullc formula CA..J 2gH is used to find:

adds moisture to the air

changing of solid directly to vapor, without passing through the liquid state is called:

specific gravity

B. C. D.

compound turbine

66. The

relative density

At any instant, the number of particles passing every cross-section of the stream is the same, the flow Is said to be:

ET - 25

design of an air supply duct of an air conditioning system:

A. B. C. D.

flow energy, kinetic energy, height above datum and internal energy

A.

61.

65. The

pressure, density, velocity and viscosity

called:

60.

D.

pressure, density and velocity

59. The ratio of the density of a substance to the

r

Elements and Terms- MODULE 2

Elements and Terms- MODULE 2

ET - 24

compound engine

absolute humidity

ET -26

72.

If the temperature ill held constant and the pressure is increased beyond the saturation pressure, we have a:

A. B. C. D. 73.

saturated vapor compressed liquid saturated liquid

-: 9.

A. B. C. D.

74.

75.

76.

77.

78.

inward flow reaction outward flow reaction

D.

pressure, height above a chosen datum, velocity of flow, density of fluid

Parson Hero Pelton Banki

\(). If the pressure of the confined gas is constant, the volume is directly proportional to the absolute temperature:

inward flow impulse

A. B. C. D.

2

5.40 x 10

4.13x10 3

22.6

X

10 5

3.35x10 5

,~

heat

A. B. C.

vaporization curve

D.

sublimation point

fusion curve boiling point

The number of protons in the nucleus of an atom of the number of electrons in the orbit of an atom:

A. B.

atomic volume

C. D.

atomic weight

atomic number atomic mass

The energy of a fluid flowing at any section in a pipeline is a function of:

Joule Charles Kelvin

theoretical body which when heated to incandescence would emit a continuous light-ray spectrum:

A. B. C. D.

kinetic energy heat of fusion

Boyle

I. A

internal energy

In a poT diagram of a pure substance, the curve separating the solid phase from the

liquid phase is:

A. B.

height above a chosen datum, density, internal energy, pressure and velocity of flow

outward flow impulse

Form of energy associated with the kinetic energy of the random motion of large number of molecles:

A. B. C. D.

C.

A. B. C. D.

subcooled liquid

The latent heat of vaporization in joules per kg is equal to:

A. B. C. D.

Ill"!

ET -27

A type of water tu rbine:

Francis turbine has what flow:

~I~I

"I

Elements and Terms- MODULE 2

Elements and Terms- MODULE 2

-:2.

black body radiation black body blue body white body

Ignition of the air fuel mixture in the intake of the exhaust manifold:

A. B. C. D.

backlash backfire exhaust pressure back pressure

'\ .~. When a substance in gaseous state is below its critical temperature it is called:

A. B. ,C. D.

steam cloud moisture

vapor

~.+. Number of molecules in a mole of any substance is a constant called:

A. B. C. D.

Rankine cycle Avogadro's number Otto cycle Thompson constant

velocity of flow only pressure only

>.; '). Is one whose temperature is below the saturation temperature corresponding to its pressure: ;\. compression

ET -28

86.

·,

Elements and Terms- MODULE 2

B.

condensation

C.

constant volume process

D.

subcooled liquid

93.

Ill"!

A.

air cooled engine

B,

air compressor

C. D.

air condenser

,.,_I •

90.

91.

92.

Redwood

entropy degrees API SSU Centipoise

air injection

94.

The chemical formula for butane:

A. B.

C,HsCI C3H 8

hydraulic gradient

C. C,H.O,

energy gradient

D.

D.

friction gradient

95.

=Cv A. B. C. D.

.

Which is not a viscosity rating:

A. B. C. D.

In sensible cooling process, the moisture content:

Cp

CCIF3 CHCI,F

B. C.

A. B. C. D.

89.

C. D.

Pump used to increase air pressure above normal, air is then used as a motive power:

87. The locus of elevations: A. critical point

88.

Elements and Terms- MODULE 2

C.H,o

When droplets of water are carried by steam in the boiler: A. priming

does not change

B.

foaming

decreases

C.

carryover

indeterminate

D.

embrittlement

Increases

+ R applies to:

96.

all pure substances enthalpy two phase states

Mechanical energy of pressure transformed into energy of heat: A. kinetic energy

B. C.

heat exchanger

D.

heat of compression

enthalpy

ideal gases

97. What air pressure is needed for air starting a Diesel engine, about:

A. B. C.

450 psi

D.

150 psi

A. B. C. D.

350 psi 250 psi

98. In the hydro-electric plant having a medium head and using a Francis turbine, the turbine speed may be regulated thru:

A. B. C.

deflector gate

D.

forebay

nozzle

wicket gate

The chemical formula for methyl chloride:

A. C,HsCI B. CH,CI

The chemical formula for methylene chloride:

CHCI,F CH 2CI2

CCIF3 CH3CI

The theory of changing heat into mechanical work:

A. B. C.

kinematics

D.

thermodynamics

horsepower inertia

()9. In the flow process, neglecting KE and PE changes, A. flow energy

B.

heat transfer

C. D.

enthalpy change

shaft work

Jv dP represents:

ET -29

Elements and Terms- MODULE 3

ET - 30

100.

back pressure partial pressure

li

2.

..

A. B. C. D.

Maximum Minimum Average Logarithmic average

9.

A. B. C. D.

can never be found if frictionless fluid regardless of its motion can never be found when the fluid is at rest depend upon cohesive forces

Kinematic viscosity/ Dynamic viscosity

C. D.

Kinematic viscosity x dynamic viscosity

kinetic viscosity

Is independent of the motion of one fluid layer relative to an adjacent layer When there is no motion of one fluid layer relative to an adjacent layer. Only if the fluid is frictionless. Only is fluid is frictionless and incompressible.

Of no practical importance to designers Always used to design pipes for strength The number at which turbulent flow changes over to laminar flow The number at which laminar flow changes into turbulent flow

10. A

2

liquid compressed in a cylinder has volume of 1 litre at 1 MN/m and a volume of 995 cu. m at MN/m'. The bulk modulus of elasticity is:

Density in terms of viscosity is:

A. B.

Darcy weisbach friction factor

The upper critical Reynold's number for pipr flow is:

Which is incorrect statement Apparent shear forces?

may occur owing to cohesion when the fluid is at rest.

pressure coefficient Weber number

The normal stress is the same in all directions at a point in fluid:

The velocity of a fluid particle at the centre of the pipe section is:

A. B. C. D.

3.

A. B. C. D.

8.

Cheap and easily available.

Which of the following is not a dimensionless parameter?

mean effective pressure

A. B. C. D.

I

7.

pressure drop

MODULE 3 1.

D.

Average pressure on a surface when a changing pressure condition exist:

A. B. C. D.

A. 200 MPa B. 1100 MPa C. 15 MPa D. 110 MPa

Dynamic viscosity/Kinematic viscosity

None of the above .

I 1. The 4.

5.

A. B. C. D.

2VD/v VD>t /8

VDp/1! VD

5/>t

51 unit of viscosity is: A. 10 times poise

B. C. D.

6.

length of mercury column at a place at an altitude will change with respect to that at ground in a

The Reynolds number for pipe flow is given as follows:

A. B. C. D.

ET - 31

Elements and Terms- MODULE 3

9.81 times poise 1/9.81 times poise 1/10 times poise

Alcohol finds use in manometers as:

A. B.

It provides a suitable meniscus for the inclined tube

( '.

A and B above are correct

Its density being less can provide longer length for a pressure difference, thus more accuracy can be obtained.

linear relation parabolic relation will remain constant

first slowly and then steeply

12. The volumetric change of a fluid A. volumetric strain B. volumetric index C. compressibility D. adhesion

13.

caused by a resitance is called:

Mass density of liquid (p) is given by which of the following:

A. r B. p C. p

= MasslVolume

= Metric slug/m = kg secvm"

2

ET - 32

D. 14.

Ull il

cohesion

"'11

Conditions remain unchanged with time at any point Rate of change of velocity opf fluid is zero

D.

compressibility

A.

adhesion

B. C.

cohesion

D.

viscosity

At every point the velocity vector is identical in magnitude and direction for any given instant The change in transverse direction

zero

'. The equation of continuity of fluids is applicable only if:

A. B. C. D.

The flow is steady The flow is one dimensional The velocity is uniform over the cros s-ser.trons all of the above

, i. The continuity equation for an ideal fluid flow 3

condition is the specific weight of water is 1000 kg/m ?

at normal pressure 760 mm

B. C.

at 4°C temperature

D.

all of the above

At mean sea level

A.

States that the net rate of in-flow uito any small volume must be zero

B. C. D.

Applies to irrotational flow only States that the energy remains constant along stream line States that energy is constant everywhere in the fluid

)-+. Neglecting the forces due to

inertia, gravity and frictional resistance, the design of a channel can be made by comparing:

pressure at a point in a fluid will not be same in all the directions if the fluid is:

A. B. C. D.

In motion viscous viscous and static

Weber number Reynolds number Froude's number Plandtl number

viscous and is in motion t

18. Which

of the following can be used to measure the flow of water in a pipe of diameter 3000 mm?

19. An

IS

surface tension

A.

A. B. C. D.

....

A. B. C.

viscosity

16. Under which

17. The

...

adhesion

Mercury does not wet glass because of the property known as:

·'1

ET - 33

Uniform flow takes place when: all of the above

Property of a fluid whereby its own molecules are attracted is known as:

A. B. C. D.

15.

Elements and Terms- MODULE 3

Elements and Terms- MODULE 3

.':;. The ratio TJ =

du / d

for turbulent flow is:

A.

venturimeter

A.

One of the physical properties of the fluid

B.

rotameter

C.

B.

Dependent upon the flow and density

nozzle pitot tube

C. D.

The viscosity divided by the density

D.

ideal fluid is one that:

A.

Is very viscous

B. C.

Obeys Newton's law of viscosity

D.

frictionless and incompressible

For smooth turbulent flow the friction factor changes as:

A. NR B. "I~ C. N R3/ 2 D. NR" 4

Is assumed in problems in conduitJlow

20. The equation of continuity of flow is applicable if: A. B. C. D.

2h.

The flow is one dimensional

A function of temperature and pressure of fluid.

.27, In

order to avoid vaporization in the pipeline, the pipeline over the ridge is laid in such a way that it is not more than: 2.4 m above the hydraulic gradient

The flow 'is compressive

A. B.

All of the above conditions together.

C

100 m above the hydraulic gradient

The flow is steady

6.4 m above the hydraulic gradient

ET - 34

Elements and Terms- MODULE 3

Elements and Terms- MODULE 3

D.

B.

5.0 m above the hydraulic gradient

28. The continuity equation is applicable to: A.

Vector difference of two velocities.

36. Which is higher head?

compressibility of fluids

C.

conservation of mass

A.

steady unsteady flow

B.31.0ftwater

C. D.

rise or fall of head "h" in a capillary tube of diameter "d" and liquid surface tension "a" and specific weight "w" is given by:

~,.II

Average velocity

D.

viscous unviscous fluids

29. The

~"I

A.

4a/wd

B.

4dCJ/w

C. D.

4wd/CJ

37.

Gas law Boyle's law

C.

Charle's law

D.

Pascal's law

_II

...

..

75.0 cm of Hg

=

4wa/d

B.

1.013 kg kern"

A.

principle of:

JHQ

~HQ

C.

A.

A high head mixed flow turbine A impulse turbine, inward flow

C.

A reaction turbine, outward flow

D.

Low head axial flow turbine

D.

38.

~HpQ

J*

A ship whose hull length is 100 m is to travel at 10 m/sec. For dynamic similarity, at what velocity a 1: 25 model be towed through water?

A.

10 m/sec

A.

Francis turbine

B.

25 m/sec

B.

Kaplan turbine

C.

2 m/sec

C.

Propeller turbine

D.

50 m/sec

D.

Pelton Wheel

32. Select one turbine that is different from the others:

39.

For stable equilibrium of floating body its metacentre should lie

of a Pelton wheel gives

A.

below the centre gravity below the centre of bouyancy above the centre of bouyancy

A.

Actual operating speed

B.

B.

No load speed

C.

Full load speed

C. D.

D.

No load speed when the governor mechanism fails.

34. Select the

'+0.

turbine that is different from others:

A.

At the centroid above the centroid At meta centre

A.

Pelton Wheel

B.

Banki turbine

C. D.

Jonval turbine

C. D.

Kaplan turbine

35. Which of the following is relative velocity? The difference between two velocities.

above the centre of gravity

Centre of pressure on an inclined plane lies B.

A.

=

B.fP

B.

33. Running away speed

=

p

30. McLeod gauge used for low pressure measurement operates on the A.

33 inch Hg

The ratio of the specific speed for a centrifugal pump based on unit discharge to that on unit power is (H Head, P HP, Q discharge) given by:

31. A Kaplan turbine is:

....

The average between the higher velocity and average velocity.

C.

B.

D.

ET·35

.f 1. The

Below the centroid

line of action of the bouyant force always acts through the centroid of the:

A.

Submerged body

B.

Volume of the floating body

ET - 36

C. D. 42.

D.

Volume of the fluid vertically above the body Displaced volume of the fluid

49.

A. B. C. D.

Has no velocity component tangent to it. Has uniformly varying dynamic pressure Has no velocity component normal to it Exists in case of rotational flow

50.

"

Increasing the flow rate

B.

Reducing the flow rate

C.

Reducing the velocity flow

D.

A. B. C. D.

Reducing the energy flow

51.

1 ""

1

44.

Stratified rocks Popping rocks Crushed rocks Swelling rocks

4-5 mls 10-12 mls 13-16 mls 20 mls

The maximum continuous power available from a hydro-electric plant under the most adverse hydraulic conditions, is called:

The lowest portion to storage basin from where the water is not drawn, is:

A. B. C.

Gravity, viscous and turbulent

Permissible velocity of water flowing through concrete tunnal, is generally:

Hydraulic jump is used to

A.

ET·37

Rocks having excessive internal stresses may produces spalling, are called that:

An equipotential line is one that:

A. B. C. D. 43.

Elements and Terms- MODULE 3

Elements and Terms- MODULE 3

A. B. C. D.

Bottom storage sub soil storage Spring reserve

Base power Firm power Primary power Secondary power

D. Dead storage 52. The

4S. The pitot tube is a device used for measurement of A. B. C. D.

lit' "II

..

....

A. B. C. D.

Pressure Flow Velocity

Utilization factor Maximum load factor Capacity factor

Orifice refers to an opening

A. B. C. D.

Hygrometer is used to find out

A. B. C. D.

Load factor

Discharge

'\3. 46.

ratio of maximum load to the rated plant capacity is called:

Specific gravity of liquids Specific gravity of solids Specific gravity of gases

With closed perimeter and of regular form through which water flows With prolonged sides having length of 2 to 3 diameters of opening in thick wall With partially full flow In hydraulic structure with regulation provision.

Relative humidity

.'::;4. The

47.

A. B. C.

D. 48.

value of coefficient of discharge in comparison to coefficient of velocity Is found to be:

Mach number is significant in case of Supersonics, as with projectiles and jet propulsion Full immersion or completely enclosed flow, such as with pipes, aircraft wing., nozzles, etc. Simultaneous motion through two fluids where there is a surface of discontinuity. gravity forces, and wave making effects, as with ship's hulls. All of the above

Gravity, pressure and viscous

( '.

Prp5SlIre. viscous and turbulent

Gravity, pressure and turbulent

More Less Same More/Less depending on flow

.::; '). Weir refers to an opening:

The fluid forces taken into consideration in the Navier Stokes equation are:

A. B.

A. B. C. D.

•

A. B. C.

Having closed perimeter and of regular from through which water flows

[).

In hydraulic structure with regulation provision.

Having prolonged sides having length of 2 to 3 diameters of opening in thick wall Having partially full flow

ET·38

56.

57.

A.

104

B. C.

6.8

D.

4.8

63.

=

=

87

82

64.

79

58. What

59.

..II

...

60.

15

12 9

D.

6

Froude number and relative roughness

C. D.

Reynolds number and relative roughness Mach number and relative roughness

67.

one-half of the total head supplied one-fourth of the total head supplied Equal to the total head supplied.

P4::=

(P, + P3)/2

P2

P, + (P, + P2)/2

Pz

JP

J

P + -VPI

2

+ P3

'f;

68.

1

1P3

2

In the polytropic process we have PV" the process is called:

= constant, if the value of n is infinitely large,

Rankine

For the same heat input and same compression ratio: Both Otto cycle and Diesel cycle are equally efficient Otto cycle is less efficient is compared to diesel cycle None of the above is correct.

The change in enthalpy for small temperature change dT for an ideal gas is given by the relation: dH

= CpdT

6H = CV6T

,-'lH = Cp/!\ T

~H = Cp/Cv ~T

I.

The 5.1. unit of pressure is: kg/cm 2

mm of water column Pascal

1). Dynes per square cm

One-third of the total head supplied

D. P2

Brayton

A. B. C.

Power transmitted through a pipe is maximum when the loss of head due to friction ;' is:

A. B. C.

62.

66.

Froude number and Mach number

Which of the following give the optimum intermediate pressure in case of two stage compression?

Isothermal process

Carnot

A. B. C. D.

Select the parameters that determine the friction factor of turbulent flow in a rough '. pipe are:

A. B. C. D.

61.

65.

A. B.

Constant temperature process

B.

D.

.

B. C.

Constant pressure process

C. Efficiency depends mainly on working substance

pressure differential, in pascals, exists at the bottom of a 3 m vertical wall when the temperature inside is 20°C and outside it is ·20°C. Assume equal pressure at the"

A.

Constant volume process

C. D.

A. B.

71

ET - 39

The thermodynamic cycle used in a thermal power plant is: A. Ericson

What will be the pressure, kPa, at height of 200 m in an isothermal atmosphere? Assuming T 20°C. Assume Patm 100 kPa.

A. B. C. D.

~

..

A. B. C. D.

5.6

~.

..

Elements and Terms- MODULE 3

The pressure force, in Newtons, on the 15 cm dia head light of an automobile travelling at 25 mls will be:

., ut ll

Elements and Terms- MODULE 3

,f1 ...

Superheated vapour behaves

lll '

A.

Just as gas

il

B.

Just as steam

ii, ,I

C. D.

Approximately as a gas

Just as ordinary vapour

A Sterling cycle has:

A. B. C. D.

Two isothermal and two adiabatic processes Two adiabatic and two isentropic processes Two adlabattc and two constant pressure processes Two isothermal and two constant volume processes

69. Brayton cycle has:

A.

Two isentroptcs and two constant volume processes

8.

Two isentropics and two constant pressure processes

:Iid

,....-­ ET -40

C. D. 70.

Two isentropics and two constant pressure processes Two adiabatic and two isothermal Two isothermal and two constant volume processes

Isentropic, isothermal, constant volume, constant pressure process Two isentropic, one constant volume, one constant pressure process

73.

Ericson cycle has:

79.

Two isothermals and two constant pressures processes Two isothermals and two isentropics processes Two adiabatic, constant volume and constant pressure processes

A. B. C. D.

Ilf"

..,,11

_I

A. B. C. D.

Brayton cycle is for low speed engines only cannot be efficiently handled In'

Otto cycle Dual cycle Rankine cycle Brayton cycle

75. Antifreeze chemicals are: A. B. C. D.

76.

A. B. C. D.

Brayton cycle is less efficient

74. Which cycle is generally used for gas turbine?

Same as refrigerants Those that are added to refrigerants for better performance Those that lower down the freeezing points of liquid Those that do not freeze at all.

Volume process Pressure process Temperature process Enthalpy process

Heat exchange process Isentropic process Throttling process Hyperbolic Process

Zeroth law of thermodynamics First law of thermodynammics Second law of thermodynamics Third law of thermodynamics

~

1 Nm/s 1 Nm/mt 1 Nm/hr 1 kNm/hr

1. For a six compression of air set, the minimum work conditions are: A. Pressure rise per stage will be equal B. Work done in successive stages will be in geometrical progression C. Cylinder volumes will be the same D. Temperature rise in the cylinders will be the same.

>.;2.

In case of steam engine the cut off ratio is the ratio of:

A. B. C. D.

Pressure at cut off to supply pressure Pressure at cut off to exhaust pressure Pressure at cut off to mean effective pressure Fraction of piston stroke which the piston has travelled when cut off occurs.

".\. The reason for insulating the pipes are:

A. B.

The point of maximum contamination of oil The level of impurities beyond which oil ceases to flow

A. B. C.

C.

The temperature at which oil solidifies

[). Heat loss from the surface is minimized.

Clog point of an oil refer to:

the process is called

~O. 1 watt is:

Otto cycle is highly efficient

Large volume of low pressure air reciprocating engines.

= C, then

Which of the following provides the basis for measuring thermodynamic property of temperature?

A. B. C. D.

Two isothermals and two constant volumes processes

Brayton cycle cannot be used in reciprocating engines even for same adlabatlc compression ratio and work output because

"Ill

.'

Two constant pressure, one constant volume, one isentropic process

n

A heat exchange process where in the product of pressure and volume remains constant called:

A. B. C. D.

Two constant volume, one constant pressure, one isothermal process

A. B. C. D. .'u

78.

Diesel cycle consists of:

The temperature at which paraffin and waxes in oil start precipitating.

If the value of n is definitely large in a polytropic PV constant:

A. B. C. D.

Two isentropics and two constant volumes processes

A. B. C. D. 72.

77.

Otto cycle consists of:

A. B. C. D. 71.

D.

One constant pressure, one constant volume, two adiabatic processes Two isothermals, constant volume and a constant pressure process

ET - 41

Elements and Terms- MODULE 3

Elements and Terms- MODULE 3

They may not break under pressure There is minimum corrosion Capacity to withstand pressure is increased

ET - 42

84.

The rate of radient energy, that is emitted by a surtace at any temperature and in small wavelengths is found from the known rate of energy, that under the same

conditions will be emitted from a black surtace, by multiplying with the absorptivity.

Above enunciation is called:

85.

86.

",'11

..

1111 ~

50% 33%

Kirchhoff's law

D.

77%

Plank's law :')2. The triple point of a substance is the temperature and pressure at which:

Stefan Boltzmann's law

A. B.

Dynamic processes

C.

Quasi-static processes

D.

Static processes

Stable processes

A. B.

Perfect gas flow

C.

Ideal fluid flow

D.

Reversible adiabatic flow

Irreversible adiabatic flow

Solar energy Chemical energy Stored energy a helical spring is an example of:

C. D.

The solid, liquid and trle qaseous phases are in equilibrium

Only depends on temperature

rn equilibrium

The solid does not melt. the liquid does not boil and the gas does not condense.

A. B.

Reality

C.

Costly

D.

Cheaper

Impossible

i. A heat engine is supplied heat at the rate of 30,000 Jls gives an output of 9 kw.

A. B. C.

30%

The

D.

5~,%

43'1'0

50°'/'J

A. B.

3838 rn/s

C. D.

4839 mls

1839 mls 839 m/s

Select the cycle that consists of two isothermal and constant volume processes?

Zero

A.

Joule cycle

Minimum

B. C,

Otto cycle

D.

Ericson cycle

Maximum

of the following relations is not applicable in a free expansion process? Heat supplied = zero

Diesel cyle

"It is impossible to construct a heat engine that operates in a cycle and receives a qiven quantity of heat from a high temperature body and does equal amount of work." Tile above statement is known as:

Heat rejected = zero Work done = zero Change in temperature

,H"

The liquid and gaseous prl;'scs are In equilibrium

The RMS velocity of hydr oqen gas at N.T.P. is approximately:

At critical point the latent enthalpy of vaporization is:

A. B. C. D.

The solid and liquid phasc.

thermal efficiency of engine is:

Kinetic energy

A. B. C. D.

A. B.

A heat engine has the following specifications: Power developed - 50 kw, Fuel burned per hour - 3 kg. Healmg value of fuel - 75,000 kJ per kg, Ternperature limits ­ 627 and 27"C, This heat engil1c is:

Exhaust gases from a engine possess:

90. Which

and exhausts heat at a

13%

B. C. D.

88. The extension and compression of A. Isothermal cycle B. Thermodynamic process C. Adiabatic process D. Reversible process 89.

A. B.

C.

A. B. C. D.

....,

DC

DC.

Lambort's law

Isentropic flow is:

87.

',I 1. An ideal engine absorbs heat at a temperature of 127 temperature of 77 Its efficiency will be:

A.

Under ideal conditions, isothermal, isobaric, isochoric and adiabatic processes are:

'1

ET - 43

Elements and Terms- MODULE 3

Elements and Terms- MODULE 3

= zero

/\.

G,ly tussac law

I~

1\11)(,1" lII"I'ly

C. D.

98.

Elements and Terms- MODULE 4

Elements and Terms- MODULE 4

ET - 44

Kelvin-planck law Joule-thomson law

B.

Bell-coleman cycle

C.

Rankine cycle

D.

Brayton cycle

ET·45

For steam nozzle, which of the following ratios will have the values less than unity?

99.

5.

A.

Pressure at inleUPressure at outlet

B.

Specific volume at inlet/Specific volume outlet

C. D.

Temperature of steam at inleUTemperature of steam at outlet

A. B. C. D.

None of the above.

In case of axial flow compressors for minimum fluid friction and blade tip clearance losses, the blades of an axial flow compressor are designed for:

A. B. C. D.

A steam nozzle changes:

")

85% reaction 60% reaction

53% reaction

100. Which if the engine is used for fighter bombers?

Heat energy into potential energy Potential energy into heal energy Heat energy into kinetic energy

Which is not correct for calculating air-standard efficiency?

A. B. C. D.

80% reaction

kinetic energy into heat enerqy

All processes are revcrsible Specific heat remains unchanged at all temperatures No account of the mechanism of heat transfer is considered Gases dissociate at higher temperatures.

According to Pettlier Thomson effect:

A.

Turbo prop

A.

Heat can be convened into work

B.

Turbo jet

B.

Work can't be converted into heat.

C. D.

Ramjet

C.

all of the above

Pulsejet

D.

none of the above

Which cycle used in thermal power plant?

A. B. C. D.

MODULE 4 1.

2.

J.

In a diesel engine fuel is injected:

A.

At the beginning of compression stroke

B.

Before the end of compression stroke

C.

At the end of compression stroke

D.

After the end of compression stroke

Stirling cycle

B.

Brayton cycle

C. D.

Joule cycle

A. B. C. D.

1\.

Two isothermals and two constant volumes

B.

Two isothermals and two constant isentropics

( '.

Two isothermals and two constant pressures

!W
,1I11,11)'ltll:~; ano

4 The constant IHn'lll\lrn /\.

(~.I! fll 11 I

'yl

I"

Carnot

25000 J 75000 J 100000 J

1J

An insulated 2 kg box falls from a balloon 3.5 km above the earth. The change in the internal energy of the box after it has hit the earth's surface will be approximately:

Carnot cycle

Ericson cycle consists of the following four processes:

1).

Rankine

Substance is flowing in a pipe of 200 mm inside diameter at an average velocity of 3 2 m/sec. At a given section of the pipe line the pressure is 1.5 MN/m absolute. What is the flow work of 0.5 cubic meter, expressed in joules passing this section.

A Bell-Coleman cycle is a reversed:

A.

Brayton Reversed carnot

two constant pressures.

u;", turbino works on the

principle of:

A. B. C. D.

70000 kJ 7 kJ 68.6 kJ

0 kJ

A control volume refers to:

A. A fixed region in space

1\. A r"wrsible process

,

ET -46

C. D. 12.

A specified mass.

Oxygen Hydrogen

Inelastic

D.

Inplastic

-~ . .w

21.

Densities less than about 0.8 times the critical density Near critical temperature None of the above

It is valid for all pressure and temperature It represents a straight line on pv versus v plot It has three roots of identical value at the critical point The equation is valid for diatomic gases only

16. A passout turbine mostly operates on A. 10-20 kg/cm 2 B. 50-100 kg/cm 2 C. 100-150 kg/cm 2 D. 150-300 kg/cm 2

18.

low pressure in the range:

Rankine cycle efficiency for fixed steam temperature of any volume up to critical temperature will be maximum for steam pressure of:

A. B.

Critical pressure 200 kg/cm

2

C. D.

100 kg/cm

2

203.5 kg/cm

Large volumes of air at low pressures Small volumes of air at high pressures Large volumes of air at high pressures Small volumes of air at low pressure

Lobe type Centrifugal type Axial flow type Reciprocating type

Relief valve Strainer Over speed shut down Over pressure shut down

In a four stage compressor system first and third stage pressure are 1 and 9 kg/em respectively. What will be the fourth stage delivery pressure?

A. B. C. D.

.24.

all of the above

9 kg/cm' 81 kg/cm' 27 I
2

243 kg/cm'

Generally steam turbines in power station operate at:

A. B. C. D.

3000 rpm 1000 rpm 4000 rpm 500 rpm

2

A Lungstorm turbine is:

A. B. C.

:2 3.

Weight of moisture/weight of dry steam (Weight of stuff - weight of moisture )/weight of stuff

Select the one that is a safety device on a compressor:

A. B. C. D.

Which of the following statement about Van der Waals equation is correct?

C. D.

17.

22.

Weight of dry steam/weight of stuff

For gas turbines compressors generally used are of:

A. B. C. D.

All pressures above atmospheric pressure

Inward flow impulse reaction turbine

Centrifugal blowers can supply:

A. B. C. D.

molecular collisions are:

The Beattie-Bridgeman equation of state is quite accurate in cases of:

A. B.

-­ .'Ilt

20.

Reaction turbine Impulse turbine Outward radial flow turbine

ET:47

Dryness factor 01 steam is:

A. B. C. D.

Helium

C.

A. B. C. D.

..

19.

Nitrogen

13. In actual gases the A. Plastic B. Elastic

15.

D.

An isolated system

Which of the following gas can be measured the lowest temperatures?

A. B. C. D.

14.

Elements and Terms- MODULE 4

Elements and Terms- MODULE 4

.~). A compound pressure gauge is used to measure:

A. B. C. D.

complex pressures variable pressures compound pressures positive and negative pressures

2

r

26. In a condensing steam engine: A. condensed steam is supplied B. steam condenses inside cylinder C. steam condenses as soon as it leaves the cylinder D. exhaust steam is condensed in condenser 27.

~l

Isothermal worklindicated work Adiabatic work/indicated work Isothermal work/adiabatic work adiabatic work/adiabatic input

1

A. B.

Discharge pressure/suction pressure

C.

Stroke volume/(stroke volume + clearance volume)

D.

(stroke volume + clearance volume)/stroke volume

A. B.

Chemically correct air-fuel ratio by volume

C.

Theoretical mixture of air for complete combustion

D.

Actual ratio of air to fuel for maximum efficiency

11

31.

A. B.

Do not exists in engines

C.

The spots where heavier functions of fuel are vaporized

D.

Hottest point within the engine cylinder .

The hottest spots in engines

large engines engines having small flywheel high speed engines

Increased Decreased Independent of compression ratio Depends on other factors

B. C. D.

air fuel ratio may be of the order of:

200 150 100

37. Vapor lock is: A. Lock of vaporization of fuel to atmospheric pressure B. Excess fuel supply to engine because of faster evaporation C. Complete or partial stoppage of fuel supply because of vaporisation

of fuel

in supply steam

D.

Locking carburetor jets because of vapor pressure.

Flash point of a liquids is the temperature at which

A.

The fuel emits vapors at a rate Which produces an inflammable mixture with air

Maximum 49°C

B.

The fuel spontaneously ignites

Maximum 200°C

C.

The fuel ignites with clearly visible flash

D. Maximum 300°C

D.

The fuel ignites without a park.

A. B. C.

32.

used for testing of:

small engines

36. During idling In a compression ignition the A. 30

38. Flash point for diesel fuel oil should be:

engines

The mean effective pressure of a diesel cycle having fixed compression ratio will increase if cut off ratio is:

A. B. C. D.

Chemically correct air-fuel ratio by weight

30. Hot spots are:

Minimum 49°C

A regenerator in a gas turbine

A. B.

Allows use of higher compression ratio

C.

Improves thermal efficiency

D.

Allows use of fuels of inferior quality

Reduces heat loss during exhaust

33. Morse test is conducted on: J

35.

Stroke volume/clearance volume

Stoichiometric ratio is:

vee engines

34. Prony brake is A. B. C. D.

ET - 49

multi cylinder engines

D. vertical

Compression ratio in engine is:

29.

•

B. C.

The performance of a reciprocating compressor can be expressed by:

A. B. C. D. 28.

Elements and Terms- MODULE 4

Elements and Terms- MODULE 4

ET -48

A.

single cylinder engines

\ l). Volumetric efficiency of a well designed engine may be in the range:

A. B.

75 to 90 % 60 to 75%

C. D.

30 to 50% Below 30%

~ (), Scavanging efficiency of a four-stroke diesel engine is:

A.

80-90%

B. C. D.

41.

C. D.

60-80% 100·95%

A. B.

Increase

C.

Decrease

D.

Depends on other factors

Remain same

A. B. C. D.

49.

Poor compression Restricted exhaust Clogging of air cleaner

50.

An orsat apparatus is used for: A. volumetric analysis of the flue gases

B. C. D.

gravimetric analysis of the flue gases smoke density analysis of the flue gases

52.

46.

47.

alloy steel carbon steel

quantity ofsteam to be generated

Tidal power is the power generated from:

A. B.

waves of the ocean rise and fall of tides

reserve generating capacity that is in operation but not in service

C.

reserve generating capacity that is available for service but not in operation

D.

capacity of the part of plant that remains under maintenance

reserve generating capacity that is connected to bus and ready to take load

A. B.

tensile strength of the shell

C.

diameter of the shell

D.

shear strength of shell material

A. B. C. D.

boiler pressure

quantity of steam

A. B.

thickness of the shell

valve tappet clearance incorrect valve springs of defective material valve guides gummed lubricating oil of poor quality

<3. Total sulphur content in

cast iron

type of fuel available

Load versus cost of power

A. B. C. D.

Total on solid impurities in feed water for a boiler depend upon:

A. B. C. D.

D.

Sticking valves:

Piston rings are made of:

copper

load versus time

51. On which does the working pressure of a boiler does not depend? A. tensile strength of shell B. thickness of shell C. factor of safety D. type of fuel being fired

all of the above.

A. B. C. D.

C.

On whi¢h factor bursting pressure of boiler does not depend?

low injection pressure

A. early timing of fuel injection B. late timing of fuel injection C. head of piston carbonized D. valve springs weak or broken

45.

raw sea water

In power station practice "spinning reserve" is:

Detonation of pinging noise is due to:

44.

thermal energy of ocean water

48. load curve refers to the plot of A. Load versus generating capacity B. Load versus current

loss of power is due to:

43.

Et-· 51

Below60%

The thermal efficiency of a dual cycle engine with fixed compression ratio and fixed quantity of heat and with increase in pressure ratio, will:

42.

Elements and Terms- MODULE 4

Elements and Terms- MODULE 4

ET - 50

a diesel fuel oil must not exceed:

0.1% 0.5% 0.2% 0.15%

'>4. In

a four stroke engine if a valve opens 25°C before bottom dead center and closes 10 0 after top dead center, the valve should be:

A. B.

puppet valve

C.

inlet valve

exhaust valve

ET·52

Elements and Terms- MODULE 4

Elements and Terms- MODULE 4

ET - 53

---------

D. spring valve

55.

In a vapor compression cycle the lowest temperature is found in:

A. B.

condenser

C.

expansion valve

D.

evaporator

A. B.

Driers

C.

Dehumidifiers

D.

Coolers

57. Which

help of:

; i.

Freon 12 Ammonia

C.

Freon 22

D.

Freon 11

compression superheated.

C.

equal to 1

D.

depends upon the make of it

Horsepower per ton of refrigeration is expressed as: A. 4.75/COP

B.

475 x COP

C.

COP/4.75

in

a vapor

compression

cyle

when

the

refrigerant

). The highest temperature in vapor compression cycle is produced during: A. condenser discharge

B.

expansion valve evaporator compressor discharge

A. B. C.

COP is reduced

C.

COP remains unchanged

D.

D.

Refrigerating effect is reduced

Work done is increased 1\

coefficient of performance of a refrigerator is given by:

A.

COP

=

B.

COP

= Work spent to cause refrigerating effect over Desired refrigerating effect

C.

COP effect

D.

COP

Input/Output

= Desired refrigerating effect = Net refrigerating cycle over

Whicn type of compressor is used in refrigeration system? A. Reciprocating

B. Centrifugal C. Rotary Sliding vane D. all of the above

over Work spent to cause refrigeratl",

Ideal refrigerating effect

. A thermometer in vapor compression system is installed in the main line close to the compressor:

A.

Because it efficiency

B.

Because temperature indicates whether liquid or vapor refrigerant is gOing to compressor

C.

All of the above

A Ball-Coleman cycle is:

A. B.

reversed Otto cycle

C.

reversed Rankine cycle

D.

reversed Carnot cycle

reversed Joule cycle

(11. Critical temperature is that temperature above which:

.1\.

A gas will never liquefy

H r, 'i,'" (

I)

is:

D.4.75xCOPx2

58. During

60.

3. The COP of a domestic refrigerator A. less than 1 B. more than 1

Evaporators

B.

50 tons 100 tons

D. 4 tons

of the following refrigerants has lowest freezing point temperature?

A.

59. The

B. C.

receiver

56. The moisture in the refrigeration system can be removed with the

II

..:. Rating of a domestic refrigerator is of the order of A. 0.1 ton

','.

>

I! 1'1

IlIlrnedlately uquety

'/"1, '! f '1',

\\,111'1,','1

I

v, 11)( ir: II (~rl

111'\1'1 j'V;qHlI lit·

helps the

operator in

adjusting compressor for greatest

D. None of the above Which refrigerant has the highest critical point temperature? A. Ammonia

B. C. D.

Freon 11 Freon 12 Freon 22

r

69.

Elements and Terms- MODULE 4

Elements and Terms- MODULE 4

ET·54

A Carnot refrigerator extracts 100 kcal of heat per minute from a cold room which is maintained at 15°C and it is discharged to atmosphere 30°C. The horsepower needed

76.

Select the one in which secondary refrigerant is used:

A. B. C. D.

to run the unit would be:

A. B. C. D.

70.

1 to 15 1.5to2 2 to 25

77. The

55t06

sub cooled water

78.

formed by blowing air during freezing

A. B. C. D. 72.

A. B. C. D.

:J

Is pure ice Contains dissolved gases

A. B. C. D.

••t

73.

19.

Is formed by blowing air during freezing.

Glycol Sodium silicate

Open cycle Closed cycle Mixed cycle Hybrid cycle

Refrigerant No. R-717 is:

A. B. C. D.

free from water

A. B. C. D.

free from dissolved air or gases

A. B. C. D.

Freon 22 Freon 12 Methyl chloride

KO. In

which part of the vapor compression cycle there is abrupt change in pressure and temperature:

solidified form of carbon dioxide

A. B. C. D.

0.5 1.5

5

Solenoid valve Evaporator Expansion valve Drier

K1. A

plate or vane used to direct or control movement of fluid or air within the confined area is called:

6 be detected by:

halide torch which on detection forms greenish flame lighting sulphur sticks which on detection from white smoke using certain reagents smelling

The lower horizontal line of the refrigeration cycle plotted on pressure-enthalpy diagram represents: A. compression of the refrigerant vapor

B. C. D.

Ammonia'

does not contain impurities

74. The leaks in a refrigeration system using freon can

75.

Brine ammonia solution

Contains dissolved air

For a heat pump cycle that operates between the condenser temperature of 27°C and evaporator temperature of·23°C, the Carnot COP will be equal to:

••

ice plant

A refrigerant cycle is generally alan:

Dry ice is:

"II~

room air conditioner deep freezer

due to dissolved air, gases and impurities

71. Clear ice:

.,111

domestic refrigerator

secondary refrigerant used in milk chilling plants is generally:

A. B. C. D.

White ice is: A. fast cooled water

B. C. D.

ET - 55

evaporation of the refrigerant liquid

A. Baffle B. C. D.

Bellows Regulator Diffuser

'\2. Brazing is

A. B. C. D.

used for joining two:

Two ferrous metal One ferrous and non-ferrous material Two non-ferrous materials Two non-metals

condensation of the refrigerant vapor metering of the refrigerant liquid

~ \. Which refrigerant is used for the air-conditioning of passenger aircraft cabin?

Elements and Terms- MODULE 4

ET - 57

Elements and Terms- MODULE 4 ET -56 ----------~--=--=-~ ._------------­

A. B. C. D. 84.

~'I~

Freon 12

91.

Air

A. B. C. D. 85.

1

Compressor and condenser Condenser and evaporator Evaporator and compressor

A. B.

Improve overall heat transfer coefficient

92.

C. D.

Reduce the size of evaporator by avoiding vapors going to evaporator All of the above.

0.255

.'1ilI

C. D.

0.500

.'11a!

93.

...

88.

94.

Wet bulb and dry bulb temperatures psychrometric temperature requirements Saturation temperature and relative humidity

95.

Moist air conditions

change to:

A. B. C. D. 89.

Yellow Red

Ethylene glycol Anyone of the above.

Dry bulb temperature Wet bulb temperature Relative humidity Humidity ratio

1% only 12 to 15% 30 to 40%

Cooling towers are used for cooling water:

;\.

In be injected in circulatinq air

-78.5°C -29.8°C -40°C

Boiling temperature of freon 22 is:

A. B. C.

-33.33°C

D.

-40°C

A. B. C. D.

Orange

10 to 20%

-33.33°C

-29.8°C -78.5°C

()6. The following gas is preferred in refrigeration system:

Green

The drift loss in cooling towers is about:

A. B. C. D.

90.

Silica gel Activated alumina

Boiling temperature of Freon 12 is:

A. B. C. D.

0.670

The color of the flame of hallide torch, in case of leakage of freon refrigerant, will

I',

Radiation Evaporation

0.333

A. B. C. D.

~

Convection

In sensible heating cooling, following parameter remains unchanged:

A. B. C. D.

The psychrometric chart in air conditioning detemines the:

I. . . .

Conduction

Which one is commonly used liquid absorbent?

A. B. C. D.

Reduce pressure losses through the evaporator

A. B.

.,1'

To be used for cooling the compressor.

Metering device and evaporator

In case during air conditioning of a space the sensible heat added as 100 kcal/sec and the latent heat added is 50 kcal/sec, then the sensible heat factor is given by:

87.

To be used for filteration of air

By which of the following processes heat mainly dissipates in cooling towers?

A. B. C. D.

A flash chamber is installed in the refrigeration circuit so as to:

86.

To be used for humidification

Freon 11

Oil separator in a refrigeration cycle is installed between the:

.111

....

B. C. D.

Ammonia

(n.

Freon 11 Freon 22 CO 2

NH3

In a hot wire anemometer the rate of heat loss

A. B.

mass rate of flow

C.

velocity of flow

pressure

fro~ sensing element is

a function of:

D. 98.

B. C. D.

~,

1

C. D. S.

A. B. C. D.

A velocity compounded turbine A velocity pressure compounded turbine.

A. B. C. D.

Reciprocating compressor

6.

A. B. C. D.

Centrifugal blower Axial flow compressor

7.

2.

500 Btu per min

B. C. D.

288 Btu per min

4.

D.

100 Btu per min

A. B. C. D.

damage the expansion valve

insufficient cooling water air in the condenser all of the above

too much cooling water insufficient refrigeration gas insufficient cooling water AandB

the absorption of temperature under heat, pressure, compression and expansion the compression of a liquid under temperature and expansion the absorption of heat under temperature, compression, pressure and expansion the conversion of a liquid to a gas

change the high-pressure liquid to low-pressure liquid regulate the amount of liquid refrigerant to the expansion coils change the gas refrigerant to a liquid shut off the flow of refrigerant to the condenser

cause leakage through the shaft seals deposit oil on the condenser tubes

10. The oil separator (trap) is located between the:

A. B. C. D.

NH 3

C02

compressor discharge valve and the condenser condenser and the receiver receiver and the king valve receiver and the expansion valve

F-12 F-22

A ton of refrigeration is equal to the removal of:

A. B.

dirty condenser

9. The function of the expansion valve is to:

The refrigerant with the lowest boiling point is:

A. B. C. D.

dirty dehydrator

200 Btu per min

Too much oil in the compressor would: A. absorb too much refrigerant from the system

B. C. D.

3.

A. B. C.

A refrigerating unit of one ton capacity can remove:

A.

king valve not open wide enough

The principle of the mechanical refrigeration is:

MODULE 5 1.

expansion valve not open wide enough expansion valve open too wide

Which of the following would cause low head pressure?

A. B. C. D. ~.

280,000 Btu per 24 hrs

Which of the following would cause high head pressure?

Vane blower

100. Choking is: A. change of mass flow rate in proportion to pressure ratio B. Change of mass flow rate in inverse proportion to pressure ratio C. Fixed mass flow rate irrespective of pressure ratio D. all of the above.

28,800 Btu per 24 hrs

Which of the following would cause a high suction pressure?

A pressure compounded turbine

Which one is a displacement compressors?

288,000 Btu per 24 hrs 28,000 Btu per 24 hrs

ET - 59

----------------

all of the above

Curtis turbine is: A. An impulse turbine

99.

Elements and Terms- MODULE 5

Elements and Terms- MODULE 5

ET·58

I I . The

purpose of the oil trap is:

A. B.

to add on to the compressor

( '.

to remove oil from the refrigerating gas

to remove oil from the charging tank

------------------------

19.

D.

)

1

20.

A. B.

A. B. C. D.

+110"F _110°F

C.

+110

D.

-110'e

oe

14. The boiling point of A. _22°F B. +22°F C. +22°e D. -22°e 15. The

16. The

21. Freon at atmospheric pressure is:

A. B. C. D.

receiver and the king valve receiver and the expansion valve

23.

A. B. C. D.

17. Which of A. B. C. D.

remove oil from the refrigerant add more refrigerant to the system remove moisture from the refrigerant

24.

A. B. C. D.

the following would you apply if a person got Freon in his eyes? soapy water sterile mineral oil sodium bicarbonate

18. The thermal expansion valve is located between the: A. receiver and the king valve B. king valve and the solenoid valve C. solenoid valve and the evaporator coils D. charging valve and the solenoid valve

emulsify the oil in the compressor freeze in the king valve clog the oil trap

control the amount of scale going to the compressor remove insoluble gases from the refrigerant remove dirt, scale and metal chips from the refrigerant dissolve scale and dirt in the system

packed only in the closed position packed in wide open or closed position operated as a suction or discharge valve removed for replacement without shutting down

can be measured with a thermometer cannot be measured with a thermometer changes in the receiver tank increases with the cold

The latent heat of fusion is the amount of heat required to convert:

remove moisture from the crankcase oil

clean water

freeze on the expansion seat and cut the flow of liquid refrigerant

Sensible heat:

condenser and receiver

purpose of the dehydrator is to:

A. B. C. D.

removes trap oil from the refrigerant

A double-seated valve allows the valve to be:

dehydrator is located between the:

condenser and the king valve

maintains a constant superheat of the gas leaving the evaporator coils controls the amount of gas going to the receiver

The purpose of the scale trap is to:

A. B. C. D.

22.

controls the amount of gas coming from the dehydrator

Water in the refrigerant is liable to:

boiling point of CO, at atmospheric pressure is:

A. B. C. D.

1"1

A. B. C. D.

ammonia at atmospheric pressure is:

nF

ET·61

The thermal expansion valve:

none of the above

12. The'boiling point of A. -28°e B. +28°e C. +28 D. _28°F 13. The

Elements and Terms- MODULE 5

Elements and Terms- MODULE 5

ET·60

25. The

two Ibs of ice at 32°F to one lb of ice at 32°F one Ib of ice at 32°F to one Ib of water at 32°F one lb of ice at 32°F to one Ib of steam at 32°F two Ibs of ice at 32°F to one Ib water at 32°F

latent heat of vaporization of water is:

A. B. C. D.

144 Btu 940 Btu 970 Btu 288 Btu

26. The latent heat of vaporization is the amount of heat required to convert:

Elements and Terms- MODULE 5

Elements and Terms- MODULE 5

ET - 62

A. B. C. D.

27. Too

one Ib of water at 212°F to one Ib of steam at 212°F one Ib of water at 180 F to om, Ih of steam at 180

cF

two Ibs of water at 212l 10 one Ib of steam at 212'F one Ib of ice CIt 32

f·

to one Ib of steam at 212"F

34.

expansron valve open too wide

leaky sucuon valves expansioll valve bulb not working properly

I). any of the above

28. How

35.

29.

144 0 below zero on the Fahrenheit scale

the same as zero on the Centigrade scale

When the evaporator coils are located in the Ice box, the system is known as a:

high-pressure system

into a bucket of lube oil

36.

back Into the compressor

B.

through the king valve

C. D.

the CO 2 will come out in liquid form pumped out with a suction pump

'

B. C. D.

the same as the C02 system with a reefer pump

38.

none of the above

B. C.

psi

)9.

insufficient cooling water to the condenser insufficient cooling water to the evaporator coils too much cooling water to the condenser

the amount of liquid in the system the amount of gas in the system the temperature in the condenser

II

the thermal switch operated by the Icebox temperature

I

The purged valve is located:

IIII

on the receiver discharge

Ii I

144 Btu

B. C.

188 Btu

D.

on the evaporator coils

940 Btu

33. Latont ho.lt

"III

I'"

11I",ISllrp.d

in the highest part of the system

,~o. The system should be purged:

I), ,,00 Btu

:\

weight

A. in the lowest part of the system

The latent heat of fusion of ice is:

A.

pressure volume

The solenoid valve Is controlled by:

A. B. C. D.

a freon-controled check valve a temperature-controlled stop valve

indirect system

37. An excessive high head pressure could be caused by: A. solenoid valve shutoff

the same as the ammonia system back to the extra supply bottle

low-pressure system

The amount of CO 2 or Freon in a cylinder is measured by:

A. B. C. D.

The solenoid valve is: A. a pressure-controlled stop valve

B. C. D.

32.

460 0 below zero on the Fahrenheit scale

into a bucket of water

A. B. C. D.

"I

970 0 below zero on the Fahrenheit scale

D.

How is a freon system purged?

3 I.

Absolute zero is:

into the atmospheric line

How is a C02 system purged? A. when C02 comes out, frost will form on a piece of metal held near the outlet'"

30.

changes as the refrigerant cools

direct system

fumes?

B. C. D.

D.

can be measured with a pyrometer

A. B. C.

is an ammonia system purged so that the operator will not be overcome by the "

A.

cannot be measured with a thermometer

A. B. C. D.

high suction pressure could be caused by:

A. B. C.

B. C.

ET -63

with a thermometer

A.

while the system is operating

B. C.

while starting up the system after the system has been shut down for a few hours

Iii ')1

I

D.

41.

once a week

A. B. C. D.

42.

increase the pressure of the refrigerant discharge the refrigerant to the condenser all of the above

+9.

43.

receiver and evaporator evaporator and compressor compressor and condenser condenser and receiver

";0.

44.

45.

A. B. C. D.

)2.

46.

suction side

C. D.

hot side

cold side

) 3.

filling side

A. 2000 Ibs of ice melting in 24 hrs

47.

2000 Ibs of ice melting in 12 hrs

C.

2000 lbs of water being converted to ice

D.

2240 Ibs of ice melting in 24 hrs

The scale trap (liquid strainer) is located between the:

A. compressor and oil separator B.

king(liquid) valve and expansion valve

C.

expansion valve and evaporator coils

D.

evaporator coils and compressor

litmus paper halide torch sulphur stick AandC

iron brass copper bronze

";4.

closed except when checking oil level open at all times closed when machine is shut down open when machine is shut down

colorless odorless nonpoisonous all of the above

Which of the following gasket materials should be used on a Freon system?

A. B. C. D.

A ton of refrigeration is equal to the cooling effect of:

B.

green

Freon is:

A. B. C. D.

The high pressure side of the system is sometimes referred to as the:

A. B.

blue white

) 1. In an ammonia system, the oil gage must be kept:

Which of the following would cause a high head pressure?

A. icebox door left open B. insufficient cooling water C. too much cooling water D. suction valve not open enough

orange

Valves and piping in an ammonia system are made of:

A. B. C. D.

If frost forms on the cylinders, the cause would be:

A. expansion valve not open wide enough B. charging valve left open C. expansion valve open too wide D. dehydrator not working properly

h~)

Which of the following could be used to check a leak in an ammonia system?

A. B. C. D.

The expansion valve is located between the:

A. B. C. D.

E: I

~~. When there is a Freon leak, the halide torch will burn:

The function of the compressor is to: A. pull the refrigerant gas through the system

B. C. D.

".

Elements and Terms- MODULE 5

Elements and Terms- MODULE 5

ET - 64

metallic asbestos rubber AandB

A double-pipe condenser has:

A. B.

two piping system side by side, one with cooling water and one with refrigrarit

C. D.

two pipes for cooling water and one for the refrigerant

a small pipe inside a larger pipe, the cooling water passing through the small pipe and the refrigerant through the large pipe none of the above

"; ";. Air can be prevented from getting into the system by:

ET - 66

Elements and Terms- MODULE 5

A. B. C. D.

56.

57.

59.

keeping the dehydrator clean at all times

B.

potassium chloride

C. D.

calcium chloride A and C

C. D.

63.

blue red green yellow

64.

A sulphur stick burning in the presence of ammonia will give off a:

"A.

dense yellow smoke

B. C. D.

dense white smoke dense red smoke dense green smoke

65.

insufficient refrigerant in the system leaks any of the above

smelling the discharge water applying litmus paper to the circulating water discharge

C_ D.

a direct system an indirect system a low-pressure system a double-evaporator system

A.

congealed oil in the system

B.

scale

C.

water in the system

D.

all of the above

Ow

Too low suction pressure could be caused by: dirty scale traps shortage of refrigerant gas too much oil in the system any of the above

66. If an electrically operated compressor failed to start, the A. an open switch B. a blown fuse C. burned-out holding coils in solenoid valve D. any of the above

cause might be:

adding water to peppermint to the system and tracing the smell applying a soapy mixture to the condenser heads and looking for bubbles

61. When purging an ammonia condenser into a bucket of water, one can tell when the air is out and

ammonia starts to come through by the:

A. B.

a lighted candle at the joints and watching for leaky spots blowing candle flame

leaky discharge valves

60. Ammonia leaks in the condenser can be detected by:

A. B. C. D.

a thin layer of mineral oil to all joints and watch for bubbles

Obstruction of the expansion valve is usually caused by:

A. B. C. D.

If the compressor were to run continuously without lowering the temperature, the'·1 trouble would probably be:

sheets of litmus paper to all joints and watch for color change a soapsuds solution, mixed with a little glycerin to hold the SOlution together, and watch for bubbles

When the evaporator coils are located in a brine solution and the brine is pumped through the icebox, the system is known as:

A. B. C. D.

An ammonia leak will turn litmus paper:

A. B. C. D. "4

A. B.

running the refngerantthrough the aerator

sodium chloride

smell of ammonia being liberated from the water

67.

The oil separator is located between the:

A. B. C. D.

evaporator and compressor compressor and condenser condenser and dehydrator solenoid valve and the thermal expansion valve

color of the water turning green

color of the water turning bluish

change of the bubbling sound of air to the crackling sound of ammonia

-lJl

in a freon system cannot always be detected with a halide torch because it changes color with the slightest amount of freon present. A large leak can be detected easier by applying:

keeping all glands and stuffing boxes on the low-pressure side tight

A.

EI

62. Large leaks

The agent used in an indirect reefer system is:

A. B. C. D. 58.

keeping all glands and stuffing boxes on the high-pressure side tight

Elements and Terms- MODULE 5

68. To help the person Who have been exposed to A. apply artificial respiration B. wrap in warm blankets C. apply cold compresses

f). douse with cold water

ammonia gas, one would:

Elements and Terms- MODULE 5 ET - 68

D. 69.

ET - 69

Elements and Terms- MODULE 5 none of the above

If the compressor short cycles on the low-pressure cutout, the trouble might be:

A. B. C. D. 70.

lack of refrigerant

The disadvantage of a CO 2 system over an ammonia system is the fact that:

A. B. C. D.

dirty trap and strainers too much frost on coils any of the above

Ammonia will corrode:

A. B. C. D. 71.

76.

copper

77.

brass

The dehydrating agent in the freon system is usually:

72. It

73.

king valve

79.

it is difficult to condense the refrigerant rf the circulating water temperature is too low

C. D.

due to high pressure it is difficult to keep oil from mixing with refrigerant

A. B. C. D.

solenoid valve condenser cooling-water inlet valve

A. B.

pressure and tetTlperature

reduce the pressure on the discharge side of the condenser hot-gas defrost pump air out of the system add refrigerant to the system

suction pressure absolute pressure head pressure condenser pressure

~(). Oil used in the refrigerating system is:

A. B. C. D.

liquid pressure and gas pressure

C. D.

it takes more refrigerant to keep the iceboxes cold

Another name for discharge pressure is:

Many pressure gages on a freon system have two dials or graduations on one gage.

suction and discharge pressure cooling-water inlet and outlet temperatures

,.~

lube oil SAE 20 straight mineral oil lube oil SAE1 0 vegetable oil

A leaky discharge valve can usually be detected by:

A. B. C. D.

75.

B.

A. B. C. D.

expansion valve

The two dials represent:

74.

it is difficult to condense the refrigerant if the circulating water temperature is too high

The crossover connection in an ammonia system can be used to:

If any of the electrically controlled devices in a freon system malfunction, which of . the following valves will also automatically shut off?

A. B. C. D.

the pipes and fittings of a CO, system must be of the high-pressure type all of the above

A.

all of the above

78.

the CO 2 system operates at a much higher pressure

One disadvantage of a CO 2 system is the fact that:

bronze

A. slaked lime B. sodium chloride C. activated alumina D. calcium chloride

the CO 2 system requires a larger prime mover

a fluctuating high-pressure gage a drop in icebox temperatures a discharge pressure lower than normal

I . The

discharge pressure of the compressor should be:

A.

the pressure which Icorresponds to a temperature from 5° to 15°F below that of the condenser discharge

B.

the pressure which corresponds to a temperature from 5° to 15°F higher than the condenser discharge

C.

the pressure which corresponds to a temperature equal to that of the condenser discharge

D.

none of the above

any of the above

The suction in a freon system should be: A. the pressure which corresponds with a temperature about 20°F below the

B.

temperature of the lee box the pressure which corresponds with a temperature equal to the temperature 01

C.

the icebox the pressure which corresponds with a temperature about 20° above the temperature of the icebox

A leaky suction valve can usually be detected by:

A.

a fluctuating suction-pressure gage

ET·70

83.

Elements and Terms- MODULE 5

B. C.

closing in on the suction valve havinq no effect on the suction pressure

D.

any of the above

a higher suction pressure

C.

D.

90.

D.

A. B. C. D.

prevent overloading in the iceboxes bypass the compressor when dehydrating prevent excessive pressure in case of stoppage on the discharge side of the system AandB

91.

A.

on the discharge pipe from the condenser

B.

on the discharge pipe from the compressor

C.

in the compressor head

D.

A or B

92.

85. The relief valve on a CO2 machine is located:

•

A.

on the discharge pipe from the condenser

B. C, D.

next to the king valve on the discharge pipe between the compressor and the discharge valve in the compressor head

I}

A. B. C. D.

keeps the icebox cooler

A. B. C. D.

reduces the efficiency of the plant

use of:

hollow sidewalls diffuser fans

88. Before securing a compressor to do maintenance on

A and B

purge the system

J\. worn IIp<Jrlngs. pins. etc.

B.

t{ln """.Il oil in crankcase

refrigerant side of condenser

A double-trunk piston is used to:

A. B.

absorb some of the side trust

C. D.

prevent oil from mixing with the refrigerant all of the above

prevent gas from getting to crankcase

3. The purpose of the receiver is to: cool the refrigerant gas separate the oil from the refrigerant condense the refrigerant

A.

30 psi

B.

14.7 psi

C.

0 psi

D.

17.4 psi

A. B. C. D.

it, be sure to:

have spare parts ready

XI). Somo causes of a noisy compressor are:

D.

() ~. The heat used to change a solid to a liquid is called:

air vents to deck

D.

salt-water side of condenser compressor crankcase

\)4. When a pressure gage reads zero, the absolute pressure is:

louver doors

pump down system

B.

D.

does not affect the system

A. B. C.

evaporator coils

C .. store the refrigerant

takes the load off the compressor

87. Air circulation in the icebox is accomplished by the

expansion valve not operating properly too much cooling water to condenser

C.

A. B.

86. Excess frost on the evaporator coils:

too much oil in the system too much refrigerant in the systern

Zinc rods are found in the:

A.

The relief valve on an ammonia machine is located:

Slugging due to flooding back of rdrlq,'r<J1I1 any of the above

Slugging is usually caused by:

The purpose of relief valves on refrigerating machines is to:

A. B. C.

84.

.

Elements and ------------ Terms- MODULi::: 5

II)

latent heat of fusion sensible heat of fusion latent heat of liquid specific heat of fusion

The heat used to change a gas to a vapor is called:

A.

latent heat of fusion

B.

latent heat of vaporization

C. specific heat of vaporization I). latent heat of the gas

ET·71

97.

C. D.

Sweating of the crankcase is caused by:

A. B. C. D.

98.

too much superneat insufficient supertH:,ll

4.

expansion v<Jlvl~ IliHl,1 up too much oil in the system

If an automatic freon system will not start up, check the:

99.

.1

Elements and Terms- MODULE 6

Elements and Terms- MODULE 6

ET -72

A. B.

high-pressure cutout

( '.

reset mechanism

I).

all of the above

low-pressure cutout

5.

A. B.

six months

C. D.

two years

year

6.

100. If

the thermal expansion valve becomes inoperative the

controlled by the:

A. B. C. D.

iceboxes will have to be

solenoid valve manual expansion valve

7.

manual solenoid valve

~

if

2.

a magnet a bellows spring tension water pressure

'I.

nonpoisonous nonexplosive noninflammable

I). all of the above : r

.'

If a Illfriger<Jting system extracted 48,000 Btu per hour, the tonnage of the machine would IJn:

!\

H

1,,",.

1.'1,,"

cut out the compressor at a set pressure cut compressor in and out at a preset pressure

The most likely cause of high superheat would be:

too much refrigerant

I.",

expansion valve open too wide expansion valve closed in too much back-pressure valve set too high

The purpose of the evaporator is to: absorb latent heat of vaporization absorb latent heat of fusion transfer latent heat of vaporization transfer latent heat of fusion

Air is removed from the system by: increasing the amount of cooling water opening the purge valve running the refrigerant through an aerator running the refrigerant through a deaerator

The suction pressure switch Is operated by: electric current thermocouple pressure on bellows a relay cutout

A hot suction line might be caused by:

A. B. C. D.

A good refrigerant should be:

A. B. C.

maintain a preset suction pressure to the compressor

A. B. C. D.

1. The low pressure cutout switch is operated by:

A. B. C. D.

maintain liquid refrigerant at the suction of the compressor

A. B. C. D.

king valve

MODULE 6

A. B. C. D.

A. B. C. D.

three months

2 tons 4 tons

The purpose of the low-pressure cutout switch is to:

A. B. C. D.

The cooling-water side of the condenser should be opened for inspection every:

ET -73

insufficient refrigerant insufficient lubrication expansion valve closed too much too much refrigerant

I. The device used for low-pressure control and high-pressure cutout on a compressor is called a:

A. B.

cutout pressure controller

( .. controller switch

I

:,

D.

cutout switch

11. Thermal expansion valves are usually of the: A. bellows type B. magnetic type C. diaphragm type D. A or C 12.

'I

the compressor short cycles on high pressure cutout, which of the following would you check?

superheating overflowing

20.

bellows-type construction magnetic-type construction

cooling water to the condenser should suddenly fail: the solenoid valve will close the expansion valve will close the compressor will shut down

all of the above

In a refrigerating system the temperature is at its highest between the: condenser and receiver compressor and condenser receiver and evaporator evaporator and compressor

grounds out frequently

high-pressure cutout switch low-water cutout switch

D.

runs too slow

stops and starts frequently runs too fast

automatic trip Freon is:

A. B. C. D.

amount of refrigerant going to the expansion valve amount of refrigerant going to the compressor

noncorrosive flammable nontoxic AandC

pressure of the refrigerant going to the evaporator coils

Freon passes through the expansion valve:

A. B. C. D.

Short-cycling means that the machine:

A. B. C.

low-pressure cutout switch

23.

B. C. D.

when operating under:

an alarm will ring to notify the engineer

The solenoid valve controls the: A. amount of refrigerant entering the evaporator coils

17. As

check for too much refrigerant in the system

2] . A freon unit will tend to short-cycle A. heavy loads B. normal conditions C. light loads D. all of the above

22. A. B. C. D.

16.

C. D.

if plenty of cooling water IS running through but it is not picking up heat, the condenser tubes need cleaninq

pilot-valve type construction

If the solenoid valve closed by accident, the compressor would be stopped by the:

t'

be sure system is getting cooling water

A. B. C. D.

diaphragm-type construction

A. B. C. D.

15.

A. B.

recycling

Pressure controllers are usually of the:

14. If the

the volume decreases and the pressure increases the volume increases and the pressure increases

ET - 75

- - - - - - - - - - -

19. If

flooding back

A. B. C. D.

e

..... .. MOD~!....!::

18. When checking zinc plates in a condenser, one should: A. paint the plates with red lead B. install all new plates C. clean the plates and renew worn-out ones D. ground each plate to the shell

Liquid reaching the compressor through the suction line is called:

A. B. C. D. 13.

Elements and Terms-

Elements and Terms- MODULE 6

ET -74

)ef. A refrigerant should have a: A. high latent heat B. high sensible heat C. low latent heat

the pressure decreases and the volume increases

r). low sensible heat

the volume decreases and the pressure decreases '':;

A mothod of reducing capacity without reducing compressor speed is called:

r

F=T -

A. B. C. D.

low-pressure by passing hot-gas by passing

..t

A.

in the middle of evaporator coils

B.

near the evaporator coil outlet

C. D.

near the evaporator coil inlet

B. C. D.

shut down the compressor and check the oil level with the machine stopped check to see if there is too much refrigerant in the system

the solenoid valve is jammed shut the expansion valve may have water frozen in it a refrigerant leak has developed any of the above

B. C.

bimetal type

D.

pilot-valve type

36.

valve type

When heavy electrical currents are involved, the thermostat will be operated by a: small circuit breaker pressure pipe fusetron relay

If the compressor runs continually, the cause might be the:

A. B. C. D.

high-pressure cutout switch is jammed open low-pressure switch is jammed shut thermal bulb is not operating properly scale trap is clogged

solenoid valve can be typed as a:

;\. thermal valve

B.

magnetic stop valve

When charging a Freon system, all the valves should be in their normal position except the:

A. B. C. D.

back-pressure-operated switch

diaphragm type

32. The

check the dehydrator cartridge

A. B. C. D.

super-heat operated switch

A. B. C. D. 31.

drain out sufficient oil to bring it down to the proper running level

the compressor had been running satisfactorily for a long period of time but suddenly the compartment temperature started to rise, the trouble might be:

pressure-operated switch

A.

tI

A.

B. C. D.

on the bottom row of evaporator coils

The elements of a thermostat switch are usually of the:

30.

bimetallic valve

34. If

A thermostat is a: A. temperature-operated switch

29.

D.

compressor had been running satisfactorily for a long period of time but the oil level was rising slowly, the thing to do would be to:

35.

..

bellows valve

33. If the

short-cycling

The bulb for \.'1e thermal expansion valve is located:

28.

C.

high-pressure by passing

26. The thermal expansion valve responds to the: A. amount of superheat in the vapor leaving the coil B. amount of superheat in the liquid C. temperature in the evaporator coils D. pressure in the evaporator coils

27.

ET -77

Elements and Terms- MODULE 6

76

37.

expansion valve purge valve king valve(liquid) solenoid valve

Abnormal discharge temperatures would be caused by:

A.

leaky suction valves

B. C.

faulty piston rings

D.

any of the above

leaky discharge valves

A device for holding open the suction valve and drawing gas from the suction manifold and returning it to the suction llne without compressing it is called a:

A.

discharge line bypass

B. C. D.

cylinder unloader suction line bypass relief valve

1X. As heat is removed from a substance it gets colder. When) no more heat can :1>e removed and the temperature cannot be lowered any further,

A. B. C.

absolute zero

D.

cold zero

perfect zero double zero

wIe have reached:

r Elements and Terms- MODULE 6 ~-----------

ET -78

39.

0

The boiling point of water in an open container at sea level is 212 F. If the pressure on the open container is decreased. such as going up to the top of a mountain, the

Elements and Terms- MODULE 6- - -

40.

increased

C. D.

the same

A. B. C. D.

decreased none of the above

41. If the

king valve

C. D. 42.

shutoff valve

a clogged scale trap air in the system automatic controls not functioning properly

C.

pumping in with an electric-driven pump shutting down the machine and pouring in through the crankcase inspection pia'

n

44.

ground joints soldered joints

When adding oil to a Freon system one must be sure that:

A. B. C. D.

45.

finished joints welded joints

all air is removed from the pump and fittings

expansion valve is not working normally

C. D.

scale trap is dirty

inlet side, the:

solenoid valve is not working normally

while the compressor

IS

in operation

Just before starting the compressor after a long period of operation SandC

, I . The

discharge side of condenser discharge side of compressor outlet of the evaporator coils receiver tank

expansion valve on a Freon system controls the:

A. B.

superheat of the gas leaving the compressor

C. D.

temperature of the icebox

back pressure in the evaporator

superheat of the gas leaving the evaporator

there is too high a suction pressure the discharge pressure is too high the condenser is shut down

If the head pressure is too high: A. the relief valve should open before the high-pressure cutout

B. C.

B.

A. B. C. D.

If no gaskets are used in the piping joints of a Freon system, the joints must be:

A. B. C. D.

AandC

.:; (). The relief valve is located on the:

opening

43.

when adding refrigerant to the system

expansion valve is working normally

C. D.

pumping in with a hand pump

D.

to remove moisture from trw system to remove air from the system

A.

A. B.

Oil is added to a Freon compressor by: pouring through oil hole in base

remove some of the refriger ant from the system

I(). The oil level in the compressor should be checked:

insufficient cooling water to the condenser

A. B.

add more refrigerant to the system

+8. If the discharge side of the thermal expansion valve is warmer than the

temperature in the icebox is too high, the trouble could be:

A. B.

••

A. B. C. D.

master valve Freon valve

increase the amount of cooling water to the condenser decrease the amount of cooling water to the condenser

+7. The dehydrator is used:

Another name for the liquid valve is the:

A. R. C. D.

~-~-

fh. If the compressor-discharge temperature is hig her than the receiver temperature:

boiling point will be:

A. B.

ET - 79

~~--~--~------~-~--

The scale trap is located between the:

A. B. C. D.

king valve and the expansion valve solenoid valve and expansion valve evaporator and receiver compressor and evaporator

the relief valve should open and let excess refrlqerant go to receiver the high-pressure cutout switch should operate before the relief valve open.

I). close in on the suction valve

If the high-pressure switch on the compressor opens and stops the compressor, a possible cause could be:

,,\, too IlllJ<:h r.oolinq water going through the condenser

ET - 80

Elements and Terms- MODULE 6

B. C. D. 54.

58.

changing the amount of refrigerant in the system any of the above

62.

leaky suction valves suction valve not adjusted properly

63.

air in the system leaky suction valves expansion valve open too wide Bore

humidifier dehydrator trap

stuck high-pressure switch

D.

stuck low-pressure switch

defective thermal bulb

Dairy products should be kept at a temperature of: 10° to 200 20° to 300

A high temperature in the icebox could not be caused by:

A. B. C. D.

aerator

C.

insufficient refrigeration air in the system expansion valve open too wide too much refrigerant in the system

64. When securing a Freon system for repairs: A. pump down to 1 or 2 Ibs pressure B. pump down to a slight vacuum C. pump down to 10 to 15 lbs pressure D. remove all refrigerant from the system

65.

The solenoid valve is located between the:

A. B. C. D.

scale trap and the thermal expansion varve thermal expansion valve and the evaporator king valve and the scale trap automatic and manual expansion valves

35° to 45° 15 to 25°

The purpose of the expansion valve bypass is to:

60. Frost on

compressor and the receiver evaporator coils and the compressor

expansion valve stuck open

clogged scale trap

A. B. C. D.

king valve and the expansion valve receiver and the condenser

A high suction pressure and a cold crankcase indicate:

A. B. C. D.

insufficient refrigeration

any of the above

The charging valve is located between the:

A. B. C. D.

changing the amount of cooling water to the condenser

A. B.

C. D. 59.

61.

changing the speed of the compressor

If the compressor runs continuously, the cause might be a:

A. B.

••

no enough cooling water going through the condenser

A device used to keep moisture from passing through the system is called a:

A. B. C. D. 57.

D.

a leak in the evaporator coils

Which of the following would not cause high suction pressure?

A. B. C. D.

56.

not enough refrigerant in the system

The capacity of a refrigerant unit can be regulated by:

A. B. C. D.

55.

Elements and Terms- MODULE 6 ET - 81 . ----."._-----­

increase the efficiency of the plant increase the capacity of the evaporator

()6. When starting a refrigeration system, always:

A. B. C. D.

vent the condenser vent the evaporator bypass the condenser none of the above

control the refrigerant to the evaporator in case the automatic valves fail bypass the compressor the outside of the thermal expansion valve may be caused by:

;\.

.ur

I ~.

too much superheat

( ..

moisture in the system

In

the system

() 7. Before securing a compressor to A. have gas mask handy B. notify the captain C. D.

do maintenance work on it, be sure to:

make arrangements to have perishables taken care of A and C

1"1

68.

A. B.

no fusible plugs

106°C

C.

two fusible plugs

110°C

D.

none of the above

212°F is equal to:

A. B. C. D. 69.

76.

100°C

have a low boiling point

('.

have a high latent heat be able to be liquified at normal sea-water temperatures

[).

all of the above

77.

A. B. C. D.

50°C

60°C 40°C

78.

55°C

72.

73.

74.

I)

7".

on the discharge side of the transfer pump between the settling tank and the service pump

Boilers "pulsations" are caused by:

150°F 160°F

D.

all of the above

158°F

79.

155 oF

leaky compressor suction valves solenoid valve not functioning properly expansion valve causing flooding back

SO.

between the condenser and the receiver between the receiver and the king valve between the king valve and the solenoid valve

tile compressor will run continuously ItlP

II

safety valve will discharge

will

I'"X

with the oil in the crankcase

Walill Illho hollnrs have:

>\

each furnace has its own fan one fan supplies air to all furnaces the fan is located in the uptake none of the above

In the closed fireroom system:

A. B. C. D.

before the receiver

insufficient air

In the forced draft system:

A. B. C. D.

air in the system

J\. the compressor will short cycle

I ~.

on the suction side of the service pump

forcing the boiler beyond capacity

If there is too much Freon in the system:

( '.

on the discharge side of the service pump

C.

The charging connection in a refrigerating system is located:

A. B. C. D.

feed-stop valve

too high fuel pressure

Low suction pressure is caused oy:

A. B. C. D.

feed-check valve

A. B.

70 c C is equivalent to:

A. B. C. D.

bottom-blow valve skin valve

The fuel oil heater is located:

A. B. C. D.

140°F is equivalent to:

71.

one fusible plug

The valve that prevents water from backing out of the boiler into the feedline is the:

A. B. C. D.

A good refrigerant should:

70.

ET - 83

100 oF

A. B.

.

Elements and Terms- MODULE 6

Elements and Terms- MODULE 6

ET·82

each boiler has its own fan each furnace has its own fan the fan is located in the uptake the fireroom is supplied with air from one fan

1. The air cock on A. B. C. D.

a boiler is located at the:

end of the superheater highest point of the steam and the water drum superheater inlet top of the return headers

:-: 2. Soot blowers should be used in proper sequence so that: A. excess stresses will not be set up in the boiler B. the decks will not be covered with soot

r

Elements and Terms- MODULE 6

ET - 84

Elements and Terms- MODULE 6

--------C. D.

83.

D.

the soot will be swept toward the uptakes there will not be a loss of steam pressure

90.

What is the first thing you would check on taking over a watch?

A. B. C. D. 84.

the periscope the water level the oil pressure

The boiler with its fan (blower) located in the uptake is operating on:

A. B. C. D.

85.

forced draft natural draft none of the above

A. B. C. D.

86.

forced draft natural draft none of the above

87.

A. B. C. D.

·"1 88.

three four

94.

less than that in the steam and water drum more than that in the steam and water drum

95.

the bilges the periscope

When you are cleaning fuel-oil burner tips, use a:

A. B. C.

steel scraper wire brush brass knife

the size of the sprayer plate the oil pressure the air pressure all of the above

top of bottom bottom of top center, alternately, toward each end top of bottom or bottom of top

96.

help preheat the air for the furnaces help preheat the feedwater protect economizer from excessive heat prevent excessive furnace heat losses

check vent to the settling tanks gooseneck vent located on the main deck check valve to the transfer pump gooseneck vent which discharges to the settlers

All fuel-oil service pump steam valves are fitted with:

A. B. C. D.

the water level in the boilers

all of the above

21'10"

All fuel-oil tanks are vented through a:

A. B. C. D.

the same as that in the steam and the water drum

On taking over a watch, the fireman should check:

A. B. C. D.

89.

A. B. C. D.

two

none of the above

21'8"

93. One of the main purposes of refractories in a boiler furnace is to:

one

If the water in the gage glass has not been blown down for a period of time, the level of the water in the glass will be:

20'10"

When installing a new gage glass in a water gage you should secure the bolts from:

A. B. C. D.

induced draft

How many feedwater lines are connected to the boiler?

A. B. C. D.

92.

20'8"

The amount of steam generated by a boiler is dependent upon:

A. B. C. D.

induced draft

A fireroom that is completely isolated (closed) operates:

.

91.

pocket knife

What is the amount of liquid in a tank if you get an ullage sounding of 11'4" and the empty ullage sounding of the tank is 32'2"7

A. B. C. D.

the bilges

ET - 85

safety locks

.

automatic controls reach rods leading to a location outside the fireroom reach rods leading to the engine room

Which of the following fire extinguishers would not be found in the fireroom?

A. B. C. D.

foam type sand

CO 2

SO,

r

Elements and Terms - MODULE 7

CT·86

'.J

MODULE 7

:

97.

What is the average fuel-oil temperature range of the oil in the discharge line to the

•,1,

1\

1.

burners?

A.

the change in enthalpy of a system

B. C. D.

B. C.

randomness or disorder

D.

the heat capacity of a substance

160°-180 2DDo22Cl

98. Which of

2.

Carnot cycle

rudd

C.

Rankine cycle Otto cycle

B &W

D.

none of the above

all of the above

3.

B.

once a day at the beginning of every watch

C.

every 12 hours

D.

every B hours

Is the attraction between like molecules:

A. B.

The boiler gage glasses should be blown down:

100.

An engine cycle containing two adiabatic and two isothermal processes:

A. B.

Retl1letlCrr

A.

the internal energy of a gas

<'()()

the following is a common type of oil burner?

A. B. C. I) . 99.

Entropy is the measure of:

A.180'· 200"

150

ET -87

absorption adhesion

C. diffusion

D. cohesion

4.

Gage pressure of 200 Ibs is equivalent to what absolute pressure?

A. 215 B. 200 C. 185 D. 115

5.

In the polytropic process PV process is called:

6.

constant volume process

B.

constant pressure process

C.

constant temperature process

D.

adiabatic process

S.

A 2/2v

Ay2 2

Av Av

The volume of a fluid passing a cross section of a stream in unit time is called:

C. D.

1

if the value of n is infinitely large, the

When a fluid flows full through a pipe of cross-section area A and with velocity v, the flow or discharge is:

A. B.

7.

= constant,

A.

A. B. C. D.

II

n

steady flow uniform flow discharge continuous flow

The weight of a body means the:

A.

mass of a body

B. C. D.

volume of a body force of gravity on a body molecular weight

Superhoated vapor behaves:

-A. B. C. D.

9.

Elements and Terms - MODULE 7

Elements and Terms - MODULE 7

ET·88

A. B. C. D.

just as gas just as steam just as ordinary vapor approximately a gas

Measure of ability of a boiler or steam generator to transfer the heat given by the

16.

furnace to the water and steam:

A. B. C. D.

10.

A. B. C. D.

boiler efficiency grate efficiency stoker efficiency

17.

A. B. C. D.

11. A valve

A. B. C. D.

omicron dicron tricron

12.

A. B. C. D.

safety valves globe valves gate valves

at which ignition point of fuel vapors rising above the heated

oil will

14.

A. B. C. D.

pour point fine point ignition point

A. B.

radiation

C.

fission

D.

fusion

.2 I . Is the

combustion

15. Difference in pressure measure above or below atmospheric pressure:

turbo-charging injecting

demand factor utilization factor load factor capacity factor

injection lubrication supercharging scavenging resistance to flow:

apparatus used to reduce the oxygen content of-the feedwater by heating and subsequentation:

flash point

Any chemical reaction accompanied by light and heat:

supercharging

20. An

occur when exposed to an open flame:

A. B. C. D.

scavenging

19. Property which measures fluid's A. volatility B. density C. viscosity D. ignition quality

Dust which are mainly fine ash particles:

13. Temperature

breeching

is the admittance of oil between two surfaces that are in contact and in relative motion to one another:

blow off valves

A. fly-ash B. soot C. cinder D. sawdust 'II

stack

18. It

steam pressure in the boiler:

A. B. C. D.

draft chimney

Peak load for a period of time divided by installed capacity:

micron

which constitute the ultimate line of defense against occurence of hazardous

1\' I

Is the removal of the burnt gases from and admitting the fresh charge into the power cylinder of an engine by the use of air:

furnace efficiency

One million of a meter:

EOj

.:2.

economizer superheater evaporator daerator

minimum temperature at which the fuel will no longer pour freely:

A. B. C.

fail point

D.

fire point

pour point flash point

A measure of ratio of inertia to viscous forces in fluids:

-ET - 9U

Elements and Terms - MODULE 7

Elements and Terms - MODULE 7

A. B. C. D.

A. B. C. D.

Moody's No. Avogadro's No. Atomic No

A. B. C. D.

30.

1000 watts 735.5 watts 784 watts

A. B. C. D.

foaming

C. D.

blow-by embrittlement

A. B. C. D.

cavitation water hammer contraction ball hammer

Atoms of the same elements which have the same atomic number and

properties but different atomic masses and molecular weights:

27.

A.

isobars

B. C.

isomers

D.

isotopes

chemical

\'

isotones

The breakdown of heavy atomic nucleus

yielding neutrons and gamma rays:

to produce nuclei of lighter

The length of time it takes for the disintegration

29.

middle life

B. C.

second life

D.

lifetime

13.

pressure, density, velocity flow energy, kinetic energy, height above datum specific gravity, viscosity, velocity

anthorium thorium

Low temperature physics which is concerned with the phenomena that occurs at extremely low temperature: . cryogenics gyrogenics tryogenics pyrogenics

\4. Entrance

losses between tank and pipe, or loss thru nozzle and valves are generally expressed as a function of:

A. B. C. D.

kinetic energy pipe diameter volume flow rate friction factor

rate of a radioactive substance to

decrease bY half:

A.

pressure, temperature, velocity

32. Cavitation is the result of: A. static pressure in a fluid becoming less than fluid B. pump under impact load C. improper welding technique D. exposure to concrete salt water

A. B. C. D.

A. fusion B. fission C. radioactivity D. disintegration 28.

moisturizing temperature

3 1. Heavy hydrogen, the isotope of hydrogen having an atomic mass of 2. A. deutron B. deuterium

carryover

An increase in pressure in a pipe caused by a sudden velocity decrease:

26.

precipitation temperature dewpoint

The total energy of a compressible or incompressible flow across any section in a pipeline is a function of:

A. B. C. D.

746 walts

Presence of impurity droplets of water in the steam flow:

25.

condensing temperature

Reynold's No.

23. One metric horsepower is equal to:

24.

ET - 91

half life

Temperature of which air must be cooled in order to condense:

\ ') Rods of cadmium or carbon steel used in a nuclear reactor to absorb neutron so as to control fission:

A. B. C. D.

welding rods control rods nuclear rods fission rods

ET -92

Elements and Terms - MODULE 7 Elements and Terms - MODULE 7

36.

Doubling the speed, N, of a centrifugal pump, all of the following are true except:

A. B.

Volume flow rate, 0, is increased by a factor of 2

C.

Head, power and volume flow rate are independent variable

D.

Horsepower, P, is increased by a factor of 8

Head, H, is increased by a factor of 4

37. Transfer of

38.

A.

convection

B.

conduction

C.

radiation

D.

emession

The hydraulic formula CA

A. B. C. D.

39.

moderator

44.

Taking place without change in volume:

A. B. C. D.

45. is used to find the:

isochoric isobaric isothermal isentropic

Measure of combustibility of diesel fuel:

A.

Diesel index

velocity of flow in a closed conduit

B.

Cetane number

length of pipe in a closed conduit

C.

Octane number

friction factor of a pipe

D.

Fuel index

quantity of discharge thru an orifice

~6.

A negatively charged particle which is present in every atom: A. electrode

B.

A. B.

ultimate analysis dialysis

C.

electron

C.

Dulong's analysis

D.

ozone

D.

proximate analysis

is a quantity called:

A.

flow velocity

B. C. D.

enthalpy entropy

Rating number Octane number

C.

Diesel index

D.

fuel number

A process with zero heat transfer:

A. B. C. D.

isentropic isothermal polytropic quasi-static

43. A substance such

as graphite. paraffin, or heavy water is used in a nuclear reactor to slow down neutrons:

proton

.~ 7. escaping An opening lava or in into the air:

internal engine

Measure of the knocking tendency of gasoline:

A. B.

42.

J2gh

reactor cladding

D. coolant

The determination of moisture, volatile matter, fixed carbon and ash in coal:

40. u + Pv

41.

energy by electromagnetic waves:

A. B. C.

ET ·93

P~.

A. B.

crater

C.

volcanic cracks

D.

crevice

a volcanic area thru which steam and other hot gases are

fumarole

Radioactive gases resulting from disintegration of radioactive element: A. emanation

B.

amanation

C.

onanation

0,

animation

I(). The lowest temperature of a fuel at which vapor are evolve fast enough to support continuous combustion:

A. B. C, D.

fire point flash point

gas point

vapor point

•(). Ratio of the amount of heat taken up by a substance to the temperature at which the substance exists:

---:

ET~----------Eiements

A. B. C. D.

51.

and Terms - MODULE 7

Elements and Terms - MODULE 7

enthalpy

B. C. D.

entropy internal energy

i

Diesel cycle Rankine cycle

I

Brayton cycle

I

flow energy

57. In

an ideal refrigeration cycle, liqutd leaves the condenser and is expanded in such manner that the enthalpy of the liquid is equal to the enthalpy of the resulting saturated mixture. This type of expansion is known as:

An adiabatic process is characterized by which of the following?

A. B. C. D.

ET -95

The entropy change is zero

A. B. C. D.

The heat transfer is zero. It is isothermal The work is zero

I

I, I

a throttling process an isothermal process

Ii

compression process an isochoric process

I,'II

52. Which of the following statements about the Carnot Efficiency is NOT TRUE?

I,I

58. In case of

A.

It is the maximum efficiency any power cycle can obtain while operating between two thermal reservoir.

B.

Absolute temperature scales must be used when performing Carnot efficiency calculations

B.

The amount of energy required during combustion is less than that required in a similar gas turbine if the power is constant.

C. D.

It depends only on the temperatures of the thermal reservoirs.

C.

The exit temperature of the regenerator is higher than the inlet temperature of the compressor.

D.

There is no heat rejected to the atmosphere in a regenerative gas turbine engine.

A.

No reversible power cycle operating between two thermal reservoirs can have an efficiency equal to the carnot efficiency.

a regenerative gas turbine engine, which of the following is false?

54.

55.

A. B.

equal to the heat transfer

C. D.

equal to the change in internal energy

59. A heat sink will dissipate heat more rapidly at:

A. its temperature is the same as the temperature of the surrounding air B. its surface area is increased

equal to the volume times the change in pressure

C. D.

equal to zero.

A. B.

I

I

Illm,

the oscillations of a plate due to turbulent fluctuations

C.

the liquid to gaseous phase transition of a fluid due to low pressure

B. C. D.

Zeroth law of thermodynamics

D.

the condensation of vapor into liquio due to high pressure

First law of thermodynamics Second law of thermodynamics

I)

I.

The isentropic process efficiency is used to compare actual devices such as turbines, compressors, nozzles, diffusers to ideal ones. Which statement is true? Only the Ideal device is considered adiabatic. The inlet state and exit pressure are the same for both the ideal and actual device. The ideal device operate irreversibly The efficiency can be greater than one.

56. A steam power cycle is modeled by the A.

I1I 1

the separation of the air flow behind a wing

Conservation of mass

C. D.

I' I'll

it is covered with a material having a high thermal resistance

A.

A. B.

pi

it is kept away from air currents.

()o. Cavitation in fluid mechanics refers to: An inventor claims to have built an engine which will revolutionize the automotive industry. Which of the following would be the best test to determine if the inventor'. claims are true?

II'i

I

53. A

rigid container is heated by the sun. There is no shaft work associated with the' container. From the first law of thermodynamics, you determine the resulting work to be:

I

The regenerator improves the efficiency of the engine.

Otto cycle

ideal cycle known as the:

1,2.

Heat is transferred at constant volume process to the thermodynamic system of a fixed mass. The thermodynamic system will produce:

A.

small amount of work

B.

zero work

C. D.

negative work

large amount of work

The Reheat Rankine Cycle is proposed to decrease:

A. B. C.

volumetric flow rate of the working fluid mass flow rate of cooling water in condenser back pressure of the turbine

n. moisture content in the 'ow pressure stages of the turbine 'ml,

Elements and Terms - MODULE 7

ET·9'7

ET·96

63.

D.

Is the condition of pressure and temperature at which a liquid and its vapor are indistinguishable:

64.

A. B. C.

dew point

D.

critical point

triple point absolute humidity

Summation of all the heads in one section is equal to the summation of all' heads in

other section:

A. Archimedes principle

B. C. D.

heat of vaporization

C.

relative heat

D.

specific heat

The ratio of the density of a substance to the density of some standard substance I.:

A. B.

relative density

C. D.

specific density

unit weight

73.

C.

viscosity

D.

all of the above

74.

number of hours the plant has been in actual use:

A.

diversity factor

B. C. D.

utilization factor ioao factor demand factor

When a certain mass of fluid in a particular state passes

processes and returns to its original state it undergoes a:

A. B.

Cycle reversible non-flow process

( '.

Irreversible process

C. D.

adiabatic

isometric polytropic

The latent of vaporization in joules per kg is equal to:

4.19

X

10 3

If the volume of the confined gas is constant, the pressure Is directly proportional to the absolute temperature. This is known as:

A. B.

Kelvin's law

C. D.

Charles law

75.

Boyle's law Joules law

When property changes cease, the bodies are said to be:

A. B.

triple point

C.

change in pressure

D.

thermal equilibrium

change in volume

Exhaust gases from an engine posses:

A. B. C. D.

mass density

68. The ratio of the kw-hr generated to the product of the capacity of the plant in kw to the:

69.

72.

relative gravity

A. B.

isobaric

D.5.40x10 2

specific gravity

Which property of fluids is of fundamental importance in the study of hydraulics?

A. B.

C.

Boyles law

B.

When a gas is heated at constant volume, the process is called:

A. 3.35 x 105 B. 22.6 x 10 5

Torrecellis Theorem

called:

67.

71.

Bernoulli's principle

65. The per unit mass per degree change in temperature is called: A. heat of fusion

66.

70.

equilibrium

solar energy kinetic energy chemical energy stored energy

Which of the following provides the basis for measuring thermodynamic property of

temperature?

A.

Zeroth law of thermodynamics

B. First law of thermodynamics C. Second law of thermodynamics D. Third law of thermodynamics

I III'

-;(i. The external pressure applied to a confined fluId increases the pressure of every

point in the fluid by an amount equal to the external pressure. This is known as;

A. B.

Archimedes principle

C.

Torrecelli's Theorem

Pascal's law

i

ET - 98

Elements and Terms - MODULE 7 Elements and Terms - MODULE 7

D. 77.

80.

81.

A. B. C. D.

francis turbine

85.

A. B. C. D.

utilization factor diversity factor

load factor

diffusion cohesion extraction

adhesion

isothermal

R7.

adiabatic isobaric

The locus of the elevations to which water will rise in the piezometer tube is termed:

A. B. C. D.

energy gradient

R8.

friction head hydraulic gradient hydraulic radius

82. The

total energy in the compressible or incompressible fluid flowing across any section in a pipeline is a function of:

A. B. C. D. X3,

pressure and velocity pressure, density, velocity and viscosity pressure, density and velocity flow energy, kinetic energy, height above datum and internal energy

The process of one substance mixing with another because of molecular motion: /\. diffusion

I ~.

~;.)turalior~

( '.

;ll>~orptl()"

1<9.

angular deformation rate only shear stress and angular deformation rate

absolute humidity specific humidity relative humidity critical humidity

A body wholly or partly immersed on a fluid is vouyed up by a force equal to the weight of the fluid it displaces. This known as:

A, B. C.

Pascal's Theorem

D.

none of the above

Bernoulli's Theorem Torrecelli's Theorem

The ratio of the average load over the designated period of time to peak load in that period:

A. B. C. D.

isometric

density and angular deformation rate density and shear stress

The mass of water vapor per unit volume of air:

demand factor

86.

adhesion

Absolute viscosity of a fluid varies with pressure and temperature and is defined as a function of:

pelton wheel

When gas is heated at constant pressure, the process is called:

A. B. C. D.

84.

reaction turbine

Is the attraction between unlike molecules:

A. B. C. D,

D.

steam turbine

The ratio of the sum of the individual demands of the system to the overall maximum demand of the whole system:

A. B. C. D, 79.

Bernoulli's Theorem

A type of water turbine where a jet of water is made to fall on the blades or buckets and due to the impulse of water the turbine starts moving:

A. B. C. D. 78.

ET - 99 -----------

diversity factor plant use foetor capacity factor none of these

Is a substance that exists, or is regarded as existing, as a continuum characterized by

low resistance to flow and the tendency to assume the shape of its container:

A. fluid

B. C.

ice

D.

volume

gas

The reason for insulating a pipe is:

A. B.

It will not break under pressure. There is minimum corrosion.

C.

Capacity to withstand pressure is increased.

D.

Heat Joss from the surface is minimized.

<)0. Which of the folloWing relations is not applicable in a free expansion process?

A.

Heat supplied equal to zero.

B.

Heat rejected is equal to zero.

ET·100

Elements and Terms - MODULE 7

C. D.

91.

Work done is ecua' to zeru Change in temperature

IS

A. B. C.

equal to zero. 2

The amount of heat passing through a body 1 m cross-section and 1 m thick in 1 hr at a temperature difference of 1 "C:

A. B. C. D.

92.

Elements and Terms - MODULE 8 ET -101 -------- -:_~----------

quantity of heat

>')8. Weight per unit volume is termed as:

A. B.

latent he:Jl uf soho thermal conductivity

B. C. D.

those that are added to refrigerants for better performance

D.

A. B. C. D.

those that do not freeze at all

93. At

the pressure and temperature, equal volumes of all gases contain equal number of molecules. This is known as:

A.

Boyle's law Charle's law

94.

A. B. C. D.

II II

Avogadro's law Faraday's law

Planck's law

96.

I)

7

hydraulic meter

A. B.

boiling point critical point

C. dew point D. vaporization point

MODULE 8

Second law ofthermodynamics Third law of thermodynamics

law states that pressure applied at a point in a confined liquid is transmitted equally to all other points:

A. B. C. D.

barometer

First law of thermodynamics

95. This

"

manometer hydrometer

The temperature to which the air must be cooled at constant pressure to produce saturation Is called:

States that a heat engine cannot transfer heat from a body to another at temperature unless external energy is supplied to the engine:

II

specific density

lOa.

II

If

density

\)9. An instrument that measures density:

those that lower down the freezing points of liquids

B. C. D.

specific gravity

C. weight density

Anti-freeze chemicals are: same as refrigerant

Cnarte's law

D. Joule's law

specific no..t

A.

Kelvin's law Boyle's law

Boyle's law Charle's law

The total stack flow loss is usually less than how many percentage of the calculated draft?

A. B.

3% 5%

C.

7%

"\. D.

9%

Lenz's law

Pascal's law

When the expansion or compression of gas takes place without transfer of heat to or from the gas, the process is called:

A. 8. C.

isothermal

I).

reversible

isentropic adiabatic

A. B. C. D.

axial centrifugal flow fan mixed axial fan mig axial fan none of the above

It acts as a throttle valve, introducing enough resistance into the system to restrict the fan output to any desired quantity:

If tlw temperature of a confined gas is constant, the product of the pressure and vol"rnp 's constant

A fan in which the fluid is accelerated parallel to the fan axis is:

This 's known as'

A. B.

throttle fan drive system

throttling calorimeter

Elements and Terms - MODULE 8

ET -102

C. D.

4.

10.

expansion system

When gas temperature below 1000°F are to be measured, which of the following should be used:

none of the above

A. B. C. D.

The most efficient method of controlling output as far as power is concerned is by:

5.

A.

constant speed

B.

accelerated speed

C. D.

constant accelerated speed

11.

none of the above

required, it is advisable to use a: four speed drive motor single speed drive motor triple speed drive motor

12.

\'

A. B. C. D.

II

20 - 25% 10 - 15%

7.

The temperature of hot metals can be estimated by their color. For steel or iron, the color scale at 2200° F is roughly:

~

II

8.

white

B.

orange

C. D.

dark red

9.

D.

none of the above

picking out impurities manually

135,000 Btu/hr-ft

2

140,000 Btu/hr-ft' 145,000 Btu/hr-ft

2

150,000 Btu/hr-ft

2

1-2% 2-3% 3-4% 5-4%

in tapping the slag has been experience when the calculated coal-ash viscosity at 2600°F exceeds how many poises?

A. B. C. D.

will

slowly creep. This is known as:

A. B. C. D.

gravity concentration

14. Difficulty

yellow

When the temperature of a thermometer is change over a wide range the glass

C.

A. B. C. D.

5 - 10%

A.

cleaning at mine face

If dust collecting equipment is installed for a cyclone furnace boiler unit, the ash escaping from the stack to the atmosphere may be diminished to how many percent of the total?

It \'

all of the above

A. B.

A. B. C. D.

13.

15 - 20%

resistance pyrometer mercury in glass thermometer

Furnaces fired with oil are usually for furnace heat release rates above:

none of the above

To ensure that a boiler unit will not be limited in performance by fans, it is necessary to add safety factors to the calculated or net fan requirements. These factors are intended to cover conditions encountered in operation that cannot be evaluated. The usual factors are in what order in net weight increase of air gas?

6.

bare thermocouple

Which of the following should not be used for cleaning anthracite and bituminous coals?

When vane control is used for mechanical draft fans and where a wide load range is

A. B. C. D.

ET - 103

250 255 260 275

thermal expansion thermal equilibrium intermediate equilibrium

15. Ash

is introduced into the crucible at an elevated temperature and held at that temperature until it becomes uniformly fluid and decomposition gases have been expelled, this temperature is usually in the range of:

none of the above

A. B. C. D.

The temperature of fluid flowing under pressure through a pipe is usually measured by:

A. B.

glass thermometer

( '.

thermocouple thermometer

I).

all of the above

electric resistance thermometer

I (). An

2400-2600°F 2600·2800°F 2800-3000°F None of the above

increase in the decomposition of slag and ash on the surface for heating of oil­ fired boilers in both marine and stationary service has affected boiler efficiency. The following are the causes, except:

ET ·104

Elements and Terms - MODULE B

A. B. C. D. 17.

high-temperature corrosion steels

B. C.

carbon dioxide

low temperature corrosion of the cold sections of air heaters and duct works

D.

methane

increase of heat transfer in the boiler

24.

B. C. D.

ammonium trisulfate hydrogen disulfide all of the above

25.

The ratio of oxygen available to the oxygen required from the stabilization of sewage is called:

A.

biochemical oxygen demand

B.

oxygen-ion.concentration

soda liquor

C. D.

relative stability

hard liquor

bacterial stability factor

none of the above

26.

Which of the following is true about the design of grit chambers?

successful range of pH value is from:

A. B. C. D. 27. With

21 . It is

95-100

inorganic salts

This term refers to controlled device which can stop at any point in its stroke and can be converted without completing its stroke:

A. B. C. D.

30-60 65-90

sodium bisulfate

19. In using the free caustic treatment, the A. 11-11.5 B. 10.5-11 C. 9.5-10 D. 7-8.5 20.

hydrogen sulfide

The quantity of chlorine required to satisfactorily chlorine sewage is usually: A. 0-25

The spent cooking liquor containing the lignin dissolved from the wood is called:

A. B. C. D.

ET - 105

slagging of high temperature superheater surfaces

Acid will react with fly ash in the cooler areas of the boiler to form a hygroscopic salts. Which of the following belongs to the group of hygroscopic salts?

A. B. C. D.

1~.

Elements and Terms - MODULE 8

throttling range control point shift floating action

1

R.

the detention period should be at least 30 min the maximum velocity of flow is 1 ftlsec

regard to corrosion of metals, passivation is the process that: intensifies deterioration

A. B. C. D.

modulating means

temperature is an important factor intensifies deterioration temporarily

intensifies deterioration temporarily changes the composition of metal inhibits further deterioration

In the process of pair formation, a pair cannot be formed unless the quantum has an energy greater than:

A.

sensible heating

A. B.

2 MoC'

B.

humidifying

C.

Y2 MV 2

C. D.

evaporative cooling

D.

hv/C

process in which water vapor is added to the air stream by adiabatic evaporation:

0.5 MeV

none of the above ) (). One of the two types of nonmaterial nuclear radiation is:

22. The

~ \

copper sulfate

A. B. C.

betatron radiation

lime

D.

rutherford radiation

chemical commonly used to speed sedimentation of sewage is:

A. B.

sulfuric acid

C. D.

methylene blue

Tho gas from sludge digestion tanks is mainly composed of: \

Ildrl.'l/I·fl

transmulation radiation gamma radiation

; (). The amount of transferred heat required to change the temperature of one unit weight of a substance one degree unit of temperature:

1\.

latent heat

ET -106

Elements and Terms - MODULE 8

-----------

B. C.

heat of fusion BTU

D.. none of the 31. Which of the

above

following is not a fixed number of characteristics of the machine?

A.

indicated engine efficiency

B. C. D.

compression efficiency Brake engine efficiency

Elements and Terms - MODULE 8

37. An example of a Newtonian A. glues B. molasses C. clay slurries D. none of the above 38.

32. Represents

the loss due to mechanical friction of the moving parts to the engine, expressed as horsepower is: indicated horsepower

C. D.

combined horsepower

33. Work

brake horsepower

39.

none of the above

output of the system divided by energy chargeable against the system is known

vortex

B. C. D.

dilatant

trixotropic vacuum

B. C.

enthalpy

D.

none of the above

pressure heads

mechanical efficiency adiabatic efficiency

40.

The vertical distance from pump centerline to the free surface of the liquid in a discharge tank or point of free discharge:

compressor efficiency

A.

D. none of the above 34.

A.

The sum of the three types of energy at any point in the system is called: A. internal energy

as:

A. B. C.

or true is which of the following?

The phenomenon by which air enters a sUbmerged suction pipe from the water surface is called:

none of the above

A. B.

ET - 107

C. D.

The amount of heat given up by the products of combustion on being cooled to the initial temperature after complete combustion at constant pressure (or volume), • corrected to a standard state of a one atmosphere end 77°F is:

A.

higher healing value

B. C.

lower heating value heating value

D.

none of the above

35. Area

of the indicator card multiplied by the scale of indicator spring divided by the length of indicator card is known as:

A.

indicated maximum pressure

B.

brake maximum pressure

C. D.

actual cylinder pressure none of the above

36. If

the viscosity of a certain liquid decreases with agitation at constant pressure, the liquid is said to be:

A.

Thixotropic

B. C.

Newtonian Dilatant

I). all of the above

static discharge head

B. total discharge head net positive discharge head potential head

41. A

law which states when two bodies, isolated from other environment are in thermal eqUilibrium with a third body, the two are in thermal equilibrium with each other is called:

A. B. C. D.

Stefan Boltzm~nn law Zeroth law Kauffman law Planck law

42. Mathematically, a thermodynamic property is which of the following: A.

a point function

B.

a path function

C. D.

discontinuous exact differential

43. Enthalpy of an

ideal gas is a function only of:

A.

internal energy

B. C.

pressure

entropy

f). temperature

Elements and Terms - MODULE 8

Elements and Terms - MODULE 8

ET -108

ET -109

------------~~

44. Power may be expressed ;n units of: A. ft-Ib B. Btu/hr

C.

Hp-hrs

D.

kw-hr

52.

45. The second law of thermodynamics states that: A. Heat energy cannot be completely transformed into work B. Energy cannot be neither created nor destroyed C. Mass is indestructible D. Internal energy is due to molecular motion

54.

49.

randomness or disorder

SS.

56.

the internal energy of a gas

isothermal

C. D.

quasi-static reversible

57.

square of the density square root of the density cube of its density density

A.

Torrecelli's Theorem

B. C. D.

Archimedes Principle Boyle's Law Bernoulli's Theorem

The type of deep well pump used for 500 gpm and 200 ft head is:

A. B. C. D.

.

piston gear turbine centrifugal

5R. The

speed at which an exact model of the pump would have to run it were designed to deliver 1 gpm against 1 It head per stage: . ;\. peripheral speed

':; \ (U + Pv) i~

il

quantity r:aIIOll'.

too high

The sum of the pressure head, elevation head, and the velocity head remains constant. This is known as:

A device which continously and indefinitely discharge more energy that it receives II

A. Carnot engine B. Refrigerating machine C. Rankine engine D. Perpetual motion machine

isentropic

In fan laws, at constant pressure the speed, capacity and power vary inversely as the:

An adiabatic process with no work done is:

known as:

A.

B.

A. B. C. D.

A. isobaric B. isometric C. throttling D. polytropic

50.

internal energy

A type of compressor which is often used for supercharging diesel engines:

Entropy is a measure of: A. the change in enthalpy of a system

D.

D.

shaft work

A. axial compressor B. rotative compressor C. roots blower D. centrifugal compressor

A. Kirchoffs law B. Avogadros law C. Joules law D. Machs law

the heat capacity of a substance

enthalpy

D. all of the above

change is a statement:

B. C.

C.

Name the process that has no heat transfer:

The change of internal energy of an ideal gas is a function only of the temperature

48.

flow energy

53. The purpose of multistage compression is to: A. prevent vaporization of the lubricating oil B. prevent its ignition should the temperature become C. reduce compressor work and thus saved power

46. The system is said to be thermodynamics equilibrium: A. when all of its parts are the same temperature B. when the system is not accelerating C. if it has no tendency to undergo further chemical reaction D. there is no tendency towards spontaneous change 47.

A. B.

B. C. D.

59.

A. B. C. D.

specific speed rotative speed translation speed

Formation of bubbles in a low pressure area in a centrifugal pump and later their sudden collapse, is called:

A. B. C. D.

60.

Elements and Terms - MODULE 8

Elements and Terms - MODULE 8

ET -110

explosion corrosion compression cavitation

The power required to deliver a given quantity of fluid against a given developed head, with no losses in the pump is called:

A. B. C. D.

brake power hydraulic power indicated power

the diesel operating temperature are in general higher the gasoline operating 'temperature are in general higher additive type lube oils should not be used in gasoline engines soot production in the diesel is less than in gasoline

66. A receiver in an air compression system is use to: A. avoid cooling air before using B. reduce the work needed during compression C. collect water and grease suspended in the D. increase the air discharge pressure

air

67. The heating value of fuel: A. cannot be determined from its Baume reading B. is of the order of 18,500 Btu per Ib at usual temperature C. varies considerably with the oil temperatures D. in Btu per Ib is less for a NO.2 than a No.6 oil

wheel power

68.

61. Heat

flow through a conduction body by transfer from one molecule to the next, without visible movement of he body is:

A. B. C. D. 62.

ET·111

In plotting the brake horsepower versus speed in a wide open throttle test for a spark ignition engine the BHP curve:

A. B. C. D.

radiation conduction convection

is a straight line tends to concave downward tends to concave upward has no characteristic shape

absorption

69. In

a four cycle gasoline engine, when properly tuned the valve operation will usually be such that the:

Heat transmission carried by the movement of heated fluids away from a hot body as in the heating of water by a hot surface:

A. B. C. D.

63.

A. B. C. D.

radiation conduction convection

70. The

64. Term

conduction

C. D.

convection

lowering the compression ratio lowering the inlet air temperature lowering the jacket water temperature advancing the spark timing

absorption

demulsibility neutralization number Conrad son number

71. In compressing air in a water jacketed air compressor the power required to drive it: A. is dependent of the quantity of water circulated for a given pressure range B. does not depend on the given pressure range C. depends on the temperature change of the air for a given pressure range D. only depends on the exponent of the expansion valve

cetane number

72. 65.

exhausts closes before bottom dead center

possibility of detonation in a spark ignition engine will be increased by:

A. B.

radiation

not used in relation to lubrlcatinq oil:

A. B. C. D.

intake closes before bottom dead center exhausts opens before bottom dead center

absorption

Transmission of heat from a hot to a cold by electromagnetic waves is called:

A. B. C. D.

intake opens after the top dead center

In comparing the operation of a diesel and gasoline engine:

In the usual commercial ammonia refrigerating system the ammonia that has just passed through the expansion valve:

A. B. C. D.

73.

Elements and Terms - MODULE 8

Elements and Terms - MODULE 8

ET - 112

has a greater enthalpy that it had before entering the expansion valve

79.

is all in a liquid state has become highly superheated

A single acting air compressor is to be preferred to a two stage compressor in some large high pressure installations because:

A. B. C. D. 74.

less power is required to drive it

80.

the discharge temperature of the air is lower a cylinder oil with a lower flash point .may be used the first cost of the compressor is lower

Reversible adiabatic expansion is at constant:

A. B. C. D.

75. The

pressure volume

76.

change of water from the solid to the vapor phase: can occur directly at elevated pressure

82:

can occur directly at extremely low pressure

As the pressure increases, the heat of vaporization per pound of water

II

decreases remains constant

83.

first increases and then decreases

One type of pipe which is not recommended for use in ammonia refrigeration system is:

A. B. C. D.

78.

brass welded

84.

steel

Based on the 1986 PSME CODE, for piping identification water pipes should be painted with what color:

A. B. C. D.

yellow white green black

a high discharge head gives exceptionally good efficiency

D.

grit in fluid being pumped is not objectionable

85.

the liquid is trapped between the gear teeth and case and is carried around to the discharge

The absolute viscosity of a fluid: is usually expressed in Saybolt minutes in centipoises is 100 times the number of poises when expressed in the English system is in the units of Ibs per second per square inch cannot be converted to a value of kinematic viscosity

If gas is expanded isothermally in a cylinder: it must have been completely insulated heat must have been added during the process heat must have been abstracted to make the process possible no work is done

With increasing load based on a steam generator having good combustion control: economizer gas outlet temperature decreases furnace pressure is approximately constant air temperature entering air heater increases air temperature leaving air heater decreases

The carbon dioxide percentage in the flue gases for perfect combustion of a fuel oil compared to coal and based on the same excess air percentage of each is:

A. B. C. D.

seamless

is decreased if a precooler is used

C.

A. B. C. D.

first decreases and then increases

does not depend on the refrigerant used

the liquid is trapped between the meshing teeth

A. B. C. D.

can occur directly at elevated pressure and elevated temperature

equals the increase in volume

A. B.

D.

always occur in two steps solid to liquid and then liquid to vapor

equals the increase in enthalpy

In the operation of the usual rotary gear pump handling a liquid:

A. B. C.

entropy

A. B. C. D.

77.

81.

temperature

A. B. C. D.

In a refrigeration system the heat absorbed in the evaporator per pound of refrigerant passing through:

A. B. C. D.

is partially vaporized

ET -113

not uniquely determined by the above conditions the same higher lower

The air off take from a surface condenser carries:

A. B. C. D.

dry air air saturated with steam air and steam at unequal temperatures air and steam at equal partial pressure

ET - 114

86.

90.

91.

A

the thermometers are in error

B. C. D.

the air is saturated

ET - 115

the reiative humidity is zero percent the mixture is completely dry

is 7 for neutral solution at any temperature

94.

ash fusion temperature ash is to decrease volatile matter

95.

9425 fe/min 785 fe/sec

1000 tt3 /min

96.

a throttling calorimeter will give the correct value for any initial quality of the steam"

C. D.

a barrel calorimeter would give the most accurate result a separating calorimeter must be used where the initial quality is high

a computed value from brake measurements greater than the indicated mean '?ffe'!lve pressure can be determined without knowlIl1j

till' "111/111(,

speed

30 years

::11:

35 years 25 years

A valve designed to allow a fluid to pass through in one direction only: A. gate valve

B. C. D.

I'~

obtained from the indicator card

The age limit of a horizontal return tubUlar. flue or cylinder boiler having a longitudinal lap joint and operating at a pressure in excess of 0.345 MPa: A. 20 years

B. C. D.

785 fe/min

a throttling calorimeter can only be used where the initial quality of the steam high

The brake mean effective pres sure of an internal combustion engine is:

A. B. C. D.

dustiness

A. B.

float valve globe valve Imll

check valve

97. A vessel

permanently connected to a system by inlet and outlet pipes for a storage of liquid refrigerant:

In the flow of the steam through a nozzle:

A. B. C. D.

the back pressure never has an effect on the flow rate the flow rate is constant for back pressure below the critical pressure the approach velocity never has any effect In the value of the exit velocity

I~I

refrigerant container liquid receiver flash tank surge tank

the critical pressure will occur at 30% of the initial pressure ;')8. It is the temperature at which vapor forms above the liquid fuel:

When considering the characteristics of a reciprocating engine:

A. B. C. D.

92.

decreases with decreasing acidity

In the testing of the quantity of steam entering a steam engine:

A. B. C. D.

II

is obtained gravimetrically

A 12 1.0. circular duct has air flowing past a given suction with an average velocity of 1000 ftlmin. The quantity of air flowing past this section is:

A. B. C. D. 89.

decreases with increasing acidity

The primary ouject of washing coal is to decrease:

A. B. C. D. 88.

Elements and Terms - MODULE 8

The pH values of a solution:

A. B. C. D. 87.

---------------

Elements and Terms - MODULE 8

A.

pour point

the steam rate is given as the pound ot steam per horsepower output

B.

flash point

the brake output is obtained from the indicator cards

C. D.

diesel index

the heat rate is expressed in terms of number of BTU per horsepower hour compounding reduces the thermal efficiency

As commonly used the pH value:

A. B. C. D.

fire point

has no relation to the hydrogen ion concentration will be lower if boiler water is treated with caustic soda for boiler water is usually kept at a value between 5 and 6

'/9. The tendency for a pump to cavitate will be increased if: A. the fluid temperature is raised B. inlet edges are rounded C. the suction line velocities are lowered D. the impeller has a smooth finish

of 7 represents a neutral solution

(n. If the dry and wet bulb readings in air are identical:

I, :1'

I~

,I

I!~

I ()().

Galvaniznd iron is a term referring to iron coated with:

i,l!

Elements and Terms - MODULE 9

Elements and Terms - MODULE 9

ET -116

D.

A. B. C. D.

tin

~

zinc

A. B. C. D.

aluminum

8.

2.

sulfuric acid

B. C. D.

copper sulfate

A. B. C. D.

lime methylene blue

9.

A. B. C. D.

3.

nitrogen hydrogen sulfide carbon dioxide methane

10.

A. B. C. D.

sewage is usually:

A. B. C. D.

I'Ii Il

4.

0-25 30-60 35-90 95-120

11.

A. B. C. D.

The ratio of the oxygen available to the oxygen required for stabilization of sewage ..

A. B. C. D.

• 5.

6.

biochemical oxygen relative stability bacterial-stability factor

0.1 1.0 10.0

remove offensive odors supply fertilizer to farmers oxidize putrescible matter neutralize sludge

a cipoletti weir

a V-notch weir a broadcrested a leaping weir

dispersion ionization crystallization composition

12. At

relatively high temperatures and low rates of strains, structures will perform better if their material is:

A. B. C. D.

parasitic saprophytic pathogenic anaerobic

In the design of grit chambers: A. temperature is an important factor

B. C.

0.01

oxygen-ion concentration

Most of the bacteria in sewage are:

A. B. C. D.

the sludge and raw sewage are not mixed

The most important factor in determining high temperature behaviour of an alloy:

called:

It

the sludge and fresh sewage are well mixed to give complete

To divert excessive flow from combined sewers designers often use:

The quantity of chlorine in parts per million required to satisfactorily chlorinate

II

there are no settling compartments

Intermittent sand filters are primarily used to:

The gas from sludge digestion tanks is mainly composed of:

A. B. C. D.

the effluent contains very little dissolved oxygen

The percent total solids in most domestic sewage is approximately:

The chemical most commonly used to speed sedimentation of sewage is:

A.

the maximum velocity to flow is 1 ft per sec

In an imhoff tank:

magnesium

MODULE 9 1.

7.

ET -117

baffles are essential there should be a 5 to 1 ratio of length to depth

I 3. With

fine-grained their favor is independent to the grain course-grained none of the above

regards to corrosion of metals, passivation is the process that:

A. B. C. D.

intensifies deterioration intensifies deterioration temporarily changes the composition of metal inhibits further deterioration

~

ET -119

Elements and Terms - MODULE 9

Elements and Terms - MODULE 9

ET -118

14. In the

C. D.

process of pair formation, a pair cannot be formed unless the quantum has an

wet bulb temperature dry bulb temperature

energy greater than:

A.

21. The

0.5 MeV

quantity of heat required to raise the temperature of 1 gram water from 14.5 to 15.5°C.

2

B. C.

2 m oC 2 y, mV

D.

3.5 MeV

A. B. C. D.

15. One of the two types of non-material nuclear radiation is: A. transmulation radiation B. walton radiation C. D.

16. The

gamma radiation

latent heat of vaporization specific heat

23.

latent heat

required to change the temperature of one unit weight of a

I.

substance one degree unit of temperature:

I

A. B. C. D.

'u "

II

18. The

.. 19. The

24.

latent heat

from a given excess air will be the same for fuel opil and when burning coke

A. B. C. D.

specific heat heating system

increased with increased excess air decreased with increased excess air

latent heat of evaporation

quantity of heat required to raise the temperature of 1 Ib pure water from 32 to

A. B. C.

Btu

D.

Heat of fusion

Specific heat

A. B. C. D.

I

26.

A. B. C. D.

measure of the ability to transfer heat to other bodies based on a reference temperature(absolute zero) where a body has given up all the thermal energy it

temperature gage

isothermal comprasslon maximum clearance adiabatic compression all of the above

In an air water vapor mixture the temperature which is the measure of the tool heat of the mixture is the:

20. A

Absolute temperature

the efficiency will be the highest

from the standpoint of thermodynamic efficiency, air compressor should approach:

Latent heat

possibly can:

the efficiency will have its lowest value

25. Solely ·r

absolute latent heat Btu

it will require great power to operate the head produced will be one-half its maximum value

.'

Heat of fusion

212 0F under standard atmospheric pressure:

A. B.

is independent of the excess air percentage

B. C. D.

When centrifugal pump for water is operated with the discharge valve closed:

quantity of heat required to change the state of a substance from solid to liquid

A. B. C. D.

"

A.

Btu

without change of temperature: "

Calorie

In the complete combustion of a fuel with excess air, the CO 2 percentage:

heater

17. Amount of transferred heat

Watt

A. hertz B. watt C. ampere D. ergs

betatron radiation

A. B. C. D.

Joule

Power expanded when 1 amp flows between two points having a potential difference of 1 volt.

quantity of heat required to evaporate 1 Ib saturated liquid:

'I

I.

22.

Btu

27. An

dew point dry bulb sum of dry and wet bulb wet bulb

orsat analysis of a flue gas shows CO 2 interpreted as follows:

=12; O =5; CO =0.0. 2

This analysis can be

A. B. C. D.

28.

more air would have produced better combustion the analysis is in error since the terms do not add or 100

greater than the indicated mean effective pressure

C.

a computed value from the brake measurements

D.

can be determined without knowing the engine speed

A. B. C. D. 30.

II

36.

equals the increase in enthalpy equals the increase in volume does not depend on the refrigerant used is decreased if a precooler is used

B.

C.

37.

is considered in Gibb's rule will measure by its change, the quantity of heat added when water is

D.

31.

defines the gas equation

38.

When heat is added to moist air in an air conditioning process:

"

"

32.

A.

the wet bulb temperature decreases

B. C. D.

the relative humidity increases the water vapor pressure increases the absolute humidity remains constant

~

.~' 39.

A.

its relative humidity will be 50%

B. C.

its vapor pressure will decrease

D.

is absolute humidity will not be changed

its relative humidity will be higher than 50%

•

40.

A. B. C.

pressure

D.

entrCllpy

volume temperature

The correct relation between Centigrade and Fahrenheit temperature Is:

I

J

41.

remains constant first decreases decrease

increase the specific volume decrease the specific gravity raise the freezing point raise the boiling point

an aftercooler Baudelot cooler cooling tower an intercooler

will be humidified at approximately constant wet bulb temperature will always leave in a saturated condition will leave the spray chamber at the same water vapor pressure will be dehumidified

gate valve globe valve reducing valve throttle valve

The area under the load curve divided by the maximum demand represents:

A. B. C. D.

Reversible adiabatic expansion is at constant:

increases

The type of valve which should be used only wide open or fully closed is the:

A. B. C. D.

heating it will be found out that:

34.

F over C - 32 = 5 over 9

When heat is added to the moist air in which the spray water is recirculated but not heated or cooled:

A. B. C. D.

Air having a relative humidity of 50% is heated in an air conditioning apparatus. After

33.

Cover F - 32 = 9 over 5

The heat exchanger through which air passes between the first and second stage of a two stage air compressor is known as:

A. B. C. D.

vaporized at constant pressure

IY

32 over F - C = 9 over 5

The addition of 0.5 kg of common salt to 5 kg of pure water will:

A. B. C. D.

.

The term enthalpy: A. is only used for the properties of steam

'.

Cover F - 32 = 5 over 9

As the pressure increases, the heat of vaporization per kg of water:

A. B. C. D.

obtained from the indicator card

passing through:

•

35.

In a refrigeration system the heat absorbed in the evaporator per kg of refrigerant

'II

ET • 121

the analysis is probably correct

The brake mean effective pressure of an internal combustion engine is:

29.

"

A. B. C. D.

no excess air was used in the combustion

A. B.

"

Elements and Terms - MODULE 9

Elements and Terms - MODULE 9

ET ·120

load factor connected load average factor diversity factor

Load curve refers to the plot of:

A.

load versus generating capacity

:I~P

B. C. D.

42. The

C. D.

load versus current load versus time load versus cost of power

permissible pH value of boiler as follows:

A. B. C. D.

01 05 07

45.

51.

,

1.:

Ii!1 ji

I'

relative humidity

I i

'j1r I'"I "

All of the following pollutants are produced because of decaying organic matter, except:

A. B. C. D.

wet bulb temperature

ammonia sulfur dioxide methane hydrogen sulfide

humidity ratio

Total solid impurities in feedwater for a boiler depend upon:

At critical point the latent enthalpy of vaporization is:

A. B. C. D.

quantity of steam to be generated type fuel available

only depends on temperature zero minimum maximum

quantity of steam

B. C. D.

air the fuel spontan€ously

D.

ignites

the fuel ignites with clearly visible flash

'\3.

Generally steam turbine in power station operate at:

A. B. C. D.

3000 rpm 1000 rpm 4000 rpm 5750 rpm '1'1;'1 1

,II',

the fuel ignites without a spark

47. Flash point for a diesel fuel A. minimum 49°C B. maximum 49°C C. maximum 200°C

oil should be:

maximum 300°C

Choking is:

j\. change of mass flow rate in proportion to pressure ratio

B.

52.

boiler pressure

Flash point of a liquid is the temperature at which: . A. the fuel emits vapors at a rate which produces an inflammable mixture wltlt·'

4:-<.

all of the above

50. Surging is: A. an unsteady, periodic and reversal of flow in the compressor B. the fixed mass flow rate irrespective of pressure ratio C. the reduction in lift force D. none of the above

dry bulb temperature

A. B. C. D.

46.

fixed mass flow rate irrespective pressure ratio

49. ASTM coal classification is based on: A. Proximate analysis B. Orsat analysis C. Ultimate analysis D. none of the above

In sensible heating cooling. following parameter remains unchanged:

A. B. C. D.

ET -123

I

slightly more than 7

43. Reserve capacity of a plant is given by: A. maximum demand - average load B. plant capacity - maximum demand C. plant capacity - average load D. plant capacity x (1 -Ioad factor)

44.

Elements and Terms - MODULE 9

Elements and Terms - MODULE 9

ET--122

(11:IIl<jP

,-L In geothermal power plants waste water is: A. B. C. D.

'III ,1'1

recirculated after cooling in cooling towers

I'

discharged back to earth

I'jl

1'1,

discharged into the sea

1

1:11

evaporated in ponds

Iii 'I ; '\. The heat of fusion of ice in calories per gram is approximately:

A. B.

540 144

I

II

III I, 1

of mass flow rate in inverse proportion to pressure ratio

::Ii ,

C. D.

56.

970

A comportable room temperature is 72°F. centigrade is:

The temperature expressed in degrees

The hydraulic formula CA 2gh is used to find the:

A. B. C. D.

58.

quantity of discharge through an orifice

A. B. C. D.

61.

Bernoulli's theorem Boyle's law

66.

critical uniform

isothermal process thermodynamic process adiabatic process reversible process

dynamic process stable processes quasi-static process static process

The negative sign is for a gage reading called:

A. B. C. D.

Archimedes theorem

vapor pressure pressure head vacuum pressure summit of a pipe

The heat transfer due to motion of matter caused by a change In density is called:

Archimedes principle

A.

radiation

Torrecelli's theorem

B. C. D.

convection

Bernoulli's theorem Flow equation

67.

discharge flow uniform flow

conduction absorption

Surging is:

A. B. C. D.

continuous flow

an unsteady, periodic and reversal of flow In the compressor the fixed mass flow rate irrespective of pressure ratio the reduction in lift force at higher angles of incidence none of the above

turbulent flow

68. The changing of solid directly to vapor, without passing through the liquid state I. called:

62.

65.

Torrecelli's theorem

laminar turbulent

Under ideal conditions, isothermal, Isobaric, Isochoric and adiabatic process are:

A. B. C. D.

friction factor of pipe

At any instant, the number of particles passing every cross-section of the stream I. the same, the flow is said to be:

A. B. C. D.

64.

A.

evaporation

B.

vaporization

C. D.

sublimation condensation

If the fluid travels parallel to the adjacent layers and the paths of the individual particles do not cross, the flow Is said to be:

ET -125

The extension and compression of a helical spring is an example of:

A. B. C. D.

length of pipe in a closed network

59. The speed with which a liquid escapes from a vessel through an orifice is given by: A. B. C. D.

63.

velocity of pipe in a closed network

The sum of the pressure head, elevation head, and the velocity head remains constant. This is known as:

60.

A. B. C. D.

80

A. 27 B. 25 C. 22 D. 30

57.

Elements and Terms - MODULE 9

Elements and Terms - MODULE 9

ET -124

In a gas turbine combined cycle plant, a waste heat boiler is used to:

A. B. C. D.

heat from intercooler gases from regenerator recover heat from exhaust gases none of the above

69. In a nozzle if back pressure is the same as inlet pressure

A. B.

no flow takesplace maximum flow takes place

l C. D. 70.

C. flow becomes subsonic in diverging section flow becomes supersonic in converging as well as supersonic sections

77. sub-sonic

A. B. C. D.

supersonic supersonic on one side and sub-sonic on the other side

72.

IS

78.

79.

Overall efficiency of a gas turbine is:

A.

equal to Carnot cycle efficiency

B. C. D.

equal to Rankine cycle efficiency Less than Diesel cycle efficiency More than Otto cycle or diesel cycle efficiency

73. Select a positive displacement rotary compressor: A. roots blower B. centrifugal compressor C. axial flow compressor D. none of the above 74.

75.

80.

81.

open cycle gas turbine with intercooling and reheating

82.

Which of the following is/are advantages of closed cycle gas turbine over an open cycle gas turbine? A. no contamination of working substance with combustion gases

B. C. D.

inferior quality fuel can be used low maintenance costs all of the above

76. The range of compression ratio in a gas turbine is as follows: A. 3 to 5 B. 5 to 8

both pressure and velocity gradually decreases

A.

mercury diphenyl oxide aluminum bromide any of the above

Ljungstrom steam turbine is a: radial flow steam turbine mixed flow steam turbine axial flow turbine any of the above

In an axial flow compressor, the pressure rise takes place in: fixed blades only moving blades only both fixed and moving blades

D. none of the above

open cycle turbine with intercooling, reheating and regeneration closed cycle gas turbine

pressure gradually gets increased and velocity is low both pressure and velocity gradually increases

B. C. D.

A. B. C.

simple open cycle gas turbine

iii."

pressure becomes low and velocity gradually decreases

Which of the following fluid can be employed in binary vapour cycle?

A. B. C. D.

Select the turbine that has least weight per bhp developed:

A. B. C. D.

Brayton cycle

In a velocity compounded steam turbine, as steam moves along moving and guide blades:

A. B. C. D.

less efficient

Brayton cycle is for slow speed engines only large volume of low pressure gas cannot be efficiently handled in reciprocating engines.

Ericson cycle Joule cycle

D. Atkinson cycle

Brayton cycle is more efficient Otto cycle

A constant volume combustion gas turbine operates on:

A. B. C.

sonic

Brayton cycle cannot be used in reciprocating engines even for same compressor ratio and work output because:

8t012

D.12t020

The flow on two sides of a normal shock wave is called:

A. B. C. D. 71.

Elements and Terms - MODULE 9

Elements and Terms - MODULE 9

!=T - 126

ET - 127

83.

An axial flow compressor is suitable for:

A.

high volume flow rates with a small pressure rise

B.

low volume flow rates with low pressure rise

C.

high volume flow rates with high pressure rise

D.

low volume flow rates with high pressure rise

r' lill ."

Which type gas turbine used in air craft?

A. B.

closed cycle type with reheating

C.

closed cycle type with reheating and regeneration

open cycle type

II

I

D.

84.

Elements and Terms - MODULE 9

Elements and Terms - MODULE 9

ET -128

91 . The

open cycle )ype with rehating, regeneration and intercooling

B. C. D.

85.

decrease velocity as well as pressure increase velocity as well as pressure

86.

gas thermometer

93.

involve transfer of energy involve temperature difference between the bodies obey first law of thermodynamics

a mathematical formula

89.

a configuration of heat conduction

95.

m/hr-oC m

0.7

A. B.

brass

C.

lead

D.

copper

aluminum

C.

density

D.

all of the above

A. B. C. D.

m/hr kcal/m

of the order of:

A fur coat on an animal will help the animal to remain:

a function of temperature

warm in winter cool in winter warm in summer cool in summer

2·hr

96. The

nature of flow of a fluid Inside a tube, whether it is turbulent or laminar, can be ascertained by:

2/hr

A. B. C. D.

Non-isotropic conductivity is shown by:

A. B. C. D. 90.

a physical property of the material

The unit of thermal diffusivity is:

A. B. C. D.

w/rn-hr-vc

94. Thermal conductivity of wood depends on: A. moisture B. temperature

obey second law of thermodynamics

Thermal diffusivity refers to:

88.

kJ/m-hr-oK

D.

Select the one that has maximum value of the thermal conductivity:

optical pyrometer

A. B. C. D.

C.

D.

alcohol thermometer

All heat transfer process:

87.

W/m-oK

C. 67

mercury thermometer

A. B. C. D.

W/m-hr·oK

92. The value of Prandtl number for air is A. 10 B. 6.7

decrease velocity and increase pressure

To measure the temperature inside a furnace we generally use:

A. B. C. D.

5.1. unit of thermal conductivity is:

A. B.

A nozzle is used to: A. increase velocity and decrease pressure

ET -129

Brass copper

flow velocity surface conditions viscosity of fluid Reynolds number

wood steel

For glass wall thermal conductivity changes from sample to sample due to changes in:

~

~

A. B.

structure

•f

density

f

C.

all of the above

D.

composition

t

97. Stefan Boltzmann law is applicable to heat transfer by: A. conduction B. radiation C. convection D. conduction and radiation combined 9X. Floating heads are

provided in heat exchangers to:

ET·130

Elements and Terms - MODULE 10

A. B. C. D. 99.

Increase the pressure drop

The first stage of crystal formation is called:

6.

foaming vortexing

7.

8.

A. 1: 2: 3

C. D.

Pulse turbocharger

C. Constant pressure turbocharger

oxygen carbon dioxide impurities settled in mud drums

embrittlement

9. One or the most popular types of compressor utilized for supercharging engine is the: A. Roots type blower

B.

B.

unchanged greatly decreased greatly increased

The form of corrosion in steam boilers caused by dissolved oxygen in boiler water.

D.

What is the absorbed by sulphites in the boiler water treatment?

A.

II

the smoothness of the surface Bell and Spigot joint

A. rusting B. carry-over

C. pitting

B.

2.

The dimensional standard to which each is manufactured Compression joints

How does the values of work per unit mass flow of air in the compressor and turbine influenced by the addition of a regenerator? A. slightly increased

B. C. D.

Foundation are preferably built of concrete in the proportions of what measures of portland cement: sand: crushed stones?

2: 4: 6 C. 2: 3: 5 D. 1: 2: 4

rusting

The fundamental difference between pipe and tubinq is:

A. B. C. D.

separation

MODULE 10

~

A.

B. pitting C. caustic embrittlement D. carry-over

avoid deformation of tubes because of thermal expansion

100. The average pH of the normal rainfall is generally A. 7 B. slightly less than 7 C. slightly more than 7 D. none of the above

• -

oil.

facilitate maintenance

nucleation

ET - 131

5. A form of corrosion in boilers caused by fatty acids from decomposition of lubricating

decrease the pressure drop

A. B. C. D.

1.

Elements and Terms - MODULE 10

D. Turbo compressor 10. The heat flow across a surface area per unit area per unit time divided by the negative rate of change of temperature with distance in direction perpendicular to the surface.

carbon dioxide and oxygen

A. Thermal conductivity

3.

A. B. D.

1

D. Permeance

Surface Coefficient Thermal Conductivity

Which is used as a moderator in certain types of nuclear reactors?

A. B. C. D.

Reflectivity

C. Emissivity

Thermal conductance

C. Reflectivity

4.

B.

The amount of heat transmitted by a material divided by the difference in temperature of the surfaces of the material.

11.

An increase in the decomposition of slag and ash on the surface for heating of oil­ fired boilers in both marine and stationary service has affected boiler efficiency. The following are the causes except:

A.

Low temperature corrosion of the cold section of air heaters and duct works

vapor heavy water

B. Siagging of high temperature superheater surfaces C. High temperature corrosion of steel

hot water

D.

cold water

Increase of heat transfer in the boiler

12. Combined process of cooling and humidifying is also known as:

\1:

:1

II

1:1" -132

Elements and Terms - MODULE 10

Elements and Terms - MODULE 10

A. B. C. D.

B.

A. fusion

heating and humidifying

B.

cooling tower evaporative cooling process

D. 20.

Indicator

D.

21. The law that states : "At constant temperature, the internal energy of a gas tends to finite limit, independent of volume as the pressure tends to be zero".

A. Kelvin-Planck Law

II II II

II

16.

Yeast as raw materials for beer making is added to the equipment called:

A.

II

B.

22.

23.

Removal of particular matter from air within an enclosed space by means of air displacement.

fermenters

It

17. A

general term for a device that receives information in the form of one or more physical quantities, modifies the information and/or its form, if required, and produces a resultant output signal:

N

18.

Scanner

In a diesel engine, what elements in the fuel that make the work of the lubricant more difficult? A. Water and ash content

B. High octane number C. High cetane number D. Sulphur and asphaltene content 19. Most commonly used pyrometer:

vacuum cleaning

B. C. D.

air purging

A.

scavenging blow-down

centrifugal pump

B. positive displacement plant C. hydraulic ram D. rotary pump

24.

In compressing air in a water jacketed air compressor, the power required to drive it:

A. is dependent of the quantity of water circulated for a given pressure range

B.

does not depend on the pressure range

C. depends on the temperature change of the air for a given pressure range

A. converter B. Transducer C. Sensor

D.

A.

A device for forcing running water to a higher level by using the kinetic energy of flow:

B. brew kettle C. cooler D. starting tubs

•

Joules Law

C. Boyles Law D. Charles Law

Uses less fuel

15. What takes place in a uniflow scavenging? A. turbo blower in exhaust header to create vacuum in cylinders B. air reversing direction in cylinders C. uses two blowers to purge cylinders D. air travelling in one direction

;

A. steam dryer B. dry pipe C. moisture separator D. cyclone separator

B. Steam comes out superheated C. It contains no steam drum II

laser

A device for separating llquld from vapor in a steam supply system.

C. Dynamometer D. Prony brake The main advantage of water tube boiler is: A. Steam pressure can be raised in a relatively short time

thermoelectric

C. radiation

moisture removal process

13. An instrument which measures power transmitted by a rotating shaft. A. Torsiometer

14.

ET - 13J

---

D.

only depends on the exponent of the re-expansion curve

25. The

condition prevailing in compressible flow where the upper limit of mass flow is reached or when the speed of sound is reached in a duct.

A. B.

hunting surging

C. choking D. overflowing 26. A point in a field of flow about a body where the fluid particles have zero velocity with respect to the body.

A. stagnation

Elements and Terms - MODULE 10

ET -134 B. C. D.

27. The

choking point emanation point

Elements and Terms - MODULE 10

quality of having a low boiling point or subliming temperature at ordinary pressure.

A. B. C. D.

I. increase in enthalpy of a substance when it undergoes some phase change at

constant pressure and temperature:

28.

latent heat heat of vaporization

A. B. C. D.

II

29. The

refrigerant volatility evaporability condensability

heat of transformation

35. Equipment designed to

reduce the amount of water vapor in the ambient atmosphere.

A. drier

B.

heat of fusion

dehumidifier

C. cooling tower D. fan

Mathematically a thermodynamic property is which of the following:

,I

13~

34. The

onanation point

A. B. C. D.

ET -

a path function discontinuous exact differential a point function

ratio of the density of a substance to the density of some standard substance is

36. The specific measurement of moisture content in air. A. relative humidity B. degree of saturation C. percent saturation D. specific humidity

called.

A. B. C. D.

II

" M

30.

specific gravity

37. A pressure vessel

in which water is heated by steam during off-peak demand periods and regenerated as steam when needed.

A. B. C. D.

specific density

relative humidity

The compression-ignition engine is also known as:

II II

It

relative density

31.

It

A. B.

Diesel engine

C.

Otto engine

D.

Gasoline engine

Gas engine

The difference between the temperature of the water leaving a cooling tower and the wet-bulb temperature of the surrounding air.

A. B.

.

range approach wet-bulb depression

C. D. cooling range

32.

Leaking of a fluid between a cylinder and its piston during operation.

A.

scavenging

B.

back pressure

C. blow by D. turbo charging

33.

Which of the following is not a fixed number of characteristics of the machine?

A. B.

indicated engine efficiency

C. D.

brake engine efficiency

compression efficiency none of the above

38. The

boiler evaporator steam accumulator steam generator

proportions of carbon, hydrogen, oxygen, nitrogen, sulfur, and ash.

A.

ultimate analysis

B. C. D.

work of compression neutralization humidification

39. A process of heat transfer due to A. absorption B. C. D.

motion of matter caused by a change in density.

radiation conduction convection

40. Piping

or tubing close to or attached to a boiler for connecting controls, gages and other instruments. '

A. B. C. D.

boiler trim blow-off drum-intervals boiler treaders

..f I. The entropy of all perfect cystalline solid is zero at absolute zero temperature. A. Zeroth Law B. First Law of Thermodynamics

~

ET -136

C. D. 42.

II

Third Law of Thermodynamics

B. C. D.

evaporator condenser

50.

II If

45.

A. B. C. D.

binary cycle electric generation cogeneration

I' It

D.

betatron radiation transmulation radiation

B.

supplies as with the lower limit for engine efficiency operates between two constant temperature reservoirs has two reversible and two irreversible processes internal combustion

engine

53. The

II

47.

scavenging

D.

induction

B.

the liquid is trapped between the meshing teeth the liquid is trapped between the gear teeth and case and is carried around to the discharge

C. a high discharge head gives exceptionally good efficiency

D.

grit in the fluid being pumped is not objectionable

48. For a confined fluid, the rate of flow of heat out of the fluid per unit area of vessel wall divided by the difference between the temperature at the interior of the fluid and the temperature at the surface wall.

A. B.

conductivity reflectivity

could have damaging effects increases efficiency

air pressure

prevent vaporization of the lubricating oil

B. prevent its ignition should the temperature become too high C. reduce compressor work and thus saved power

D.

supercharging

In the operation of the usual rotary gear pump handling a liquid

A.

maximum volume

purpose of the multi-stage compression is to:

A.

cylinder and

A. blow by

B. C.

clearance volume

52. What is the effect of altitude on engine power? A. high altitude increase engine power B. high altitude means high air density because of lowered C. less air density means more air for burning fuel D. high altitude reduces power

provides of the fictitious which is of little use

of spent gases from an replacement by a fresh change of air.

It

C.

gamma radiation

46. Removal

engine displacement cut-off volume

A. has no effect B. decreases efficiency

C.

D.

in Btu per lb is less for a No.2 than a NO.6 oil

51. Decreasing back pressure on a turbine or engine.

A Carnot engine:

A.

II

is of the order of 18,500 Btu per Ib at usual temperature varies considerably with the oil temperature

Volume displaced by each piston moving from bottom-dead center to top-dead center multiplied by the number of cylinder.

44. One of the two types of nonmaterial radiation is: A. Rutherford radiation II

thermal resistance

49. The heating value of a fuel: A. cannot be determined from its Baume reading

accumulator

D. combined cycle

B. C. D.

ET - 137

D. fluid coefficient

The simultaneous on site generation of electric energy and process steam or heat from the same plant output.

A. B. C.

II

C.

Joule's Law

In a refrigeration system this is a chamber for storing low side liquid refrigerant in a system. Which also serve as a surge drum. A. agitator

B. C. D. 43.

Elements and Terms - MODULE 10

Elements and Terms - MODULE 10

54. Coal

all of the above

is ranked according to:

A. heating value

B. C.

combustibility

D.

flame characteristics

degree of hardness

55. Cooling tower water is treated to A. B. C. D.

prevent

algae growth and corrosion foaming excessive blow downs of boilers priming

')6. Intercooler are used on: A. oil heater

Elements and Terms - MODULE 10

ET -138 B. C. D.

B.

a tire

steam turbine

C.

jet nozzle

gas turbine

D.

a turbine

,I

B.

85% carbon, 15% hydrogen

C.

80% carbon, 20% hydrogen

D.

90% carbon, 10% hydrogen

In the flow of steam through a nozzle A. the back pressure never has an effect on the flow rate B. the flow rate is constant for back pressure below the critical pressure

C. D.

II

A. B. C. D. 60.

It II

61. II It

.. 62.

load factor

:IIIII

A.

cools crankcase oils

B. C. D.

remove moisture or dew droplets condenses steam between stages in the air and removes condensate

, 1.1,1 1 1

.1

II

,'~I'I'I

1

cools air so it can't back up into 1st stage

'11 ,:111

Static head is: H20 in a vertical pipe with pressure and no motion refers only to high viscosity fluids water is motion water in a horizontal pipe with no pair

68.

A. B.

engine high speed

C. D.

high compression ratio

poor cooling system

til'

Main steam line to a prime mover must be:

A.

level all the way

flash point

fire point boiling point

B. C.

inclined toward boiler

C. D.

D.

inclined toward prime mover

69.

]1

engine friction losses

pour point

in a continuous loop in all situations

Corrosion in boilers is chiefly caused by:

A.

too lean fuel mixture

B. C. D.

forced draft fan failure

B.

gas baffle broke

C. H20 D. CO 2

A. O2

dirty burner cup

Superheater located in the first pass of a furnace is:

70.

Alkaline H2 0 III I

A continuous blowdown valve controls:

conduction type

A.

impurities in solution

radiant type

B. C. D.

total dissolved boiler chemicals

flue type convection type

63. A condenser function converts gas to liquid steam to vapor

total dissolved silica calcium-carbonate scale particle

71. A graphical representation A. hectograph

B.

gas to vapor vapor to heavy gas

64. Which if the following would A. a pump

!,

I

A. B.

A. B. C. D.

I

mean effective pressure is higher than theoretical mean effective pressure on account of:

diversity factor

A. B. C. D.

II' "

67. Brake

use factor

If stack temperature rises with no load increase.

, ,

I

Intercooler in a compressor

A. B. C. D.

demand factor

The temperature at which vapors will flare up and then die out:

N

66.

the critical pressure will occur at 30% of the initial pressure

Ratio of the average load to the peak load over a period of time

II

65.

the approach velocity never has any effect in the value of the exit velocity

II

59.

ET -139

gas compressor

57. Chemical composition of fuel oil A. 70% carbon, 30% hydrogen

58.

Elements and Terms - MODULE 10

between discharge and time is known as:

monograph

C. hydrograph D. topograph be considered a system rather than a control volume? I

,i

ET -140

Elements and Terms - MODULE 10

Elements and Terms - MOOUlE 10

72. What is a process whereby a fissionable species is utilized as a source of neutrons to

D.

produce more nuclei of its own kind than are used up?

A. Developing B. Culturing

C. D.

,f II

Flash point Stagnation point Porosity point

74. In a power plant, what instrument indicates percentage of CO 2 in the flue gases. A. Ranarex indicator B. Microtector

C. D.

A. vented to the atmosphere

A. B. C. D.

..

",. "

II It

.

76. Part

Ash, moisture, volatile, fixed carbon

B.

spinning reserve

C.

primary power

D.

secondary power

77. Heat loss that is inherent in a boiler is due to: A. excess air

B. C.

boiler can: inhibit circulation and heat transfer cause foaming create impure steam quality overheat blow off line

A. incomplete combustion visible light visible flame only ultraviolet and or infrared energy

83. In a low speed engine, which of the following may cause black smoky exhaust. A. too heavy oil B. too much lUbricating oil

C. D. 84.

too high fuel pressure too light fuel

The hydraulic formula CA square root of 2gh is used to find:

85. How

A. B.

quantity of discharge through an orifice velocity of flow in a closed conduit

C. D.

length of pipe in a closed network friction factor of a pipe

do you increase the output of a centrifugal pump?

dry chimney gases

A. speed up rotation

unburned gaseous combustible

B. C. D.

D. radiation from the furnace setting 78. How does the expansion of cylinder wall relieve piston friction? A. by reducing clearance space between cylinder wall and piston

B.

by increasing clearance space between cylinder wall and piston

C.

by increasing temperature of cylinder water jacket

D.

by reducing temperature cylinder water jacket

79. Water behind the dam at the plant. A. storage

B. C.

installed With safety valve

detector verifies:

B. C. D.

Hydrogen, oxygen, moisture

of the capacity of a hydraulic plant available at all times when energy is needed. A. firm power .

installed at least 10ft higher than feed pumps

82. Flame

Doppler meter

Carbon, hydrogen, oxygen

tilted to the feed pumps

C. D.

D.

hydrometer

CO, carbon monoxide, excess oxygen

B.

81. Scale in A. B. C.

75. What components are included in the proximate analysis in fuel? II

spillwater

Receivers must be:

Multiplying Breeding

73. Under saturated condition, what is the lowest point at which fuel starts to flow. A. Pour point

B. C. D.

80.

reservoir pondage

ET ·141

install recirculation line increase the suction pipe area increase the discharge pipe area

86. What is the process whereby a fissionable species is utilized as a source of neutrons to produce more nuclei of its own kind than are used up? A. Developing B. Culturing

C.

Multiplying

D.

Breeding

87. The principal disadvantage of fire tube boilers is: A. uncontrollable output steam temperature

ET - 142

Elements and Terms - MODULE 10 Elements and Terms - MODULE 10

B.

uses too much fuel

C.

contains too large volume of water and requires too long time interval to raise temperature

D.

only wet steam is generated

D. 95. How do

a piping system, detrimental distortion of connected equipment resulting from excessive thrusts and moment: is avoided by provldlnq an expansion loop

D.

may be eliminated by using welded connectors

causes excessive vibration

A. B. C.

Freon 22

D.

Ammonia

96.

Rate of deceleration of flow Relative compressibility of liqUid tom expansion

An accessory often installed on modern boilers to heat combustion of air before it enters the boiler furnace.

A. B. C. D.

Freon 12

economizer air heater reheater forced draft fan

Freon refrigerants

important factor to be considered in designing exhaust systems for diesel engines.

A.

Arrangements of external systems to minimize back pressure

B. C. D.

Proper filtration of exhaust gas to eliminate odors Baffling to eliminate exhaust noise Provide exhaust gas to recovery system

91. What

do you call the changing of atom of an element into an atom of a element with a different atomic mass?

A.

atomization

B.

atomic transmulation

C.

atomic mile

D.

atomic energy

92. The diagonal lines in the

Psychrometric chart represent?

A. Effective temperature

B. Dry-bulb temperature C. Wet·bulb temperature Dew-point temperature

93. Assuming

real process, the net entropy change in the universe is:

A. must be calculated equai to zero negative positive

94. What is the function of radiation pyrometer? A. boiler water weight B. boiler pressure

( '.

C. D.

its boiling point varies over a wide range of temperatures.

90. An

B. C. D.

you differentiate surge from water hammer?

is desirable for stability

89. An odorless refrigerant:

D.

boiler drum pressure

A. Time for a pressure to transverse the pipe B. The pressure of the reservoir at the end of the pipe

88. In designing A. B. C.

ET - 143

furnace temperature

97. Specific heat capacity is an A. J/kg B. W/m-K C. J/m 3 D. J/kg-K

9~.

51 derived unit described as:

Which of the following is a physical property of lUbricating oil? A. Cetane number

B. C. D.

Viscosity index Aniline point Octane number

99. What characterizes a reaction turbine? A. steam losses velocity as it leaves the diaphragm

B.

steam strikes the blades at right angles

C.

steam will react with a force in the diaphragm steam is deflected

D.

100. Pneumatic tool are powered by: A. steam

B. C. D.

water natural gas air

PB -1

ME Board October 1994 MECHANICAL ENGINEER Licensure Examination Tuesday, October 25, 1994

8:00 AM- 4:00 PM

POWER AND INDUSTRIAL PLANT ENGINEERING

SET A

INSTRUCTION: Select the correct answer for each of the following Mark only one answer for each item by shading the box questions. corresponding to the letter of your choice on the answer sheet provided. STRICTLY NO ERASURES ALLOWED. Use pencil NO.1 only. MULTIPLE CHOICE

1. A back pressure steam turbine of 100,000 kw serves as a prime mover in a cogeneration system. The boiler admits the return water at a temperature of 66°C and produces the steam at 6.5 Mpa and 455°C. Steam then enters a back-pressure turbine and expands to the pressure of the process, which is 0.52 Mpa. Assuming a boiler efficiency of 80% and neglecting the effect of pumping and the pressure drops at various location, what is the incremental heat rate for electric? The following enthalpies have been found: turbine entrance 3306.8 kJ/kg, exit = 2700.8; boiler entrance = 276.23 kJ/kg, exit 3306.8. C. 25,200 kJ/kw-hr A. 22,504 kJ/kw-hr D. 30,506 kj/kw-hr B. 24,500 kJ/kw-hr Solution: W T = turbine work =

m(h 1

-

h2 )

= m(3306.8 - 27008) Q A =

= = =

=

heat supplied in the boiler

mx3600(h 1 - h 2 ) 11b m(3600)(3306.8 - 276.23)

0.80 13,637,565 m kJ/hr

606 m

kw

= =

PB - 2

ME Board October 1994

=

13,637,565m 606m

Heat Rate =

ME Board October 1994

22,504 kwkJ _ hr

By heat balance in the condenser:

m(h 2

2. A coal fired power plant has turbine-generator rated at 1000 MW gross. The plant required about 9% of this power for its internal operations. It uses 9800 tons of coal per day. The coal has a heating value of 6,388.9 kcalfkg and the steam generator efficiency is 86%. What is the net station efficiency of the plant in percent? A. 33.07% C. 37.05% D. 42.05% B. 35.70%

h3 ) = mwCpLH

-

0.153(377 - 238.5)

= 1OOO( 1 -

V

w

0.723(60)

=

=

mtOh

0.09)

Net Station Efficiency

- -

910,000 2,752,001

4338

3.7854

= 11.46 GPM

4. Air enters a fan through a duct at a velocity of 6.3 m/s and an inlet static pressure of 2.5 cm of water less than atmospheric pressure. The air leaves the fan through a duct at a velocity of 11.25 m/s and a discharge. static pressure of 7.62 cm of water above atmospheric pressure. If the3/s, specific weight of the air is 1.20 kg/m 3 and the fan delivers 9.45 m what is the fan efficiency when the power input to the fan is 13.75 kw at the coupling? A. 71.8% C. 81.7% B. 78.1% D. 87.1%

9800(907) (6,388.9 x 4.187) 24(3600)

_ Net Output Heat Input

=

43.38 Ii/min

1

==

= 910 MW = 910,000 kw Heat Input

mw(4.187)(7)

mw = 0.723 kg/s

Solution: Net Output

=

Solution:

= 33.07%

H = total head

== static pressure head

+ velocity head

3. A freon-12 waste water system operating at a SoC suction temperature and a 40°C condensing temperature has "an evaporator load of 5 tons. If the condenser is selected for a 7°C water temperature rise, how many gpm must be circulated through the condenser? The following enthalpies have been found: condenser entrance 377.0 kJfkg, exit 238.5; evaporator entrance 238.5 kJfkg, exit 353.6 kJfkg. C. 15.85 GPM A. 11.46 GPM D. 25.61 GPM B. 12.95 GPM

=

=

=

Solution:

m

.

P2

-

PI

(

+ V2

w

2

-

) )

VI ~

2g

= (0.0762 + 0.025)1000 + 1.20 ==

(J 1.25Y' - (6.Jy 2(9.81)

88.76 m of air

Air Power = Q w h

= 9.45(1.20 x 0.00981 )(88.76)

REF. Effect 5(3.516)

=

==

= m(h 1 -

= m(353.6

= 0.153 kgfs

h4 )

==

- 238.5) Fan Efficiency

9.874 kw

=

Air Power Input Power

x 100

PB-4

ME Board October 1994

=

ME -._ ­

13.

9.874 x 100 = 71.81 % 13.75

5. When

a substance in temperature, it is called: A. Vapor B. cloud

gaseous

state

is

below

the

critical

9

(t,,°F)

=~ 9

(18)

15. A type of water turbine: A. Parson B Hero

= 10°C

7. Is the condition of pressure and temperature at which a liquid and its vapor are indistinguishable: C. absolute humidity A. critical point D. relative humidity B. dew point If the temperature is held constant and the pressure is increased beyond the saturation pressure, we have a : A. saturated vapor C. saturated liquid B. compressed liquid D. subcooled liquid

~

8.

•

9. A francis turbine has what flow: A. inward flow reaction B. outward flow impulse

•

."

C. Pelton D. Banki

16. If the pressure of the confined gas is constant, the volume is directly proportional to the absolute temperature: A Boyle C. Charles D. Kelvin B. Joule

17. A theoretical body which when heated to encandescence would emit a continuous light -ray spectrum: A black body radiation C. blue body B. black body D. white body 18. A water temperature rise of 18°F in the water cooled condenser is equivalent in °c to: A -9.44°C C. 10°C B. 26356°K D. 7.78°C

C. outward flow reaction D. inward flow impulse

10. The latent heat of vaporization in joules per kg is equal to: 5 2 A. 5.40 x 10 C. 22.6 X 10 5 3 B. 4.13 X 10 D. 3.35 X 10 11. Form of energy associated with the kinetic energy of the motion of large number of molecules: A. internal energy C. heat of fusion B. kinetic energy D. heat

The number of protons in the nucleus of an atom of the number of electrons in the orbit of an atom: A. atomic volume C. atomic weight B. atomic number D. atomic mass

C. height above a chosen datum, density, internal energy, pressure and velocity of flow D. pressure, height above a chosen datum, velocity of flow, density of fluid

Solution:

=~

- - P B -5

14. The energy of a fluid flowing at any section in a pipeline is a function of: A. velocity of flow only B. pressure only

C. moisture D. steam

6. A water temperature rise of 18°F in the water cooled condenser is equivalent in °c to: A. 7.78°C C. 263.56°K oC B. 10°C D. -9.44

t,,°C

Board October 1994

Solution:

random

12. In a poT diagram of a pure substance, the curve separating the solid phase from the liquid phase is: A. vaporization curve C. boiling point B. fusion curve D. sublimation point

.:; 18 . 9

.z:

10'I

e

19. Ignition of the air fuel mixture in the intake of the exhaust manifold: A. backlash C. exhaust pressure D. back pressure B. backfire 20. Is the condition of pressure and temperature at which a liquid and its vapor are indistinguishable: A relative humidity C. critical point

B absolute humidity

D. dew point

PB -6

ME Board October 1994

ME-Board ----- - October 1994

21. When a substance in gaseous state is below its critical temperature it is called: A. steam C. moisture B. cloud D. vapor 22. Which A. B. C. D.

30. Steam flows into a turbine at the rate of 10 kg/s and 10 kw of heat are lost from the turbine. Ignoring elevation and kinetic energy effects, calculate the power output from the turbine. Given: h, ;: 2739.0 and h 2 = 2300.5 kJ/kg. A. 4605 kw C. 4375 kw B. 4973 kw D. 4000 kw

Molecular weight of air = 28.97 kg/kg mole Solving for theyolume per kg mole at 101.325 kPa and 273°K:

Solution:

PV = mRT

V

=

28.97(0.287)(273) 101.325

C. energy gradient D. friction gradient

29. In sensible cooling process, the moisture content: A. does not change C. indeterminate B. decreases D. increases

of the following a set of standard condition: 3/kg 1 atm, 255 K, 22.41 m mole o 3/kg 101.325, 273 K, 22.4 m mole 0K, 3/kg 101.325, 273 23.66 m

mole 1 atm, 10°C, 22.41 m3/kg mole

Solution:

II

28. The locus of elevations: A. critical point B. hydraulic gradient

W

= 22..4 m 3/kg mole

= m(h l - =

h2)

-

q

10(2739.0 - 2300.5) - 10

= 4375 kw

•

23. Number of molecules in a mole of any substance is a constant called: A. Rankine cycle C. Otto cycle D. Thompson constant B. Avogadro's number

•

24. A simultaneous generation of electricity and steam (or heat) in single power plant: C. waste heat recovery A. gas turbine B. steam turbine-gas turbine plant D. cogeneration

~

"

a

25. Is one whose temperature is below the saturation temperature corresponding to its pressure: C. constant volume process A. compression D. subcooled liquid B. condensation 26. Pump used to increase air pressure above normal, air is then used as a motive power: A. air cooled engine C. air condenser B. air compressor D. air injection

27. If the temperature is held constant and the pressure is increased beyond the saturation pressure, we have a : A. compressed liquid C. saturated vapor B. subcooled liquid D. saturated liquid

31. The compression ratio of an ideal Otto cycle is 6:1. Initial conditions are 101.3 kPa and 20°C. Find the pressure and temperature at the end of adiabatic compression. A. 1244.5 kPa, 599.96°K C. 1244.5 kPa gage, 60°C B. 1244.5 kPa, 60°C D. 1244.5 kPa, 599.96 oC

Solution: Vi V,

1',

6

II

PN/ = P2V2 K

:~ (~~ =

~

=

r

(6)14

J0 1.3

P2 = 1244.5 kPa

(~~

r I

To 20+273 = (6)14-1

°

T 2 = 599.96 K

PB -8

ME Board October 1994

ME Board October 1994

"

32. What pressure is a column of water 100 cm high equivalent to? A. 9807 Dynes/ern" C. 0.1 bar 2 2 B. 9807 N/m D. 98,100 N/m

=

I~

II

= 9807 N/m

2

33. An ideal vapor compression refrigeration cycle requires 2.5 kw to power the compressor. You have found the following data for the cycle: the enthalpy at the condenser entrance 203 kJ/kg, exit 55; evaporator entrance = 55 kJ/kg, exit = 178. If the mass flow rate of the refrigerant is 0.10 kg/s, then the coefficient of performance of this refrigeration cycle is most nearly: A. 592 C. 5.92 B. 59.2 D. 4.92

=

=

=

N R

=

tI

i It

II

. II

DV

11

where: 0

II

=

12.3 2.5

= hi -h 4 h 2 -h]

COP

=

178 - 55

203-178

Solution:

ta Q

= 0.5 ft

= 50

(~J

= kA(t a

- tb )

- tb

x

1.131 = kimernatic' "VISCOSIty = -_

997.9

= 4.92

34. Calculate the energy transfer rate across 6" wall of firebrick with a temperature difference across the wall of 50°C. The thermal conductivity of the firebrick is 0.65 Btu/hr-tt-OF at the temperature interest. 2 2 C.112W/m A. 285 W/m 2 D. 429 W/m 2 B. 369 W/m

x =,6 in

= 2(25.4) = 50.8 cm = 0.508 m

v = 5 m/s

= 4.92

11

Or:

=

Solution:

REF Effect = m(h 1 - h2 ) = 0.10(178 - 55) = 12.3 kw

CpP

1055J hr (3.28)2ft2 Btu x -- x -­ x hr - ft2 Btu 3600sec m2

35. Water is flowing in a pipe with radius of 25.4 cm at a velocity of 5 m/s at the temperature in the pipe. The density and viscosity of the water are as follows: density 997.9 kg/m 3 , viscosity 1.131 Pa­ s. What is the Reynolds Number for this situation? A. 2241 C. 3100 B. 88.2 D. 1140

Solution: II

= 90°F = 0.65(1)(90) = 117 Btu 0.5 hr-ft 2

'j

= 369 ~ m2

Solution:

Pressure = wh = 9807(1)

117

PB -

= N R

=

0.508(5) 0.0011334

=

0.0011334 m%ec 2241

PB -10

ME Board Apri/1995

MECHANICAL ENGINEER Licensure Examination Sunday,Ap~123, 1995

ME Board Apri/1995

8:00 AM - 4:00 PM

POWER AND INDUSTRIAL PLANT ENGINEERING

SET A

INSTRUCTION: Select the correct answer for each of the following questions. Mark only one answer for each item by shading the box corresponding to the letter of your choice on the answer sheet provided. STRICTLY NO ERASURES ALLOWED. Use pencil NO.1 only.

8.

Work done per unit charge when charge is moved from one point to another: A. equipotential surface C. electrostatic unit B. potential at a point D. potential difference (Ref. Weber, etc. p. 589)

9. A pressure of 1 millibar is equivalent to: 2 A. 1000 dynes/cm C. 1000 psi B. 1000 cm of Hg D. 1000 kg/cm 2

MULTIPLE CHOICE I~

II

Solution: 1. What is the process that has no heat transfer? A. reversible C. polytropic B. isothermal D. adiabatic

II

" "I'

" It

If

= 0.1 kPa

= 0.1 kN

-Z

m

2. The internal combustion engines never work on A. Rankine C. dual combustion B. diesel D. Otto It

1 millibar = 0.001 bar cycle:

3. The dividing point between the high-pressure and low-pressure sides of the refrigeration cycle occurs at the: A. expansion valve C. condenser B. compressor D. cooling coil 4. What is the force which tends to draw a body toward the center about which it is rotating? A. centrifugal force C. centrifugal aadvance B. centrifugal in motion D. centripetal force 5. A simultaneous generation of electricity and steam (or heat) in a single power plant: A. steam turbine - gas turbine C. gas turbine plant D. waste heat boiler B. cogeneration 6. Percent excess air is the difference between air actually supplied and the theoretically required divided by: A. the theoretically air supplied C. the actually air supplied B. the deficiency air supplied D. none of these 7. What amount of air is required in a low bypass factor? A. greater C. indeterminate B. lesser D. does not change (Source: Ref. Jordan and Priester p. 295)

kN = o.1 -z

x

m

1000 N

kN

x

mZ

100,000 dynes X

N

J

10,000 em"

= 1000 dynes cm 2

10. Heat transfer due to density differential:

A convection C. conduction

B. nuclear

D. radiation

11. When a system deviates infinitesimally from equilibrium at every instant of its state, it is undergoing:

A isobaric process C. isometric process

B. quasi-static process D. cyclic process

12. The ratio of the average load to the peak load over a designated period of time is called: A. load factor B. reactive factor

C. diversity factor D. plant use factor

13. A supercharged six-cylinder four stroke cycle diesel engine of 10.48 cm bore and 12.7 cm stroke has a compression ratio of 15. When it is tested on a dynamometer with a 53.34 cm arm at 2500 rpm, the scare reads 81.65 kg, 2.86 kg of fuel of 45,822.20 kJ/kg heating value are burned during a 6 min test, and air metered to the cylinders at the rate of 0.182 kg's. Find the brake thermal efficiency. A. 0.327 C. 0.307 B. 0.367 D. 0.357

/ I

PB -12

ME Board Apri/1995

ME Board April 1995

PB -13

Solution:

Solution: T = 81.65(0.00981 )(0.5334) Brake Power

= 2nTN = =

mr If

=

2.86 6(60)

= 0.42725 kN-m

Work of single stage

nPV'

=

_1_1

n~1

2500j' 2n(0.42725) ( 60

111.854 kw

=

(1.30)(9X56{

=

II

1.30- 1

1

PI

f

~Ji(985.6)~~~

= 0.00794 kg/sec

J

P 1]-1 (--.1...)' -

I 98.56

~ 'I

.j(98.56)(985.6)

=

42.43 kw

Brake Thermal Efficiency

I'

For Two Stage:

_ Brake Power

mrQ h

=

It

I' III

III It

II It

0.307

111.854

P x ==

(0.00794)(45,822.20)

==

= 30.7%

14. The gaseous mixture has dew point temperature of 15°C. The total pressure is 143.27 kPa. Determine the amount of water vapor present in 100 moles of the mixture. Note: Saturation pressure at ~ 15°C is 1.7051 kPa. " A. 1.10 C. 1.19 B. 2.19 D. 2.0

Work ofTwo Stage:

= =

_ (VV

v) p

2np'V'l( ~~

f ~ 'J

f(

)~~2

2(1.30)(98.56{W-)

Solution:

Pv -

M

Saving

1.30 -1

l

311.67 98.56

311.67 kPa

-'j

36.83 kw

= 42.43 - 36.83

= 5.6 kw

III

1.7051 =

16. The enthalpy of air is increased by 139.586 kJ/kg in a compressor. The rate of air flow is 16.42 kg/min. The power input is 48.2 kw. Which of the following values most nearly equals the heat loss from the ccmpressor-rn kw? A. -10.0 C -9.95 B. +10.2 D. +9.95

(V100v J143.27

V v = 1.19 moles 3

15. An air compressor is to compress 8.5 m per min from 98.5t kPa to 985.6 kPa. Assuming conditions ideal, and with n 1.3, what will be the saving in work due to two staging? A. 4.6 kw C. 5.6 kw B. zero D. 3.5 kw

=

Solution:

By first law of thermodynamics (energy balance) H 1 + W = H2 + (-q)

PB ~ 14

~

ME Board Apri/1995

,q

=

H2

=

1642 (L\9.586) _ 48.2 60

=

-

H1

W

-

= m(h

2 -

h 1)

-

20. A gaseous fuel mixture has a molal analysis:

W

-10 kw

17. What is the clockwork-operated device which records continuously the humidity of the atmosphere? C. hydrodeik A hetrograph D. hygrograph B hygrometer

If

18. What is' an apparatus used in the analysis of combustible gases?

,.

A. calorimeter differential B. calorimeter gas

I.

, iii

II

CH 4

= 3%

co =

O 2 = 0.6%

CO 2

= 4.5%

N2

for air. A. 565 B. 535

27%

= 50.9%

Determine the theoretical air-fuel ratio for complete combustion on molal basis. A. 2.13 C. 1.233 B. 3.230 D. 1.130 Solution:

+ 0.14 H 2 0.03 CH 4 + 0.27 CO +

0.070 O 2 0.060 O 2 0.135 O 2

= 0.14

=

=

H2 0 0.03 CO 2 + 0.06 H 2 0 0.27 CO 2

0.265 O 2 -0.006 O 2 from fuel itself

height of stack in meters is needed when no draft fans are used? Assume that the gas constant for the flue gases is the same as that

0.259 O 2 from air

C. 545 D. 550

Theo. A/F

=

0.259 + 0.259(3.76) 1

Solution: p

II

H2 = 14%

Chemical reaction with Oxygen:

C. calorimetry D. calorimeter

19. A steam generator with economizer and air heater has an overall draft loss of 21.78 cm of water. If the stack gases are at 177 deg. C and if the atmosphere is at 101.3 kPa and 26 deg C, what theoretical I.

PB -15

ME Board Apri/1995

d,

.

d g

= density of air = n.r, =

lOU

0.287(26 + 273)

101.3 = density of flue gas = 0.287(177 + 273) =

II

Pressure = height x density Draft

= 0.2178(1000) = 217.8

Draft

= H(d a

217.8

-

= H(1.18

H = 550 m

dg)

kg/m

3

=

1.J8~3 m

0.784

~3 m

1.233 mols air mol fuel

21. A fan delivers 4.7 m 3/s at a static pressure of 5.08 cm of water when operating at a speed of 400 rpm. The power input required is 2.963 3/s kw. If 7.05 m are desired in the same fan and installation, find the pressure in cm of water. A. 7.62 B. 17.14

C. 11.43 D. 5.08

Solution: QI Q 2

= ~

N2

~ H = l~J N 2

2

- 0.784)

4.7

400

7.05

N2

-- =­

N2 = 600 rpm

5.08 = (400r H2 600

H2 = 11.43 cm of water

PB -16

ME Board Apri/1995

ME Board Apri/1995

22. A fan described in a manufacturer's table is rated to deliver 500 mJ/min at a static pressure gage of 254 cm of water when running at 250 rpm and requiring 3.6 kw. If the fan speed is changed to 305 rpm and the air handled were at 65°C instead of standard 21°C, find

25. A single stage air compressor handles 0.454 mJ/sec of atmospheric pressure, 27°C air, and delivers it to a receiver at 652.75 kPa. Its

the power in kw. A. 3.82 B. 5.08

C. 4.66 D. 5.68

Solution:

volumetrlc efficiency is 0.72, its compression efficiency on an isothermal basis is 0.85 and its mechanical efficiency is 0.90. If it rotates at 350 rpm, what power in kw is required to drive it? A. 95 C. 120 B. 112 D. 100

Solution:

Solving for the power required at 305 rpm and 21 DC:

I~

~

=

Pz

It

(~1

Po Isothermal Power ::: P 1V 1 In -=-­

3

PI

NZ )

~ = Pz

=

(250)3

It

"I.

= 85.685 kw

=

It II

d1

~

=

_ ,%.T - ,%.T

1

=

RT

T2 TI

2

Drive Power

6.5

-

P' z

dz

=

It

P2 '

= 5.68 kw

23. If the fluid travels parallel to the adjacent layers and the paths of individual particles do not cross, the flow is said to be: A. turbulent C. dynamic B. critical D. laminar

(Thermo. Faires pp. 84-87)

= 112 kw

Enthalpy (kJ/kg)

Temp. DC

........... -....... ------ -- ... -_..-... -- ... -- .......

Abs. Pressure kPa Sat. Liquid Evap. Sat. Vapor

hf

2 26

462.49 1033.97

A. 9.02

190.4 303.6 C. 91.08 D. 8.92

B. 90.98 Solution h 3 = h,

24. What equation applies in the first law of thermodynamics for an ideal gas in a reversible open steady-state system? A. Q - W = U z - U 1 C. Q - VdP = Hz - H 1 B. Q + VdP = Hz - H 1 D. Q - PdV = H2 - H1

85.685

0.85(0.90)

expansion valve. The temperature of the vaporizing ammonia in the evaporator is 2°C. Find the percentage of liquid vaporized while flowing through the expansion valve.

65 + 273 21 + 273

=

26. liquid ammonia at a temperature of 26°C is available at the

~=~ Pz

652.75

101.3

Solving for the power required at 305 rpm and 65°C: P density d

It

101.3(0.454) In

305

P z = 6.5 kw If

PB -17

h3

= hf

+ x hfg

303.6 ::: 190.4 + x(1255.2)

x = 9.02%

hfg

1255.2 1162.0

hg

1445.6 1465.6

PB -18

ME Board April 1995

ME Board April 1995

r~ PB -19

i'

27. Is one whose pressure is higher than the saturation pressure corresponding to its temperature: A. saturated liquid C. saturated vapor B. compressed liquid D. compressed gas

35. Type of turbine that has high pressure and low pressure is called: A. compound engine C. impulse turbine B. gas turbine D. compound turbine

28. The locus of elevations to which water will rise in the piezometer tube is termed: A. energy gradient C. hydraulic gradient B. friction head D. critical path

36. The design of an air supply duct of an air conditioning system: A. adds moisture to the air B. lowers the temperature of the air C. does not affect the distribution of air D. affects the distribution of air

29. The total energy in a compressible or incompressible fluid flowing across any section in a pipeline is a function of: A. pressure and velocity B. pressure, density and velocity C. pressure, density, velocity and viscosity D. flow energy, kinetic energy, height above datum and internal energy 30. The ratio of the density of a substance to the density of some standard substance is called: C. specific density A. relative density B. specific gravity D. relative gravity

38. The volume of a fluid passing a cross section stream in unit time is called: A. steady flow C. discharge B. uniform flow D. continuous flow

32. The hydraulic formula CA~2gh is used to find:

Problem Solving:

33. The sum of the energies of all appear in several complex forms, A. kinetic energy B. potential energy

molecules in a system, is the: C. internal energy D. thermal energy

energies

34. The temperature at which its vapor pressure is equal to the pressure exerted on the liquid: A. absolute humidity C. boiling point B. calorimeter D. thermal energy

III i :/11/ I

''''I I

39. Weight per unit volume is termed as: A. specific gravity C. weight density B. density D. specific qravity 40. S.1. unit of force: A. pounds B. Newton

quantity of discharge through an orifice velocity of flow in a closed conduit length of pipe in a closed network friction factor of a pipe

III

37. The changing of solid directly to vapor, without passing through the

liquid state is called:

A. evaporation C. sublimation B. vaporization D. condensation

31. At any instant, the number of particles passing every cross-section of the stream is the same, the flow is said to be: A. steady flow C. continuous flow B. uniform flow D. turbulent flow

A. B. C. D.

'~I

C. kilograms O. dyne

1. In an air standard diesel cycle, compression starts at 100 kP;I and 300 K. the compression ratio is 16 to 1. The maximum ,;ycle temperature is 2031 K. Determine the thermal efficiency. A. 60.3% C. 70.3% B. 63.0% D. 85.5% Solution:

Process 1-2, isentrop ic process:

~~ T,

H

=

(~l i 2)

]1)0 = (16)' 4-1

PB - 20

1,

ME Board Apri/1995

,

ME Board Apri/1995

1'1\

.: I

I

T2

= 909.43K

d9

P

= density of flue gas =

RgTg

Process 2-3, isobaric process:

IOU V c = V3 T2 T3

rc

=

T3 T2

V3 V,

_ - 1 -

Draft

2031 909.43

Cycle Thermal Efficiency

=

=

1 ­

1 rr TkK=l L

0.02286 (

1 [(2.233)14 (16)14-1 1.4(2.233 -1)

-

I

I

0.001005)

Vel

Il

J

Flow

60.27%

=

Cv~2gh

=

10.2m/s

= Area

46.72 0.686

=

=

22.746

~2 m

= mass flow rate of flue gases 18.54(2.52) = 46.72 kg/s

= 30:

0.40.12(9.81)( 22.746) 0.686

x Vel

~D2(10.2) 4

D = 2.9 m 3. The following is an analysis of coal in percent: C H2

= 74 =6

O2 N2

=8

= 1.6

5 = 1 Ash = 9.4

If burned in a boiler, the coal produces the following Orsat analysis in percent:

CO 2 = 12

Flow gases have higher molecular weight than air, assume M

J

m

Solving for the velocity of the flue gases considering a velocity coeffient of OAO:

I]

~(TC -I) K

Solution:

=

=

2.233

2. 2.52 kg of coal per second are consumed by a steam boiler plant and· produced 18.54 kg of dry flue gas per kg of coal fired. The air temperature outside is 32°C, the average temperature of the flue

gases entering the chimney is 343°C and the average temperature of

the flue gases in the chimney is 260°C. The gage fluid specific volume is 1.005 x 10.3 m 3/kg and a theoretical draft of 2.286 cm of water at the chimney base is needed when the barometric pressure is 101.3 kPa. Find the diameter of the chimney in meters. A. 2.9 m C. 3.5 m B. 2.1 m D. 3.9 m

mg

0.686 kg

0.277(260 + 273)

CO = 0.1

O 2 = 6.5

The refuse contains 0.008 kg of carbon per kg of coal burned. Determine the percentage excess air used. A. 45.6% C. 46.5% D. 75%

B. 49.8% Solution:

Rg

=

8.3143 30

= 0.277 Thea AJF

= 11.5 C

+

34.5

(H- ~ J

+

4.3 S

~

ME Board Apri/1995

PB -22

+

= 11.5(0.74)

34.5(0.06 _

0.~8j

+ 4.3 (0.01)

I

- 6.5 = 81.4% by volume

Total kg in products = 0.12(44) + 0.001(28) + 0.065(32) = 5.28 + 0.028 + 2.08 + 22.792 = 30.18

+ 0.814(28)

PB·23

MECHANICAL ENGINEER Licensure Examination Weclnesclrlv October 18, 1995 POWER AND INDUSTRIAL PLANT ENGINEERING

= 10.278 kg air per kg coal N2 in product = 100 - 12 - 0.'1

14

ME Board October 1995

SET A

INSTRUCTION: Select the correct answer for each of the following questions. Mark only one answer for each item by shading the box corresponding to the letter of your choice on the answer sheet provided. STRICTLY NO ERASURES ALLOWED. Use pencil NO.1 only. MULTIPLE CHOICE

kg N z kg prod

22.792

1. Heat exchanger used to provide heat transfer between the exhaust gases and the air prior to its entrance to the combustor: A. evaporator C. regenerator B. combustion chamber D. heater

0.7552

30.18

C burned

=

0.74- 0.008

0.732

kg coal

C in prod

Note:

, kg gas kg coal

0.028 5.28 + -­ 30.18(2.33)

30.18(3.67)

=

= 0.0481 kg

1 kg C + 2.67 kg Oz = 3.67 kg COz

1 kg C + 1.33 kg Oz = 2.33 kg CO

3. What are the immediate undesirable products from the petroleum­ based lubricating oil when subjected to high pressure and temperature? A. gums, resins and acidsb C. soots and ashes B. sulfur D. carbon residue

1

0.732 x - - = 15.218

0.0481

Nzsupplied kg coal

Air supplied kg coal burned

= 15.218(0.7552) =11.493

= 11.493 0.768

4. The intake pipe to a hydraulic turbine from a dam is: A. tailrace C. surge tank B. spiral casing D. penstock

14.965

5. When 1 mol of carbon with 1 mol oxygen: A. 2 mols carbon dioxide C. 1 mol carbon and 1 mol CO 2 B. 1 mol carbon dioxide D. 1 mol carbon monoxide

Note: N2 is 76.8% by weight in air

Percentage of Excess Air = 14.965 -10.278 10.278

2. Heat normally flowing from a high temperature body to a low temperature body wherein it is impossible to convert heat without other effects is called the: A. second law of thermodynamics B. first law of thermodynamics C. third law of thermodynamics D. Zeroth law of thermodynamics

= 45.6%

Solution: 1 C + 1 Oz =

1 CO 2

6. A device for measuring the velocity of wind: A. aneroid barometer C. anemoscope B. anemometer D. anemograph

---------

PB -24

~---_. ~ - _ . ~ - - - -

ME Board October 1995

, ,

--------

ME Board October 1995

PB -25

--------_-----.::...=-=-=-==-----=-::.-:....._--_----..:.-=--~

Solution: 7. Air standard efficiency of a diesel engine depends on: A. speed C. fuel B. compression ratio D. torque 8. Heavy water is: A. 820 (2 is written as subscript) C. WzO (2 is written as subscript) 8. HzO (2 is written as subscript) D. 0 20 (2 is written as subscript) 9. The ratio of the sum of individual maximum demands of the system to the overall maximum demand of the whole system: A. demand factor C. power factor D. utilization factor B. diversity factor 10. Percent excess air is the difference between the air actually supplied and the theoretically divided by: A. the deficiency air supplied C. none of these B. the actually air supplied D. the theoretically air supplied

Converting the given mass analysis to molal analysis: Component C Hz S

N2

II

13. The viscosity of most commercially available petroleum lubricating oil changes rapidly above: A. 120°F C. 150°F B. 180°F D. 130°F

Molal Analysis 85.3/12 = 7.108 14.1/2 = 7.050 0.5/32 = 0.016 0.1/28 = 0.004 14.178

Combustion reaction with 125% theoretical air: 7.108C + 7.050 Hz + 0.016S + 0.004N z + 1.25(101.649)Oz + 1.25(10.649) (3.76)N 2 = 7.108 CO 2 + 7.050 H20 + 0.016 S02 + 50.054 N 2 + 0.25(10.649) O 2 Total mols in products

11. Mechanism designed to lower the temperature of air passing through it: C. air spillover A. air cooler B. air defense D. air cycle 12. The term "exposure" in radiological effects is used as a measure of a Gamma ray or an X-ray field in the surface of an exposed object. Since this radiation produces ionization of the air surrounding the object, the exposure is obtained as: A. x = no. of ions produced per mass of air x coulombs per kg B. x = mass of air x surface area of an exposed object C. x = mass of air over surface area of an exposed object D. x = no. of ions produced per mass of air + coulombs per kg

Mass Analysis 85.3 14.1 0.5 0.1 100.0

= 7.108 = 66.89

+ 7.050 + 0.016 + 50.054 + 2.662 mols

Partial Pressure (H 20)

=

(7.05°)170 = 17.92kPa 66.890

3

15. What is the m of gravel required for a 5 m 3 of 1 : 2 : 4 concrete mixture, given the follOWing properties of materials: Material

Relative Density

Density (kg/m 3 )

Cement 3.10 Sand 2.64 Gravel 2.50 Use 26 liters of water per bag of cement. cement loose volume as 0.028 rn", 3 A. 6.12m C.2.16m 3 B. 4.73 rn' D. 3.92 m 3

1428 1680 1525 Assume one bag of

Solution: 14. A steam generator burns fuel oil that has the following chemical analysis by mass in percent: C =85.3 H 2 = 14.1 S = 0.5 N2 = 0.1 Combustion takes place in 125 percent in theoretical air. The flue gases leave the air pre-heater at 0.17 Mpa. What is the partial pressure of the stack gases to avoid condensation in kPa? Take molecular weight of the flue gases as 28.8. A. 19.85 C. 17.93 B. 11.14 0 14.20

V c , Vs, V g , V w = compact volume of cement, sand, gravel and water, respectively.

Vc

=

1428(0.028)1 3.10(1000)

= 0.0129 m 3/batch

PB -26

"

ME Board October 1995 1680(0.028)2

V s =

2.64(1000) 1525(0.028)4

V 9 =

2.50(1000) 26

=

Vw

1000

=

0.0356 m

3/batch

0.0683 m

3/batch

ME Board October 1995 Solving for h2 :

~

=

= 0.0260 m

3/batch

= 0.1428 m

3/batch

S1

=

S,

= (sf + x sfg)z

6.5763

5 Total no. of batches = - 0.1428

=

= 2.1345

= hf

h

X2

(4.4555)

+ x hfg

h 2 = 760.88

35 batches

+

= 0.9969

X2

VTotal

S2

= 27711.4

+ 0.9969(20168)

kJ/kg

By continuity equation: = 3.92 m

Volume of gravel required = 35(0.028)4

3

A,V,

16. A venturi meter is placed in a line carrying dry saturated steam at . 1.03 M pa to enable estimates of steam flow rate to be made.' The inlet throat diameters of the venturi are 22.86 cm and 17.78 em, . respectively, and it is found that between these two positions the steam pressure falls by 0.04 MPa. Assuming that the flow is isentropic, what is the rate of steam flow in kg/s? Properties of Steam

Press

Temp t (0C)

Sp. Vol. vg (m

3/kg)

Enthalpy hf hfg

179.47 181.19

sf

sfg

s9

2.1345 2.1512

0.99 MPa

hi +

2

..•.

_1

2gJ

where: J h,

................~. 1

V

= h, + -2..­

-

.,r-

.

:

O2

-I

~ :

2

= 0.605 V2

2

+ VJ 2

2gJ

.2

~

(0.605 yo)2 - 2(9.81)(102)

+

= 157.4

Flow

1.03 MPa

By energy balance: y

2779.25

V2

C. 19.49 D. 29.20

Solution:

h

VI 2gJ

4.4555 6.5894 4.4252 6.5713

It

A. 25.50 B. 12.15

= (0.1778)2

(0.2286)2 Y2

VI

Entropy hg

760.88 2016.8 2717.7 768.50 2010.7 2719.25

0.1963 0.18905

D/V 2

2

II

0.99 1.03

=

D,2v,

hi +

Saturation:

P(Mpa)

= A 2V2

.

.. ~

I

m

=

.,

V,'

+

2(9.HI)(I02)

m/s

= Area

= -4 I TD-. ,

= 2771.4

x velocity

V,. =

mass flow rate

IT,

-(0 177;-1)'(157.4)

4

3.908

= - -

0.] 963

=

= 3908

3

m /s

19.91 kg/s

2gJ

= conversion constant = 102 kg-m/kJ = 2779.25 kJ/kg

17. What is the required base area of the foundation to support an engine with specified speed of 1200 rpm and weight of 9,000 kg. Assume bearing capacity of soil as 47.867 kPa. Use c = 0.11. 2 A 5.57 m C. 7.75 m 2 2 B. 8.87 m D. 10.5 m 2

PB ·28

ME Board October 1995

ME Board October 1995

PB - 29

Solution: :::

WF

:::

705.645 (3600)

= 2,540,323 kw-s or kJ

weight of foundation

:::

e x WM x

Indicated Thermal Efficiency

.,IN

::: 0.11 (9000) ../1200

-+­

::: 34,295 kg

QOOO) 0.00981 A

=

2,540,323 143.724(44,620)

::: 39.6%

19. Air enters an auditorium at the rate of 26.5 m 3/s. The air is at 250C dry bulb temperature and 16°C wet bulb temperature, and is at 100 kPa. What will be the mass rate of flow of water vapor (kg/min) ? Note: Saturation pressure at 16°C::: 1.8181 kPa. A. 10.2 C. 18.1 B. 6.3 D. 14.1

Solution:

II

II

II

I'

I'

18. A 2000 kw diesel engine unit uses 1 bbl oil per 525 kw-h produced. Oil is 25° API. Efficiency of generator 93%, mechanical efficiency of engine 80%. What is the thermal efficiency of the engine based on indicated power (%) ? C.39.6 A. 31.69 D. 35.6 B. 29.47

P

y

L/ _ _

P - Py

At 16°C, saturated:

W 2

Solution: 1 bbl

1.8181 0.622 100-1.8181

:::

= 0.0115

On the absence of given data, the enthalpies of water vapor, hg , will be calculated by the formula:

::: 42 gallons

Solving for the density: 0API ::: 141.5 _ 131.5 SG

II

hg 1

1061 +

:::

141.5 25 ::: - ­ - 131.5 SG SG 0.904

II

1061 + 0.444 teJb

:::

hg

II

0.444(~(25)

(teJb in OF)

+ 32) :::

1095.2 Btu/lb

1095.2 (1.055)(2.205) = 2547.7 kJ/kg

:::

=

hg 2

Btu/lb

+

0.444(~(16)

:::

1061

:::

1088.0 (1.055)(2.205)

w ::: density ::: 0.904(1) ::: 0.904 kg/Ii

+ 32)

::: 1088.0 Btu/lb

= 2531.0 kJ/kg

rn, ::: fuel consumed ::: 42(3.7854)(0.904) ::: 143.724 kg h Qh

:::

:::

::: C p

+ Whg

41,130 + 139.6 (oAPI) 41,130 + 139.6 (25) = 44,620 kJ/kg

Indicated work

=

525 0.93(0.80)

= 705.645 kw-h

Assuming that the constant wet bulb line coincides with the constant enthalpy line: h,

::: h 2

1(25)

+ W 1 (2547.7)

= 1(16)

+ 0.0115(2531.0)

ME B0:!rd October

ME Board October 1995

PB -30

21.

W 1 = 0.00789 PV = mRT

.100(26.5 x 60) = m, (0.287)(25 + 273)

m, = 1859 kg/min

w

'!~~~

A waste heat recovery boiler produces 4.8 Mpa (dry saturated) steam from 104°C feedwater. The boiler receives energy from 5 kg/s of 954°C dry air. After passing through the waste heat boiler, the temperature of the air has been reduced to 343°C. How much steam in kg is produced per second? Note: At 4.80 Mpa dry saturated, h= 2796.0 kJ/kg. A. 1.3 C. 2.1 B. 0.92 D. 3.4

Solution:

= mv

rna hf

= enthalpy of feedwater = Cp t

rnv = 0.00789 (1859) = 14.7 kg/min = II

20. A diesel engine is operating on a 4-stroke cycle, has a heat rate of 11,315.6 kJ/kw-hr brake. The compression ratio is 13. The cut-off ratio is 2. Using k = 1.32, what is the brake engine efficiency? A. 63.5 C. 73.5 B. 51.2 D. 45.3

4.187 (104)

= 435.45 kJ/kg

Heat loss = Heat gain

mgCp (t, - t2 )

= ms(h s - hf)

5(1.0)(954 - 343) = ms (2796.0 - 435.45)

II

Solutit>n:

tl

wcle efficiency

=.

II

II

=

It

II

=

W QA

1.32(2 -1)

=

II

s:) =

kw - hr (3600

=

"

llb

-

1

r

1[,'-1]

K

1 [(2)'' - 1]

(13)132-1

.rake thermal efficiency

9b

=

k-I

= 50.1%

0.3181 0.5010

--

=

63.5%

22. A piece of silver weighing 600 grams in air weighs 500 grams when immersed in glycerine whose specific gravity. is 1.25. Find the volume of the cavity inside the silver. A. 24.32 cc C. 21.12 cc B. 22.86 cc D. 26.21 cc

Solution:

B

W QA

Densityof silver

Vc

=

b

W W

=

= 10,500 kg/m

Density of glycerine

31.81%

11,315.6 kJ

brake engine efficiency

k(r c -1)

ms = 1.3 kg/s

~ e

3

= 1.25(1000) = 1250 kg/m

= volume of cavity

V s = volume of silver = Fs = buoyant for ce

F s = (V s + Vel 1250

0.600 m 3 10,500

3

PB·32

=

(0.600 - 0.500)

Vc

Ii

=

22.86

X

.

II

(0.600 + V ) 1250 10,500 c

6

10.

m3

= 22.86

= 0.069

h o for still air A. 93% B.98%

= 9.36

W/m

Where:

W/m·K

Q

= 16,427.4W = = ms (h, - h2 )

x

Solution:

I'

It

5.08 em

r1 = 10.10 -2

=

5.05 em

10.10 em

r2 5.08 em

= 5.05 + 5.08 = 10.13 em

0.125(2800.0 - h2 )

= hf

+ x hfg

= 914.52

+ x(1885.5)

= 93%

24. A superheat steam Rankine Cycle has turbine inlet conditions of 17.5 Mpa and 530°C expand in a turbine to 0.007 Mpa. The turbine and pump polytropic efficiencies are 0.9 and 0.7, respectively, pressure losses between pump and turbine inlet are 1.5 Mpa. What should be the pump work in kJ/kg? A. 17.3 C. 37.3 B. 27.3 D. 47.3 Solution: Wp

I'

=

16.4274kw

h2 = 2668.6

2668.6

II

nr2L

213.67 - 22 1n(0.1013/0.0505) 1 -' + - ­ 2n(0.069)(l52) (96.746)(9.36)

=

16.4274

h

2·K

II

Ao = 2

PB - 33

= 2n (0.1013) (152) = 96.746 m2 Q

em"

C.84% D.76%

II

ME Board October 1995

"

23. Steam, initially saturated at 2.05 Mpa, passes through a 10.10 em standard steel pipe for a total distance of 152 m. The steam line is

insulated with a 5.08 em thickness of 85% magnesia. For an ambient

temperature of 22°C, what is the quality of the steam which arises at

its destination if the mass flow rate is 0.125 kg steam/sec?

Properties of Steam:

Enthalpy

Press Temp hf hfg hg

2.05 213.67 914.52 1885.5 2800.0 k for 85% magnesia

II

.~

ME Board October 1995

=

V 3 (P4 ­

P3 )

TJp

Q

where:

hI

= = =

_1 = 0.001 m 3/kg 1000 P4 17.5 + 1.5 19 Mpa P3 0.007 Mpa = 7 kPa TJp = 0.70 V3

=

=

19,000 kPa

152 m Wp

Q

=

ti In([2

/ [1)

to 1

.~._-+--

2nkL

A"h"

=

0.001(19,000 - 7) 0.70

=

27.1 kJ/kg

25. Water flows steadily with a velocity of 3.05 m/s in a horizontal pipe having a diameter of 15.24 em. At one section of tho pipe, the temperature and pressure of the water are 21°C and 689.3 kPa,

PB ·34

ME Board October 1995

respectively. At a distance of 304.8 rn downstream, the pressure is 516.9 kPa. What is the friction factor? A. 0.134 C. 0.0189 D. 0.641 B. 0.0050 Solution: hf

=

ME Board October 1995 By continuity equation:

= A 2V2

D/V 1 = D}V 2

AN1

friction head loss

V1 689.3-516.9 9.81

= I~I

III

(10.16)2 (15.24)2 V2

=

= 17.574

=

0.444 V 2

SUbstituting in the Bernuolli's Equation: By Darcy Equation:

= fLV

hf

2 V2 - (0.444V2)2 + 1.061 2(9.81)

70

2

9.81

2gD V z

17.574

=

f(304.8)(3.05)2

2(9.81)(0.1524)

= 12.184 m/s

Q = C A 2 V 2

II' III

PB - 15

=

0.985

(~J

(0.1016/ (12.184)

f = 0.0185

= 0.0973 m 3/s

:~ III

III III

III

26. A venturi meter with a 10.16 cm throat is installed in a 15.24 cm pipe which is inclined upward at an angle of 45 degrees to the horizontal. If the distance between pressure tape along the pipe is 1.5 rn, the o differential pressure Is 70 kPa, and the water temperature is 70 e, 3/sec? what is the discharge of water in m Assume coefficient of 0.985. A. 1.0021 C. 0.5110 B. 0.0121 D. 0.0986 Solution:

3/s

27. It is desired to deliver 5 m at a head of 640 m in a single stage pump having specific speed not to exceed 40. If the speed is not to exceed 1352 rpm, how many stages are required? A. 3 C. 5 B.4 D.2 Solution:

Let n = no. of stages

By Bernuolli's Equation: h = head per stage

.!l+ W

PI -P2 W

VI 2 2g

+

zl

P2 -

V2 2

+ -

W

2g

+

Z2

ns =

-zd

40

where: P 1 - Pz = 70 kPa w = 9.81 kN/m 3 · 0 · ZZ-Z1 = 1.5sln45 = 1.061 m

n

V/ - V,2 + 2g

(Z2

=

=

NJQ hJI4 135215

(6~or4

2

=

640

n

PB -36

ME Board October 1995

28. A hydroelectric generating station is supplied from a reservoir of 3

capacity 6,000,000 m at a head of 170 m. Assume hydraulic efficiency of 80% and electrical efficiency of 90%. The fall in the reservoir level after a load of 15 MW has been supplied for 3 hours, if the area of the reservoir is 2.5 sq. km is closest to: A. 5.39 cm C. 5.98 cm B. 4.32 em D. 4.83 cm Solution: I~I

Q w h Tlh TIe

15,000 = Q (9.81)(170)(0.80) (0.90)

Q

Solving for the density of air:

d =

P

RT

da =

101.325

0.287(21 + 273)

1.2 kg/m 3

=

Solving for the density of flue gas:

=

Output

ME Board October 1995

= 12.492 mJ/s

d 9 =

III

8.3143

R = 8.3]43 M

30

] 01.325

0.277(149 + 273)

= 0.277

=

0.867 kg/m 3

In 3 hours, volume of water consumed:

= 12.492 (3) (3600)

H

III

:p Iii

III III

.

'

Volume

= Area x height

134,914

=

H

=

(2.5 x 10

0.0539 m

-

0.72 = H(1.2

= 134,914 m 3

III

hw = H(d a

6

)

H

= 5.39

cm

29. If the actual draft required for a furnace is 6.239 cm of water and the frictional losses in the stack are 15 percent of theoretical draft, calculate the required stack height in meters. Assume that the flue DC gas have an average temperature of 149 and molecular weight of 30. Assume air temperature of 21DC. A 215 C. 220 B. 230 D. 210

=

dgt g

- 0.867) 0.00981

220 m

30. A fuel gas has the following volumetric analysis: CH 4 = 68% C2H s = 32% Assume complete combustion with 15% excess air at 101.325 kPa, 21°C wet bulb and 27°C dry bulb. What is the partial pressure of the water vapor in kPa? A. 9.62 C. 17.28 B. 12.81 D. 15.94 Solution:

Combustion reaction with theoretical air:

0.68 CH 4 + 0.32 C 2H 6 + 2.48 O 2 + 2.48 (3.76) N2 = 1.32 CO 2 + 2.32 H 20 + 2.48 (3.76) N2

Solution:

hw

= total draft

hw

=

6.239 + 0.15 hw

hw

=

7.34 em water

hw

=

0.0734 (9.81)

Combustion reaction with 15% excess air:

=

0.68 CH 4 + 0.32 C 2H 6 + 1.15 (2.48) O 2 + 1.15 (2.48) (3.76) N 2 = 1.32 CO 2 + 2.32 H20 + 1.15 (2.48)(3.76) N2 + 0.15(2.48)0 2 0.72 kPa

Total Mols in products: = 1.32 + 2.32 + 10.723 + 0.372 = 14.735

PB -38

ME Board October 1995

ME Board October 1995

Partial Pressure of Water Vapor

= mCp (T 2 -

We

= (~)101.325

14.735

=

T 1)

=

PB - 39

5.81 (1 0) (579 - 300)

1621 kw

= 15.95 kPa 0K

31. Air enters the compressor of a gas turbine at 100 kPa and 300 with a volume flow rate of 5 m 3/sec. The compressor pressure ratio is 10

and its isentropic efficiency is 85%. At the inlet to the turbine, the

oK. pressure is 950 kPa and the temperature is 1400 The turbine has

an isentropic efficiency of 88% and the exit pressure is 100 kPa. On

the basis of an air standard analysis, what is the thermal efficiency

of the cycle in percent?

C. 31.89 A. 42.06 D. 25.15 8. 60.20

1,1

II~

Solution:

=

WT

=

mCp(T3 - T4 )

=

3858 kw

W T'

=

3858 (0.88)

3395 kw

W N'

=

WT'

3395 - 1907

Q A

Solving for the mass flow rate: PV

=

100(5) = m(0.287)(300)

Yl

=

II~

m

:~

=

5.81 kg/s

Solving for T 2: k-l

II~

T1

(~~)k

'II ,III

Note:

Tz ( 1.4-1 300 = 10)1:4

T2

1907 kw

5.81 (1.0) (1400 - 736)

We'

-

m Cp (T 3

-

T2)

= 5.81

= 1488 kw

(1.0) (1400 - 579)

W' N

1-1;-;;-;

QA

477()

=

31.2%

32. Steam enters a throttling calorimeter at a pressure of 1.03 Mpa. The calorimeter downstream pressure and temperature are respectively, 0.100 Mpa and 125°C. What is the percentage moisture of the supply

steam? Properties of Steam: P, Mpa hf hfg hg 1.03 2010.7 2779.25

lit

T2

=

0.85

= 4770 kw

= mRT

Itt

1621

We'

= 579 0 K

C. 3.15 D. 1.98

'li

Solution:

ii

Solving for T 4 :

I

k-l

T) T4

1:

= 2726.6kJ/kg

At 0.100 Mpa and 125°C, h

A. 2.62 B. 5.21

1111:

1

hf 1

(::Tk

= 2779.25

- 2010.7 =

768.55

For throttling process:

I

~!II ,I

!

1.4-1

1400

T4

( ~)1:4 1000

T 4 = 736°K

1

hi =- h2

(hf + x hfg)1 (fm ~)~

=

!IIII

h2

+ x (20107)

=- 2726.6

PB ·40

,

ME Board October 1995

ME Board October 1995

----------x

=

= 97.38%

0.9738

Percentage moisture

h3 = hg at 1.04 MPa = 2779fi k.Jlkg

= 100 - 97.38 = 2.62%

33. A liquid dominated geothermal plant with a single flash separator receives water at 204°C. The separator pressure is 1.04 Mpa. A direct-contact condenser operates at 0.034 Mpa. The turbine has a polytropic efficiency of 0.75. For a cycle output of 50 MW, what is the mass flow rate of the well-water in kg/s? Steam Properties: At 204°C: hf = 870.51 kJ/kg At 1.04 Mpa: hf = 770.38 hfg = 2009.2

Solving for h.: ,I

.,

A. 2871 B. 2100

=

Solving for the quality X2 (after throttling): h1 = h 2 = (h. + x hfgh 870.51 770.38 + X2 (2009.2) X2 0.049836

C. 186 D. 2444

=

Solution:

Illg

-ms

I

'T' ___ L:_

_

=

Solving for the mass flow rate of the well water: rn, = X2 (m g ) 121.8 = 0.049836 (m g ) m g == 2,444 kg/s

3

1.04 ~ MPa

=

6.5729

Solving for the mass flow rate to the turbine, m s : W T ::: m s (h 3 - h 4 ) n T

50,000 m s(27796 - 2232.3)0.75

m, = 121.8 kg/s

hg = 2779.6 Sg = 6.5729

=

=

S4 = (Sf + X Sf~)4

0.9793 + x4(67463)

X4 0.829

h, (h, + xh fg)4

= 301.4 + 0.829(2328.8)

= 2232.3

S3 =

= =

hfg = 2328.8 sfg 6.7463

hf = 301.40 0.9793 Sf

At 0.034 Mpa:

PB -41

---------

..u.... 50 MW

34. A fuel oil is burned with 50% excess air. What is the volume rate of 3/min flow in m of the wet products at a pressure of 102 kPa and a temperature of 350°C when the fuel is burned at the rate of 45 kg/min? Assume that the combustion requirements of the fuel oil are similar to those of C 12H 26 • A. 1892 C. 2462 B. 3526 D. 4563

mw

Solution: T-S Diagram:

Combustion reaction with 50% excess air:

C 12H26 + 1.50(18.5)0 2 + 1.50 (18.5) (3.76) N2 12C02 + 13H 20

+ 1.50 (18.5) (376) N 2 + 0.50 (18.5) O 2

=

T

~

t

I ,

S

, ~

1

Air

'" 1.50(18.5) + 1.50(18.5)(3.76)

Fuel

1

=

132.09 mols air

mol fuel

PB -42

,

ME Board October 1995

ME Board October 1995

PB

~

4:1

f 132.09(28.97)

=

= 22.51

12(12) + 26(1)

Amount of wet products

kg air

°API

141.5

=

kg fuel

= 22.51 + 1 = 23.51

- 131.5

SG 1S. 6

kg air

28

=

kg fuel

SG 15 6

141.5 SG 15 .6 = 0.887

. 131.5

= 23.51 (45) = 1058 kglmin

= 0.887(1)

Density at 15.6°C

=

0.887 kg/Ii

Solving for the gas constant of the wet products: Solving for density at 28°C: Components CO 2 H2 O N2 O2

M

=

R =

No. of Mols 12 13 104.34 9.25 138.59 3,979.52

=

=

= 1058 (0.2896)(350 1,871 m

0.887[1 - 0.0007(28 - 15.6)]

=

= P5.50 0.887

0.879(1)

=

=

=

0.879

0.879 kg/Ii

P6.20 per kg

Cost Per kw-hr

+ 273)

3/min

35. A diesel electric plant supplies energy for Meralco. During a 24-hr period, the plant consumed 200 gallons of fuel at 2SoC and produced 3930 kw-hr. Industrial fuel used is 28°API and was purchased at P5.50 per liter at 15.6°C. What should the cost of fuel to be produce one kw-hr? A. P1.05 C. P1.069 B. P1.10 D. P1.00

'I

200gal 3.7854li 0.879kg P6.20

--=--x x x-­ 3930kw - hr gal Ii kg

=

P1.05 per kW-hr

36. A pelton wheel is to be designed to run at 300 rpm under an effective head of 150 m. The ratio of the nozzle diameter to the diameter of the pitch circle is 1/12. Assuming efficiency of 84%, what is the size of the wheel in meters. Assume a speed ratio of 0.45. A. 1.05 C. 1.55 B. 2.00 D. 2.86

Solution:

¢

=

Solution: Solving for density at 15.6°C:

=

Density at 28°C

0.2896

PV = mRT

V

SG 28, C

SG 15 6[1 - 00007(t - 15.6)]

Price per kg

Solving for the volume flow of the wet products:

102 V

=

SGt

= 28.71

138.59 8.3143 28.71

No. of kg

12 x44 = 528.00

= 13 x 18 234.00

104.34 x 28 = 2,921.52

296.00

9.25 x 32 = 3,979.52

0.45

rrDN ~2gh

_ rrD(~J -

o

~2(9.8l)(150)

= 1.55m

PB -44

,.

ME Board October 1995

ME Board October 1995 3

37. A certain gas at 101.325 kPa and 16°C whose volume is 2.83 m are 3 compressed into a storage vessel of 0.31 m capacity. Before admission, the storage vessel contained the gas at a pressure and temperature of 137.8 kPa and 24°C; after admission the pressure has increased to 1171.8 kPa. What should be the final temperature of the gas in the vessel in Kelvin? A. 298.0 C. 180.0 B. 319.8 D. 420.0

from the top of the draft tube. Neglect velocities of whirl ilnd leakage losses. What is the total head on the turbine in meters? A. 34.72 C. 55.20 B. 43.27 D. 48.12 Solution: h = total head

Solution:

2

=

P + Z + V A ~ VB w 2g

=

38

Solving for the mass of gas which is to be compressed:

2

PV = mRT + (1 + 3)

+ (5)2 - 0

2(9.81)

101.325 (2.83) = rn, R (16 + 273)

ml

=

0.9922

= 43.27

kg

R

Solving for the mass of gas initially contained in the vessel:

PV

= mRT

137.8 (0.31)

m2 =

=

0.1438

R

m2 R (24 + 273)

.

,

kg

Solving for the final temperature:

+ 0.1:38

)RT

39. The hot combustion gases of a furnace are separated from the ambient air and its surrounding, which are at 25°C, by a brick wall 0.15 m thick. The brick has a thermal conductivity of 1.2 W/m- OK and a surface emissivity of 0.8. Under steady state conditions and outer surface temperature of 100°C is measured. Free convection heat transfer to the air adjoining this surface is characterized by a convection coefficient of 20 W/m 2 _oK. What is the brick inner surface temperature in DC? A. 623.7 C. 461.4 B. 352.5 D. 256.3

= 319.8°K

38. A Francis turbine is installed with a vertical draft tube. The total head to the center of the spiral casing at the inlet is sa m and 3/s. velocity of water at the inlet is 5 m/s. The discharge is 2.1 m The hydraulic efficiency is 0.87 and overall efficiency is 0.84. The velocities at the inlet and exit of the draft tube in 1 m water below the centerline of the spiral casing while the tailrace water level is 3 m

qR

I

r

. qC A m bitent air .

2S'c

1

Q

Hot

Gases T

y

m

K = 1.2 W/m-IlK

= (0.9:22

.

Solution:

PV = mRT

1171.8 (0.31)

,

/!

t~mner

I100°C

I..

outer

I~ -- ·1 Consider per unit area, that is, A = 1 m 2

Q =qc + qR

~

PB - 47

ME Board October 1995

ME Board October 1995

PB ·46

By energy balance. considering 1 kg air:

Heat Transmitted by conduction = Total heat transmitted by convection and radiation in the outside surface

Let rn,

qc = heat transmitted by convection

= hdt 1 - t2 )

2 = 20(100 -25) = 1500 W/m qR

Q

Q Q

= heat transmitted8 by radiation = 20,408.4 x 10-8 E (T 14 - T24)

h 1 + 1,12 (1) V/ + Q A 503.02 + 2

(43/ 2(1000)

= (1

+ rn.) h 2 + 1,12 (1 + rn.) V/

+ rn. (43,000) (0.95)

J/hr-m = 20,408.4 x 10- (0.8)[(100 + 273)4 - (25 + 273)41 = 1,872,793 J/hr-m 2 2

= 1,872,793/3600 = 520 W/m

rn, = 0.0222485 kg fuel/kg air

= total heat transmitted = heat transmitted by conduction 2 = 1500 + 520 = 2020 W/m

A/F

=. k(ta -tb )

2020

=

= 352.5°C

40. Air enters the combustion chamber of a gas turbine unit at 550m ,.•~. kPa, 227°C and 43 m/s. The products of combustion leave the combustor at 517 kPa, 1007°C and 140 m/s. Liquid fuel enters with '. a heating value of 43,000 kJ/kg. The combustor efficiency is 95%.

, I

What is the air-fuel ratio? Properties of Air:

.,

=

0.0222485

= 44.95 kg air/kg fuel

Flight width and depth Quantity of material Coefficient of friction elements Material coefficient of friction

Assume an engineering type chain with sleeve bearing rollers weighing with flights, 89.3 kg/m. Calculate the chain pull in kg. C. 1555.36

A. 2180.33 B. 4550.10

D. 3166.40

Solution:

~-o~

503.02 1372.25

C. 56.93

A. 47.39 B. 32.16

46 m

D. 44.95 W

Solution:

Fuel nQA m, 1\ = 43,000 kJ/kg

o.

1

550 kPa

227°(' (500'K)

610 mm x 200 mm 3/m 0.108 m 0.10 0.59

I,

h (kJ/kg)

500

1280

(1 + rn.) (1372.25)

41. Given a horizontal conveyor, 46 m centers, 175 Ibs per hour capacity handling bitumlr-ous coal at 0.5 m/s with 80 kg per m", Other data as follows:

l.2(t a -100) 0.15

T (K)

=

(140)2 + (1 + m ) f - 2(1000)

x

t,

= kg fuel per kg air

Combustion Chamber

=

weight of material per meter

800kg -3 m

X

0.108 m 3 m

'" 86.4 kg/m

2517kl'a

PI = pull to move the weight of material on loaded run I 01l7"(' ( I ZXU",,) 140111/\

•

PB -48

~

ME Board October 1995

ME Board October 1995

= 86.4(46)(0.59)

= 2344.90 + 410.78 = 3166.46 kg

P2 = pull to move conveyor parts on loaded run

=

PB - 49

= 2344.90 kg

89.3 (46) (0.10)

= 410.78 kg

Power = Force x velocity

P 3 = pull to move conveyor parts on empty run

= 89.3 (46) (0.10) = L110.78 kg

P = total chain pull = 2344.90 + 410.78 = 3166.46 kg

,

+ 410.78

C. 15.53 kw D. 30.15 kw

A. 10.20 kw B. 20.50 kw

=

1583.23 76.042

=

1583.23kg-m/s

20.82 hp

= 15.53 kw

43. A steam plant operates with initial pressure of 1.70 Mpa and 3700C temperature and exhaust to a heating system at 0.17 Mpa. The condensaate from the heating system is returned to the boiler at 65.5°C and the heating system utilizes from its intended purpose 90% of the energy transferred from the steam it receives. The n, is 70%. If the boiler efficiency is 80%, what is the cogeneration efficiency of the system in percent. Neglect pump work.

610 mm x 200 mm 3/m 0.108 m 0.10 0.59

Assume an engineering type chain with sleeve bearing rollers and weighing with flights, 89.3 kg/m. Let Fp = 76.042 kg-m/s-HP.

= 3166.46(0.5) =

= 20.82 (0.746)

42. What is the power in kw required to drive a horizontal conveyor 46 m centers, 175 tons per hour capacity of bituminous coal at 0.5 m/s 3 with 800 kg/m material? Other data are as follows: Flight width and depth Quantity of material Coefficient of friction of elements Material coefficient of friction

+ 410.78

Steam Properties:

f

t

At 1.70 Mpa and 370°C: h = 3187.1 kJ/kg s = 7.1081 kJ/kg.oK At 0.170 Mpa : hf = 483.20 sf = 1.4752 hfg 2216.0 sfg = 5.7062 0C: At 65.5 hf 274.14

A. 78 C. 91.24 B. 102.10 D. 69

= =

Solution:

(This problem is a continuation of Problem No. 41)

Solution:

W

= weight of material per meter

800kg = ----x 3

0.108

m

P 1

3

ill

=

[!]

86.4 kg/m

ill

WI'

= pull to move the weight of material on loaded run 86.4(46)(0.59)

QA

= 2344.90 kg

P 2 = pull to move conveyor parts on loaded run

= 89.3 (46) (0.10) 410.78 kg

~l

=

P3

~

= pull to move conveyor parts on empty run

= 89.3 (46) (0.10) = 410.78 kg

P = total chain pull

h,

:: 3187.1 kJ/kg

J...

~.l

6S.SuC

'-QR

--,

MECHANICAL ENGINEER Licensure Examination Sunday, April 14, 1996

Solving for h 2 :

S1

= S2 = (St

+ xStgh

= 0.9871

"1

8:00 AM- 4 O() I'M

POWER AND INDUSTRIAL PLANT ENGINEERING

7.1081 = 1.4752 + x2(5.7062) X2

I) I\

ME Board Apri/1996

ME Board October 1995

PB - 50

SET A

Select the correct answer for each of the following INSTRUCTION: Mark only one answer for each item by shading the box questions. corresponding to the letter of your choice on the answer sheet provided. STRICTLY NO ERASURES ALLOWED. Use pencil NO.1 only.

h 2 = (h, + xh tg) = 483.20 + 0.9871 (2216.0) = 2670.6

MULTIPLE CHOICE h3 = h, = 274.14 W T = (h 1-h 2 )nt = (3187.1-2670.6)(0.70) =,361.55 kJ/kg QR

= 0.90(h rh 3 ) = 0.90(2670.6 - 274.14) = 2156.81 kJ/Kg

1. There are 20 kg of flue gases formed per kg of fuel oil burned in the combustion of a fuel oil C 12H 26 • What is the excess air in percent? A. 20.17 C. 26.67 B. 16.56 D.8.21 Solution:

Q A

=

hI -h 4

C 12H 26 + 18.5 O 2 + 18.5(3.76)N 2 = 12C0 2 + 13 H 20 + 18.5(3.76)N 2

~

• •

3187.1-274.14

= 3641.2

kJ/kg

0.80

Thea A/F

Cogeneration Efficiency:

=

18.5 + 18.5(3.76)

= 88.06

1

88.06(28.97)

=

= 15

12(12) + 26(1)

= N II

=

"

Solving for the theoretical air-fuel ratio:

n b

~

malsair rnolfuel

kgair kgfuel

WT+QR

QA 361.55 + 2156.81

Actual A/F

= 20 kg flue gases

1 kg fuel

= 19

kgair kgfuel

= 69.16 %

3641.2 % Excess air

Actual A/F - Thea A/F

Thea A/F

-

19-15 15

x 100%

x 100%

= 26.67% 2. A single-acting, four cylinder, 4-stroke cycle diesel engine with a bore to stroke of 21.59 x 27.94 em, operating at 275 rpm, consumes 8.189 kg/hr of fuel whose heating value is 43,961.4 kJ/kg. The indicated mean effective pressure is 475.7 kPa. The load on the

~

ME Board April 1996

PB - 52

brake ann, which is 93.98 cm is 113.4 kg. mean effective pressure in kPa? A. 415.20 C.319.95 B. 124.17 0.645.53

What is the brake arm

V2

:::

3/sec

,

T ::: Torque::: 113.4(0.00981)(0.9394) ::: 1.045 KN-m

Brake Power

j

• •

, •

=

211TN =

BrakePower::: VD

=

275\ 211(1.045) ( ~~ I \. 60 )

30 009376

=

:::

'.

:::

0.493 ::: 49.3%

VI

P1 = ::: T 1 ::: P z ::: Tz :::

150.578V1 298

1

-

T o.1S g

I,

To m

"

,I

where: Ta Ts

•

To

Ag

=

c, In

Ta

Tb

= 648 + 273 = 921°K = 148 + 273 = 421°K = 311°K

I '1

1

25{1.088)(921-421) - 311 (25) (1.088) In 921 421

:::

13,600 - 6,622.1

::: 6,977.9 kw

5. A large furnace can supply energy in the form of heat at 2000 0K at a

~2V2 T2

where:

Qg

319.97 kPa

steady rate of 3143 kw. Assuming an environment temperature of 25°C, what is the available energy for the furnace in kw? A. 3416 C. 1136 8. 2675 O. 1623

It

T1

= 1.493VI - VI

I

= mCp(Ta-T b )

Solution: 0=

l

Solution:

Ag :::

30 kw

3. An air bubble rises from the bottom of a well where the temperature is 25°C, to the surface where the temperature is 27°C. Find the percent increase in the volume of the bubble if the depth of the well is 5 m. Atmospheric pressure is 101,528 Pascals. A. 49.3 C.56.7 B.41.3 0.38.6

PJVJ...

2

gases leave the gas turbine at 64SoC and may be cooled to 14SoC. The water enters the heater at 93°C. The rate of gas flow is 25 kg/s and the water flow is 31.5 kg/so Assume that the mean specific heat of the gas and water are respectively 1.088 and 4.27 kJ/kg_oC. What is the available energy removed from the hot gases in kw? Take available sink temperature as 311°K. A. 8345.6 C. 6041.6 8. 4862.5 O. 6977.9

(%) 02LNC

\ (4) = 0.09376 m 2x60)

\4

~

V - V

:::

VI

:: (~')I (0.2159)2(0.2794)( 275

Pmb

',\

4. Water is being heated by the exhaust gases from a gas turbine. The

piston volume displacement

=:

PH

= 1.493 V 1

% Increase

Solution: Vo

ME Board Apri/1996

5(9.81) + 101.528 150.578 kPa 25 + 273 = 298 "K 101.528 kPa

27 + 273 = 300 "K

101.528V2 300

27°C 101.528 kPa

Solution:

2 Sm

To

= 25

+ 273 ::: 298°K

A ::: Q ­

T o.15

1 =

25°C

=

To( iJ

- 298 (3143J 2000 3143 - 468 ::: 2675 kw

Q

-

= 3143

I

9

ME Board April 1996

ME Board April 1996

6. The rate of flow of water in a pump installation is 60.6 kg/sec. The

7. In a cogeneration plant, steam enters the turbine at 4 MPa and 400°C. One fourth of the steam is extracted from the turbine at 600 kPa pressure for process heating. The remaining steam continues to expand to 10 kPa. The extracted steam is then condensed and mixed with feedwater at constant pressure and the mixture is pumped to the boiler pressure of 4 MPa. The mass flow rate of steam through the boiler is 30 kg/so Disregarding any pressure drops and heat losses in the piping, and assuming the turbine and pump to be isentropic, how much process heat is required in kw?

PB - 54

intake static gage is located 1.22 m below the pump centerline and reads 68.95 kPa gage; the discharge static gage is 0.61 m below the pump centerline and reads 344.75 kPa gage. The gages are located close to the pump as much as possible. The area of the intake and 2 discharge pipes are 0.Q93 m 2 and 0.069 m ,respectively. The pump 3 efficiency is 70%. Take density of water equals 1000 kg/m • What is the hydraulic power in kw? C. 31.9 A. 17.0 D. 15.2 B. 24.5

II

= 3213.6 kJ/kg, s = 6.7690 kJ/kg-OK = 670.56 Sf = 1.9312

=2086.3 Sfg = 4.8288

At 4 MPa and 400°C: At 600 kPa: h f h fg

II

V'

0.61 m

h

A. 15,646.8

344.75 kPag

C. 3,578.5 D. 1,026.9

B. 2,468.2

68.95 kPag

II

',',

Steam Properties:

Solution:

1.22 m

1'1\

Solution:

\I

Q == 60.6/1000

• • " "

Q A

Vs =

5

Q

= 0.0606

_ 0.0606 - 0.093

3/s

m

=

= 0.652 m/s

l­'II ,:(

_ 0.0606. == 0.878 mrs

0.069

A -

Vd =

d

2

Z Vd -Vs - Pd-Ps + ----"----" H - -- + w

II

i~'~'

2

==

Hydraulic Power (Water Power)

= QwH

= 0.0606(9.81 )(28.742)

= 17.1 kw

=

2

344.75 - 68.95 06 1 2 ) (0.878 ) - (0.652) + (- . 1 + . 2 + --'--------'-------'------''--­ 9.81 2(9.81)

28.742 m

h2 = (h. + hrgh

h2 = 67056 + 1.00(2086.3)

2756.9

h 3 = h, = 670.56

Q = m 1(h r h3 )

2g

2

=

S1 = S2 S1 (s, + Srg)z 6.7690 = 1.9312 + x(4.8288)

x = 1.00 (saturated vapor)

30

= -4

(2756.9 - 670.56)

30 kg/s

~

= 15,647.5 kw

8. 45 kw of the shaft power is developed by a turbine working under an available head of 40 meters. The energy transferred from the water to the runner is 350 J. Assuming a mechanical efficiency of 95%, what is the discharge through the turbine in cu. m/s? A. 0.0345 C. 1.511 B. 0.135 D. 1.234

y

PB - 56

ME Board Apri/1996

ME Board Apri/1996

Solution:

177°C respectively. What is the increase of entropy of the system kJ/kg? A. 1.002 C. 0.00173 B. 0.5080 D. 0.1080

Since the given power of 45 kw is a shaft power, a hydraulic efficiency of, say, 87% will be assumed.

=0

Shaft Power

= 0.139 m

Q

II

II

"

II

I

8 h nm nh

,~

= 0(9.81 )(40)(0.95)(0.87)

45

"

9. A vertical draft tube is installed on a Francis turbine and the total head to the center of the spiral casing at the inlet is 38 meters and velocity of water at the inlet is 5 m/s. The discharge is 2.1 cu. m/s. The hydraulic efficiency is 0.87 and overall efficiency is 0.84. The velocities at the inlet and exit of the draft tube are 5 mls and 1.5 mIs, respectively. The top of the draft is 1 m below the center line of the spiral casing while the tailrace(water) level is 3 meters from the top of the draft tube. There is no velocity of whirl at either top or bottom of the draft tube and leakage losses are negligible. What is the power output of the turbine in kw? A. 748.8 C. 901.3 B. 632.9 D. 832.6

h

" II

.'

~

= -

=

8

Volume of each part T1

= 27 + 273 = 300 0 K

T2 = 177 + 273

= 450 K

= mRT:

= 137.8(0.029) = 0.0464 kg 0.287(300)

m2

=

+

.'Il

38 m

Z

y2 + y2

+

~

2g

2.1 m~/s

!

~ s: ...-I co

tu..-

l i

413.4(0.029) 0.287(450)

Heat loss

1 'I

= 0.0928

0.029 m 3

137.8 kPa 27°C 0.029 nr'

413.4 kPa 177°C 0.029 nr'

mt

~

kg

+ (1 + 3) +

Turbine Output

0

(5 h

(5)2 -0.5)2

nt

= m 1Cy , ( tf - t 1 )

0.0928 (0.716) (177-tf )

= 400 0K

= m C, In ­

Tf TJ 400

~S1 = 0.0464 (0.716) In _

2.1 (9.81 )(43.16)(0.84)

= 746.9 kw

10. A vessel of 0.058 m 3 capacity is well insulated and is divided equally by a rigid conducting diaphragm. Initially both halves contain air at pressure of 137.8 kPa and 413.4 kPa and temperature of 27°C and

= 0.0464 (0.716) (tf - 2 7 )

= 127°C

T, = 127 + 273 ~S

=

= Heat gain

m2 CYZ(t2-tf )

\

\

43.16 m

=

0

m1

2(9.81)

=

=

2

tf 38

0.058

=

Solving for the final temperature tf :

total head p

Solution:

From PV

Solution:

I

It

, !

3/sec

PB - 57

300 400 ~S2 = 0.0928 (0.716) In _ 450

= 0.00956 = -0.00783

~S of the system:

= 0.00956 - 0.00783

= 0.00173 kJfC

In

.~

PB - 58

ME Board Apri/1996

ME Board Apri/1996

PB - 59

Solution:

11. A refrigeration system operates on an ideal vapor compression using R-12 with an evaporator temperature of minus 30°C and a condenser exit temperature of 49.3°C and requires a 74.6 kw motor to drive the compressor. What is the capacity of the refrigerator in tons of refrigeration?

,

Enthalpy at condenser entrance = 382 kJ/kg, exit = 248.15 kJ/kg; at evaporator entrance = 248.15, exit = 338.14. A. 43.1 C. 21.3 B. 34.5 D. 18.2

Sm

t

60m

,I

I~

. , l..-lOem

Solution:

QR

f2l

II

Q = 151i/s = 0.015 m 3/s

Vs W

II

= m(h z-h1 )

Ad

W

•

74.6= m(382-338.14) m

QA

It

=

~(0.10)2

1.91 m/s

4

v, = ~=

I

"

74.6 kw

As

0.Ql5

QA

II

"

=

= ~=

=1.7 kg/s

4

',I

H

= (Zd _Zs)

3.516

=

43.5 tons of refrigeration

12. Water in the rural areas is often extracted from underground water source whose free surface is 60 m below ground level. The water is to be raised 5 m above the ground by a pump. The diameter of the pipe is 10 cm at the inlet and 15 cm at the exit. Neglecting any heat interaction with the surroundings and frictional heating effects, what is the necessary power input to the pump for a steady flow of water at the rate of 15 liters/s in kw? (Apr 96) A. 9.54 C. 7.82 B. 534 D. 11.23

2

+

Vd

2

-

Vg

2g

= [5-(-60)]

=

= 0.85 mls

~(O.15)2

I'' "

= m(h 1 - h4 ) = 1.7(338.14 - 248.15) = 153 kw 153

0.Ql5

+

(0.85)2_(1.91)2

2(9.81)

= 64.85 m Water Power = Q w H

= 0,015(9.81 )(64.85)

= 9.54 kw

(Note: 9.54 kw is the water power; the power input to the pump cannot be solved because no efficiency is given.)

'l

ME Board April 1996

PB -60

ME Board Apri/1996

13. A mechanical draft dry cooling tower cools the cooling water from 600C to 25°C at the rate of some 149.4 giga grams per hour. Atmospheric air enters the tower at 20°C and leaves at 35°C. The fan is driven by a 7460 kw motor. What is the mass flow rate of the air into the cooling tower in kg per second? A. 105,628 C. 254,168 B. 541,752 D. 413,919 Solution: 9

mw =

149.4x10 = 41,500kg/s

1000(3600)

23.5(3195.7 - 610.63)

=

2.75(25,102)

=

88 %

15. In a gas turbine unit, air enters the combustion chamber at 550 kPa, 227°C and 43 m/s. The products of combustion leave the combustor at 511 kPa, 1004°C and 140 m/s. Liquid fuel enters with a heating value of 43,000 kJ/kg. For fuel-air ratio of 0.0229, what is the combustor efficiency of. the unit in percent? (Apr 96)

c.n

A. ~ B. 92

Heat loss by water = Heat gain by air

D. 102

Solution:

(mCp~t)water = (mCp~t)air

41,500(4.187)(60-25) =

Fuel

ma(1.006)(35-20)

PB·61

~ " ~ 0.0229

I

1

m, = 403,023 kg/s

Combustion Chamber

2

14. 23.5 kg of steam per second at 5 MPa and 400°C is produced by a steam generator. The feedwater enters the economizer at 145°C and leaves at 205°C. The steam leaves the boiler drum with a quality of 98%. The unit consumes 2.75 kg of coal per second as received having a heating value of 25,102 kJ/kg. What would be the overall efficiency of the unit in percent? (Apr 96) Steam At At At At

Properties:

5 MPa and 400°C: h = 3195.7 kJ/kg

5 MPa: hI 1154.23 hlg 1640.1

205°C: h, 875.04 145°C: hI 610.63

=

23.5 kg/.s

i

!

I

Stearn 5 Mpa, 400°C

Solution: Overall Efficiency =

=

HeatAbsorbed HeatSupplied

ffis(h s - h r) ffirQh

(v/ - v/)

= 785.9 kJ/kg air

C. 88 D. 78

A. 65 B. 95

Heat Absorbed

= Cp(T 2-T1 ) + 'lh.

= 1.0(1004 _ 227) + 'lh. [(140)2 -(43)2]

1000

=

= =

Heat Supplied by fuel

= rn, Q h = 0.0229(43,000) = 984.7 kJ/kg air

Boiler Feedwater

:~I

2.75kg/' o, = 25,102 kJ/kg

JOC

14~('

Combustor Efficiency

= 785.9 = 79.8 % 984.7

I h. Ammonla weighing 22 kgs is confined inside a cylinder equipped with a piston has an initial pressure of 413 kPa at 38°C. If 2900 kJ of heat is added to the ammonia until its final pressure and temperature are 413 kPa and 100°C, respectively, what is the amount of work done by the fluid in kJ? A. 630 C. 420 B. 304 D. 502

~

11.5(0.74) + 34.5Io.06-0.08J \ 8

=

Solution:

= molecular weight of NH 3 =

M

= gas constant =

8.3143

;7

=

= 100

+ 273

,.

= 373°K

mRT

= -P-

V1

=

:~:

413

=

8.101 m

<=u 2900 kJ

413 kPa 38°C

22(0.489)(311)

, !

:::1::: V

10.278 kg air per kg coal

0.489

T 1 = 38 + 273 = 311°K T2

413 kPa

100°C

3

0.825(28) _ 0.77

30

kg N 2 kg prod kg gas

15.03 (given)

kg coal N 2 supplied

=

V2

=

w = P(V 2

-

V1)

= 9.716

= 413(9.716

kg coal

m3

- 8.101)

= 667kJ

17. A test run using this coal showed a dry products of combustion analysis by volume of nitrogen equals 82.5%, molecular weight of 30 kg flue gas per mol dry flue g~s, and the weight of this dry flue gas is 15.03 kg per kg of coal. The actual ash-pit sample was 0.15 kg per kg of coal, of which 20% was carbon. What is the percentage excess air supplied to the fuel combustion in percent? A.46.11 C.51.12 B. 60.86 D. 72.41

15.03 (0.77)

= 11.573

kg coal Air sup plied

22(0.489)(373) 413

+ 4.3(001)

17 =

R

PB - 63

ME Board Apri/1996

ME Board Apri/1996

PB - 62

11.573 = 15.069

0.768

(Note: N 2 is 76.8% by weight in air) Percent excess air = 15.69-10.278 10.278

= 46.61%

18. A type of water turbine where a jet of water is made to fall on the blades or buckets and due to the impulse of water, the turbine starts to move: A. Pelton wheel C. Francis turbine B. Steam turbine D. reaction turbine

19. What condition exists in an adiabatic throttling process?

Solution: Consider an ultimate analysis the same as that given in Bd. Exam April 1995, as follows: C = 74% H 2 = 6%

Theo A/F

= 11.5 C

A. enthalpy is variable B. enthalpy is constant

C. entropy is constant D. specific volume is constant

20. The specific gravity of a substance is the ratio of its density to the O 2 = 8%

S = 1%

N2 = 1.6%

Ash = 9.4%

+ 34.5

(H - ~ J

+ 4.3 S

density of: A. mercury B. ~dS

C. air D. water

21. Which is used as a moderator in certain types of nuclear reactors? A. vapor C. hot water B. heavy water

D. cold water

PB - 64

ME Board April 1996

22. Yeast as raw material for beer making is added to the equipment called: C. cooler A. fermenters B. brew kettle D. starting tubs

~

-_.­

ME Board April 1996

PB - (,',

31. What is the main power generating plant that produces the

most

electricity per unit thermal energy in the fuel input and has the greatest surplus of electricity for most cogeneration systems? A. steam engine C. gas turbine B. steam turbine D. diesel engine

23. What keeps the moisture fro-n passing through the system? A. dehydrator

B. aerator

C. trap D. humidifier

24. What are the main components in a combined cycle power plant? A. diesel engine and air compressor B. gas engines and waste heat boiler C. steam boiler and turbine D. nuclear reactor and steam boiler

25. What do you call the changing of an atom of an element into an atom of a different element with a different atomic mass? A. atomization C. atomic pile D. atomic energy B. atomic transmulation

26. What do you call the weight of the column of air above the earth's surface? A. air pressure B. aerostatic pressure

C. wind pressure D. atmospheric pressure

27. Combined process of cooling and humidifying is also known as: A. heating and humidifying

C. evaporative cooling process

B. cooling tower

D. moisture removal process

28. What is the force required to accelerate a mass of 1 gram at a rate of 1 cm/sec/sec? A. dyne B. poundal

C. slug D. kg force

29. What type of turbine has low head and high discharge? A. Pelton Wheel

B. Francis turbine

C. Jonval turbine D. Kaplan turbine

30. What is a Bull Head Tee? A. a pipe tee with head shaped like a bull B. a welded built-up tee C. a pipe tee with its run larger than its branch D. a pipe tee the branch of which is larger than the run

32. What is the term as the ratio of the volume at the end of heat addition to the volume at the start of heat addition? A. compression ratio C. VOlumetric ratio D. cut-off ratio B. air-fuel ratio

33. What is the ideal cycle for gas turbine work? A. Brayton cycle B. Stag combined cycle

C. Bottom cycle Ericson cycle

D.

34. What do you call the passing of heat energy from molecule to molecule through a substance? A. conduction B. radiation

C. conservation

D. convection

35. What is the lowest temperature to which water could possibly be cooled in a cooling tower? A. the effective temperature

B. the temperature of adiabatic saturation C. the wet bulb depression D. the dew point temperature of the air

36. The indicator used to determine the anti-knock characteristics of gasoline: A. aniline point B. Cetane No.

C. Octane No. D. Diesel index

37. Dew point is defined as: A. the temperature to which the air must be cooled at constant pressure to produce saturation B. the point where the pressure and temperature lines meet C. the temperature which dew is formed in the air D. the pressure which dew is formed in the air

38. What type of lubricating oils are produced entirely form the crudes chosen through elimination of undesirable constituents by suitable refining processes? A. additives C. straight B. inert D. premium

PB - 66

~

ME Board April 1996

ME Board April 1996

39. In a liquid-dominated geothermal plant, what process occurs when

A. B. C. D.

the saturated steam passes through the turbine? A. isobaric C, isometric D. isentropic B. polytropic

40. Gas being heated at constant volume is undergoing the process of: A. isotropic C. isometric B. adaibatic

A. does not indicated contamination

D. isobaric

1

41. A receiver in an air compression system is used to: avoid cooling air before using increase the air discharge pressure collect the water and grease suspended in the air reduce the work needed during compression t~

what measures of portland cement: sand: crushed stones? A. 1 : 2 : 5 C. 2: 3 : 4 B. 2: 4 : 6 D. 1 : 2 : 4

by

the

addition

of

a

C. greatly decreased D. greatly increased

(Faires, Design of Machine Elements, 4t h Ed., p. 319)

50. What is the suggested maximum permissible dose (MPD) of gamma ray exposure for general individuals not working in a nuclear setting, by choice, in rem/year? A. 1 C. 1/2 B. 5 D. 3

meters is converted entirely into kinetic energy is expressed by the equation: A. RL = 2MV 2 C. RL %MV 2 B. RL = RL N-m D. RL % MV

= =

45. What is the total required heating energy in raising the temperature of a given amount of water when the energy applied is 1000 kw-h with heat losses of 25%? A. 1000 C. 1333 B. 1500 D. 1250 Solution: Q - 0.25 Q Q 4(). In

=

= 1000

1333 kw-h

a steam generator with good combustion control, what occurs if

the load is increased?

combined

starting from operating temperature of: A. 150°F C. 3000F B. 200°F D. 2500F

44. The work done by a force of R newtons moving in a distance of L

•t

engine, driven eqUipment and foundation should be kept: A. anywhere B. above the foundation top C. in line with the surface of the foundation D. below the foundation top

49. Most commercially available petroleum lubricating oil deteriorates

43. How does the values for work per unit mass flow of air in the influenced

B. does not indicates qualities C. qualities D. viscosity

48. For design stability, the center of gravity of the total

42. Foundations are preferably built of concrete in the proportion of

compressor and turbine regenerator? A. slightly increased B. unchanged

air temperature leaving air heater decreases air temperature entering heater increases furnace pressure approximately constant economizer gas outlet temperature decreases

47. The color of lubricating oil indicates: i

A. B. C. D.

ps'.-. 67

.,

PB -68

,

ME Board October 1996

ME Board October 1996

MECHANICAL ENGINEER licensure Examination Saturday, October 12, 1996 POWER AND INDUSTRIAL PLANT ENGINEERING

8:00 AM - 4:00 PM

3.

SET A

INSTRUCTION: Select the correct answer for each of the following questions. Mark only one answer for each item by shading the box corresponding to the letter of your choice on the answer sheet provided. STRICTLY NO ERASURES ALLOWED. Use pencil NO.1 only.

There are 20 kg of flue gases formed per kg of fuel oil burned in tho combustion of a fuel oil e 12 H 26 . What is the excess air in percent? C. 20.17 C. 26.67 D. 16.56 0.8.21 Solution: Solving for the theoretical air-fuel ratio:

MULTIPLE CHOICE

C 12H26 + 18.502 + 18.5(3.76)N 2

1. A room being air conditioned is being held at 25°e dry bulb and 50% 3 relative humidity. A flow rate of 5 m /s of supply air at 15°e dry bulb

Theo AJF =

and 80% relative humidity is being delivered to the room to maintain that steady condition, What is the sensible heat absorbed from the room air in kw? (Oct 96) C. 40.5 A. 50.8 D. 70.9 B. 60.8

=

=

12C02 + 13H 20 + 18.5(3.76)N

18.5+18.5(3.76)

=

1

88.06(28,97)

88.06

= 15

12(12) + 26(1)

PV = mRT 100(5) = m(0.287)(15 + 273) m = 6.049 kg/s

% Excess air

molsair molfuel

kgair kgfuel

Actual AJF = 20 kg flue gases - 1 kg fuel

Solution:

2

kgair = 19 _ _ kgfuel

Actual A/F - Thea A/F

;:_

x 100%

Thea A/F

',:.1 ­

"

•t •

=

Q s = sensible heat

= mCp(trt 1 )

= 6.049(1.003)(25-15)

= 60.8 kw

15

x 100%

= 26.67%

2. A 60 MW turbine generator running at 3600 rpm receives steam at 4.0 Mpa and 450 0e with a back pressure of 10 kPa. Engine efficiency is 78% and the combined mechanical and electrical efficiency is 95%. What would be the exhaust enthalpy of the steam in kJ/kg? A. 28,124.20 C. 20,432.10 B. 2400.12 D. 30,101.15

4.

Determine the vacuum efficiency of a surface condenser which operates at a vacuum of 635 mm Hg and exhaust steam enters the condenser at 45.81°e. The barometric pressure is 760 mm Hg. A. 80.4% C.92.7% B. 85.2% D. 98.3% Solution:

Solution: Generator Output = mth, - h2 )

19 -15

1']t 1']g

Since the mass flow rate m and initial enthalpy Q1 are not given, h 2 cannot be solved. However, among the given choices, only B has a reasonable value of enthalpy, the other values are not possible, Therefore, h 2 = 2400.12 kJ/kg

From steam table at 45.81 °C:

P cond =

Psat = 0.010 MPa

(760- 635)0.1013 760

= 0.01666 MPa

PB -70

•

ME Board October 1996

Vacuum Efficiency

= =

P bar - Pcond

P bar

-

=

0.1013-0.01666 0.1013-0.010

=

= = =

92.7%

drier and the air leaving it has a humidity ratio of 0.02343 kg moisture per kg of dry air. The outside air is initially at 15°C dry bulb and has a relative humidity of 50%. The air is heated to a temperature of 69.1°C by steam coils and between the heater and the drier air inlet a drop of 9.1°C occurs in the air temperature. How much steam is required in kg/s if the steam supplied is at 135 kPa and 0.98 quality? C. 1.26 A. 1.55 O. 1.66 B. 1.02

m,

Outside

Air I

• • •

is'c db

o

SO%RH

:"

:>~

Humid Air W. = 0.02343 kg/kg

By heat balance in the heater:

·Ji(i

o I

Drying Chamber Heated Air

69.1°C

60°C

: ::=:::=­

8]

Wet Feed

"11

~

i!.' ~ '~

~

hr

Solving for the mass flow rate of air, ma:

Moisture removed from materials ::: Moisture absorbed by air

::: ma (W 3 -W 2 )

3287 ::: m a(0.02343 - 0.0054)

rna ::: 182,307 kg/hr

::: 50.64 kg/s

.-,------'~I

I hs

[!) rna

=

:~-

A

•

From steam table, at 135 kPa:

hi ::: 453.83 h rg ::: 2235.0 hg ::: 2688.8

where: hs = h, + x h rg

453.83 + 0.98(2235)

= 2644.1 kJ/kg

~l

Solution: Steaam(135 kPa) 0.98 quality

PB - 71

From Psychrometric Chart, at 15°C db and 50% RH:

W 1 = W 2 = 0.0054 kg/kg

h1 28.5 kJ/kg dry air

From steam table, at 69.1 DC: h g = 2625.3 kJ/kg Cp t + W hg

where: h2 1.0(69.1) + 0.0054(2625.3)

83.3 kJ/kg

P sat

5. 3287 kg of moisture per hour is being removed from a material by a

• •

ME Board October 1996

)

heat absorbed by air ::: heat rejected by steam

m a(h 2-hd ::: ms(hs-h r)

50.64(83.3 - 28.5) ::: ms(2644.1 - 453.83)

1.267 kg/s

ms

=

6. What is the external heating surface area in square feet of a tube with the following dimensions: tube inside diameter thickness % in, length 18 ft. A. 26.5 C. 19.25 B. 24.25 O. 28.26

=

Dried Product

=

= 5 in, wall

Solution:

00

=5

+ 2(1/2) ::: 6 in

I W3

SA :::

1

-.J.-W,=W2

7t

0 L

= 7t (1~ J 18

= 28.27

fe

,

( (The values of the air and steam properties should have been given in the problem)

7. Air is flowing in a duct with velocity of 7.62

m/s and static pressure of 2.16 cm water gauge. The duct diameter is 1.22 meters. the barometer pressure 99.4 kPa and the gauge fluid temperature and air temperature are 30°C. What is the total pressure of air against which the fan will operate in cm of water?

.~

ME Board October 1996

ME Board October 1996

PB -72

C. 3.75 D. 1.25

A. 3.25 B. 2.5

13. What is the term used to express the ratio of specific humidities, actual versus saturated? A. relative humidity B. absolute humidity

Solution: hv = velocity head

_ (7.62)2 -

P d, = density of air = RT

h

v­

-

2.959(1.143) 1000

99.4

= 1.143 kg/m

3

0.287(30 + 273)

15. A process of heat transfer due to motion of matter caused by a

= 0.0034 meters of water = 0.34 cm of water

• I

•,

•~ •

= 2.16

= 2.5 cm of water

+ 0.34

8. There are two broad types in the classification of lubricating oils, they are: straight and A. active B. inactive

C. crocked D. additives

9. Amount of air required in the low by-pass factor A. does not change B. greater

C. lesser D. indeterminate

10. What is the function of the compression joint of pipes or tubes? A. it is used to connect two pipes by welding B. it is used to connect two pipes by pressing both ends C. when tightened, compress tapered sleeves so that they form a tight joint on the periphery of the tubings they connect D. it connects two pipes with the use of threaded cuoplings

11. The component of a rotary pump: A. gears B. piston

D. percent saturation

source of neutrons to produce more nuclei of its own kind than are used up? A. developing C. multiplying B. culturing D. breeding

.(

Total Pressure

C. degree of saturation

14. What is the process whereby a fissionable species is utilized as a

= 2.959 meters of air

2(9.81)

PB -73

C. impeller D. screw

12. An instrument commonly used in most Research and Engineering Laboratories because it is small and fast among the other thermometers: A. mercury thermometer C. gas thermometer B. liquid-in-gas thermometer D. thermocouple

,;1

change in density: A. absorption B. radiation

C. conduction D. convection

16. What is the most efficient thermodynamics cycle? A. carnot . B. diesel

C. rankine D. brayton

17. How do you treat a statement that is considered a scientific law? A. B. C. D.

We postulate to be true Accept as a summary of experimental observation We generally observed to be true Believe to be derived from mathematical theorem

18. The transmission of heat from one place to another by fluid circulation between spots of different temperature is called: A. convection C. conservation B. radiation D. conduction

19. What is referred by volume control? A. an isolated system B. closed system

C. fixed region in space D. reversible process only

20. Which of the following types of flow meters is most accurate? A. venturi tube B. pitot tube

C. flow nozzle D. foam type

21. Pneumatic tools are powered by: A. steam B. water

C. natural gas D. air

22. A graphical representation between discharge and time is known as: A. hectograph C. hydrograph

R monograph

D. topograph

ME Board October 1996

PB -74

"

24. What is the function of a radiation pyrometer? A. boiler water weight C. furnace temperature B. boiler pressure D. boiler drum pressure

26. Highest pressure drop in refrigeration cycle: A. compressor C. expansion valve B. condenser D. evaporator

I

I I

I

•

•~

,

27. What is an expansion loop? A. a double long radius elbow to minimize friction losses B. a pipe bent to a loop to change direction C. a pipe expander fitting D. a large radius bend in a pipe line to absorb longitudinal expansion in the pipe line due to heat

PB - 75

32. What is the prime purpose of providing the lubricating 011 pro-hunter in an emergency stand-by diesel genset? A. to keep the lube oil viscosity down under cold condition and enhance the starting of the cold engine B. to avoid moisture condensation in the engine C. to avoid corrosion to engine parts D. to see to it that the lubrication system is functioning properly

23. In a diesel engine, what elements in the fuel that make the work of the lubricant more difficult? C. high cetane number A. water and ash content D. sulphur and asphaltene content B. high octane number

25. The specific measurement of moisture content in air: A. relative humidity C. degree of saturation B. percent saturation D. specific humudity

ME Board October 1996

­

~

33. Which of the following refrigerants is most highly toxic? A. ammonia C. sulfur dioxide D. methyl chloride B. freon 12

.•1

34. Water turbine converts: A. mechanical energy into electrical energy B. hydraulic energy into electrical energy C. mechanical energy into hydraulic energy D. hydraulic energy into mechanical energy 35. How do you differentiate surge from water hammer? A. time for a pressure to traverse the pipe B. the pressure of reservoir at the end of the pipe

Crate 01 deceleration of flow

D. relative compressibility of liquid to expansion

28. What is the color code of steam pipe lines? A. silver gray C. red B. green D. yellow

36. Throttling of the refrigerant through the expansion valve in a vapor refrigeration cycle is: A. reversible adiabatic process C. irreversible adiabatic process B. constant entropy process D. isometric process

29. What is absorbed by sulphites in boiler water treatment? A. oxygen C. impurities settled in mud drums B. carbon dioxide D. carbon dioxide and oxygen

37. Assuming real process, the net entropy change in the universe is: A. must be calculated C. negative B. equal to zero D. positive

30. What is meant by choking in pipe flow?

38. What characterizes a reaction turbine? A. steam losses velocity as it leaves the diaphragm B. steam strikes the blades at right angles C. steam will react with a force in the diaphragm D. steam is deflected

A. B. C. D.

the specified mass flow rate cannot accur shock waves always occur a valve is closed in a line a restriction in flow area occurs

31. What is a check valve? A. a valve designed to allow a fluid to pass through in one direction only B. a valve designed to release the excess pressure C a valve which allows flow of fluid in either direction D. a valve used for checking the pressure of fluid

'19. The work done in an adiabatic process in a system: A. is equal to the change in total energy in a closed system B. is equal to the net heat transfer plus the entropy change C is equal to the change in total energy of closed system plus entropy change o is equal to the change in total energy of closed system plus net heat transfer

PB -76

ME Board October 1996

40. How do you increase the output of a centrifuqalpump? A. B. C. D.

"

speed up rotation install circulation line increase the suction pipe area increase the discharge pipe area

C. hydrogen dioxide D. nitrogen dioxide

43. What takes place in a uniflow scavenging? turbo blower in exhaust header to create vacuum in cylinders air reversing direction in cylinders uses two blowers to purge cylinders air travelling in one direction

44. The diagonal lines in the Psychrometric Chart represent: C. Wet-bulb temperature D. dew-point temperature

45. An ideal gas is compressed isothermally. The enthalpy change is: A. sometimes negative B. zero

C. sometimes positives D. indeterminate

46. A system with paddle wheel work is irreversible, therefore, the change in its entropy: A. is zero B. greater than zero

C. maybe negative D. maybe positive, negative or zero

j

47. What is meant by brake horsepower? A. B. C. D.

power developed in the engine cylinder final horsepower delivered to the equipment actual horsepower delivered to the engine drive shaft work required to raise a weight of 33,000 pounds at a height of one foot in one minute time

"I 4!

48. Enthalpy of an ideal gas is a function only of: A. entropy B. internal energy

C. temperature D. pressure

49. When droplets of water are carried by steam in the boiler:

A. kinetic energy B. enthalpy

42. The main cause of air pollution as a result of burning fuel oil is:

A. Effective temperature B. dry-bulb temperature

PB - 77

C. carryover D. embrittlement

50. Mechanical energy of pressure transformed into energy of haat.

wrong? A. the heat transfer equals the work plus energy change B. the heat transfer cannot exceed the work done

C.' the net heat transfer equals the net work of the cycle

D. the net heat transfer equals the energy change if no work is done

A. B. C. D.

I

ME Board October 1996

A. priming B. foaming

41. Based on the first law of thermodynamics, which of the following is

A. sulfur dioxide B. silicon dioxide

..,

C. heat exchanger D. heat of compression

~

PB -78

ME BOARD April 1997

MECHANICAL ENGINEERING Licensure Examination Saturday, April 12, 1997 POWER AND INDUSTRIAL PLANT ENGINEERING

_ _ _ _ _ _ _ _ _ _... ME BOARD Apri/1997

Solution:

8:00 AM - 4:00 PM

F ::: rna

::: 0.05(0.3)

= 0.015 N

SETA

MULTIPLE CHOiCE:

4. An ideal gas at 45 psig and 80°F is heated in a closed container to 130°F. What is the final pressure? A. 54 psia C. 75 psia B. 65 psia D. 43 psia

1. A Carnot engine receives 130 Btu of heat from a hot reservoir at 700°F and rejects 49 Btu of heat. Calculate the temperature of the cold reservoir. . D C. -20.a DF A. -21.9 F DF D. -22.7°F

B. -24.2

Solution:

Solution:

TH

:::

700 +460 ::: 1160

Efficiency:::

W

QA

130-49

1160- Tc

130

1160

Tc = 437.23

QA-QR QA

TH -TL

TH

~

~

<:1

\t

If<

2. The maximum thermal efficiency possible for a power cycle 0F operating between 1200 and'2250F is: A. 58% C. 57.54% B. 58.n% D. 57.40% Solution:

0R

Tc

= 225 + 460

1200 + 460 ::: 1160

Efficiency

::: 685

0R

45 + 14.7 ::: 59.7 psia

T 1

:::

80 + 460 = 540 0F

T2

:::

130 + 460 = 590 DR

TH 1660- 685 1660

!i.

P2

"=

T]

59.7

-

To =

P2 590

P 2 = 65.23 psia

:t.

~

5. A six cylinder, four stroke diesel engine with 76 mm bore x 89 mm stroke was run in the laboratory at 2000 rpm, when it was found that the engine torque was 153.5 N-m with all cylinders firing 1:':..It 123 N-m when one cylinder was out. The engine consumed 12.2 kg of fuel per oC hour with a heating value of 54,120 kJ/kg and 252.2 kg of air Ai 15.6 per hour. Determine the indicated power. A. 32.1 kw C. 23.3 kw B. 38.4 kw D. 48.3 kw Solution:

_ TH -Tc

:::

:::

540

o tc ::: 437.23 - 460 = -22.77 F

:::

P 1 DR

0R

TH

PB - 7!1

Brake Power = 2nTN ::: 58.73%

3. Determine the force in Newtons required to produce an acceleration 2 of 0.3 m/s on a 0.05 kg mass. A. 0.018 N C. 0.015 N B. 0.025 N D 0.200 N

::: 2n(0.1535)

(60 l

2000)

= 32.15 kw

Friction Power Per Cylinder ::: 32.15

::: 1.031 kw

(i)

1

_ 2n(0.123) (2000 ()()J

ME BOARD April 1997

PB·80

Friction Power (Total)

= 1.031 (6) =

'"

ME BOARD Aprl/ 1997 Air Power = Qdah

6.19 kw

Indicated Power ::: 32.15 + 6.19 = 38.34 kw

8. A pump delivers SOO gpm of water against a total head of 200 ft and operating at 1770 rpm. Changes have increased the total head to 375 ft. At what rpm should the pump be operated to achieve the new head at the same efficiency?

A 2800 rpm C. 3434 rpm

B. 3600 rpm D. 2424 rpm

rate for a steady-state operation? A. 25 gal/min C. 23 gal/min B. 20 gal/min D. 24 gal/min

Solution:

Solution: Q = m w(h 1

•

, 1

-

~=(~r H N

h2 )

= mw(168.07 - 158.03)

45(42.4)

V w

190.04 = 3.0455 = _~

ft

2 /

2

= 190.04Ib/min

200 375

.-

3/min

62.4

= 3.0455(7.481)

= 22.8 gal/min

7. What is Hp supplied to air moving at 20 fpm through a 2 x 3 duct under a pressure of 3 in water gage? A. 0.786 hp C. 0.642 hp B. 0.741 hp D. 0.0566 hp Solution: Q

2dJ 15.6)

\, d a

= 0.0567 hp 550

=

6. In a test laboratory, it was found out that of the 8q Bhp developed by an engine on test, 45 Hp are absorbed by the cooling water that is pumped through the water jacket and the radiator. The water enters the top of the radiator at 200 DF. At that temperature, enthalpy of the water is 168.07 Btu/lbm. Water leaves the bottom of the radiator at 190DF and with an enthalpy of 158.03 Btullbm. What is the water flow

rn,

-

N2

9.

=Cno 1\ 2

r

= 2424 rpm

A Carnot engine requires 35 kJ/sec from the hot source. The engine DC. produces 15 kw of power and the temperature of the sink ;5 26 What is the temperature of the hot source in DC? A 245.57 C. 250.18 B. 210.10 D. 260.68 Solution:

= capacity of fan = AV = (2 x 3)(20/60) = 2 fe/s

Tc :: 26 + 273 = 299 oK Efficiency =

h

W

QA

= head = hwd w da

where:

c,

= density of air in Ib/ft

3

~ =

35

TH h

PH . Hl

= (K2~2.4 da

1~ dJ

ft of air

::

T H -TL

TH

T H -299 . TH 523.25 OK

t H = 523.25 - 273 :: 250.2S

DC

ME BOARD April 1997

PB - 82

'"

Solution:

= heat trasnter area = nDL = n(0.050)(2.5)

Q eon

= 0.3927 m

Solution:

2

Item

= heA(t2 - t.) = 20.1 (0.3927)(1 00 - 20)

Weight

Cement

1 x 94

] 1. A hydro-electric plant having 50 sq. krn reservoir area and 100 m

,

head is used to generate power. The energy utilized by the consumers whose load is connected to the power plant during a five-hour period is 13.5 x 10 to the 6th power kw-hr. The overall generation efficiency is 75%. Find the fall in the height of water in the reservoir after the 5-hour period. A.2.13m C.3.21m B. 1.32 m D. 0.53 m

"I

l'

94 3.1(62.4)

2 x 105

= 210lbs

210 :: 1.246 ft3

2.7(62.4)

Stone

3 x 105

= 315 Ibs

315 :: 1.870 fe 2.7( 62.4)

I

Solution: 3/sec

..

Energy Output = Q(p)H x nT x Time 13.5

X

~

3/sec

3669.725(5

x 3600) = 66,055,050 m

Volume = Area x Height 6 66,055,050 = (50 x 10 ) h

h = 1.321 m

3

50 62.4

-

6691bs

I

Weight Per Ft 3

In 5 hours, the volume of water consumed:

v =

6 --(62.4) = 50lbs 7.481

106 = Q(9.81)(100)(0.75)(5)

Q = 3669.725 m

= 0.486 ft3

Sand

Water

Q = flow in m

Compact Volume

= 941bs

= 631.5W

,

PB ·83

12. A 1 : 2 : 3 mix of concrete with a six gallons of water per bag cement is being prepared. Determine the weight of one cubic foot of finished concrete of this mixture. The materials to be used have the following characteristics: 1 bag cement (1 cu. ft) weighs 941bs

1 cu. ft sand weighs 1051bs

specific gravity of cement 3.1

specific gravity of sand 2.7

specific gravity of broken stone 2.7

A. 164Ib/cu.ft C. 162 Ib/cu. ft B. 172 Ib/cu. ft D. 152 Ib/cu. ft

10. At an average temperature of 100°C, hot air flows through a 2.5 m long tube with an inside diameter of 50 mm. The temperature of the tube is 20°C along its entire length. Convective film coefficient is 20.1 W/m 2 • 0 K. Determine the convective heat transfer from air to the tube. C. 624 W A. 900 W D. 632W B. 909 W

A

ME BOARD April 1997

::

669 4.403

= 0.801

ft3

4.403 fe = 1521b/ftJ

13. Steam is admitted to the cylinder of an engine in such a manner that the average pressure is 120 psi. The diameter of the piston is 10" and the length of the stroke is 12". What is the hp of the engine when it is making 300 rpm? A. 171.5 C. 173.2 B. 175 D. 174.4 Solution: VD = piston displacement

..

ME BOARD April 1997

PB - 84

Solution:

= 327.25 fe/min

Q

Indicated Power = P ml V D (120)(144)(327.25) = 171.4 hp 33,000

Solution:

d, = density of air in Ib/ft

,

I

3

hs = static pressure head

=

hwd w

(;{2~2.4

d a

da

10.4 ft of air da

Q

60,00~(d \~IO'~J 3600 \

a

da

550

i

1 J

I'~

, )

= 0.315hp

S ~

Static Air Power

Brake (Input) Power =

-

Static Fan Efficiency

0.315 0.40

m­

= 0.79 hp

Use 1-hp motor. I ~ The sun generates 1 KW/m 2 when used as a source for solar 2 collectors. A collector with an area of 1 m heat water. The flow rate is 3.0 liters/min. What is the temperature rise in the water? The specific heat of water is 4200 J/kg_oC.

2

=

m)

1 kw

=

1000 w

3 Ii 1 kg min --x--x-nun Ii 60 sec

0.05 kg / sec

= mep~t

1000 =

Static Air Power = Qdahs

_

1 kw = -)(I

m =

14. A fan whose static efficiency is 40% has a capacity of 60,000 fe/hr at 60°F and barometer of 30 in Hg and gives s static pressure of 2 in of water column on full delivery. What size electric motor should be used to drive this fan? e. 2 HP A. 1/2 HP O. 1 1/2 HP B. 1 HP

•

e. 0.50 0e 0.84

o.

B. 0.48°e

= (rc/4) (210)2(12/2)(300) x 2

PB - 85

0e

A. 4.8°C

= (rc/4)02LNXe

=

ME BOARD April 1997

0.05(4200)(~t)

~t = 4.76°C

16. A steam boiler on a test generates 885,000 Ib of steam in a 4-hour period. The avera~e steam pressure is 400 psia, the average steam temperature is 700 F, and the average temperature of the feedwater supplied to the boiler is 280°F. If the boiler efficiency for the period is 82.5 percent, and if the coal has a heating value of 13,850 Btu per Ib as fired, find the average amount of coal burned in short tons per hour. A. 9.84 short tons per hour e. 12.05 short tons per hour B. 10.75 short tons per hour O. 11.45 short tons per hour

Solution: The following enthalpies have been given in the problem. Steam table: At 400 psia and 700°F, h 2 = 1362.7 Btu/lb At 280°F, h 1 = 249.1 Btu/lb

= 221,250 Ib/hr rn, = 885,000 4 Boiler Efficiency =

ms(h 2 -hd mfQh

0.825 =

221,250(1,362.7 - 249.1)

mrC 13,850)

From

1

ME BOARD April 1997

PB·86

rn,

21563 = 21,563 Ib/hr = '- = 2000

~

A. white B. orange

10.78 short tons/hr

PB -87

ME BOARD April 1997 C. dark red D. yellow

26. Mathematically, a thermodynamic property is which following? A. a point function C. a path function B. discontinuous D. exact differential

17. The ratio between the actual power and the apparent power in any circuit is known as the of that circuit. A. Measured Power C. Power Factor B. Capacity D. KVAR

of

the

27. A device whose function is to pass an information in an unchanged

18. The products of complete combustion of gaseous hydrocarbons. A. Carbon dioxide and water B. Carbon monoxide C. Carbon monoxide, water and ammonia D. Water, carbon monoxide and carbon dioxide

form or in some modified form: A. relay B. sensor

28. A device whose primary function is to meter the flow of refrigerant

to the evaporator: A. sniffer valve B. equalizers

19. The

part that directs the flow of the refrigerant through the compressor: C. piston A. wrist pin D. connecting rod B. valve

•

compression stroke: A. air cell B. combustion chamber

~

.

30. Specific heat capacity is an SI derived unit described as as: 3 A. J/kg C. J/m

.}

B. W/moK oF C. -38.40 oF D. -31.40

D. J/kgOK

31. The fundamental difference between pipe and tubing is: A. The dimensional standard to which each is manufactured B. Compression joints C. The smoothness of the surface D. Bell and spigot joint

22. Medium pressure when applied to valves and fittings, implies they are suitable for a working pressure of from: A. 862 to 1200 kPa C. 500 to 1000 kPa D.658t01050kPa B. 758t01000kPa

32. One of the most popular supercharging engine is the: A. Roots type blower B. Pulse turbocharger

23. A general term for a device that receives information in the form of one or more physical quantities, modifies the information and/or its form, if required, and produces a resultant output signal: A. Converter C. Sensor D. Scanner B. Transducer

types

of compressor

utilized

for

C. Constant pressure turbocharger D. Turbo compressor

33. Crankshaft of reciprocating type compressor is basically made of: A. semi-steel C. cast iron B. aluminum alloy D. steel forging

24. In the process of pair formation, a pair cannot be formed unless the quantum has an energy greater than: C. 0.5MeV A. 2m sub 0 C2 D. hv/C Il. 1/2 mV 2

.'~ The temperature of hot metals can be estimated by their color. For 0F steel or iron, the color scale at 2200 is roughly:

C. turbulence chamber D. pre-combustion chamber

t

I

2J. The boiling point of Freon 22 is: A. -41.04°F oF B. 40.60

•

C. Freon refrigerants D. Ammonia

C. thermostatic expansion valve D. crossover valves

29. The volume remaining when the piston reaches the end of the

20. An odorless refrigerant, its bolling point varies over a wide range of

temperatures: A. Freon 22 B. Freon 12

C. transmitter D. transducer

34. A chemical method of feedwater treatment which uses calcium hydroxide and sodium carbonate as reagents: A. thermal theatment C. demineralization process D. ion exchange treatment B. lime soda treatment

J

PB - 88

•

ME BOARD April 1997

ME BOARD October 1997

35. Engines using heavy fuels require heating of the fuel so that the viscosity at the injector is: A. around 200 SSU C. 200 SSU±50 D. 150 SSU or slightly higher B. 100 SSU or less

MECHANICAL ENGINEER Licensure Examination

October 1997

i'

1.

C. thermocouple D. all of the above

38. The type of filter where the filtering element is replaceable: A. paper edge filter C. pressure filter B. metal edge filter D. filter with element

•

39. Which does not belong to the group? A. air injection system B. mechanical injection system

In a water tuba boiler, where is heat and gases of combustion passed? A. B. C. D.

37. An increase in the deposition of slag and ash on the surface for heating of oil-fired boilers in both marine and stationary service has affected boiler efficiency. The following are the causes except: A. Low temperature corrosion of the cold section of air heaters and duct works B. Siagging of high temperature superheater surfaces C High temperature corrosion steel D. Increase of heat transfer in the boiler

, •

8:00 AM - 4:00 PM

POWER AND INDUSTRIAL PLANT ENGINEERING

36. The temperature of the fluid flowing under pressure through a pipe

is usually measured by: A. glass thermometer B. electric-resistance thermometer

PB·89

through the combustion chamber only through the tubes away from the tubes aroundthetubes

2. A pneumatic tool is generally powered by: A. water C. steam B. electricity D. air

"t

3.

The instrument used to measure atmospheric pressure is: A. rotameter C. venturi D. barometer B. manometer

4.

Determine the average Cp value in kJ/kg.oK of a gas if 522 kJ of heat is necessary to raise the temperature from 300 degree K to 800 degree K making the pressure constant: A. 1.440 C. 1.038 B. 1.044 D. 1.026

'f

C. time injection system D. gas admission system

Solution:

•

t

40. Cooling water system consists of equipment to dissipate heat absorbed by the engine jacket water, lub oil and the heat to be removed from air intercooler is measurable to keep the engine outlet water temperature constant and the differential of the cooling water at a minimum preferably not to exceed: A. 10 to 30°F C. 10 to 20°F B. 10 to 50°F D. 10 to 40°F

Q = mCpL'iT

522 = 1(C p)(800 - 300) C p = 1.044 kJ/kg.oK

I I

5.

A refrigeration system in which only part of the refrigerant passes over the heat transfer surface is evaporated and the balance is separated from the vapor and recirculated: A. direct expansion system C. flooded system 13. chilled water system D. multiple system

6.

When four events take place in one revolution of a crankshaft of an engine, the engine is called: A. rotary engine C. two-stroke engine B. steam engine D. four-stroke engine

i i

! "

~

PB - 90

ME BOARD October 1997

,

ME BOARD October 1997

7. The thermal efficiency of a particular engine operating on an ideal cycle is 35%. Calculate the heat supplied per 1200 watt-hr of work developed in kJ. C. 14,218 A. 12,343 D. 11,108 B. 10,216

PB - 91

9. How much work is necessary to compress air in all IIlSlllo1tncl cylinder from 0.20 cu. m to 0.01 cu. m. Use T = 20 degree C and P 1 = 100 kPa. A.113.4kJ C.110.1kJ B. 121.4kJ D.115.6kJ Solution:

Solution:

w = 1200 watt-hr

= 1.2 kw-hr

2

P PI

=

P z

=

= 1.2(3600) = 4320 kw-sec or kJ

(~r V 2

r 4

Efficiency 0.35

=

W

Q A

100 (0 - '20.01

PlV2 -PlVl

W =

= 4320

k -1

Q"

Q A

•

,

= 12,342 kJ

8. A large mining company was provided with a 3 cu. meters of compressed air tank. Air pressure in the tank drops from 700 kPa to 180 kPa while the temperature remains unchanged at 28 degree C. What percentage has the mass of air in the tank been reduced? A. 74 C. 76 B. 72 D. 78 Solution:

(

~

= mRT

= m1(0.287)(28 + 273)

rn. = 24.31 kg

PV

= mRT

= mz(0.287)(28 + 273)

= 625 kg

= 24.31 = 74.29%

=

115.7 kJ/kg

C. 152 D. 145

Solution: r

=

compression ratio

e

=

1 - ~

=

e

QA

r

=

1

= -

l+c c

1+0.07 --0.07

(15.286)14-1

=

=

15.286

0.664

W --

QA

=

300

QA

.= 452 kw

w = OA - OR 300

Percentage mass reduced: 24.31- 6.25

(6628.9)0.01- (I 00)0.2 1.4 -1

A. 170 B. 160

Solving for the mass of air at 180 kPa:

PV

=

It produces 300 kw power. What is the amount of heat rejected in kw?

0.664

180(3) mz

6628.9 kPa

10. An Otto engine has clearance volume of 7%.

Solving for the mass of air at 700 kPa:

700(3)

=

OR

=452 -OR

= 152 kw

11. What occurs in a reversible polytropic process? A. enthalpy remains constant C. some heat transfer occurs B. internal energy does not change

D. Entropy remains constant

...

ME BOARD October 1997

ME BOARD October 1997

PB -92

Solution:

12. In a deepwell installation or operation, the difference between static water level and operating water level is called: A. suction lift C. priming level B. drawdown D. clogging

From R-22 Table: At T cond = 40 °C: h3 = hI = 249.686 kJ/kg At T evap = -10°C: hI = 188.426 kJ/kg hg = 401.555 kJ/kg

13. An ideal single-stage air compressor without clearance takes in air at 100 kPa with a temperature of 16 degree C and delivered it at 413 kPa after isentropic compression. What is the discharge work done by the compressor in kJ/kg? C. -54.75 A. -59.22 D. -56.13 B. -52.43 Solution:

W=

-kmRTl(~: f

I

•

,

=

_

llOO)

1.4-1

ill

For throttling process:

h3 h3 249.686 x

JJ

Solution:

15. Air receives in a compressed air plant must be:

= =

C. overheat blow-off line D. inhibit circulation and heat transfer

19. In a double-acting, 2 stroke compression ignition engine, 8-cylinder, the diameter of the cylinder is 700 mm, stroke is 1350 mm and the piston rod diameter is 250 mm. When running at 108 rpm, the indicated mean effective pressures above and below the pistons are 5.80 bar and 4.90 bar respectively. Calculate the brake power of the engine with a mechanical efficiency of 80% in kilowatts. A. 6050 C. 6010 B. 6030 D. 6070

14. What characteristics an impulse turbine? A. steam striking blades on angle B. no steam reaction to velocity C. steam striking blades at zero angle D. steam reversing direction C. rectangular in shape D. installed with safety valve and drain valve

16. A refrigeration system using R-22 has a capacity of 320 kw of refrigeration. The evaporating temperature is minus 10 degree C and the condensing temperature is 40 degree C. Calculate the fraction of vapor in the mixture before the evaporator. Properties of R-22 are: At -10 degree C h g = 401.60 kJ/kg hI 188.426 kJ/kg At 40 degree C hI 249.686 kJ/kg A. 0.287 C. 0.245 B 0.315 D. 0.227

4

18. Scale in boiler can: A. create low steam quality B. cause foaming

-145 kJ/kg

A. without pressure gauges B. vented to the atmosphere

=h = (h, + xhlg )4

= 188.426 + x(401.555 - 188.426) = 0.287

17. A gas which will not be found in the flue gases produced by the complete combustion of fuel oil is: A. carbon dioxide C. oxygen D. nitrogen B. hydrogen

-I]

_1.4(0.287)(l6+273)1(4131114~1

w

PB - 93

Solving for the Indicated Power at Head End: V 0 1

f

~

= (~J D

2LNC

= (~) (0.70)2(1.35)C;;) (8) = 7.481 m

3/s

Indicated Power (1)

= Pmi X V0 1 = 5.80(100)(7.481) = 4,339 kw

Solving for the Indicated Power at Crank End:

Te l

2

2

V 0 2 = ( 4) [D - d ]LNC

PB -94

ME BOARD October 1997

==

(~) [(0.7)2

== 6.527 m

- (0.25)2](1.35)

C~~ }8)

3/sec

Indicated Power (2) == Pm; X VD2 = 4.9(100)(6.527) == 3,198 m3/sec Total Indicated Power Brake Power

= 4,339 + 3,198 = 7,537 kw

= 7,537 x 0.80

== 6,030 kw

20. The effectiveness of a body as a thermal radiator at a given temperature. C. conductivity A. absorptivity D. reflectivity B. emissivity 21. In a cooling tower, the water is cooled mainly by: A. condensation C. convection B. evaporation D. conduction

22. Where is lithium bromide used in a refrigeration system? A. condensate return lines C. centrifugal compressors B. absorbers D. ion exchangers

, ~

1

II11 1.

ME BOARD October 1997

PB -95

Ii,

28. In a refrigeration system, the heat absorbed in the evaporator per kg

'I'i,

mass of refrigerant passing through is: A. equals the increase in enthalpy B. does not depend on the refrigerant used C. is decreased if pre-cooler is used D. equals the increase in volume

I

:1

li[1!

(f I I'

liii

29. Air that controls the rate of combustion in the combustion chamber is known as: A. secondary air C. control air B. excess air D. primary air

:il

~.I

30. A fan draws 1.42 cu. meters per second of air at a static pressure of 2.54 cm of water through a duct 300 mm diameter and discharges it through a duct of 275 mm diameter. Determine the static fan efficiency if total fan mechanical is 70% and air is measured at 25 degree C and 760 mm Hg. A. 60% C.30% B. 50% 0.40%

IiI:

II:

Solution:

= density of air

d,

P

=

101.325

il

---

RT

(0.2871(25 + 273)

= 1.18 kg/m 3

II I

",1

23. Amount of heat liberated by the complete combustion of a unit weight or volume of fuel is: C. sensible heat A. heating value D. work or compression B. latent heat 24. A temperature above which a given gas cannot be liquified: A. cryogenic temperature C. absolute temperature B. vaporization temperature D. critical temperature

eT == Total efficiency =

Total air power Brake power

es == Static efficiency ==

Static power Brake power

=

PT

= =

I

Pr PB

'I;JI!'

ilil

Ps PB

j!llj'

Ps e s

eT

i

'I

I'

I

25. The ratio of the sum of individual maximum demands of the system to the overall maximum demand of the whole system is: A. diversity factor C. power factor B. utilization factor D. demand factor

PSe T

es ==

PT

==

Qdahse T

oe,u,

=

hSeT

1

h T

1

11)

1

1:1 11

where:

26. When fuel oil has a high viscosity, we mean that the fuel oil will: A. evaporate easily C. bum without smoke B. have a low specific gravity D. flow slowly through pipes

27. Percentage of excess air is the difference between the air actually supplied and the theoretically required divided by: A. actual air supplied C. theoretical less actual supplied B. theoretical air supplied D. deficiency air supplied

hs = static head

hwd w

d.

I

(0.0254)(1000) == 21.52 meters of air 1.18

Solvinq for the velocity head:

V

==

Q A

I

Ii

PB - 96

"

ME BOARD October 1997

VS

Vd

hv hT

es

1.42

= (%1/--, = 20.09 m/s

rs 14·

01,)" " 1.42

v/ -V

2 S

= total

head

= h s + hv = 21.52

21.52(07) 30.06

=

= 0.50

= 295 0K =

.!2.=.!J..

_

8.54 meters of air

+ 8.54

T3

= 10noC + 273

= 9

P4

PI

2(9.81)­

2g

= 22 + 273

Pressure ratio

= (23.9)2 -(20.09)2

PB·97

Solution: T,

= (n/} 5' 4 0.275)2 = 23.9 rn/s =

ME BOARD October 1997

= 13500K

k ->I

= 30.06 meters of air

~=[.!2.Jk r, PI

= 50%

552.665 0K

T 2 = 295(9)'4-XA ==

31. A centrifugal pump delivers 80 liters per second of water on test. Suction gauge reads 10 mm Hg vacuum and 1.2 meters below pump centerline. Power input is 70 kw. Find the total dynamic head in meters. A. 66 C 62 B. 60 D. 64

We

T)T 4

= compressor work =

1.0

kJ kg_ O K

(552.665

0K)

= 257.665 kJ/kg

k-I

=

(~Jk p) 14-1

Solution: Power

T4 = 1350

= Od HT Q A == 1.0

Q

= 80~sec

lm'

x --1000lit

0.08 m 3 ! sec

W T ==

1.0

(~JIA kJ

kg_ O K kJ kg_ O K

Since no pump efficiency is given, use the usual pump efficiency used which is 74%. Pump Efficiency

0.74(70) HT

=

P{JUlput

QdH

P iJ1 [1111

Pill

T

= (9.81 )(0.08)H T

= 66 m

32. A gas turbine working on an air standard Brayton cycle has air enter into the compressor at atmospheric condition and 22 degree C. The

pressure ratio is 9 and the maximum temperature in the cycle is

1077 degree C. Compute for the cycle efficiency per kg of air in percent.

A. 44.85% C. 41.65% B. 43.92% D. 46.67%

, 'l<

;] ~

I

.

Cycle Efficiency

_

==

720.598°K

(1350 - 552.665) oK == 797.335 kJ/kg (1350 - 720.598)OK :::: 629.402 kJ/kg

W T -We

QA

629.402-257.665 797.335

x 100

== 46.6%

33. An aftercooler on a reciprocating air compressor is used primarily to: A. cool the lubricatinq oil

B. condense the moisture in the compressed air C. improve compressor efficiency D. increase compressor capacity 34. In a hydro-electric plant using a Francis turbine with medium head, the speed can be regulated by using the:

A. deflector gate C. wicket gate B. nozzle D. weir

PB - 98

.

ME BOARD October 1997

ME BOARD October 1997

35. Ton of refrigeration is a unit equivalent to: A. 50.4 kcal/sec C. 3413 kw-hr

13

12660 kN-m/hr

1

Pj

0.2545 Btu/hr

-

V

+

21

HT

= 3.516 kJ/sec 3.516 kJ

x

sec

3600 sec

hr

= 12,660 kJ/hr or kN-m/hr

37. A centrifugal pump delivers 300,000 liters per hour of water to a pressurized tank whose pressure is 280 kPa. The source of water is 5 meter below the pump. The diameter of the suction pipe is 300 mm and the discharge pipe is 250 mm. Calculate the KW rating of the driving motor assuming the pump efficiency to be 72%. A. 41.75 kw C. 43.28 kw B. 35.75 kw D. 38.16 kw

Po

Vl_V~

d

2g

280 = --

HT :::

36. To protect adequately the engine bearings, what type and better arrangement of lubricating oil filter is most practical? A. full-flow type filter installed between the lubricating oil pump and the bearings B. duplex filter installed before the lubricating pump C. by pass filter with cleanable and replaceable elements D. splash lubricating system in the crankcase

Po

d

2g

-- +

:::

2

+ - l- + H T

Solution'

=

+

2

I

2

2

2

+

V 2 2

2g

7

+ 5

2(9.81)

Water Power = (0.0833 m

27.473 = -=

Input Power

+

+

(1.697)2 _(1.178)2

9.81 33.62 m

3/sec)(9.81kN/m 3)(33.62

m) ::: 27.473 kw

38.16 kw

0.72

".

,

.'•

38. A pump with a 400 m diameter suction pipe and a 350 mm diameter discharge pipe is to deliver 20,000 liters per minute of 15.6 degree C water. Calculate the pump head in meters if suction gage is 7.5 cm below pump centerline and reads 127 mm Hg vacuum and discharge gage is 45 cm above the pump centerline and reads 75 kPa. A. 15 m C. 20 m B. 5m D.10m Solution:

Solution: Q

l

3

= 300,000 ~ x hr 1000 lit 1 m

X

1 hr

-----

Q ::: 20,000

0.0833

.3600 sec

~

x

rrun

111

PI :::

1 m'

1min

127 mm Hg vacuum x

_

x -- 60 sec

1000 lit

sec

Water Power

Pump Efficiency =

101.325 kPa

760 mmHg

0.33 m 3/sec ::: '16.93 kPa

Brake Input Power

Total Dynamic Head (TDH) ::: P2 -PI d

Water Power = Q x density x H T

Q

V 1

( !! ID ~ !\:I )

V;,

=

0.0833 111' /sec ------

("4 j
n

0.0833 m'/sec

l

\

V 1

1.178 m/sec

:::

"

,

V 2 =

= 1.697 m/sec

Q

0.33

A

~ (0.4)2 4

~ =

~(0.35)2

= 2.626

2 + V2

_

2g

V l 2

+

m/sec

3.429 m/sec

4

' )

I(O.25)-m­ 4 ) IT

­

.Ijl)

From Bernoulli's Equation:

d

1 Ton Ref

PB

TDH

75 - (-16) 9.81 ::: 10.05 m

+

(3.429) 2

_

(2.626) 2

2(9.81)

+ 0.45 + 0.075

2 2 -2 1

PB -100 39. In radiation, the heat transfer depends on: A. temperature C heat flow from cold to hot 13. heat rays D. humidity

"

40. Air at 29 degree C db and 23.5 degree C wb enters a cooling tower at

a rate of 102 kg per minute. It leaves the cooling tower at 38 degree C db and humidity ratio of 0.0436 kg moisture per kg dry air. Hot water enters the tower at 46.5 degree C and a flow rate of 142.2 kg

per minute. Determine the cooling tower efficiency in percent.

Air Properties: At 29 degree C db and 23.5 degree C wb,

h ::: 70.02 kJ/kg dry air w ::: 0.016 kg moisture per kg dry air At 38 degree c db and w ::: 0.0436 kg moisture per kg dry air h ::: 149.24 kJ/kg dry air

.'

ME BOARD October 1997

150 degree C to 80 degree C. Water is available at the rate of 0.30 kg per second and at a temperature of 12 degree C. Calculate the exit temperature of the water in degree C. A. 48 C. 46 B. 42 D. 44 Solution:

Heat balance: Heat loss ::: Heat gain

mwCpw(t b - ta ) ::: mgCpg(t, - t2 )

I'

~

where: Cp ::: specific heat of the gas =

B. 43%

R ::: -R-

8.3143 --::: 0.2969 28 1.32(0.2669) ::: 1.2247

MW

C p =

=

Actual Range

la - I h

"-~----

Theoretical Range

II] - I"h

Heat Balance:

mwCpw(L] - tn) = ma(h z - h.) (142.2)(4187)(46.5 - tb) =; 102 (149.24 - 70.02)

27,685.7 - 595.4 tb = 8080.4

th ::: 32.90C

>

46 ..5- 32.9 X 1OO'}o )/ 46 ..5-23.5

--

(030)(4.18 7J(tb - 12)::: (0.5)(1.2247)(150-80)

tb

:::

46.125 C

43. A heat engine is operated between temperature limits of 1370 degree C and 260 degree C. Engine supplied with 14,142 kJ per KWH. Find the carnot cycle efficiency in percent. A. 70.10 C. 67.56 B. 65.05 D. 69.32

Heat loss = Heat gain

. " T ower Erfictency C 00 IIng

-

1.32-I

Solution: Ccolinq Tower Efficiency

kR k-1

C.60% D.48%

A. 56%

PB -101

Solution:

= 59 .1 3/0

0/

41. The main purpose of a subcooler in a refrigerating system especially

a 2-stage system is to: A. increase the heat rejection per ton and avoid system shutdown B. improve the flow of evaporator gas per ton and increase the temperature C. reduce the total power requirements and return oil to the compressor D. reduce the total power requirements and heat rejection to the 2nd stage 12 A heat exchanger was installed purposely to cool 0.50 kg of gas per second. Molecular weight is 28 and k::: 1.32. The gas is cooled from

T, ::: 1370 + 273 ::: 1643 oK T 2 ::: 260 + 273 ::: 533 0 K Eft ::: 1 - -T 2 T)

::: 1 - _533 ::: 67.56% 1643

44. The performance of a reciprocating compressor can be expressed by: A. adiabatic work divided by adiabatic input B. adiabatic work divided by indicated work C. isothermal work divided by indicated work

D. isothermal work divided by adiabatic work 45. A reciprocating pump is considered positive displacement pump because:

....

PB ·102

ME BOARD October 1997

A. displacement of the liquid is affected by the displacement of

the piston B. positive pressure is given to the liquid C. liquid is discharge with positive pressure D. liquid is lifted due to the vacuum created inside the cylinder 46. Steam expands adiabatically in a turbine from 2000 kPa, 400 degree C to 400 kPa, 250 degree C. What is the effectiveness of the process in percent assuming an atmospheric pressure of 15 degree C. Neglect changes in kinetic and potential energy. Steam PropertiesAre: At 2000 kPa and 400 degree C. 3247.6 kJ/kg h s 7.1271 kJ/kgOK At 400 kPa and 250 degree C

h 2964.2 kJ/kg

s = 7.3789 kJ/kgOK

A. 82 C. 80 13. 84 D. 86

= = =

PB

=

=

Q = i\.h 3247.6 - 2964.2 283.4 kJ/kg

Qu T(lIS) (15 + 273)(7.3789 - 7.1271)

=

Effec tiiveness =

283.4 283.4 + 72.5

= 72.5

= 79 .6%

=

=

=

=

=

Solution: Cogeneration Efficiency

47. Steam enters the superheaters of a boiler at a pressure of 25 bar and dryness of 0.98 and leaves at the same pressure at a temperature of 370 degree C. Calculate the heat energy supplied per kg of steam supplied in the superheaters. Steam Properties are:

At 25 bar and 370°C:

h = 3171.8 kJ/kg

At 25 bar and 0.98 dryness:

hf = 962.11 kJ/kg

hfg 1841.0 kJ/kg

A. 407.46 C. 405.51 B. 408.57 D. 406.54

=

Solution:

=

h hf + x hfg

h 1 = 962.11 + 0.98(1841.0) = 2766.3

q = h2 - h1

= 3171.8

- 2766.3

= 405.5 kJ/kg

111 I

48. Steam enters the turbine of a cogeneration plant at 7.0 MPa and 500 degree C. Steam at a flow rate of 7.6 kg per second is extracted from the turbine at 600 kPa pressure for process heating. The remaining steam continues to expand to 10 kPa. The recovered condensates are pumped back to the boiler. The mass flow rate of steam that enters the turbine is 30 kg per second. Calculate the cogeneration efficiency in percent. Steam Properties are: At 7.0 MPa and 500 degree C: h = 3410.3 kJ/kg s 6.7975 kJ/kgOK At 600 kPa: hf 670.56 kJ/kg hfg = 2086.3 kJ/k~ sf 1.9312 kJ/kg K sfg 4.8288 kJ/kgOK At 10 kPa: hf 191.83 kJ/kg hfg = 2392.8 kJ/k~ sf 0.6493 kJ/kg K sfg = 7.5009 kJ/kgOK A. 60 C. 65 B. 50 D. 55

=

Solution:

=

ME BOARD October 1997

_

-

W T + QR

Q

A

WT = m1(h 1 ­ h2) + (rn, - m2)(h 2 - h3) S1 = S2 6.7975 = sf 2 + X2 sfg 2 6.7976= 1.9312 + x2(4.8288) X2 1.0 (sat. vapor)

=

h2

= hf2 + = S3

X2 hfg 2

= 676.56

+ 1.0(2086.3)

= 2756.86 kJ/kg

S1 6.7975 = sf 3 + X3 sfg 3 6.7976 = 0.6493 + x3(7.50146) X3 = 0.8196 h3 = hf 3 + X3 hfg 3 = 191.83 + 0.8196(2392.8) WT

= 30(3410.3 - 2756.86) = 33,126.976 kw

= 2152.96

+ (30 - 7.6)(2756.86 - 215312)

kJ/kg

I" II

,

PB -104

ME BOARD October 1997

= =

OR m2(h2 - hf4 ) but hf 4 = hf 3 so, OR 7.6(2756.86 - 191.83) OA = m1(h1 - hf 4

)

= 19,494.228

- -ME - Board Apri/199B

MECHANICAL ENGINEERING Licensure Examination Saturday, April 4, 1998 08:00 a.m. _ 04:00 p.m

kw

--------------------------------------------------------------- .. _-----------------------------------­ POWER AND INDUSTRIAL PLANT ENGINEERING

= 30(3410,3 - 191.83) = 96,554.1 kw

Cogeneration Efficiency = 33,126.979 + 19,494.228 96,554.1

SET A

INSTRUCTION: Select the correct answer for each of the following questions. Mark only one answer for each item by shading the box corresponding to the letter of your choice on the answer sheet provided. STRICTLY NO ERASURES ALLOWED. Use pencil No.1 only.

x 100

= 54.5%

MULTIPLE CHOICE

49, A change in the efficiency of combustion in a boiler can usually be determined by comparing the previously recorded readings with the current readings of the: A. stack temperature and CO C. Ringelman chart and CO 2 B. over-the-fire draft and CO D. stack temperature and CO 2

1. A 140 mm x 140 mm single effect, tWin-cylinder, single acting Freon 12 compressor with a refrigeration capacity of 40 kw operates between a discharge pressure of 1300 kPa and a suction pressure of 350 kPa. The speed of the compressor is 600 rpm. If the discharge pressure shall be raised to 1400 kPa, at what speed (rpm) should the compressor be run to produce the same refrigeration capacity and assuming the volumetric efficiency to remain the same?

50. A boiler steam gauge should have a range of at least: A. one-half the working steam pressure B. 1 1/2 times the maximum allowable working pressure C the working steam pressure D. twice the maximum allowable working pressure.

Freon 12 Properties:. At 350 kPa.

h = 189.023 kJ/kg

v = 0.04923 cu. m/kg

\I

At 1300 kPa.

h 211.314 kJ/kg

hf 87.796 kJ/kg

= =

At 1400 kPa.

h = 213.692 kJ/kg

hf 91.355 kJ/kg

~

=

A. 610 B. 615

C. 620 D. 630

Solution:

I

Solving for the volumetric efficiency, discharge pressure

of 1300 kPa and Speed of 600 rpm:

Refrigerating Effect = m(h 1 - h4 )

40 = m(189.023 - 87.796)

m = 0.39515 kg/sec

j

V1 = mV1 = 0.39515(0.04933) = 0.01949 m 3/sec

."

ME Board Apri/1998

ME Board Apri/1998

PB -106

VD

:::

(

P2 ::: 287 kPa abs

%j 02 LN x C

P2::: 287 - 101.2::: 185.8kPag

: : (%) (0.140)2(0.140{ 6~~) x ::: 0.04310 m

-~

nv :::

0=

VD

(No exact answer in the choices)

2

3/sec

3.

0.01949 ::: 0.45217 0.04310

Refrigerating Effect ::: rn'(h­ - h,') 40 ::: m'(189.023 - 91.355) m' ::: 0.40955 kg/sec

V'

~

V' o

.

_I

0.45217 V D'

I'

:::

0.02020 V' o 3/sec 0.04467 m

~

ft

(~\0.140)2 (0.140)l(N'1 x l4) 60)

2

(KENT'S p. 12-74) 6.

A closed vessel contains air at a pressure of 160 kN/m

2

gauge and temperature of 30 degree C. The air is heated at constant volume to 60 degree C with the atmospheric pressure as 759 mm Hg. What is the final gauge pressure? A. 174 B. 169

j

1 ~~

C. 167 O. 172

. I Solution:

(101.325

kPa) : :

Patm ::: 759 mm Hg x l760 mmHg

~ 1'1 (I

0=

P1 T1

oo + 101.2) (10 I 273)

The relationship of water vapor in the air at the dew point temperature to the amount that would be in the air if the air were saturated at the dry bulb temperature is: A. partial pressure actual at dew point B. percentage humidity C. relative humidity D. partial pressure of water

"['.

N' ::: 621 rpm 2.

5.

.·1'f'···•

:::

0.04467:::

Pres. F. V. Ramos approved on February 12, 1998 a Republic Act, which is an act to regulate the practice of Mechanical Engineering in the Philippines, otherwise known as the new M.E. Law. What is this act? A. RA No. 9845 C. RA No. 8594 D. RA No. 8945 B. RA No. 8495

t!

rn'v, ::: 0.40951(0.04933) 3/sec ::: 0.02020 m

nv :::

4.

. ~I

:::

,~

P1

i

101.2 kPa

t ,;

(60+273)

A manometer is an instrument that is used to measure: C. condensate water level A. air pressure B. heat radiation D. air volume (KENT'S p. 18-15)

Solving the new speed N' when the discharge pressure is raised to 1400 kPa:

V1'

PB ·107

The evaporative condenser of an ammonia refrigeration plant has a water flowrate of 126 kgs per second and enters a natural draft DC DC. cooling tower at 40 The water is cooled to 29 by air entering at DC DC DC 38 db and 24 wb. The air leaves the tower as saturated at 40 db. Calculate the make-up water required in kgs. per hour. Water properties: DC, At 40 hf = 167.48 kJ/kg DC, At 29 hg = 121.43 kJ/kg Air Properties: DC DC wb: At 38 db and 24 h = 72.5 kJ/kg w = 0.013 kg water vapor per kg dry air DC At 40 db saturated: h = 166 kJ/kg w = 0.0488 kg water vapor per kg dry air A. 8977 B. 8699

C. 8055 D. 8388

...

PB -108

ME Board Apri/199Q

ME Board Apri/1998

Solution:

12. A pump discharges 150 liters per second of water to a height of 75 meters. If the efficiency is 75% and the speed of the pump is 1800 rpm, what is the torque in N-m to which the drive shaft is SUbjected? A. 771 C. 791 B. 781 D. 681

Heat balance in the cooling tower' Heat absorbed by air = Heat rejected by water mih 2-h 1) = mwCpwL'lT w

m a(166- 72.5) = 126(4.187)(40-29)

m, = 62.1 kg/sec

rn,

= = =

=

Solution:

=

" ~

=

= 110.4 kw

PumpWork

I lOA

Eff

0.75

= 2rrTN 1800) 147,200 Watts = 2rrT 60 (

T = 781 N-m

Brake Power

D. violet

= 147.2 kw

13. What should be the temperature of both the water and steam Whenever they are present together? A. saturation temperature for the eXisting pressure B. boiling point of water at 101.325 kPa C. superheated temperature D. one hundred degree centigrade

8. The CO 2 (carbon dioxide) percentage in the flue gas of an efficiently fired boiler should be approximately: A. 1% C. 18% B. 12% D. 20% (Morse p. 137) 9. An unloader is used on air compressor to: A. to relief air pressure C. stop easier B. start easier D. run faster

(Van Wylen p.34) 14. An air standard engine has a compression ratio of 20 and a cut-off ratio of 5. If the intake air pressure and temperature are 100 kPa and 27°C, find the work in kJ per kg. A. 2976 C. 2437 B. 2166 D. 2751

10. How many pounds of air are theoretically needed to burn one pound of diesel fuel oil? C. 18 A. 28 B. 14 D. 22 (Morse p. 159). 11. Which of the following is a great advantage of a fire-tube boiler? A. steam pressure is not steady B. contains a large volume of water and requires long interval of time to raise steam and not so flexible as to changes in steam demand. C. can not use impure water D. radiation losses are higher because fire is on the inside of the boiler and is surrounded by water

(0.150)(9.81)(75)

Brake Power (Pump)

7. What is the color code of air pipelines? A. light blue C. brown

"

= Qwh

Pump Work

mass flow rate of make-up water miW 2 - W,) 62.1 (.0488 - 0.013) 2.22318 kg/sec 8003.45 kglhr make-up water

B. red

PB - 109

Solution:

eT =

1 _ _I_[_r..::...k_-_I_J c

rk k-l \

d

k(rc - I)

_I_((5)14_ 1) = 0.541 (20(H 1.4(5 - I) )

eT = T2

= T1[~~r-J =

T3

=

(Morse p. 297/KENT'S p. 7-07). T2

300(20)14-1

=

54.1%

= 994.34 oK

(~: J = 994.34 (5) = 4971.7 oK

,.

ME Board Apri/1998

ME Board Apri/1998

PB·110 Q

A

e

= =

W

=

mC p(T3-T z)

=

(1.006)(4971.7-994.34)

=

I'll

111

19. A pump receives 8 kg/s of water at 220 kPa and 110 degree C and discharges it at 1100 kPa. Compute for the power required in kilowatts. A. 8.126 C. 7.041 B. 5.082 D. 6.104

4001.3kJ/kg

w Q"

(0.541)(4001.3) = 2165kJ/kg

Solution: 15. What is the temperature in degree C of 2 liters of water at 30 degree

II

C after 500 calories of heat have been added to? A. 35.70 C. 38.00 B. 30.25 D. 39.75

= mV1(P2 - Pd

Pump Work

=

=

Q mCp(Tz - Td 0.500 kcal ( 4187 kJfkcal) T2 = 30.25 DC

2 lit (1 kgflit)(4.187 kJfkg_oC)(T 2

-

.

30°C)

~

.~

20. In an open feedwater heater for a steam power plant, saturated

steam at 7 bar is mixed with subcooled liquid at 7 bar and 25 degree C. Just enough steam is supplied to ensure that the mixed steam leaving the heater will be saturated liquid at 7 bar when heater efficiency is 90%. Calculate the mass flow rate of subcooled liquid if steam flowrate is 0.865 kg per second. Steam Properties are:

At 7 bar, saturated vapor:

hg 2763.5 kJ/kg

At 7 bar and 25 degree C:

hf = 105.5 kJ/kg

At 7 bar, saturated liquid:

hf = 697.22 kJ/kg

"

=

II

C. velocity gradient D. draft

A. 2.725 B. 3.356

(Morse p. 484).

~

sec

3

m ](1100-nO)kN -m 1000kg ill Z

= 7.04 kw

Solution

II

8~(

18. A fuel pump is delivering 10 gallons per minute of oil with a specific gravity of 0.83. The total head is 9.14 meters, find how much energy does the pump consumes in kJ per hour. A. 169 C. 189 B. 199 D. 179

C. 2.286 D. 3.948

Solution: Efficiency = 0.90

Solution:

mL

=

=

ffi L

Heat Absorbed

m L (h 3 - h Z )

Heat Supplied

mS(h 1 -h 3 )

(697.22 -105.5)

0.865(2763.5 - 697.22)

2.725 kg/sec

Pump Work = Qwh 3

min lit x -m- -) 10 Gal x 60-x 37854hr Gal 1000ht [ mm

(0.83 x 9.81

= 169 kJ/hr

:~}9.14 m)

x

21. A volume of 450 cc of air is measured at a pressure of 740 mm Hg DC. absolute and a temperature of 20 What is the volume in cc at 760 mm Hg absolute and DoC? A. 516.12 C. 620.76 B. 408.25 D. 375.85

ME Board Apri/1998

PB -112

..

Assume 80% efficiency of the motors, 95% for line transmission efficiency and 92% for generator. Find the rated capacity of the generator in kw assuming that all motors deliver their rated power simultaneously. A. 204 C. 196 B. 192 D. 200

Solution:

PIv! T1

-

P2V2

==­ T2

(740)(450) 20+ 273 V2

It

II

1 II II

=

760V2

0+273

Solution:

408.25 cc Rated Capacity of Generator

22. What kind of a heat exchanger where water is heated to a point that dissolved gases are liberated? C. intercooler A. evaporator D. deaerator B. condenser (Potter p. 377) 23. What is the function of steam separators? A. trapping the steam and letting water through B. throttling C. changing direction of the steam flow D. steam metering

~

t

1

(Morse p. 612).

24. Which of the following is not a main part of a typical coal burner? A. air registers C. an atomizer B. a nozzle D. an ignitor

25. Which of the following types of air dryers works by absorbing moisture on a solid dessicant or drying material such as activated alumina, silicon gel, or molecular sieve?

A. Regenerative dryer C. Spray dryer

D. Refrigerated dryer B. Deliquescent dryer

26. A heat-transfer device that reduces a thermodynamic fluid from its vapor phase to its liquid phase such as in vapor-compression refrigeration plant or in a condensing steam power plant. A. flash vessel C. condenser B. cooling tower D. steam separator (Mark's p. 9 - 75).

27. A metal fabrication company has two 50 hp motors for stamping and shearing operations and five 20 hp motors for other operations.

[2(50)+5(20)] x 0.746 0.80xO.95

=

196 kw

29. The law that states entropy of all perfect crystalline solids is zero at absolute at absolute zero temperature. A. Newton Law B. Third Law of Thermodynamics C. First Law of Thermodynamics D. Second Law of Thermodynamics (Van Wylem pA88).

30. What is the percent theoretical air for a combustion process to which the fuel and combustion gas analysis are known as follows: Fuel: % by volume

COz CO

t,

t,

c

= 12.4% = 27%

Combustion gas: % by

COz = 24.6% Oz = 1.0%

j\

(Ref & Aircon by Jordan & Priester p. 319).

=

28. A goose neck is installed in the line connecting a steam gauge to a boiler to: A. maintain constant steam flow B. protect the gauge element C. prevent steam knocking D. maintain steam pressure

(Mark's p. 19-34).

~

PB -113

ME Board Apri/1998

A. 111 B. 121

= 2.2% = 58.4% volume

Nz = 74.4%

Hz

N2

C. 116 D. 126

Solution: Combustion Reaction with Theoretical Air

Air

0.124C02 + O.27CO + 0.022H 2 + 0.584N 2 + 0.1460 2 + 0.146(3.76)N 2 c:: 0.394C0 2 + 0.22H 20 + 0.584N 2 + O.146(3.76)N 2

PB -114

"

ME Board Apri/1998

Combustion Reaction with Excess Air

Air

ME Board Apri/1998

PB -

11~)

32. In the processing section, there is an instrument frequently used to measure the flow rate of fluids. What is the instrument consisting of a vertical passage with variable cross-sectional area, a float and a calibrated scale? A. rotameter C. rota-aire B. pitot-tube D. manometer

0.124C0 2 + 0.27CO + 0.022H 2 + 0.584N 2 + (1 + x)0.1460 2 + (1 + x)(0.146)(3.76)N 2

<= 0.394C0 2 + 0.22H 20 + 0.584N 2 + 0.146(3.76)(1 + x)N 2 + x(0.146)02

(PSME Code p. 228). Expressing the percentage of oxygen in the products excluding the water:

=

0.01 "

x

=

0.11

II

Percent Theoretical Air

1 I' Ii

33. How much heat, kJ must be transferred to 20 kgs of air to increase the temperature from 20 degree C to 280 degree C if the pressure is maintained constant: A. 2500 C. 5200 B. 2050 D. 5500

0.146x 0.394 + 0.584 + 0.146(3.76)(l+x) + 0.146x

=

1 + 0.11

= 1.11

-

= 111 %

31. A steam boiler plant consumes 9,000 kgs. of coal per hour and produces 20 kgs. of dry flue gases per kg. of coal fired. Outside air temperature is 32 degree C. , average temperature of flue gas entering the chimney is 343 degree C, and average temperature of the dry flue gas in the chimney is 260 degree C. The gage fluid density is 994.78 kg per cu. meter and the theoretical draft of 2.286 cm of H 2 0 at the chimney base is needed when the barometric pressure is 760 mm Hg. Determine the height of the chimney in meters. C.40 A. 46 D. 56 B. 50

Q

\ 'f

,·t

hw

=

rn kg 2.286 em x - - x 994.78100em rn 3 p

d, = - - == RaTa

. dg

hw

=

101.325

- - == (0.287)(260 + 273) RgTg

= 1.157 = 0.662

kg/m

kg/m

2 Solution: P 1V1 = P2V2

2(V 1 ) = 42(6)

V 1 = 126m 3

3

kg/m

=

34. How do you describe a non-flow process where in the volume remains constant? A. isometric C. isobaric B. isentropic D. isenthalpic

=

3

36. A 2 -stage air compressor operates between constant pressure limits of 98.6 kPa and 1.103 MPa. The swept volume of the low pressure piston is 0.142 cu. meter. Due to failure of the cooling water supply to the intercooler, air is passed to the high pressure cylinder without reduction in temperature. Using PV 1 .2 C, determine the percentage increase in power. A. 26 C. 11 B. 21 D. 16

= H(da - dg)

22.74 H

P

101.325 (0.287)(32 + 273)

= 22.74

= mCp(T 2 - T 1 ) = 20(1.0)(280 - 20) = 5200 kJ

35. Assuming compression is according to the law pV constant. Calculate the initial volume of gas at a pressure of 2 bar which will occupy a volume of 6 cubic meters when it is compressed to a pressure of 42 bar. A. 126 cu. meters C. 130 cu. meters B. 120 cu. meters D. 136 cu. meters

Solution:

~

Solution:

=

H(1.157 - 0.662)

= 46 m

J

PB -116

ME Board April 1998

Solution: Px

=

.JP:P:

Po

=

Compressor Power by Double Staging

=

•

= 329.8 kPa

.j98.6(1103)

t

" ,np'V'l(:; f' -11 =

2(1.2)(98.6)(0.142) 1.2 -1

Ps

Il329.8)\2~1

l

_

98.6

JJ

37.45 kJ

=

Compressor Power by Single Staging

=

1.2(98.6)(0142)1(1103)112~1

=

l

98.6

_

JJ

41.63 kJ

Increase = 41.63-37.45 37.45

01 . 10

= 111601 . 10

i ~'

"

p w

=

8 +

= =

137 = 21.96 m 9.81 QwH (0.283)(9.81 )(21.96) 61 kw

42. A hydro-electric plant discharges water at the rate of 0.75 cubic meter per second and enters the turbine at 0.35 mps with a pressure of 275 kPa. Runner inside diameter is 550 mm, speed is 520 rpm and the turbine efficiency is 88%. Find the turbine speed factor. A. 0.638 C. 0.368 B. 0.386 D. 0.836

I

"

I

I

Power = QwH 50,000 Q(9.81)(100)

3/sec 50.968 m Q 50.968(1000) 50,968 kg/sec Q

=

Solution: y2

p h = - + ­ w 2g

=

=

38. A branched system of pipes to carry waste emissions away from the piston chambers of an internal combustion engine is called: A. exhaust nozzle C. exhaust pipes B. exhaust deflection pipe D. exhaust manifold

= z +

41. A major cause of air pollution resulting from the burning of fuel oils is: A. nitrous C. sulfur dioxide B. hydrogen D. silicon

',.

~

=

H = total head

40. Measure of ability of a boiler to transfer the heat given by the furnace to the water and steam is: A. grate efficiency C. furnace efficiency B. stoker efficiency D. boiler efficiency

~;:'

I

=

Solution:

Power

37. A hydraulic turbine receives water from a reservoir at an elevation of 100 meters above it. What is the minimum water flow in kgs per second to produce a steady turbine output of 50 MW? A. 50,247 C. 50,672 B. 50,968 D. 50,465 Solution:

PB -11.7

39. A pump lifts water at a rate of 283 Ips from a lake and force it into a tank 8 meters above the level of the water at a pressure of 137 kPa. What is the power required in kilowatts? A. 71 C. 61 B. 41 D. 51

=

=

1.2-1

t •

ME Board April 1998



= _

t \

_

275

-

9.81

nDN

+

(0.35) 2

2(9.81)

speed factor

.J2gh n(0.550{ 520

60

J



.J2(9.81)(28.039)

J

= 28.039 m

=

0.628

PB -118

ME Board April 1998

"

43. An engine indicator is generally used to measure: A. steam temperature C. steam cylinder pressure B. heat losses D. errors in gauge reading

(Morse p. 365).

By Heat Balance in the Condenser: Heat rejected by steam = Heat absorbed by water ms(h 1 - h 2 ) = mwCpllT w 10(2570 -160) = mw(4.187)(24 -13) mw = 523.2 kg/sec 50. Peak load for a period of time divided by installed capacity is: A. capacity factor C. utilization factor B. demand factor D. load factor

45. A liquid whose temperature is lower than the saturation temperature

corresponding to the existing pressure. A. subcooled liquid C. pure liquid B. saturated liquid D. compressed liquid

starting load. D. prevent excess pressure in the receiver.

I ./

,.{

.,

47. Fluids that are pumped in processing work are frequently more viscous than water. Which of the following statements is correct? A. Reynolds number varies directly as the viscosity B. Efficiency of a pump increases as the viscosity increases C. Increased fluid friction between the pump parts and the passing fluid increases useful work D. Working head increases as the viscosity increases. 48. The size of a steam reciprocating pump is generally designated by a three-digit number size as 646. What would the be the first number deslqnate? A. stroke of the pump in inches B. inside diameter of the steam cylinder measured in inches C. percent clearance D. number of cylinders 49. A steam condenser receives 10 kgs per second of steam with an enthalpy of 2570 kJ/kg. Steam condenses into a liquid and leaves with an 'enthalpy of 160 kJ/kg. Cooling water passes through the condenser with temperature increases from 13 degree C to 24 degree C. Calculate the cooling water flowrate in kgs per second. A. 533 C. 523 13. 518 D. 528

PB ·119

Solution:

44. The power required to deliver a given quantity of fluid against a given head with no losses in the pump is called: A. wheel power C. hydraulic power B. brake power D. indicated power

46. The function of an un loader on an electric motor-driven compressor is to: A. reduce the speed of the motor when the maximum pressure is reached. B. drain the condensate from the cylinder C. release the pressure in the cylinders in order to reduce the

ME Board April 1998

.v

.~

PB -120

ME BOARD APRIL 1999

ME BOARD APRIL 1999

MECHANICAL ENGINEERING Licensure Examination April 1999 08:00 a.m. - 04:00 p.m

A. 201.02 kN/m z B. 462.78 kN/m 2

POWER AND INDUSTRIAL PLANT ENGINEERING

Solution:

SET A

Pj w

L\P

constant specific humidity. A. critical point B. dew point temp (ans)

Solution:

= m[Cp1(t1 -

tf ) + h L + Cpz(tf

-

y2

+

tz)]

,, ,

=

_I

2g

(0-1.5)

2

Z 2 + -P2 + _2 y w 2g

(Z2 - ZI ) + Yi - -- y2 I 2g

w

= 10.6 L\P

+

15.912 - 3.97 2 2(9.81)

m

5000 J[0.7(4.187)(6--2.2) + 55.5(4.187) + 0.3(4.187)(-2.2-14] _24(3600)

= 10.6(9.81) = 103.986kN/m2

6. At what temperature wherein an oil at any grade becomes cloudy and it

freezes, thus its application is limited.

C. pour point (ans) A. cold point B. flash point D. freeze point 7. For positive slip, the coefficient of discharge of a positive displacement

reciprocating compressor is:

A. Cd = 1 C. Cd < 1 (ans) B. Cd > 1 D. Cd = 0

=

average temperature: A. increases B. decreases

C. constant (ans) D. zero

15.7 kw

. Cooling Load

=

15.7 kw x

tonof ref

9. When the boiler pressure increases or when the exhaust pressure decreases, the amount of moisture: A. Increases (ans) C. constant D. zero B. decreases

= 4.46 tons of ref

3.516 kw

4. The sensible heat ratio is 0.8. That is: A. 80 latent heat and 20 sensible heat B. 80 sensible heat and 20 sensible and latent C. 80 sensible heat and 20 latent heat (ans) D. 20 latent heat and 80 sensible and latent

10. The purpose of the nozzle in a combustor of a gas turbine plant is to: A. increase the velocity(ans) C. decrease the velocity B. increase the power D. decrease the power 3/s

5. A cylindrical pipe with water flowing downward at 0.02 m having a top diameter of 0.08 m, a bottom diameter of 0.04 m and a height of 1.5 m. Find the pressure between the two ends of the pipe.

[1 .:,

8. When the number of reheat stages in a reheat cycle is increased, the

= [

I

Ii

PI -P2

=

C. dry bulb D. wet bulb

3. Fish weighing 5000 kg with a temperature of 6 deg C is brought to a cold storage and which shall be cooled to -14 deg C in 24 hours. Find the cooling load required if the specific of fish if 0.7 kcal per kg per deg C above freezing and 0.3 kcal per kg per deg C below freezing which is -2.2 deg C. The latent heat of freezing is 55.5 kcal per kg. A. 4.46 tons of refrigeration (ans) C. 15.7 tons of refrigeration D. 19.8 tons of refrigeration B. 6.44 tons of refrigeration

Cooling Load

=

w

2. The temperature measurement in an ordinary thermometer which has

I I

ZI + -

1. For negative slip, the coefficient of discharged for a positive displacement reciprocating compressor is : C. Cd < 1 A. Cd = 1 B. Cd> 1 (ans) D. Cd = 0

I

C. 304.56 kN/m z D. 104.04 kN/m 2 (ans)

Bernoulli's Principle:

MULTIPLE CHOICE:

•

PB . 1 L 1

,

11. During sensible heating, the absolute humidity remains constant but the relative humidity: A. increases C. remains constant B. decreases (ans) D. zero

...

ME BOARD APRIL 1999

ME BOARD APRIL 1999

PB -122

PB -123

16. The amount of sensible heat for a sensible heat ratio of 0.8 and a total cooling load of 100: C. 100 A. 80 (ans) B. 20 D. 60

12. Compute the amount of condensate formed during 10 minutes warm-up of 150 m pipe conveys the saturated steam with enthalpy of vaporization hfg = 1947.8kJ/kg. The minimum external temperature of pipe is 2 DC, the final temperature of the pipe is 95 DC. The specific heat of the pipe material is 0.6 kJ/kg-DC. The specific weight is 28 kg/meter. A. 0.20 kg/s (ans) C. 2 kg/s B. 0.4 kg/s D. 12 kg/s

Solution: Sensible heat ratio, SHR = Qs QT

Solution:

0.8 = Qs 100 Qs = 80

Heat balance: Heat gain by pipe

=

Heat loss by steam

rL~8kg x x min 1 m ] Omin 150m

[0.6

60secJ

I •

ms

=

kJ

) (95 - 2)OC

ms

kg _0 C

17. The hydraulic efficiency of hydro-electric turbine is 85%, find the discharge Q in liters per second. Power developed is 10,500 kwand operating under a head of 320 m. C. 9533 LIs A. 3935 Us (ans) B. 3395 LIs D. 5933 LIs

(1947.S~~j

0.2 kg/s

Solution:

13. Water flowing at a velocity of 18 m/s. Determine the velocity head in meters. A. 16.5 m (ans) B. 18.5 m

Brake Power, = Q w H x eff

C. 20.1 m D. 25.2 m

10,500 = Q (9.81) (320) x 0.85

Solution:

Q

velocity head, h = h

y2

(IS?

2g

2(9.81)

3

Q = 3.935 m

= 16.5 m

Q

14. A turbine pipe determined its nominal size refers to: A. outside diameter C. thickness D. approximate size B. inside diameter (ans) 15. In a gas turbine plant, the mass flow rate is 6.2 kg/s, the enthalpy at the combustor entrance is 250 kJ/kg and the enthalpy at the exit is 980 kJ/kg. What is the capacity of the combustor in kw? A. 4526 (ans) C. 5426 B. 4625 D. 6425

Heat added in the combustor, QA = m (h 2 ­ h.) Q A = 6.2 (980 - 250) QA 4526 kw

s = 3935 LIs

x

1000 lit

m 3

18. The relative humidity becomes 100% and where the water vapor starts to condensate. A. critical temperature C. dew point (ans) B. saturated point D. steam point

t .\ ,/

i

i .i I

Solution:

m3 = 3.935­ s

I

=

19. A Reversed Carnot refrigeration used to produce ice at OOC, water is available at 301 DK, brine mixture is -16°C, find the coefficient of performance. C.8.54 A. 5.84 (ans) D. 5.48 B. 4.85 Solution:

COP =

J

TL TH -TL

~

ME BOARD APRIL 1999

ME BOARD APRIL 1999

PB -124

Solution:

(-16+ 273) COP = 301- (-16+ 273)

COP = 5.84

nv = 1 + c - c ( pP~

_

We

1

1

QA

COP

4.2786

23. Water at 55°C is cooled in a cooling tower which has an efficiency of 65%. The ambient air is at 32°C dry bulb and 27°C wet bulb. The heat rejected in the condenser is n640 kJ/sec. Find the capacity in liters per second of the pump used in the cooling tower if the specific volume of water is 1.0067/iters per kg. . A. 6.5 C. 8.5 (ans) B. 7.5 D. 9.5

= 0.2337 kw power kw ref 21. A refrigeration system operates in a reversed Carnot cycle with refrigerant higher temperature of 50°C, COP of 5 and capacity of 50 tons. Determine the change of entropy in kJ/min-°K. C. 23.9 A. 39.2 (ans) B. 32.9 D. 29.3

Solution: Note: The capacity of the pump is the volume flow of water in the condenser and in the cooling tower. t - _ tb

Cooling tower Eff = _a_ t a - twb

Solution: 0,65

= 50 tons = 175.8 kw

Ref Capacity. OA

We

=

=

55 - tb 55-27

tb = 36.8°C

COP = QA

5

= 0.8782

nv = 87.82%

Solution:

-

JX

nv = 1 + 0.05 - 0.05 (5)1/1.304

20. Determine the power per kw of refrigeration if the COP is 4.2786. C. 0.7332 A..·{).3372 D. 0.3732 B. "0.2337 (ans)

Power per kw of ref

PB - 125

175.8 We

We = 35.16 kw

OR = We + OA = 35.16 + 175.8 = 210.96 kw OR

=

i1S T 2

i1S

=

QR T2

=

210.96~X 60sec sec min (50 + 273)OK

=

39.2

~

O

min- K

» i

OR

= heat rejected in the condenser

OR

= m Cp i1T

640

= m (4.187) (55 -

36.8)

= 8.3985 ~

t'

m

J

Capacity of pump

sec

=

8.3985

~

x 1.0067 liters

sec kg

= 8.455 liters/sec .~

22. An ammonia compressor has a clearance of 5% and a pressure ratio of 5.

Determine the volumetric efficiency if k for ammonia is 1.304.

A. 82.82% C. 87.82% (ans) B. 89.82% D. 85.82%

24. What is the resulting pressure when 1 kilogram of airat t 05 kPaa and 94°C is heated at constant volume to 425°C? C. 179.7 kPaa A. 199.7 kPaa (ans) B. 189.7 kPaa D. 169.7 kPaa

PB -126

ME BOARD APRIL 1999

.'

Solution:

T]

Pz

Tz

33. A vapor compression refrigeration system is designed to have a capacity of 100 tons. Its actual COP is 5.86 and 35% of the power supplied to the compressor is lost in the form of friction and cylinder cooling losses. Determine the motor power in kw. A. 72.3 C. 92.3(ans) B. 82.3 D. 62.3

~=~

94 + 273 425 + 273

'P 2 199.7 kPaa

=

25. When vane control is used for mechanical draft fan and where a wide load range is required it is advisable to use a: A. two speed drive motor(ans) C, single speed drive motor B. four speed drive motor D triple speed drive motor

I

Solution: QA

COP

26. The system of refrigeration which uses heat energy to change the condition required in the refrigeration cycle: A. ICE Refrigeration C. Absorption Refrigeration (ans) B, Vapor Compression D. steam jet Refrigeration

31. An ideal reversible Carnot Cycle involves 4 basic processes. What type of processes are they? A. all isothermal B. two adiabatic and two isentropic C. all adiabatic

D, two isothermal and two isentropic (ans)

= QA

5.86 =

351.6 We

We

=

60 kw

Motor Power

28. The pressure of fluid resistance when acted upon by external forces is called: C. flash point A. density D. pour point B. viscosity (ans)

30. A ton of refrigeration is a heat unit equivalent to: A. 2545 Btu/hr C. 12660 kJ/hr(ans) B. 3413 kw-hrs D. 12243 kcalls

= 100 tons of ref = 351.6 kw We

27. The temperature of air that has gone through an adiabatic saturation process: C. dry bulb temp A. dew point temp D. boiling point B. wet bulb temp (ans)

29. In a refrigeration system, the following are the results of increasing the evaporator temperature, except: A. the refrigerating effect per unit mass increases B. the mass flow rate per ton increases (ans) C. the COP increases D. the heat rejected in the condenser increases

PB - 127

32, The bUilding code of the Philippines: C. RA 1030 A. RA 1096 (ans) B. RA 1609 D. RA 1960

Constant Volume Process:

.!1.- =

ME BOARD APRIL 1999

=

60 1- 0.35

= 92.3 kw

34. An air conditioning system has a capacity of 300 kw refrigeration and uses R-12 with evaporating temperature of OOC (hf = 200 kJ/kg, hg 351.48 kJ/kg). The mass of flash gas per kilogram of refrigerant circulated is 0.2212. Determine the COP if the work of compression is 42 kw. A. 5.14 C. 7.14 (ans) B. 6.14 D. 8.14

=

v

.l

t

4

Solution: COP = QA

*

i..

== 300 42

W

I>

= 7.14

35. Air at 20°C flows at the rate of 0.5 cubic meter per second through a straight circular sheet metal duct 300 mm in diameter. Determine the pressure drop for a 15 meter duct length if friction factor is 0.0195 . C. 25.4 Pa A. 29.4 piJ (ans) B. 27.4 Pa D. 23.4 Pa Solution: hf

=

fLyz 2gD

_

0.0195(15)(7.073)2

2(9.81)(0.3)

= 2.486 m

PB -128

..

ME BOARD APRIL 1999

Pressure Drop

= density of air

x friction head

36. One thousand kilograms of dressed chicken enter a chiller at 100C are 0C frozen and chilled to a final temperature of -15 for storage in 24 hours. Compute the product load. Specific heat above freezing --------------------­ 3.2 kJ/kg-K Specific heat below freezing---------------------1.6 kJ/kg-K Latent heat -----------------------------------------250 kJ/kg _5 0C Freezing Tem perature ----------------------------­ C. 5.67 kw D. 6.67 kw

B. 4.67 kw

I

Solution:

h,

= hg =

h2

=

h3

= h4 = 312.87

QA

= 20 tons of ref

QA

= m (h, -

Solution: 70.32

= m[Cp1(t1 -

Product load

=

1000 ( 24(3600)

tF ) + h L + Cp2(tF - t2)]

j'I [ 3.2(10--5)

+ 250 +

m

1.6(-5--15) ]

= 3.63 kw 37. A pump operating at 1800 rpm delivers 600 gpm against a total head of 200 ft. Changes in the piping system have increased the total head to 260 feet. At what rpm should the pump be operated to achieve this new head at the same efficiency. A. 2052 (ans) C. 2072 B. 2062 D. 2082 Solution:

~ h 2

(

=

PB -129

temperature. The enthalpy of the refrigerant after the compression is 1657 kJ/kg. Determine the power per ton of refrigeration. A. 0.4772 kw/ton C. 0.6772 kw/ton (ans) B. 0.5772 kw/ton D. 0.7772 kw/ton

_ kg m - 1.2 - 3 x 9.812 x 2.486m m s = 29.3 Pa

A. 3.67 kw (ans)

ME BOARD APRIL 1999

,2

l~l N ) 2

200 = (1800J2 260 N2 N 2 = 2052 rpm 38. A simple vapor compression cycle develops 20 tons of refrigeration 0C which uses ammonia and operates at 24 (hf = 312.87 kJ/kg) condensing temperature and -18°C (hg = 1439.94 kJ/kg) evaporating

1439.94

1657

h4 )

= m ( 1439.94 -

312.87)

= 0.0624 kg/s

= m (h2 -

Comp Work, We We

= 70.32 kw

= 0.0624 (1657 -

h.)

1439.94)

= 13.54 kw

W 13.54 =~ = - = 0.677 kw/ton

Power per Ton

QA

20

39. A R-12 compressor operates operates between evaporating temp of 4 0C (hg = 353.18 kJ/kg, vg = 0.04895) and condensing temperature of 43 0C (hf = 241.6 kJ/kg). Determine the bore diameter of the 4 cylinder, 1000 rpm compressor if the piston speed is 200 meters per minute and actual volumetric efficiency is 82% and refrigeration load is 25 tons. A. 7.5 cm C. 9.5 em (ans) B. 8.5 em D. 10.5 cm Solution:

QA QA

= 25 tons = 87.9

= m (h, -

kw

h4 )

87.9 = m (353.18-241.6)

= 0.7877 kg/s

Density, d = 1 m

v

0.04895

= 20.42

kg/m 3

...

PB ·130

ME BOARD APRIL 1999

=

V l'

mass density

_ 0.7877 - -20.42

ME BOARD APRIL 1999

1.32Cv - Cv = 0.297

3

= 0.03857 ~ sec

Cv = 0.928

Piston Speed = 2LN Cp = 1.32 (0.928) = 1.225 200 ~ = 2 L (1000) L = 0.1 m = 10 cm

II

I II

II

0.3(4.187)(t-12) = 0.5 (1.225)(150-80)

= ­ Y;

t = 46.1°C

Yo

0.82 = 0.03857

41. Determine the average Cp value in kJ/kg- oK of a gas if 522 kJ of heat is necessary to raise the temperature from 3000K to 800 0K making the pressure constant. A. 1.440 C.1.144 B. 1.044 (ens) D. 1.414

Yo 3

V D = 0.047036 m sec 1t

kg_OK

mwCpw ~Tw = m g Cpg~Tg

nv = volumetric efficiency nv

~

Heat Balance:

Heat gain by water = Heat loss by gas

min

I'

2

V D = -D LNC 4

Solution:

0.047036 = "::D 2(0.1)(1000) (4) 4 60

Q=mCp~T

522 = 1 Cp (800 - 300) kJ Cp = 1.044­

o = 0.0947 m = 9.47 em 40. A heat exchanger was installed purposely to cool 0.50 kg of gas per second. Molecular weight is 28 and k = 1.32. the gas is cooled from 0C 150 to 80oC. Water is available at the rate of 0.30 kg/sec and at a temperature of 12°C. Calculate the exit temperature of the water in deg centigrade. A. 48 C.44 B. 46 (ans) D.42

kg-OK

42. Determine the barometric pressure if saturated air at 300C has a humidity ratio of 0.029 kg water per kg dry air. Saturation pressure at 300C is 4.241 kPa. A. 92.5 kPa C. 93.5 kPa B. 95.2 kPa (ans) D. 94.2 kPa

~ /

;.

Solution:

Solution:

Gas Constant, R = 8.3143 = 0.297 ~ 28 kg-OK

Cp Cv

PB - 131

Saturated air is 100% RH.

Pv = RH x P sat

k = 1.32

Cp = 1.32 Cv Cp - Cv = R

Pv = 1 x 4.241 = 4.241 kPa W

j

P

= 0.622 ~ P-Py

= total pressure and the barometric pressure of air

'F

0.029 P

= 0.622

4.241 P -4.241

= 95.2 kPa

Solution:

43. In an air conditioning unit 3.5 cubic meters per second of air at 27°C dry bulb and 50% RH. (v 0.85 cu. m/kg\ h 55.2 kJ/kg. w 0.0112 kg/kg) and standard atmospheric pressure enters the unit. The leaving condition of air is 13°C dry bulb and 90% RH. (h = 34 kJ/kg. w =

0.0083 kg/kg). Calculate the refrigerating effect in kw and the rate of water removal kg/sec. C. 87.3 and 0.012 (ans) A. 83.7 and 0.021 D. 73.8 and 0.120 B. 78.3 and 0.102

=

=

Eff Eft

I

v

RE = m (h 1 - h 2 ) = -

- ­

1

k-l rk

=

Solution: Brake Thermal Eff

=

Brake Power

(55.2 - 34) 0.85 87.3 kw

Moisture Removal

It

::

=

= m (W 1 -

W 2)

= :!.(W 1 VI

W2) mf

~ (0.0112 - 0.0083)

mf

0.85 0.012 kg/sec

=

= mf

= 1 liter 12 min utes = 1.11 X 10- 3

=

Brake Power mf Qh

x Q h x Brake thermal eff min

lkg x 0.80 liter

x -- x

60s kg/sec

Brake Power

= (1.11 x 10-3 ) (45 x 106 ) (0.25) = 12487.5 watts = 12487.5 w x -HP­

Brake Power

= 16.7 HP

Brake Power

44. A cooling tower receives 30 cu. m per minute of air at 32°C db and 34°C wb and leaves saturated at 29°C. The entering are has the following 0.0156 kg/kg). properties (h = 72.5 kJ/kg, v = 0.884 cu. m/kg and w Water enters the tower at 38°C (hf = 159.21 kJ/kg) with a mass flow rate of 35 kg/min. Determine the enthalpy of the leaving water in kJ/kg. Properties of the leaving air are (h = 95 kJ/kg, w = 0.025 kg/kg). C.118.74 A. 128.4 B. 148.74 D. 137.4 (ans)

746

w

47. A device produces 37.5 kJ per cycle. There is one power stroke per cycle. Calculate the power output if the device is run at 45 rpm. C. 24.2 kw A. 28.2 kw (ans) B. 26.2 kw D. 22.2 kw SOlution:

Solution:

Power Output

Heat Balance in the Cooling Tower; Heat Rejected by water mw (h, - h4 )

1

(6Y4-1

= 0.512 = 51.2%

= ~

"

1 _

(h, - h 2)

VI

RE

=1

46. An engine burns a liter of fuel each 12 minutes. The fuel has specific gravity of 0.8, and a heating value of 45 MJ/kg. The engine has an efficiency of 25%. What is the brake horsepower of the engine? A. 16.7 (ans) C. 14.7 B. 15.7 D. 13.7

Solution: It

PB -133

45. What is the efficiency of an Otto cycle with a compression ratio of 6:1. The gas used is air. C. 61.2% A. 41.2% B. 51.2% (ans) D. 71.2%

=

,.

ME BOARD APRIL 1999

ME BOARD APRIL 1999

PB -132

= ma (h2 -

=

= Heat Gain by Air h.)

30 35 (159.21 - h4 ) = - - (95 - 72.5) 0.884 h 4 = 137.4 kJ/kg

= 37.5

j

~ cycle

x 45 rev min

X

min X cycle 60s rev

28.125 kw

48. The equilibrium temperature that an ordinary thermometer measures if exposed to atmosphere: C. dew point A. dry bulb temperature (ans) D. critical temperature B. wet bulb temperature

..,

PB -134

l

ME BOARD APRIL 1999

49. A horizontal tube supplies 280 liters per second of water to a hydraulic turbine. The net head is 46.50 m. Determine the power supplied to the turbine. A. 117.7 kw C. 137.7 kw B. 127.7 kw (ans) D. 157.7 kw

ME BOARD APRIL 1999 54. In a rigid tank contains air at initial pressure and temperature of 450 kPa and 135 deg C. The temperature and pressure in the tank was drop to 55 deg C and 380 kPa. There's a heat transfer in the tank done by the surrounding. What is work done at the boundary of the system? A. Zero (ans) C. 5,600 kJ/kg B. 24,750 kJ/kg D. 6,400 kJ/kg

Solution: Solution: Water Power

= (0.280~3)(9.81~)(46.5 = 127.73 kw

II

It

I It

IJ

= QwH Rigid container, the work done is zero. (Constant Volume)

m)

50. In a rankine cycle when the no. of stages in reheat stages is increased, the average temperature of the reheat process is: C. increased A. Constant (ans) B. zero D. decreased

55. Water is extracted from underground water source whose free surface is 20 m below the ground level. The diameter of the pipe is 10 cm inlet and 30 cm at the exit. What is the necessary power of the pump for a staedy flow of water at the rate of 80 ~.g/sec in kw? A. 11.6kw(ans) C. 21.1 kw B. 16.1 kw D. 26.7 kw Solution:

51. If C 2H 6 air-fuel A. B.

fuel for air combustion and using 20% excess air. Determine the ratio. 19.3 (ans) C. 25.9 21.3 D. 30.3

Vs

Solution: Theoretical Combustion of air and fuel:

C2H 6 + 3.5 O2 + 3.5(3.76) N2

Theo

A

F

A Actual F

Q

3.5 + 3.5(3.76)

= 2C0 2

= 16.66

1 16.66(1.20)(28.97) 2(12) + 6(1)

=

VD

sec

=

H

=

7[

sec

10.18 m/s

4(0.10)2

0.08

= (Zo -

= 1.13 m/s

Zs) +

= (0 - - 20)

Power

53. For practical solution, frequent used method for decreasing and preventing excessive the amount of moisture content in the turbine. C. subcooling A. Reheating (ans) B. intercooling D. heating

1000 Ii

0.08

As

kg fuel

52. A type of condenser that is water cooled: A. evaporative condenser C. shell and tube (ans) B. tube condensers D. finned tube

kg

3

0.08~

2:(0.3)2

4

H kg air

li m3 x 1-x-­

= 5l

+ 3H 20 + 3.5 (3.76) N2

mols air mol fuel

19.3

kg = 80-

V D 2 -Vs 2

2g +

(1.13)2 - (10.18)2

2(81)

= 20-5.21

= 14.8 m

= QwH = (0.08) (9.81) (14.8) = 11.6 kw

56. For a vacuum pressure, absolute pressure is nearest to: A. vacuum gage B. zero absolute C. 1 atmospheric pressure (ans) D. 100 atmospheric pressure

57. The barometer reads 88 kPa. What is the absolute pressure of a 127.5 cm liquid with a specific gravity of 0.32 ?

,.

PB -136

ME BOARD OCTOBER 1999

ME BOARD APRIL 1999

A. 90 kPa B. 92 kPa (ans)

MECHANICAL ENGINEERING Licensure Examination October 1999 08:00 a.m. - 04:00 p.m

C. 95 kPa D. 101 kPa

Solution: Pg

POWER AND INDUSTRIAL PLANT ENGINEERING

= wh = 0.32(9.81 )(1.275) = 4 kPa g

88 + 4

SET A

MULTIPLE CHOICE:

Pabs = Palm + Pg

=

PB -137

1. What is the temperature where the water and vapor are in equilibrium to the atmospheric pressure? A. ice point C. critical point (ans) B. steam point D. freezing point

= 92 kPa

58. An engineer use to design an air conditioning system to a building. An economical design is by using a duct for several rooms. Which of the following units is suitable? A. unit air conditioner B. Package air conditioner C. central air conditioner (ans) D. window type air conditioner 59. Control and direct the flow of refrigerant to the evaporator coils: A. suction line valve C. discharge line valve B. solenoid valve D. expansion valve (ans)

2. Given the velocity of 10 m/s. Compute the velocity head. A. 5.1 m (ans) C. 7.9 m B. 6.8 m D. 9.4 m Solution:

:,

235Ii

900 kw-hr

= 0.234

~

=

h

=

y2

2g

I I

•

60. A diesel generating set consumes 235 lit~rs of fuel during one hour operation and produces 900 kw power. The density of fuel used is 0.8955 kg per liter. Determine the specific fuel consumption of the diesel generating set in kg per kw-hr . C. 0.254 A. 0.234 (ans) D. 0.245

B. 0.243 Solution:

Over-all spec. fuel consumption =

h

(10)2

2(9.81)

=

5.1 m

3. The length of a pipe is 168 m. If the pressure drop is 50 kPa for every 30 m, what is the total pressure drop? C. 350 kPa A. 220 kPa D. 410 kPa B. 280 kPa (ans) Solution:

x 0.8955 kg

u

Pressure drop

= 168 m x

50 kPa 30

= 280 kPa

ill

"

kw-hr

t

,. ~;

4. A 30 kg iron was put in a container with water. The 30 kg water is at 10 deg C and the iron has an initial temperature of 493 deg K. Until the iron was in thermal equilibrium with water. Find the change in entropy. (Cp for iron = 0.4 kJ per kg per deg K). A. 7.6 kJ per deg K (ans) C. 5.5 kJ per deg K B. 6.5 kJ per deg K D. 0 Solution: Heat Balance:

mw Cpw AT w = rn, CPt ~TI

T'

PB -138

ME BOARD OCTOBER 1999

30(4.187)(T-10) = 30(0.4)(220-T) T

= 28.3 0C

Change in entropy

=

Q

T

i1S = 30(0.4)(220 - 28.3) 28.3+ 273

=

7.6~ oK

5. In pipe specification, schedule is used, when the pipe specified as "schedule 80" the pipe corresponds to the: A. extra standard weight (extra strong) (ans) B. internal pressure C. allowable stress D. old standard weight

ME BOARD OCTOBER 1999

PB - 139

9. In a Rankine Cycle steam enters the turbine at 2.5 Mpa (enthalpy and entropy given) and condenser pressure of 50 kPa (properties given), what is the thermal efficiency of the cycle? At 2.5 Mpa:

hg ::: 2803.1 sq > 6.2575

At 50 kPa: sf::: 1.091 vf ::: 1.03 x 10.3 hf ::: 340.49 hfg::: 2305.4 sfg::: 6.5029 A. 18,9% B, 21.4%

C. 25.6% (ans)

D. 26.5%

Solution: Cycle Efficiency :::

Wr-~i

QA

h, ::: 2803,1

(PSME Code p. 187)

h2 ::: (hf + xhfgh

6. The entropy of a pure substance at a temperature of absolute zero is: A. unity C. infinity B. zero (ans) D. 100

7. Find the air -fuel ratio for a combustion process to which the fuel is CaH 1a . A. 20 C. 17 B. 19 D.15(ans)

S1 ::: S2 ::: (Sf + x Sfgh

6.2575 ::: 1,091 + x2(6.5029)

X2 ::: 0.7945

h2 h2

= 340.49 ==

+ 0.7945(2305.4)

2172.13 kJ/kg

W T == h1 - h 2 == 2803.1 - 2172.1

Solution:

W p == V3(P 4

Theoretical Combustion Reaction:

W p == h4 - h 3 2.5235 = h, - 340.49

h, = 343.01 kJ/kg

CaH 1a + 12.5 O 2 + 12.5(3.76) N2

Theo

Theo

FA A

F

_

:::

8C0 2 + 9H 20 + 12.5(3.76)N 2

[12.5 + 12.5(3.76)]28.97

Q A

:::

-

P3) ::: (1.03 x 10'3) (2500 - 50) ::: 2.5235 kJ/kg

h 1 - h, ::: 2803.1 - 343,01 == 2460.09 kJ/kg

8(12) + 18(1) Cycle Efficiency == ::: 15.12 kg air kg fuel

8. The effect of superheating the refrigerant is : A. increase the COP (ans) C. low COP B. decrease the COP D. increase the compressor power

::: 631 kJ/kg

h~1_'J "'J~"

V-'" ~.-'~-'-'

:::

25.55%

2460.09 10. The absolute zero in celcius scale: A. 100 B. zero

C. -273 (ans) D. +273

11. The property of fuel oil in which how liquid is the fuel? A. cloud point C. pour point

D. velocity

B, viscosity (ans)

PB -140

ME BOARD OCTOBER 1999

""

12. The water in the products of combustion is in its vapor state: A. lower heating value (ans) C. higher heating value B. calorific value D. higher calorific value

ME BOARD OCTOBER 1999 A. 5.8 kw

PB - 141

C. 6.2 kw D. 2.2 kw (ans)

B. 3.6 kw Solution:

13. The actual head, neglecting the kinetic energy, in which the pump work against. A. delivery head C. suction Head D. velocity head B. pressure head (ans)

Q Q

= =

kAAt

x 2.16 kw

1.8(0.7)(25 -13) 0.007

19. What is the coefficient of a vapor compression refrigeration system having the following data. Enthalpy entering the compressor is 181.79 kJ/kg; enthalpy after compression work is 207.3 kJ/kg; after condensation the enthalpy is 58.2 kJ/kg and throttled from 0.19 Mpa to 0.18 Mpa. A. 5.84 C. 4.84 (ans) B. 3.2 D. 5.6

14. The ice making capacity is always: A. directly proportional to the refrigerating effect B. less than the refrigerating effect C. greater than the refrigerating effect D. equal to the refrigerating effect (ans) 15. When the air is saturated, the wet bulb depression is : A. Zero (ans) C. 100% B. unity D. positive

Solution: COP = QA W

16. A 4m x 4m x 4m room has a relative humidity of 80%. The pressure in the room is 120 kPa and temperature is 35 deg C (Ps = 5.628 kPa ). 3/kg-deg What is the mass of vapor in the room? (Rv = 0.4615 kPa-m

COP =

=

hI -h 4 h z -h]

181.79-58.2 207.3 -·181.79

=

4.84

K). A. 2.03 kg (ans)

C. 0.80 kg D. 4.80 kg

B. 1.50 kg

20. The refrigerating capacity of a R-12 system is 22 kw. Compressor power is 7.8 hp. Determine the COP of the refrigeration system. A. 3.78 (ans) C. 2.22 B. 2.82 D. 1.85

Solution: Py

= RH x P

sat

Py V

= 0.80 x 5.628 = 4.5024 kPa

=my Ry T

COP

~.

R for water vapor = 0.461 -

kJ

kg-K

4.5024( 4 x 4 x 4)

Solution: <j~

= my (0.461) (35 + 273)

;,

~

:~

1,(

, 1

my

= 2.029 kg

17. The process in which the heat energy ·is transferred to a thermal energy storage device. It is known as: C. intercooling (ans) A. adiabatic D. isentropic B. regenerator

1 (

COP

= =

QA = W

22 7.8(0.746)

3.78

21. Find the power of the (rotating) shaft 188 N-m and 1350 rpm. A. 101.54 hp C. 45.7 hp D. 52.3 hp B. 35.6 hp (ans) Solution:

~

18. What is the heat transfer in the glass surface area of 0.7 m 2 having an inside temperature (room) of 25 deg C and 13 deg C outside temperature (surrounding). The thickness of glass surface is 0.007 m. The thermal conductivity is 1.8 W per m per deg K.

Power

= 27t T N = 27t (188)

Power

= 35.6 hp

1350) - xhp ­ ( 60 746

22. An instrument that indicates records and integrates the steam flow from the steam generator and also records the rate of flow of air for combustion to the furnace is known as: J

PH

-142

ME BOARD OCTOBER 1999

A. fluid flow meter (ans) B. manometer

ME BOARD OCTOBER 1999

C. venturi tube D. boiler meter

23. A 4m x 411' x 3m office room contains air at 27 .deg C. If the pressure of dry air is 95 kPa, calculate the mass of air if the air fills completely the room. C. 45.85 kg A. 25.46 kg D. 52.96 kg (ans) B. 32.45 kg

A. magnitude (ans) B. adhesion

'., ~ .~

PV = mRT

(95)(4 x 4 x 3) = m (0.287) (27 + 273)

m 52.96 kg

Solution:

=

= 693.25 kJ/kg = 554.6 kJ/kg

1515.2 - 821.95 Turbine work 693.25 x 0.80 Actual turbine work

=

26. The ratio of the input work necessary to bring the pressure of a gas to a speed value in an isentropic process to the actual work input is known as: A. thermal efficiency of the compressor B. compressor efficiency C. adiabatic efficiency of the compressor (ans) D. volumetric efficiency

29. The ratio of cross-sectional area of flow to the wetted perimeter. A. hydraulic head C. hydraulic energy D. hydraulic gradient B. hydraulic radius (ans) 30. The critical temperature where water and vapor are in equilibrium: C. ice point A. steam point (ans) B. freezing point D. load point

=

25. A power plant operates on an ideal Brayton Cycle. The gas temperature at the turbine inlet is 14000K (1515.2 kJ/kg) and the gas temperature at the turbine exit is 8000K (821.95 kJ/kg). Assume a turbine efficiency of 80%, what is the actual turbine work in kJ/kg ? A. 421.6 C. 554.6 (ans) B. 750.8 D. 522.4

C. cohesion D. intensity

28. The thermal efficiency of a gas-vapor cycle as compared to steam turbine

or gas turbine.

A. equal to C. greater than (ans) B. none of these D. lower than

Solution:

24. If water is present in lubricant then it may cause the valve seat of the expansion device to freeze and may clog the refrigerant flow, the lubricant must be: A. average water content C. low solubility to water D. high solubility to water B. high water content (ans)

PB -143

"

,I

~

•

it f

:4

t

f

,.= ,~

f~ "

,',

.

31. It is an abrupt reduction in flow velocity due to sudden increase of water depth in the downstream direction: A. hydraulic energy \ C. weirs B. hydraulic gradient D. hydraulic jump (ans) 32. Property of lubricating oil that responds at very low temperature, the oil is known as: A. cloud C. viscous (ans) B. pour D. solid

,>

iI

I

33. Is a valve that regulates the flow of refrigerants: A. direct expansion valve C. thermostatic expansion valve (ans) B. throttle valve D. control valve :1

34. In a cooling tower the temperature of water is lower than the wet bulb temperature of entering air and it is found that air cannot cool. What is the temperature of water in cooling water: A. lower C. constant D. none of these B. above (ans) 35. A turbine in which all available energy of the flow is converted by a nozzle into kinetic energy before in contact to moving blades. A. Kaplan C. Propeller D. Francis B. Impulse (ans)

Solution: Adiabatic Efficiency of comp

=

isentropic work actual fluid work

27. The liquid pressure in the surface per area to the surface at the bottom is:

36. A certain company manager want to used comfort air, what is the most efficient setting of the conditioning unit: A. most attainable value C. maximum value (ans) B. moderate value D. minimum value

"l III I,II

...

PB -144

ME BOARD APRIL 2000

ME BOARD OCTOBER 1999

PB -145

MECHANICAL ENGINEERING Licensure Examination

April 2000 08:00 a.m. - 04:00 p.m

37. A type of throttle of air fuel ratio is constant charging. A. quantitative C. qualitative B. hit and miss D. none of these (ans)

POWER AND INDUSTRIAL PLANT ENGINEERING

SET A

38. A valve that senses the loss of ignition in a diesel engine. A. combustion control C. fire extinguisher B. fire control D. flame detector (ans)

MULTIPLE CHOICE:

39. If oil clogs in the evaporator, it cause: A. increase in heat transfer C. vaporized oil B. low suction pressure (ans) D. high pressure

1. How many tons of ice can a 20 ton ice plant produce in 24 hours at 5 deg F from raw water at 80 deg F ? A. 0.59 C. 19.8 D. 23 B. 14 (ans)

I I

40. In cooling process, if humidity ratio remains unchanged: C. pre-cooling A. sensible cooling (ans) B. sensible heating D. latent cooling

SOlution: Cooling Load

41. A system of a refrigeration in which the wet bulb temperature is not more than the temperature of air: C. indirect system(ans) A. evaporator load system D. chilling system B. direct system

20 tons x . hr [ ton of ref

43. A form of green or black, slimy plant life that grows in water system. A. Algae (ans) C. fungi B. Allen D. bellows

= 1167.88

m

=

-

t2)]

i

J=

m[1.0(80-32) + 144 + 0.5(32-5)] ­

Btu

Ib

Ib ton hr x 2000 lb x 24 hrs

14tons

3. A pump is delivering 160 liters per sec of water using an impeller diameter of 254 mm and operating at a speed of 1800 rpm. If the speed is held constant and the impeller diameter is changed to 203.2 mm, what is the new discharged of the pump in liters per second? A. 130 C. 180 D. 145 B. 128 (ans)

45. 180 grams of saturated water of temperature 95°C undergoes evaporation process until all vapor completely vaporized. Determine the changed in volume in m", Steam Properties: 3/kg 0.0010397 m 3/kg, vg 1.9819 m At 95°C. vf C. 0.4566 A. 0.3565 (ans) D. 0.6047 B. 0.4085

= Sp. Volume x mass

= (Vg - Vf) x mass

= (1.9819-0.0010397)(0.18 kg)

= 0.3565 m 3

m

t f ) + h L + CP2(tf

2. The most economical and low maintenance cost condenser: A. water-cooled C. evaporative B. air-cooled (ans) D. sub-cooled

44. Air distribution outlet designed to direct airflow into desired forms. C. air cycle A. air diffuser (ans) B. air blocks D. air coil

Solution:

Volume Volume Volume Volume

= m[Cp1(t 1 -

12'000 B tu

42. A system which use two or more refrigerant cycles, where the evaporator of one cools the condenser of the other. A. cascade system (ans) C. direct system B. flooded system D. multiple system

=

11111

III' I ,

Solution:

=

I

2L=~ Q2

160 -

II

02

254

"

=-­

203.2

Q2

1

O 2

J

=

1

128 lit/sec

!

'11

~

I

I ~.i

PB -146

ME BOARD APRIL 2000

ME BOARD APRIL 2000

8. The fuel has a chemical formula of CH 4 with 15 % excess air. Find the actual mass of air in kg per mass of kg fuel. A. 17.2 C. 22.3 B. 19.8 (ans) D. 25,9

4. What is the area of the diagram from the relation of temperature and entropy plane? C. heat (ans) A. entropy D. work B. energy

Solution:

5. A reversed carnot cycle is operating under the temperature limits -8 deg C and 18 deg C. Find the COP. C. 16.8 A. 10.2 (ans) D. 19.2 B. 14

Theoretical Combustion Reaction: CH 4 + 2 O2 + 2(3.76)N 2

Solution: COP

COP 6.

Theo A F

= ----.:!i

7.

2 + 2(3.76) 1

+ 2(3.76) N 2

mol fuel

Actual air - fuel ratio with 15% excess air:

-8 + 273 (18 + 273) - (-8 + 273)

= 10.2

150 grams of water at 75 deg C is heated at constant pressure. water is completely vaporized. What is the heat added? A. 355 kJ (ans) C. 144 kJ B. 335 kJ D. 120 kJ

The

./

Q

= mCp~T + mhg hg = 2257 latent heat of vaporization of water

Q

= (0.150)(4.187)(100-75) + 6.15(2257)

Q

= 354.2 kJ

A

9.52(28.97)(1.15)

F

1(12) + 4(1)

Actual ­

Solution:

I'

co

= CO 2 + 2 H2 0 = 9.52 mol air

TH -TL

=

I­

PB -147

If 120 kg of air has a dry bulb temperature of 18 deg C. What is the standard air volume in cu.meter ? A. 0.31 C. 98.9 (ans) B. 12.0 D. 210

=

19.8 kg air kg fuel

9. In order to avoid cavitation the NPSH of an installation should be atleast _-----,---_ _-----,--- than the NPSH of the pump. C. greater A. equal or greater (ans) B. equal or lower D. lower

(PSME Code 1984 Ed. p. 173)

10. Mr. De la Cruz wanted to buy a pump for his farm. What is the suitable for deepwell installation? A. reciprocating C. hand lift D. centrifugal (ans) B. air lift 11. Which of the following hydraulic turbines is a high head turbine? A. Impulse (ans) C. Reaction B. Francis D. Propeller 12. In a two phase system, 30% moisture means: A. 70% liquid and 30% vapor B. 70% vapor and 30% steam C. 70% vapor and 30% liquid (ans) D. 70% liquid and 30% steam

Solution: PV = mRT (101.325) V = (120)(0.287)(18 + 273) V

= 98.9 m

3

13. An engine is required to produce 4500 kg of dry steam per hour. The quality if steam in it is 90%. What must be the weight of the wet steam? A. 4778 kg/hr C. 5258 kg/hr D. 6000 kg/hr B. 5000 kg/hr (ans)

Y'

PB -148

ME BOARD APRIL 2000

ME BOARD APRIL 2000 Solution:

Solution: quality, x 0.90

=

_

my

Coounq Load

mT

kJ 630 ~"~

15. Air at atmospheric pressure of 760 mm Hg at sea level with a temperature

of 22 deg K, what is the specific weight in kN per cu. meter?

A. 0.651 C. 0.371 B. 0.516 D. 0.157 (ans)

/\. 833.3 (ans) B. rs199

~~.'; cl!(jl.ion:

PV = mRT Specific Weight,

m

=

V

101.325 0.287(22 + 273)

=

k~

::. (hf + x hfgh =: 251.4 + 0.9(2358.3) h;,=: 2373.87 h

I' (5

P

tl·

-­ RT

16

~3

Turbine work

m

x 9.81 m/s 2 = 156.96

~3

=

h 1 ­ h2 3207.2 - 2373.87 _. 833.33 kJ/kg

m

m

s

C 633.3 D. 423.2

A

Solution:

16

kg

18, ThE: [,f::'ssure and temperature entering the turbine is 1800 kPa and 380 deg c: The pressure leaving the turbine is 20 kPa. The quality of steam entf"[i'I) the condenser is 90%. What is the turbine work in kJ per kg. SIB;""] Properties: l'.~ j(J Mpa and 380 deg C: ~l = 3207.2 Al 002 Mpa hfg = 2358.3 hf =: 2514

II

=

j

m :::: 2.86 kg/hr

14. The first law of thermodynamics states about: A. conservation of velocity B. conservation of energy (ifns) C. conservation of enthalpy D. conservation of mass

(5

m .:\H

kJ =:. ) m ') _,,-0-­

111'

4500 mT

=

=

\

mT = 5000 kg/hr

(5

PB - 149

1D. The heart of the vapor-compression system, A. condenser C. compressor(ans)

leN

= 0.156963 m

B

evaporator

D. expander

16. In two revolutions of a four stroke engine, has how many cycle? A. three C. 4 times B. twice D. once (ans)

20. What is the basis of continuity flow? A. mass balance (ans) C. heat balance 13 f'II!':rgy balance D diameter balance

17. The refrigeration system has a refrigeration cycle per kg of 220 kJ. The heat required to remove is 630 kJ/hr. Calculate the mass circulated per hour. C.8 A. 3.186 kg 'D. 2.86 kg (ans) B. 10

?1. A type of condenser which can operate with a lower condensing te: :LJer;?!ljrc and conserve energy compared to other refrigeration condensers : A. Evaporative (ans) C water' tube

,

j

E3

shell and tube

D. air cooled

(Ref and Air-Con by Stoecker and Jones p. 377)

ME BOARD APRIL 2000

ME BOARD APRIL 2000

PB ·150

29. The removal of molasses from sugarcane is done by the process of: A. filtration(ans) C. condensation B. absorption D. separation

22. The length of the pipe is 168 meters. If the pressure drop is 50 kPa for every 30 meters length, what is the total pressure drop? A. 260 kPa C. 280 kPa (ans) B.300kPa D.500kPa

30. A pump is delivering 100 lilsec of water at a total head of 50 meters. Find the water power. A. 19 kw C. 39kw D. 49lcw(ans) B. 29 kw

23. Determine the velocity head of water flowing through a pipe with a velocity of 10 m/s.

C. 100 m A. 5.1 m (ans) D. 151 m B. 50.1 m

Solution:

Solution: h II

=­

V2

(10)2

2g

2(9.81)

Water Power = QwH = (0.100)(9.81 )(50) = 49 kw

= 5.1 m

31. In a gas turbine unit, the temperature will depend on its: A. allowable maximum C. allowable minimum B. maximum value(ans) D. minimum value

24. A steam turbine has an inlet enthalpy of 2800 kJ/kg with a velocity of 40 m/s. The exit steam condition is 2650 kJ/kg. Find the exit velocity. A. 549 m/s (ans) C. 456 mls B. 233 mls D. 784 mls

32. Average boiling temperature of liquid water is: A. 273 deg C C. 212 deg K D. 32 deg F B. 100 deg Crans)

Solution:

h, + 1/2 mV/

= hz +

2

2800 +

40 2(1000)

112 mV/

= 2650

33. An engineer found that the fluid flowing in the pipe is low. What diameter of pipe should be recommended? C. reduce the diameter(ans) A. increase the diameter D. no diameter B. constant diameter

'

+

PB -151

vi

2(1000)

V z = 549 mls 25. A mechanical engineer is assigned in a steam power plant. He noticed that a boiler feed pump has enough capacity to deliver feedwater in the boiler. If you are the engineer of such power plant, how many pumps of the same capacity would you recommend? A. 1 C. 3 B. 2(ans) D. 4

34. Number that is used to determine the type of flow in any system: A. Froude number C. Mach number B. Average number D. Reynolds number (ans)

I

,f

35. Atmospheric air with 30 deg C dry bulb and 20 deg C wet bulb. What is the relative humidity? A. 20% C. 40%(ans) B. 30% D. 50%

.'

26. When there is a reduction in humidity ratio, it means: A. humidifying C. dehumidifying(ans) } B. subcooling D. reheating

Solution: Using the Psychrometric Chart:

27. Leads the exit water of the turbine is: A. tailrace (ans) C. spillway B. dam D. none of these

At 30°C db and 20°C wb:

28. The exit pressure of impulse turbine casing is: A. above atm (ans) C. below atm B. vacuum D. none of these

J

RH

=

40%

PB -152

ME BOARD APRIL 2000

ME BOARD APRIL 2000 mass of steam is turbine entrance. A. 10 kw B. 15 kw

36. An ammonia refrigerator operates between 30 deg C condensing temperature and -6 deg C evaporator temperature. Find the quality after expansion. At -6 deg C hf = 172.371 kJ/kg hg = 1455.00 kJ/kg hg = 1486.14 kJ/kg At 30 deg C hf = 341.769 kJ/kg

PB -153

kg/s, find the heat loss between the boiler: exit and C. 30 kw D. 50 kw (ans)

Solution: A. 9.51% B. 11.2%

C. 13.2% (ans) Q Q

D. 15.4%

Q = 50 kw

Solution:

II

h 3 = h,

h3 = hf + xhfg

341.769 = 172.371 + x(1455 - 172.371) x = 13.2%

40. The initial pressure of the system during isometric process is 100 kPa. If the heat during the process is 10 kw, find the enthalpy change. A. 5 kw C. 15 kw B. 10 kw (ans) D. 20 kw Solution:

37. Air is flowing through a 20 cm diameter pipe with a velocity of 5 m/s. If the temperature of air is 25 deg C and 120 kPa pressure, find the rate of air in the pipe. A. 0.11 kg/s C. 0.33 kg/s B. 0.22 kg/s (ans) D. 0.44 kg/s

Q ~u

Q Q Q

= A x Vel = = = 0.157m 3/s

PV = mRT

120(0.157) = m(0.287)(25 + 273)

m 0.22 kg/s

=

38. The pressure at the bottom of an 8 m column of water is: A. 33.5 kPa C. 66.2 kPa B. 45.5 kPa D. 78.5 kPa (ans) Solution: P = w h

P = 9.81 (8) = 78.5 kPa

39. The available enthalpy of steam at the exit of boiler in a Rankine Cycle is 3000 kJ/kg and enthalpy at the entrance of turbine is 2950 kJ/kg. If the

= ~U = mCp(T 2 - T 1 )

= 10 kw

41. Find the degree superheat of steam at 0.89 Mpa and 180 deg C. At 0.89 Mpa: t (sat) = 174.90 oC A. 4.4 deg C C. 5.1 deg C (ans) B. 4.9 deg C D. 7.4 deg C

Solution: Q

= m (h. - h2 )

= 1 (3000 - 2950)

Solution:

r

Degree Superheat = t(actual) - t(sat)

= 180 -o174.90

5.10 C

=

42. A turbine has an available enthalpy of 3000 kJ/kg in a Rankine Cycle. The pump work is 20 kJ/kg. For a flow of 2 kg/s, find the system output. A. 5960 kw (ans) C. 6343 kw B. 6008 kw D. 7522 kw Solution: System Output System Output

= W T - W p

= 2(3000 - 20) = 5960 kw

43. Swamps gas (or vegetable decay) is: A. propane C. methane (ans) B. octane D. ethane

0, ..

ME BOARD OCTOBER 2000

ME BOARD APRIL 2000

PB ·154

44. How many tons of ice can a 20-ton ice plant produce in 24 hours? A. 20 (ans) C. 60 B. 30 D. 240

MECHANICAL ENGINEERING Licensure Examination Monday, October 9, 2000 8:00 AM - 4:00 PM POWER AND INDUSTRIAL PLANT ENGINEERING

Solution: One (1) ton of refrigeration can produce approximately one (1) ton of ice in 24 hours (or 1 day).

Therefore, 20-ton ice plant (means 20 tons of refrigeration) can

produce 20 tons of ice in 24 hours.

PB ·155

SET A

INSTRUCTION: Select the correct answer for each of the following questions. Mark only one answer for each item by shading the box corresponding to the letter of your choice on the answer sheet provided. STRICTLY NO ERASURES ALLOWED. Use Pencil NO.1 only. MULTIPLE CHOICE

45. A 30 cm x 40 cm reciprocating pump running at 250 rpm discharges 210 Ii/s of water. Find the percentage slippage of the pump. A. 3.4% C. 6.7% B. 8.2% D. 10.7%(ans) It

1. The property of liquid in which they extend resistance to angular or shear deformation is C. viscosity (ans) A. Specific gravity D. Density B. Specific weight

Solution: V o

= 2(1-)D

2LN

Vo = 2 (1-)(0.3)2(0.4)( 2: J = 0.2356 m 00 % slip

=

3/s

2. After checking on the properties and Phase descriptions of water, the quality is found to be x = 0.70. How many % of the mass is in the liquid phase? C. 100% A. 70% D. 30% (ans) B. 0.70%

Yo-Q Yo

0.2356 - 0.21 0 % slip = 0.2356

Solution: Quality, x

= 10.8%

x

=

=

my

mt- +my

70 30+70 = 70% =0.70

3. The volumetric efficiency of an engine normally decreases wi A. Higher fuel-viscosity C. A decrease in speed B. an increase in speed (ans) D. A decrease in jet velocity 4. In order to increase the gas velocity, gas turbines generally have fixed nozzles. This is to allow the: C. expansion of gases (ans) A. Compression of gasses D. evaporation of gasses B. condensation of gasses 5. What does the area under the curve on a temp. entropy diagram indicates? C. work A. volume D. entropy B. heat (ans) 6

The diameter of a pipe at the larger end is 0.5 cm., and at the smaller end is 0.2 cm., the larger and smaller ends are located 7 meters and 3 meters, respectively, datum line. If at the larger end, the velocity is 12 meters per

"

ME BOARD OCTOBER 2000

PB - 156

2 and the pressure is 5200 kN/m , compute pressure at the end. C. 7815.99 kN/sq.m. 6501.84 kN/sq.m D. 5211.82 kN/sq.m. (ans) 4800.92 kN/sq.m.

second smaller A. B.

Solution:

4 3/sec 0.000023561 m

= O 2 = A2V2 0.000023561 = ~(0.2xl0-2 )V2

4 V 2 = 7.5 m/s

0,

.

3m datum

Po V?; P V12 -.1...+_ +ZI = -=--+-- +Z2 5 2g 0 2g

9.81

P2

+7 =

2(9.81)

~+ (7.5~ 9.81

+3

2(9.81)

7. How can the average temperature during heat rejection process of a rankine cycle be decreased? A. increase boiler pressure B. Bring condenser pressure C increase turbine pressure D. reduce turbine exit pressure (ans) 8. Convert a vacuum pressure of 110 mm of mercury into absolute pressure if atmospheric pressure is 10.5 meters H 20. A. 3.7 m of H20 C. 9. 01 m of H20 (ans) B. 45.6m of H20 D. 99.5 m of H20 Solution: 101.325kPa x m H 20 Pg = 110 mm Hg x 760mmHg 9.81 leN

m

= P(gage)

C. Condenser (ans) D. evaporator

A. line after the expansion valve B. over most half of compressor

12. What is the result when the fluid's kinetic energy during a stagnation process is transformed to enthalpy? A. decrease in fluid's volume

B. rise in the temperature and pressure of fluid (ans) C. rise in fluids volume D. Decrease in the temperature and pressure of fluid 13. What is the value of the Mach no. at the throat of a converging- diverging nozzle? A. zero C. One (ans) B. Two D. Ten

= 5211.83 kN/m 2

P(abs)

The high pressure of refrigeration system consist of the line to expansion valve, the receiver, the uppermost half of the compressor and the

11. A property of lubricating oil that measures the thickness of the oil and will help determine how long oil will flow at a given temp. is known as. A. viscosity (ans) C. cloud pt. B. flash pt. D. fire pt.

7m

Bernoulli's Equation:

520~.+ (1.2)l

9.

PB -157

10. What is the pressure at the exit of a draft tube in a turbine? A. below atmospheric C. atmospheric (ans) B. Vacuum D. Gauge

o = AN, = ~(0.5Xl 0- 2) (1.2)

=

ME BOARD OCTOBER 2000

= 1.49 m H20 (vacuum)

14. For a double acting reciprocating pump, there are two suction stroked for every revolution if the crank wheel. How many delivery strokes does it have? A. 4 C. 2 (ans) D. 1 B. 3

II

!I

15. Which of the following materials is suitable for tubing in refrigeration application where refrigerant ammonia is employed? A. plastic C. steel B. Brass D. Copper (ans) 16.

A tank contains H20. What is the intensity of pressure at a depth of 6

meters? A. 68 kPa B. 58.8 kPa (ans)

C. 78.0 kPa D. 48.7 kPa

Solution:

3

+ P(atm) = -1.49 + 10.5 = 9.01 m H 20

I

Pressure

= Spec. weight x height = 9.81 (6) = 58.86 kPa

I,ll III III

III

I, I

PB -158

ME BOARD OCTOBER 2000

"

17. What do you call a conversation technology that yields electricity straight from sunlight without the aid of a working substance like gas or steam without the use of any mechanical cycle? A. Power conversion C. Solar thermal conversion (ans) B. Sterling cycle conversion D. photoVoltaic-energy conversion

22. The minimum amount of air required for a complete combustion of fuel is called A. 90% air C. theoretical air (ans) B. excess air D.110%air 23. For pipes extending more than 1000 times the diameter what are the major losses of hydraulic head due to ? . A. cross-sectional change C. velocity B. friction (ans) D. pressure

18. If the composition of hydrocarbon fuel is known, the ratio between the nitrogen and oxygen that is supplied in air is A. equal C. intensity B. constant (ans) D. fixed

24. Three tons of fish is to be stored at a temp. of -10 degree C for 24 hours. The product enters the chiller at a temp. are 0.41 kcal/kg-degree C and 0.76 kcal/ kg-degree C, respectively, and its latent heat of fusion is 51 kcal/kg. If the freezing temp of the product is -2.2 degree C and initially enters at 7.3 degree C. Determine the product load in Kcal/24/hrs. A. 153,000 C. 158.019 B. 167,120(ans) D. 10,000

19. Which of the following is a reason for a motor head loss in long pipeline? A. pressure C. friction (ans) B. velocity D. elevation 20. Water flow through a pipe at 15 Ii/sec and operating under a head of B.2 m. The inlet diameter of pipe is 12 em and its exit diameter is 15 ern. If H20 is to be pumped from H20 source and heat losses is 2 kw, determine the power input to the pump.. C. 1.2 Kw A. 2.2 Kw D. 4.2 Kw B. 3.2 Kw (ans)

Solution: Q = m[Cp1(t 1 - tf ) + hL + CP2(tf - t2)] 3tons(907 kg)

Solution: Q

~

= 15 Ii/sec = 0.015

V = ~ == 1

m

Q = 167, 118 kcal/24 hrs

= 1.32 m/sec

~(12xlO-2)2

4

Al

25. When changes in kinetic energy of a compress gas are negligible or _ insignificant, the work input to an adiabatic compressor is A. negligible C. equal zero B. equal to change in enthalpy (ans) D. infinity

V = ~ == 0.015 = 0.848 m/sec 2 A 2 ~(15xl0-2)2

4

H

= 8.2

2

2

26. A boiler has a bursting pressure, BP of 600 Kpa and a factor of safety, FS, of 8 is employed in design. As an engineer, would you advice to have a working pressure, WP, of 500 Kpa? A. No, WP must be higher than 500 Kpa B. No, WP is only 75 Kpa at a FS of 8 C. Yes, since BP is 600 kPa (ans) D. Yes, to attain better efficiency

=

0.828 -1.32 8.15 m

2(9.81)

Power Input = QwH + losses

= (0.015)(9.81)(8.15) + 2

= 3.2 kw

+

]h~

= --'--------"--[0.76(7.3 - -2.2) + 51 + 0.41(-2.2 - -10)-­ 24 hrs kg

3/sec

0.015

PB -159

ME BOARD OCTOBER 2000

21. The engineer was tested to design the air-conditioning system, for a ballroom Dance Hall. Considering that this involve a lot of activity from its users, the engineer would design that will require

27. The analysis of a products of combustion on a dry basis, when C 8 H 18 was burned with atmospheric air, is as follows: CO2 = 12%, CO = 0.75%, O2 = 3.01 %, N 2 = 84.24%. Compute the % theoretical air used for combustion, A. 100% C. 121% B. 113% (ans) D. 112%

A. maximum attainable effective

B. Constant effective temperature (ans) C. Higher effective temp D. Lower

j

rF PB -160

MJE BOARD OCTOBER 2000

ME BOARD OCTOBER 2000

Solution: Combustion Reaction with Theoretical Air: CSH 1S + 4.650 2 + 4.65(3.76)N z

'I

~

i

0.12C0 2 + 0.0075CO + 0.03010 2 + 0.8424N 2 + ~Hz6 + 4.65(3.76)N z

I

I

Balancing hydrogen, H: 18 = 2a Balancing Oxygen, 0:

a = 9

PB - 161

31. The temperature at which oil gives off vapor that burns temporarily when ignited: A. dew point C. wet bulb B. drop point D. flash point (ans)

32. In a Rankine Cycle, when the no. of stages in reheat stages is increased, the average temperature of the reheat process is: C. increased

A. constant (ans) B. zero D. decreased

33. The process in which heat energy is transferred to a thermal energy storage device. It is known as: A. adiabatic C. intercooling (ans) B. regenerator D. isentropic

2(b) = 2(0.12) + 1(0.0075) + 2(0.0301) 1(9) b = 4.65

Combustion Reaction with Excess Air:

CSH 1S + 4.65(1 + X)02 + 4.65(1 + x)(3.76)N 2

34. The length of pipe is 168 m. If the pressure drop is 50 kPa for every 30 m, what is the total pressure drop? A. 220 kPa C. 350 kPa B. 280 kPa (ans) D. 410 kPa

~

0.12C0 2 + 0.0075CO + 0.03010 2 + 0.8424N 2 + J!HzO +

4.65(1 + x)(3.76)N 2 + 4.65x02

Expressing the percentage of oxygen in the products excluding water: 0.0301 + 4.65x ".0.301 = 1 + 4.65(3.76)(1 + x) + 4.65x x = 0.132 Percent Theoretical Air = 1 + 0.132 = 1.132 = 113.2% 28. If the actual kinetic energy of a nozzle is Ka and Ki in the max. value that can be attained by an isentropic expansion from initial to final state, then efficiency ofa nozzle is A. KalKi (ans) C. KaxKi B. Ki=Ka D. KilKa Solution: Eff = Output _ K, Input - IZ1 29. A device which converts heat energy directly to electrical energy: A. Thermoionic converter (ans) C. Fuel Cell B. Turbine D. Magneto 30. The temperature at which oil will no longer pour freely or oil will solidify: A. pour point (ans) C. flash point B. cloud point D. dew point

Solution:

50kPa

Pressure Drop = 168 m x - - = 280 kPa 30m

.'~

35. Without having excessive moisture in the final stage of the turbine, an engineer took advantage to increase the efficiency of the boiler by: A. subcooling the steam C. Reheating the steam (ans) B. superheating to low temp D. heating the steam 36. The ratio of compressor to the turbine pressure of a gas turbine unit is: A. back work ratio C. cut-off ratio B. pressure ratio (ans) D. compressor ratio 37. The quantity of heat from the outside to be cooled at desired temperature which can be used to determine in air-condition unit: A. specific heat C. latent heat B. sensible heat D. cooling load (ans) 38.

Which of the following has a minimal effect on the penetration of the air in the combustion chamber? C. fuel viscosity A. jet velocity D. air density B. orifice size (ans)

39. Which energy A. B.

of the following components of a pump converts mechanical to pressure energy? impeller (ans) C. shaft valve D. delivery pipe

PB -162

.

ME BOARD OCTOBER 2000

ME BOARD OCTOBER 2000

46. The temperature of a solution is 31 degree C. Convert the equivalent Fahrenheit reading to absolute Fahrenheit temperature. A. 560.8 degree R C. 520.2 degree R B. 575.5 degree R D. 547.8 degree R (ans)

40. The convergent section of a nozzle increases the velocity of the flow gas. What does it do in its pressure? A. pressure becomes constant B. decrease the pressure C. increase the pressure (ans) D. pressure is equal to velocity

Solution: F

41. What is the relative humidity of dry air? A. 150 % C. 50 % B. 100 % D. 0 % (ans)

R

48.

Solution: actual

Heat transfer processes which include a change of phase of a fluid are considered. A. convection (ans) C. conduction B. thermal radiation D. radiation

theoretical 49. In a closed vessel, when vaporization takes place, the temperature rises. Due to the rising temperature, the pressure increases until an equilibrium is established between the temperature and pressure. The temperature of equilibrium is called A. dew point C. superheated temperature (ans) B. ice point D. boiling point

t - t

Effectiveness = _a_ _b

t a - t wb

. 45 -30 Effectiveness = = 75% 45 -25 43. Flow of fluids wherein its particles do not have definite paths and the paths of the individual and distinct particles cross one another is A. non-uniform flow C. laminar flow B. unsteady flow D. turbulent flow (ans)

50. What is the ton of refrigeration required to cool 15,000 Ib of fresh pork from a temperature of 89 degree F to 32 degree F in 24 hours? Specific heat above freezing of fresh pork is 0.68 BTU/lb-degree F. A. 2.01 tons (ans) C. 4.1 tons B. 5.1 tons D. 4.2 tons

44. When hot soup was served in a cup during dinner, an engineer was so eager to drink it. Since it was hot, he added cubes of ice to cool the soup and stirred it. He noticed that dew starts to form on the outermost surface of the cup. He wanted to check the temperature of the outmost surface of the cup. What is this temperature equal to? A. superheated temperature B. equal to zero C. standard temperature D. equal to air's dew point temperature (ans) 45.

= 2.(oC) + 32 = 2.(31) + 32 = 87.8°F 5 5

= 87.8 + 460 = 547.8 oR

47. One kilogram of air is compressed adiabatically and in steady flow. The compression efficiency is 80% and work done is 265kJ/kg. Determine the heat added to the air. A. 212 kJ/kg C. 0 (ans) B. 1 kJ/kg D. 331.25 kJ/kg

42. Water enters the cooling tower at 45 degree C. The approximate leaving water temperature is 30 degree C. If the atmospheric condition is 25 degree C wet-bulb, determine the cooling effectiveness of the cooling tower. C. 75% (ans)

A. 95% D.50%

B.25%

Effectiveness =

PB -163

Both Sterling and Ericson engines are A. internal combustion engines (ans) C. Carnot engines B. external combustion engines D. Brayton engines

Solution: Q Q

= mCpLlT = 15,000 (0.68X89-32) = 24225 Btu/hr

24

Q

j

= 24225

ton of ref Btu x hr 12,000 Btu/hr

= 2.01 tons of ref

51. A room is 10 feet long,' 11 feet wide and 8 feet high. The inside and outside temperatures are 8 degree F and 65 degree F, respectively. Compute the heat transmitted through the walls if the coefficient of heat

'

....

~'

transmission is 0.12 BTU/ft-degree F-hour. The wall thickness is 6 inches. C. 2407.68 BTU/hr A. 4596.28 BTUlhr (ans) D. 1203.84 BTU/hr B. 996.81 BTU/hr Solution: Area, A Q

=

= 10(8)(2)

kA~T

=

x

= 336 fe

+ 11(8)(2)

0.12(336)(65-8) 0.5

= 4596.48

(18 + 273) - (-6 + 273)

Q A + 33.33

18 + 273

QA

Q A

= 36.3 kw

WN

= OA

- OR

= 36.3 -

33.33

= 3 kw

56. In the absence of any irreversibilities, a thermoelectric generator, a device that incorporates both thermal and electric effects, will have the efficiency of a A. Carnot cycle C. Diesel cycle D. Rankine cycle B. Thermoionic converter (ans)

Btu/hr

52. When H20 in the products of combustion is in liquid form, the heating value is known as A. higher heating value (ans) C. low and medium heat value B. lower heating value D. lower and higher heat value

57. A refrigerating machine that is classified as a one-ton machine has the capacity to produce a cooling effect of : C. 300 kcal I hr A. 500 kcal I hr B. 3000 kcal I hr (ans) D. 40 kcal I hr

53. Nozzles does not involved any work interaction. The fluid through this device experiences. A. no change in potential energy B. no change in kinetic energy C. vacuum D. no change in enthalpy (ans)

Solution: 1 ton of ref

x

3.5161'L x 3600 sec sec hr

kcal

= 3023

ton of ref

54. A refrigerator is maintained at 5 degree C. Heat is removed from the stored food at a rate of 330 kJ/min. What is the refrigerator's Coefficient of Performance if the necessary power input to the refrigerator is 3.5 kW? A. 0.45 C. 8.95 B. 1.57 (ans) D. 94.28

W

=

330~x~

59. When can a Francis turbine obtain a correct disposition of the moving blades and the guide? A. at half the load C. at any load B. at full load only (ans) D. at all loads

= 1.57

3.5kw

55. A building has to be maintained at 18 degree C at all times. A heat pump is required for this. When the temperature outside the building drops to­ 6 degree C, the building loses heat at a rate of 120,000 kJ/hr. Compute the least power necessary to drive the heat pumps. A. 48.15 kW C. 25.06 kW D.3.0kW(ans) B. 0.16 kW

60. A rapid increase in boiler pressure occurs when there is A. moderate drop in steam load B. abrupt drop in steam load (ans) C. constant drop in steam load D. gradual drop in steam load 61. Using the Psychrometric Chart, what is the wet-bulb temperature of air contained in a room at a temperature of 308 degree K, relative humidity of 40% and a pressure of 1 atmosphere? A. 350 degree K C. 297 degree K (ans) B. 294 degree K D. 290 degree K

Solution: QR

= 120,000

kJ x~ hr 3600sec

Carnot Cycle Eff = TH

-

TH

TL

kcal hr

58. At steam point, the temperatures of water and its vapor at standard pressure are C. in equilibrium (ans) A. in its maximum B. unity D. zero

Solution: COP = QA

PB -165

ME BOARD OCTOBER 2000

ME BOARD OCTOBER 2000

PB -164

= 33.33 kJ/sec Q A -QR

QA

~

..... /

,

PB-166

----.,,-._.

ME BOARD OCTOBER 2000

-------,~-_._--

ME BOARD OCTOBER 2000----PB -167­ ",-_.

Solution.

-

--_...- --_._. ------,- --- --'--

._--_._--~_._._--.,

-

----"---------­

68. 300 k,1 of heat flow by conduction from the outside to the inside a cold storage in one hour. If the temperature and all other conditions are the same what is the heat flowing through the cold storage in two hours? A. 600 kJ (ans) C. 300 kJ B. 900 k,J D. 1,200 kJ

Using the Psychrometric Chart, at 308 deg K (35°C) and 40% RH: Wet bulb temperature

--'---',

= 24°C (297 0K)

62. Which of the following ascertains the eftectiveru ss and the size of the condenser? A. ru llber of passes C. tube sizes 8. th kness of the shell D. heat transfer fans)

Solution: ()

-

\00 kJ x )~

'IT L)

II!

= 600 k.J

69. Drrt dnd foreign mator.als no-rnally bUl!d-~Jp on the side of the condenser lL;t'cs To ensure adequate condenser capacity. a certain factor is used

63. What do bo 'es at a temperature above absolute zero emit? A. enerq, C. thermal radfatio '1 (ans) B. heat ot convection D. heat of compress.on

if, calculating the over-all heal transfer through the walls of the tubes !pc1udl/!g the heat transfer rate of the layers of dirt and foreign materials. v,n-lal is this factor called?

64 A refrigerant control in a refrigeration system that is used to prevent the flow of refrigerant gas from the condenser back to the corrrressor during off cycles is A. check valve C hold-back valve 8. solenoid valve (ans) D. safety valve

/, booster 8. foulin[i tector (ans) 70 Dry air can be approximated as n.troqon by mole numbers. A. 30'Yo I 70% B. 70% ! 30%

65. A device used in steam power plant which is required on engine and turbine exhaust casings, on condensers and heater shells or on area where it is possible to have pressures hir:-h(;r than the design pressure of the casings, is a A. steam hold-back valve B. pressure-operated check valve C. steam-generator safety valve D. relief valve (ans)

G factor of safety

D. compression factor .._ % oxygen and

_ t}~

C. 21% / 79% (ans) D, 79% I 21%

7'1. \/\/hich of the followil1g is the preferred criterion for a high-speed engine? A

higher internal stresses

U IO"J piston speed

C. High RPM (ans) D high mean piston speed

~'2 in order that cavitation will not take place in the suction line of a pump,

what should be the sum of the velocity head and pressure head at suction compared to the vapor pressure of the liquid? A. sufficiently lower C. adequately greater (ans) B. constant D. equal

66. A body that is hot compared to its surroundings illuminates more energy than it receives, while its surroundings absorbs more energy than they give. The heat is transferred from one body to another by energy wave motion. What is this mode of heat transfer? A. radiation (ans) C. convection B. conduction D. condensation

73. Using the Psychorrnetric Chart, find the dew point temperature of air contained in a room at a temperature of 308 degree f<. relative nurmdit, of '~O(/, ano a pressure j 1 atmosphere ::\ 292;) <Jegre:;; K (ans) C 290.5 degree t( B. 2885 degree )< D. 2945 degree K

Solutron .

67. An engineer inspected an air-conditioning unit. He found out that the unit does not produce any cooling effect, however, the air-conditioning unit is running. He checked the temperatures of the condenser and evaporator and had the unit run. He found out that there was no change in the temperature What should he do? A. replace fuse C. replace relay B. charge with new refrigerant (ans) D. adjust door seal

Using the Psychrometric Chart: at 308°K (3S°C) and 40% RH Dew Point Ternperature > 19.5°C (292,SoK)

j

,

PB -168

ME BOARD OCTOBER 2000

ME BOARD OCTOBER 2001

74. What is the part of an oil pressure governor that is used to continuously draw oil for as long as the turbine is working? A. speed governor C. governing device B. servomotor D. gear pump (ans)

MECHANICAL ENGINEER Licensure Examination Monday, October 8, 2001

PB -169

8:00 AM - 4:00 PM

POWER AND INDUSTRIAL PLANT ENGINEERING

75. A hot block is cooled by blowing cool air over its top surface. The heat that is first transferred to the air layer close to the block is by conduction.

It is eventually carried away from the surface by

A. convection (ans) C. conduction B. radiation D. thermal radiation

SET A

MULTIPLE CHOICE 1.

If a liquid is heated in a container, then it expands and becomes less dense and lighter. It rises upward to the container because of its reduced density and replaced by colder fluid. If the process continues, heat is transferred and distributed throughout. What is this mode of heat transfer? A. radiation C. conduction B. condensation D. convection (ans)

77. In order to avoid cavitation the NPSH of an installation should be at least _ _ _ _ than the NPSH of the pump. A. equal or greater (ans) C. greater B. equal or lower D. lower

2.

If the bypass factor of the cooling tower for one row is 0.7. What is the bypass factor of 10 coils in one row? A. 0.7 (ans) C. 0.028 B. 7 D. 0.49

78. Ice produces what poisonous substance: C. Hydrogen A. SUlphur dioxide (ans) B. Carbon dioxide D. f'litrogen

3.

A steam boiler on a test generates 885,000 Ib of steam in a 4-hr period. The average steam pressure is 400 psia, the average steam temperature is 700°F (h = 1362.7 Btu/lb) and the average temperature of the feedwater supplied to the boiler is 280°F (h = 249.1 Btu/lb). If the boiler efficiency for the period is 82.5%, and if the coal has a heating value of 13,850 Btu per Ib as fired, find the average amount of coal burned in short tons per hour. (ME Bd. Apr 97) A. 8.85 C. 11.80 B. 9.85 D. 10.75 (ans)

76. The heating value obtained when the water in the products of combustion is in the liquid state: A. higher heating value (ans) C. lower heating value B. calorific value D. average heat value

Solution: ms

=

885.000 Ib == 221,250 Ib/hr 4 hr

BoilerEff 0.825

J

=

ills(h 2-h 1) illfQh

=

221,250(1362.7--249.1) illf(13,850) 21,563 Ib/hr

rn,

=

rn,

= 21563

Ib short ton -x hr 2000 Ib

= 10.78shorttonsperhr

:,.,. PB -170

ME BOARD OCTOBER 2001

ME BOARD OCTOBER 2001

Solution:

4. In steady flow of fluids, velocity at a section at the stream lines remains

A. uniform (ans) B. unsteady

PB - 171

COP C. equal D. constant

=

QA We

COP 5. An equipment used to cool the back pressure in the steam turbine generating steam and convert steam to water. A. cooling tower C. separator B. condenser (ans) D. gas engine

=

22kw

7.5hpx()·71 6.j<\v.

= 3.93

hp

13. The relative humidity become 100% and where the water vapor starts to condense. A. dew point (ans) C. dry bulb B. wet bulb D. saturated

6. In thermodynamic law PV raised to n is constant: A. adiabatic C. isobaric B. isentropic D. polytropic (ans)

14. A 45 HP motor runs at 74% efficiency, what is the watts per hp rate? A. 746 C. 1008.1(ans) B. 552 D. 486

7. If the combustion chamber is concern. What will happen if the power output is increase? A. decrease the combustion time (ans) B. increase the combustion chamber volume C. decrease the combustion chamber volume D. increase the combustion time

Solution: Motor Eff

8. Amount of heat surface to cooled, is the amount of heat absorbed by the cooling coils. C. refrigerating effect (ans) A. enthalpy B. compression D. flow work

0.74

=

Power Output Power Input

=~ Pin

Pin

= 60.81

Rate

9. What is the head develop if the pump that has a capacity of 0 1 and head H1 connected in series with another pump with a capacity of O 2 and H 2 , if O 2 is less than 0 1 ? A. H1 + H2 (ans) C. H1 H 2 D. H 1/H 2 B. H 1- H2

=

HP

60.81 HPx 746W HP

45HP

= 1008.1 ~ HP

15. What is that one main part of an equipment, through the air movement of the ventilation, heating, refrigerating and also used to discharge to the ventilating outlet? A. duct C. blower (ans) B. dehumidifier D. strainer

=

10. Which of the following cycle is for a spark-ignition reciprocating engine? A. Diesel cycle C. Dual cycle B. Rankine cycle D. Otto cycle (ans)

16. Where thus the percentage of moisture and refrigerant-vapor in the absorption last rejected? A. analyser C. generator B. condenser D. rectifier (ans)

11. Room air-conditioning needs abundant supply of air, beca use it uses what type of condenser? A. chilled water system C. shell and tube D. air cooled (ans) B. water cooled

(KENT's Handook p. 11-33)

12. A system needs 7.5 HP to compress a liquid, 22 kw was extracted from the cooled space. What is the coefficient of performance ? A. 3.63 C. 4.74 D. 4.55 B. 3.93 (ans)

~

17. A 25 cm x 38 cm cylinder, 4-stroke and 4-cylinder engine running at 260 rpm. The engine rate is 150 kw. Determine the engine displacement per brake power. A. 0.231 C. 0.001 (ans)

B 0.098 D. 0.153

PB -172

ME BOARD OCTOBER 2001

ME BOARD OCTOBER 2001

Solution: Vo

PB -173

Solution:

= ~D2LNxC = ~(0.25)2(0.38)( 260 J4 = 0.16166 m 4 4 2x60

3/sec

m/(

Vo = 0.16166 = 0.001 BP 150 kw

18. To obtain equilibrium in the condenser, what should be the range of the tower, in relation to the temperature difference in the condenser.

.A. should be higher C. should be lesser

B. indirectly proportional D. it should be equal (ans) 19. A refrigeration system operates on an ideal vapor compression using R­ 12 with a saturated temperature of -UDC,(h g = 351.003 kJ/kg) and a DC liquid R-12 temperature at 30 (hI = 288.54 kJ/kg). What is the refrigerating capacity in tons of refrigeration if R-12 mass flow rate is 0.1 kg/sec? A. 21.53 C. 6.20 D. 3.67 B. 1.78 (ans) Solution: Refrigerating Capacity

= m(h 1 -

h4 )

= 6.2463 kw x

= m(h 2 -

h.)

= 0.09(208.65 -

180.8)

= 2.5056 kw

OA = m(h 1 - h4 )

10.21 = 0.09( 180.8 - h4 )

h4 = 67.35 kJ/kg

OR

= m(h 2 - h 3 )

= 0.09(208.65 = 12.717 kw

67.35)

QR _ 12.717 - 5

---- We 2.5056

23. Heat pump used to control the room temperature. Inside temperature is 20°C and outside temperature is -5°C. Room losses of 100,000 kw, determine the power of the pump needed. A. 8532.5 kw (ans) C. 9528.1 kw B. 9235.7 kw D. 10,500 kw

Solution:

= 0.1(351.003 - 288.54) = 6.2463 kw Refrigerating Capacity

We

ton of ref 3.516 kw

= 1.776 ton of ref

20. An energy conserved device which utilize air and water as a cooling medium. And used as a cooling tower and condenser as one. A. shell and tube C. air cooled condenser B. evaporative (ans) D. water cooled 21. Water regulating valve should be located or installed in a refrigerating system. A. at the suction line to the compressor B. anywhere in the system C. at a line to the condenser (ans) D. at the expansion valve 22. A refrigeration cycle having 0.18 Mpa (hg = 180.8 kJ/kg) and 0.8 Mpa (h = 208.65). The mass flow rate in the cycle is 0.09 kg/sec with 10.21 kw rate of heat removal. Determine the heat rejected per power. A. 5 (ans) C. 7 B. 6 D.9

OR

= 100,000 kw

T1 T2

= -5°C = 268°K

= 20°C = 293 0K

OR = T 2f1S

100,000 = 293(""S)

""S = 341.3 kwfK

OA

= T1 (f1S)

=

268 (341.3)

= 91,467.58 kw

We = OR - OA = 100,000 - 91,467.58 24. Viscosity is a measure of: A. volume B. temperatu re

= 8532.42 kw

C. thickness (ans) D. pressure

25. When required, the water regulator valve should be on: A. water inlet (ans) C. suction at compressor vessel B. water outlet D. anywhere

PB -174

ME BOARD OCTOBER 2001

26. The divergent section of the nozzle is subsonic or supersonic, supersonic is: A. less than unity C. near unity B. unity D. greater than unity (ans) (KENT's Handbook p. 15-28) Supersonic flow when M > 1.0

Subsonic flow when M < 1.0

M - Mach Number

27. Moving air reduces bodies warm temperature and humidity. This process is a combination of evaporation and ' A. heat transfer C. radiation B. conduction D. convection (ans) 28. What is the temperature between the hot entering the cooling tower and leaving at a cold temperature in a cooling tower? A. cooling range (ans) C. approach B. net wet bulb temperature D. wet bulb temperature 29. In a flow of fluids through channel wherein the velocity changes along the length of a channel from point to point on the account of changing its depth, width and direction of flow is: A. constant flow C. unsteady flow B. non uniform flow (ans) D. uniform flow 30. A steady flow device used to increase pressure by slowing down the fluid. A. turbine C. generator B. diffuser D. nozzle (ans) 31. The temperature at which oil gives off vapor that burns temporarily when ignited: A. dew point C. wet bulb D. flash point (ans) B. drop point 32. The length of pipe 150 m. If the pressure drop is 40 kPa per 20 m length. What is the total pressure drop? A. 300 kPa (ans) C. 280 kPa B. 240 kPa D. 160 kPa Solution: 40kPa x 150m 20m

= 300 kPa

ME BOARD OCTOBER 2001

PB -175

33. The quantity of heat from the outside to be cooled at desired temperature which can be used to determine in an air condition unit: A. specific heat C. latent heat B. sensible heat D. cooling load (ans) 34. A component used in absorption refrigeration so that the vapor from the evaporator is coming into contact with the weak liquor is absorbed. C. heat exchanger A. Absorber (ans) B. evaporator D. generator

PB ·176

ME BOARD APRIL 2002

ME BOARD APRIL 2002

MECHANICAL ENGINEER Licensure Examination Saturday. April 13, 2002

Volume displacement per brakepower 8:00 AM - 4:00 PM

POWER AND INDUSTRIAL PLANT ENGINEERING

SETA

INSTRUCTION: Select the correct answer for each of the following questions. Mark only one answer for each item by shading the box corresponding to the letter of your choice on the answer sheet provided. STRICKLY NO ERASURES ALLOWED. Use pencil NO.1 only. MULTIPLE CHOICE 1. For supersonic and subsonic divergent nozzle, what 'is the Mach number for supersonic: C. 1 A. greater than 1 (Ans) B. less than 1 D.O 2. In replacement studies, the existing process on piece equipment is known as the: C. waste material A. retired equipment (Ans) B. defender D. challenger 3. Fluid which exhibits linear stress-strain rate relationship: C. Mercury A. Newtonian fluid (Ans) B. semi-solid D. acidic fluids 4. One mode of heat transfer that occurs in a material due to molecular motion in the material where a temperature gradient exists. The mode of heat transfer is called: C. convection A. conduction (Ans) B. radiation D. transformation 5. Two pumps are connected in series, if 0 1 is the discharge of Pump 1 and O2 is the discharge of Pump 2 where O2 < 0 1 • what is the discharge? C. 0 1 +0 2 A. O 2 (Ans) B. Q 1 D. 0 1/02 6. A 20 cm x 35cm diesel engine with 4 cylinders and operating on a four stroke, has a rated power of 160 kw and is running at 250 rpm. Find the volume displacement per brakepower developed. A. 0.9 cu.rn/rnin-kw C. 0.06 cu.m/min-kw B. 0.1 cu.m/min-kw D. 0.0344 cu.m/min-kw (Ans) Solution:

v, = ~

(0.20)2(0.35)(2;°)4)

=5.498 cu.rn/rnin

PB -177

--_._­

= 5.498 = 0.0344 cu.m/min-kw 160 7. What cycle is used for vapor cycle in power plant? A. Brayton cycle C. Ericson cycle B. Diesel cycle D. Rankine cycle (Ans) 8. What is the BTU equivalent for one horsepower? A. 778 C. 746 B. 2545 (Ans) D, 3.41

(Note: One Hp = 2545 Btu per hr)

9. If Oa is the actual discharge flow and Ob is the theoretical discharge flow, what will the coefficient of discharge be equal to during positive displacement slip? A. Qa x Qb C. Qa/Qb (Ans) B. Ob/Qa D. 1 - Oa/Ob 10. What is the unit of electromagnetic wave frequency? A. volts C. hertz (Ans) B. horsepower D. knot 11. At 101.325 kPa, the boiling point decreased, the boiling temperature A. increase B. decrease (Ans)

of water is 100"C. If the pressure is will C. remain the same D. greater than

12. The temperature at which lubricating oil will form a cloud. C. critical point A. cold point (Ans) D. boiling point

B. pour point (Accurate term is cloud point)

13. What is the pressure above zero? A. gage pressure (Ans) B. absolute pressure

C. vacuum pressure D. atmospheric pressure

14. Tidal power plant is attractive because it has A. low head and intermittent power B. cheap energy source (Ans) C. high head D. expensive energy source 15. A high temperature source at 950 OK provides 580 KJ heat to a heat engine. The heat engine conver 200 KJ net work and rejects the balance to a temperature sink at 295 OK. Compare the thermal effictency Ft of

ME BOARD APRIL 2002

ME BOARD APRIL 2002

PB -178

this engine to the thermal efficiency Erev of the Carnot cycle reversible heat engine. C. Erev < Et A. Et = Erev D. Not equal B. Et < Erev (Ans)

Q.

Erev =

200 580

T 1-T2 T1

Therefore:

= 0.345 950 - 295 950

= 0.689

Et < Erev

16. How many tons of refrigeration in Btu/24 hours? A. 288,000 (Ans) B. 28,800

22. Using the Psychometric Chart, what is the enthalpy at dry bulb temperature of 308 degrees Kelvin and relative humidity of 40%? A. 70.6 C. 74.6 B. 71.6 (Ans) D. 75.6 Solution: From psychometric chart, at 308K(35°C) dry bulb and 40% RH: h = 71.6 KJ/kg

Solution:

Et = ~ =

PB - 179

C. 290,000 D. 29,000

23. The ideal cycle based on the concept that the combustion process is both diesel and gasoline in the combination of heat transfer processes that is constant pressure and constant volume. A. Ericson cycle C. Brayton cycle B. Dual cycle (Ans) D. Rarkine cycle 24. What is the value of air stratification in air conditioning design fit for human comfort? C. less than air temperature (Ans) A. minimum D. equal to air temperature B. maximum

Solution: One ton ref = 12,000 Btu/hr

= 12,000(24)

= 288,000 Btu/24 hrs.

17. R - 22 is A. dichlorodiflouromethane B. methyl chloride C. monochlorodiflouromethane (Ans) D. trichlorodiflouromelhane

18. One N - m is equal to one A. Joule (Ans) B. Btu

C. Calorie D. watt

19. Instrument used to measure fluid velocity C. manometer A. Pitot tube (Ans) B. Orsat apparatus D. speedometer 20. It prevents the refrigerant from the condenser to go back to the compressor

C. expansion valve A. check valve (Ans) D. low side float B. float switch 21. Gauge cock in the boiler is designed to determine A. level of steam C. level of water (Ans) B. specific heat D. pressure

25. A refrigeration plant stored 8 metric tons of eggs at a temperature of 15°C. To preserve the eggs by not spoiling them, they have to be cooled at -8°C. What is the refrigerating capacity of the plant in tons, if it is cooled in 12 hours? The specific heat of the eggs above and below freezing is 0.95 kcal/kg-OC and 0.4 kcal/kg-OC respectively. The latent heat of fusion is 68.5 kcallkg. The freezing temperature is -3°C. A. 15.5 tons C. 23.4 tons B. 19.3 tons (Ans) D. 29.8 tons Solution: Refrigerating Capacity =

8(1000)

12

[0.95(15 + 3) + 68.5 + 0.4(-3 + 8)]

= 58,400 kcallhr = =

58,400(4.187) 3600

67.9 3.516

= 67.9 kw

= 19.3 tons ref.

26. A refrigeration plant stored 8 metric tons of eggs at a temperature of 15°C. To preserve the. eggs by not spoiling them, they have to be cooled at -8°C. What is the refrigerating capacity of the plant in kcal? The specific heat of the eggs above and below freezing 0.95 kcal/kg-OC and 0.4

PB -180

>

ME BOARD APRIL 2002

kcal/kg-OC respectively. The latent heat of fusion is 68.5 kcal/kg. The freezing temperature is -3°C. A. 180,000.6 C. 14,000.2 B. 700,800 (Ans) D. 142,000

ME BOARD APRIL 2002 33. Which of the following is/are compressed in gasoline engines? A. only air C. both air and fuel (Ans) B. only fuel D. neither air nor fuel 34. Capillarity results from:

A. turbulent flow B. surface tension (Ans)

Solution:

Refrigerating capacity = 8(1000)[0.95(15 + 3) + 68.5 + 0.4(-3 + 8)]

= 700,800 kcal

27. If PV id the power required for a vapor-compression refrigeration system, then what is the power required for an air refrigeration system, assuming

that they have same capacity? A. 5 PV (Ans) C. PV/10 B. 2 PV D. 1/PV

PB -181

C. low fluid pressure D. inadequate compaction

35. A fluid flows at a constant velocity in a pipe. The fluid completely fills the pipe, and the Reynolds number is such that the flow is just subcritical and laminar. If all other parameters remain unchanged and the viscosity of

the fluid is decreased a significant amount, one would generally expect

the flow to:

C. become more laminar A. not change D. increase B. become turbulent (Ans)

'i'

(Power in air-refrigeration system is five times that for a vapor­ compression refrigeration system for the same refrigerating capacity) n

28. Thermodynamic process following the law PV = constant: A. isentropic C. adiabatic B. polytropic (Ans) D. isobaric 29. At which temperature would air be able to hold the most water vapor? A. 5 DC C. 20 DC DC B. 15 D. 40°C (Ans) , Ii The highest temperature among the given will give the most water vapor. 30. Heat absorbed by a liquid in changing it to gas. A. heat of fusion C. calorie B. heat of vaporization (Ans) D. heat of condensation 31. Heat added to warm 1 g of water to 1DC. A. 1DC C. Celsius B. calorie (Ans) D. Joule

Ii

I I

I II

32. Find the number of calories needed to change 20 g of ice at OD C to steam D 100 C? A. 2000 cal C. 20,000 cal B. 14,400 cal (Ans) D. 25,000 cal

I

Solution: I

Q

= 20(80) + 20(1.0)(100)+ 20(540) = 14,400 cal

I

,

PB -182

ME BOARD OCTOBER 2002

MECHANICAL ENGINEER Licensure Examination Tuesday, October 8, 2002

linE BOARD OCTOBER 2002 8:00 AM - 4:00 PM

POWER AND INDUSTRIAL PLANT ENGINEERING

V2

INSTRUCTION: Select the correct answer for each of the following questions. Mark only one answer for each item by shading the box corresponding to the letter of your choice on the answer sheet provided. STRICKLY NO ERASURES ALLOWED. Use pencil No.1 only. MULTIPLE CHOICE: 1. In hydraulics, the length of the channel which has water contact. A. wetted perimeter (Ans) C. wet well B. weir D. water table 2. If E is the efficiency and if K is the maximum kinetic energy attained, what is the actual kinetic energy? A. KE (ans) C. K+ E D.

!

K

>

0.02

A2

*(0.12)2

= 25

o

= 1.768m/s

1

+ (1.768)~ -(0.9947)~ 2(9.81)

Water Power

= Q d H = 0.02

= 25.1 m (9.81) (25.1)

= 4.92 kw

Input Power (Brake Power) = 4.92 + 2 = 6.92 kw 5. The latent heat of vaporization decreases as the pressure and temperatun­ of the liquid increases, at the critical point the heat of vaporization _ A. decreases C. becomes zero (ans) B. constant D. increases 6. A fluid flowing in a reversible adiabatic deceleration to zero velocity will

reach a state of:

A isentropic expansion B. isentropic stagnation (ans) C. isentropic compression D. adiabatic irreversibility Engineering Thermodynamics(4 th Ed) by Burghardt p. 682

Solution: Eff

Q -=

SETA H

B. K E

=

output = K actual

input K (max imum)

K actual = EK (maximum)

3. What is the temperature range of air in an air conditioning application where in that range dr~ air can be considered as an ideal gases? DC A.100-125C C.75-100 B. 50 - 75 DC D. 10 - 50°C (ans) 4. Water is to be raised to a height of 25 m at 20 kg/so Inlet diameter is 16 cm, exit diameter is 12 cm and heat loss is 2 kw. Determine the power input to the pump. C. 7.5 kw A. 6.9 kw (ans) D. 9.7 kw B. 3.4 kw

7. One Newton-meter per second is an SI derivation unit known as:

A pascal C. watt (ans)

B. joule D. kilojoule 8. The helpful consequence of nitrogen, one of the composition of air, it

prevents rapid combustion. This combustion process, nitrogen and the

element of fuel will:

A does not react (ans)

C. mix spontaneously B. slowly mix D. react 9. What would be the velocity at all points in the pipe?

A unity C. steady

B. constant D. equal (ans) Assuming that the pipe is uniform and the fluid is incompressible, the velocity at all points are equal.

Solution:

Q

m _~ = 0.02 m 3/s = -;;--1000

V1

Q 0.02 = ~= ~(0.16)2 = 0.9947 m/s 4

10. What part of the unloader that maintains the pressure? A suction valve C. discharge valve B. manifold D. exhaust pipe DC and rejected 11. An DC engine gains 493 kJ of heat from a heat source at 600 at 30 What is the amount of heat rejected? ­

,

--

PB -184

A. 171.3 kJ (ans) B. 175.4 kJ

= I1S (T 1 )

493 I1S

= 0.5647 kJ/kg

= I1S(600 + 273)

=

0.5647 (30 + 273) 171.1 kJ

1

QA

T 1 =T 4

Vo

:02

T 2=Tr

= I1S (T 2)

QR

I

83 = 84

81 = 82

8

t4 )

T

I t

Therefore, if the load is decreased the exhaust temperature (t4 ) increases.

I

W T = m(h 1 - h2) nT 4500 m(1140.9) 0.70

m = 5.63 kg/s

=

=

1; ~

5.63465~x 3600 sec sec hr

4500 kw

kg

= 4.5 kw-hr

14. A single-acting, four cylinder, 4-stroke cycle diesel engine with a bore to stroke of 21.59 x 27.94 em, operating at 275 rpm, consumes 8.189 kg/hr of fuel whose heating value is 43,961.4 kJ/kg. The indicated mean effective pressure is 475.7 kPa. The load on the brake arm, which is 93.98 cm is 113.4 kg. What is the brake arm mean effective pressure in kPa?

Pm b

J(4)

=

=

113.4(0.00981 )(0.9394)

=

2nTN

Torque

=

275

2x60

(2:14) D2LNC

BrakePower

YD

=

-=

0.09376 m 3/sec

= 1.045 KN-m

275 \

2n(1.045) ( -

I

60 )

=

30 kw

30 = 319.97 kPa 0.09376

15. A steam reciprocating pump has a nameplate df 8 in x 6 in x 10 in. What is the steam bore equal to: A. 6 in C. 48 in D. 10 in B. 8 in (ans) 16. In a gas, which flow into an expansion control and without doing any work. This process is called: A. condensing C. priming B. throttling (ans) D. knocking

13. The available energy of a turbine is 1140.9 kJ/kg, efficiency of the engine is 70% and power output at full load is 4500 kw. What is the turbine flow rate at full load in kg/kw-hr? A. 4.09 C. 4.501 (ans) B. 5.185 D. 3.975 Solution:

=

=

piston volume displacement

Brake Power

t, - exhaust temperature

Turbine flow rate

=

\. 4

Solution:

= mCp(t 3 -

C.319.95 D.645.53

= (~) (0.2159)2(0.2794)(

12. If the load is decreased in a gas power plant, the exhaust temperature: A. increases (ans) C. constant B. decreases D. unity

WT

PB - 185

Solution:

T

QA

=

A. 415.20 B. 124.17

C. 179.8 kJ D. 295.5 kJ

Solution:

QR

ME BOARD OCTOBER 2002 ---------------------

ME BOARD OCTOBER 2002

17. What is the refrigeration control use to protect the compressor from overloading due to the loads from warm and defrosting in the evaporator. A. overload relay B. condenser C. expansion valve D. thermostatic expansion valve (ans)

18. In a gas turbine unit, energy entering mass of 4 kg. Energy leaving the turbine loss is 10 kJ. What is the turbine work? A. 171.2 kJ C. B. 258.2 kJ D.

is 600 kJ/kg at 250 m/sec and a is 486 kJ/kg at 170 m/sec. Heat 356.2 kJ 513.2 kJ

Solution: WT

= m(h 3 - h4 )

+ m(Y}-Yl) 2

- QL

,

PB -186

-----

ME BOARD OCTOBER 2002

= 4(600 - 486) +

~1(250)2 - (170)2 J

ME BOARD OCTOBER 2002

_ 10

A.

E =

2(1000)

=

456 + 67.2 - 10

=

513.2 kJ

B.

E

Q

C. E = QmD (ans)

md D

D. E = mOlD

Qm 19. What is the minimum piping size of bottom blow down line? A. % in (ans) C. 2 % in B. 3/8 in D. 1 in

27. In a compression-ignition engine what is being compressed is: A. fuel C. combustible material B. air (ans) D. fuel & air

From PSME Code (1983) p. 124 20. In a uniform steady flow, the velocity at all points is :-A. constant C. equal (ans) B. increasing D. decreasing

_

21. Vapor passing through the compressor is superheated by heat: A. from the condenser C. due to compression (ans) B. from the evaporator D. by the lubrication 22. The heat required to change a substance from solid to liquid state without change the temperature is latent heat of: A. vaporization C. fusion (ans) B. condensation D. evaporization 23. If A is the cross section of the flow and Pw is the wetted perimeter, then the hydraulic head, Hd, is equal to: Pw A C. Hd (ans) A. Hd A Pw D. Hd B. Hd = PwxA Pw-A

=

PB -187

=-

=

24. In a francis turbine, power is controlled by actuating the movable wicket gates and the runner vanes are not. What load obtained a high efficiency? A. at half load C. any load B. at full load (ans) D. all of these 25. Refrigerants that are commonly used have almost the same HP requirements and coefficient of performance except carbon dioxides, because of carbon dioxides: C. very high critical point A. very low critical point D. high toxicity B. very low HP requirement per ton

I

28. In thermodynamics cycle, a process which represented by an equation PV to the n is constant, if n = O. A. adiabatic process C. isobaric process (ans) B. volume is constant D. isentropic process 29. What would be the result if there is shortage of refrigerant in the refrigerating system? A. high head and back pressure(ans) C. high head B. low head and back pressure D. high back pressure 30. Expansion valve used to regulate the refrigerant flow to the evaporator in order to: A. reduce refrigerant vapor C. reduce liquid refrigerant (ans) B. increase liquid refrigerant D. decrease refrigerant vapor 31. Which of the following units of energy is mainly used by reaction turbine? A. heat C. potential energy B. work D. kinetic energy (ans) 32. The pressure of air in the air receiver is 1035 kPa and has a 4450 N force. Determine the piston diameter that can support this force. A. 7.39 cm (ans) C. 11.92 cm B. 10.52 cm D. 9.34 cm Solution: F P = ­ A

1035,000

=

4450

-"-D2 4

Kents Handbook, p. 11-17, (Power Volume) D 26. If D is the height between elevation in feet, 0 is the volume of fluid in gallons and m is the weight of fluid in Ib per gallon. What is energy E is required to raised the given volume fro1'n a lower to a higher elevation?

= 0.07398 m = 7.398 cm

33. E 1 is the water that evaporates from the cooling tower. E 2 is the water blowdown and wastes of the cooling tower. How much make-up water will is needed in the cooling tower?

PB -188

ME BOARD OCTOBER 2002

A. E 1 + E 2 (ans)

C. E 1 X E2

-.S

B.

D. E 2

E1

F2

34. Which of the following operates entirely on manual operations? A. sludge pump C. deep well pump B. reciprocating pump (ans) D. centrifugal pump 2

35. Determine the height equivalent in meters of 50 kN/m of water. A. 5.1 m (ans) C. 7.1 m D. 8.1 m B. 6.1 m Solution:

H

=

P w

=

50

9.81

=

5.0968 m

36. In a certain process, energy entering energy leaving is 1080 kJ/kg, determine the A. 493 m/s C B. 567 mls D.

is 1200 kJ/kg and 60 m/s. If the velocity at the exit? 685 mls 965 mls

Solution:

vi

V2

h

+_1

1

= h2

2(1000) 2

1200 +

(60)

2(1000)

V2 37. Pumps A. B. C. D.

+ 2(1000)

= 1080

+

vi 2(1000)

= 493.558 m/s installed in parallel. What;s the head? Either h 1 or h 2 (ans) the difference of the pump heads only head of pump 1 only sum of the pump heads

38. Moisture content of air is equal to the content of dry air at 100% relative humidity. If further, there are moisture drop caused by: A. condensation of some of the moistures of refrigerant B. evaporation of some of the moistures of refrigerant C. condensation of some of the moistures of air (ans) D. evaporation of some of the moistures of air