Ipe Problems.docx

1. An air compressor consumed 1200 kw-hr per day of energy. The electric motor driving the compressor has an efficiency of 80%. If indicated power of the compressor is 34 kw, find the mechanical efficiency of the compressor. A. 117.65 % B. 75 % *C. 85 % D. 90 % Solution: P/m = 1200kw-hr/24 hrs = 50 kw BP = 50(0.80) = 40 kw em = 34/40 = 85 % 2. An air compressor has a power of 40 kw at 4 % clearance. If clearance will increase to 70 %, what is the new power? A. 70 kw *B. 40 kw C. 53kw D. 60 kw Solution: The power of compressor will not be affected with the changes in clearance. Therefore the power will still be 40 kw. 3. What is the hydraulic gradient of a 1 mile, 17 inches inside diameter pipe when 3300 gal/min of water flow with f…. 0.03 *A. 0.00714 B. 0.00614 C. 0.00234 D. 0.00187 Solution: v = (3300/7.481)/(π/4)(17/12)2(60) = 4.66 ft/s L = 1 mile = 5280 ft hL =fLv2/2gD = 0.03(5280)(4.66)2/2(32.2)(17/12) = 37.7 ft Hydraulic gradient = 37.7/5280 = 0.00714 4. Find the loss of head in the pipe entrance if speed of flow is 10 m/s. A. 5.10 m B. 10.2 m C. 17.4 m *D. 2.55 m Solution: Loss at entrance = 0.5 (v2/2g) = 0.5[102/ 2(9.81)] = 2.55 m A three stages air compressor compresses air from 100 kpa to 1000 kpa. Find the intercooler pressure between the first and second stage. A. 505.44 kpa B. 108.44 kpa C. 316.23 kpa *D. 215.44 kpa Solution: Px = (P12P2)1/3 Px = [(100)2(1000)]1/3 = 215.44 kpa A 10-stages air compressor compresses air from 100 kpa to 800 kpa. Find the intercooler pressure between 1st and 2nd stage. A. 282.84 kpa B. 113.21 kpa *C. 123.11 kpa D. 333.51 kpa Solution: Px = (P1s-1P2)1/s Px = [(100)10-1(1000)]1/10 = 123.11 kpa A 3-stages air compressor compresses air from 100 kpa to 700 kpa. Find the intercooler pressure between the 2nd and 3rd stage. *A. 365.88 kpa B. 375.88 kpa C. 385.88 kpa D. 395.88 kpa Solution: Px = (P12P2)1/3 Px = [(100)2(700)]1/3 = 191.28 kpa Px/P1 = Py/Px Py = Px2/P1 = (191.28)2/100 = 365.88 kpa The discharge pressure of an air compressor is 5 times the suction pressure. If volume flow at suction is 0.1 m3/sec, what is the suction pressure if compressor work is 19.57 kw? (use n=1.35) A. 97 kpa*B.98 kpa C. 99 kpa D.100 kpa SOLUTION: W= [(P2/P1)n-1/n – 1] 19.57 = 1.35(P1)(0.1)/(1.35-1)[(5)1.35-1/1.35 – 1] P1 = 98 KPa

The initial condition of air in an air compressor is 98 KPa and 27C and discharge air at 450 KPa. The bpre and stroke are 355 mm and 381 mm, respectively with percent cleared of 8% running at 300 rpm. Find the volume of air at suction. A. 541.62 m3/hr B. 551.62 m3/hr C. 561.62 m3/hr *D. 571.62 m3/hr SOLUTION: ev = 1 + c – c(P2/P1)1/n = 1 + 0.08 - 0.08(450/98)1/1.4 = 0.842 VD = D2 LN = (0.355)2 (0.381)(300/60) = 0.1885 m3/sec V1 = 0.1885(0.842) = 0.15878 m3/sec = 571.62 m3/hr An air compressor has a suction volume of 0.35 m3/sec t 97 KPa and discharges to 650 KPa. How much power saved by the compressor of there are two stages? A. 18.27 KW B. 16.54 KW C. 13.86 KW *D. 11.58 KW SOLUTION: W= [(P2/P1)n-1/n – 1] = (1.4 x 97 x 0.35)/(1.4 -1) [(650/97)1.4-1/1.4 – 1] = 85.79 KW For two stages : Px = (P1P2)1/2 = (97 x 650)1/2 = 251.097 KPa W= [(Px/P1)n-1/n – 1] = 2(1.4)(97)(0.35)/(1.4 – 1) [(251.0.97/97)1.4-1/1.4 – 1] = 74.208 KW POWER SAVED = 85.79 – 74.208 = 11.582 KW A twop stage air compressor has an intercooler pressure of 4 kg/cm2. What is the discharge pressure if suction pressure is 1 kg/cm2? A. 3 kg/cm2 B. 9 kg/cm2 C. 12 kg/cm2 *D. 16 kg/cm2 SOLUTION: Px = (P1P2)1/2 Px2 = P1(P2) 42 = 16 kg/cm2 A two stage air compressor compresses air at 100 KPa and 22C discharges to 750 KPa. If intercooler intake is 105C. Determine the value of n. A. 1.400 *B. 1.325 C. 1.345 D. 1.288 SOLUTION: Px = (100 x 750)1/2 =273.86 KPa Tx/T1 = (Px/P1)n-1/n (105 + 273)/(22 + 273) = (273.86/100)n-1/n 1.281 = (2.6268)n-1/n n = 1.326 A single acting compressor has a volumetric efficiency of 89%, operates at 500 rpm. It takes in air at 900 KPa and 30C and discharges it at 600 KPa. The air handled is 8 m3/min measured at discharge condition. If compression is isentropic, find mean effective pressure in KPa. *A. 233.34 B. 973.17 C. 198.34 D. 204.82 SOLUTION: P1V1K = P2V2K 100(V11.4) = 600(6)1.4 V1 = 28.768 m3/min VD = 28.768/0.89 = 32.32 m3/min W = n P1V1/n-1 x [(P2 / P1)n-1/n – 1] = [(1.4 x 100 x 32.32)/(1.4 – 1)] x [(600/100)1.4-1/1.4 – 1] W = 7562.19 KJ/min W = Pm x Vd 7562.19 = Pm x 32.32 Pm = 233.34 KPa

A water-jacketed air compressed handles 0.343 m3/s of air entering at 96.5 KPa and 21C and leaving at 460 KPa and 132C; 10.9 kg/h of cooling water enters the jacket at 15C and leaves at 21C. Determine the compressor brake power. A. 26.163 KW *B. 62.650 KW C. 34.44 KW D. 19.33 KW SOLUTION: T2/T1 = (P2/P1) n-1/n (132+273) / (21+273) = (480/96.5)n-1/n n = 1.249 W = (1.249 x 96.5 x 0.343) / (1.249-1) [(480 / 96.5)1.249-1/1.249 – 1] W = 62.57 KW Q = heat loss = mcp(t2 – t1) = (10.9/3600)(4.187)(21 – 15) 0.075 KW Brake power = W + Q = 62.57 + 0.076 = 62.65 KW A double suction centrifugal pumps delivers 20 ft3/sec of water at a head of 12 m and running at 650 rpm. What is the specific speed of the pump? A. 5014.12 rpm B. 6453.12 rpm *C. 2770.73 rpm D. 9966.73 rpm SOLUTION: N = N(Q)1/2 / h3/4 Q = 20/2 ft3/sec x 7.481 gal/ft3 x 60 sec/1min = 4,488.6 gal/min h = 12 x 3.281 = 39.37 ft N = (650 x (4,488.6)1/2)/(39.37)3/4 N = 2,770.73 rpm Determine the number of stages needed for a centrifugal pump if it is used to deliver 400 gal/min of water and pump power of 15 Hp. Each impeller develops a head of 30 ft. A. 6 B. 4 *C. 5 D. 7 SOLUTION: Wp = w Q h 15 x 0.746 = 9.81(400 gal/min x 0.00785m3/gal x 1/60)h h = 45.20 m x 3.281 ft/m = 148.317 ft Number of stages = 148.317/40 = 4.94 stages = 5 stages The suction pressure of a pump reads 3 in. of mercury vacuum and discharge pressure reads 140 psi is use to deliver 120 gpm of water with specific volume of 0.0163 ft3/lb. Determine the pump work. A. 4.6 KW B. 5.7 KW *C. 7.4 KW D. 8.4 KW SOLUTION: P1 = -3 in Hg x 101.325/29.92 = -10.16 KPa P2 = 140 psi x 101.325/14.7 = 965 KPa w = 1/v = 1/0.163 = 61.35 lb/ft3 x 9.81/62.3 = 9.645 KN/m3 h = (P2 – P1)/w = (965 +10.16)/9.645 = 101.105 m Q = 120 gal/min x 3.785/1gal x 1m3/1000li x 1/60 = 0.00757 m3/sec P = w Q h = 9.645(0.00757)(101.105) = 7.38 KW A submersible pump delivers 350 gpm of water to a height of 5 ft from the ground. The pump were installed 150 ft below the ground level and draw down of 8 ft during the operation. If water level is 25 ft above the pump, determine the pump power. A. 7.13 KW B. 4.86 KW C. 7.24 KW *D. 9.27 KW SOLUTION: h = 5 + 150 – (25 – 8) = 138/3.281 = 42.06 m Q = 350 gal/min x 0.003785 m3/gal x 1 min/60sec = 0.02246 m3/sec Wp = w Q h = 9.81(0.02246)(42.06) = 9.27 KW A vacuum pump is used to drain a flooded mine shaft of water. The pump pressure of water at this temperature is 2.34 KPa. The pump is incapable of lifting the water higher than 16 m. What is the atmospheric pressure? *A. 159.30 B. 32.33 C. 196.22 D. 171.9

SOLUTION: Using Bernoulli’s Theorem: P1/w + V12/2g + z1 = P2/w + V2/2g + z2 P1/w = P2/w + (V22 - V12)/2g + (z2 - z1) P1/9.81 = 2.34/9.81 + 0 + 16 P1 = 159.30 KPa A submersible, multi-stage, centrifugal deep well pump 260 gpm capacity is installed in a well 27 feet below the static water level and running at 3000 rpm. Drawdown when pumping at rated capacity is 10 feet. The pump delivers the water into a 25,000 gallons capacity overhead storage tank. Total discharge head developed by pump, including friction in piping is 243 feet. Calculate the diameter of the impeller of this pump in inches if each impeller diameter developed a head of 38 ft. A. 3.28 B. 5.33 *C. 3.71 D. 6.34 SOLUTION: V= DN V= D (3000/60) = (2(32.2)(38))1/2 D = 0.315 ft = 3.708 inches A fan pressure of 2.54 cm of water t 1.42 m3 per second of air at static pressure of 2.54 cm of water through a duct 300 mm diameter and discharges it through a duct 275 mm diameter. Determine the static fan efficiency if total fan mechanical is 75% and air measured at and 60 mm Hg. A. 50.11% *B. 53.69% C. 65.67% D. 45.34% SOLUTION: wA = P/RT = 101.325/(0.287)(25 + 273) = 1.18 kg/m3 hA = hwww/wA = (0.0254)(1000)/1.18 = 21.52 m vA = 1.42/( 𝝅/4)(0.3)2 = 20.09 m/s Vd = 1.42/(𝝅 /4)(0.275)2 = 23.9 m/s hv = (23.9)2 – (20.09)2 / 2(9.81) = 8.54 m h = ha + hv = 21.52 + 8.54 = 30.06 m eT = wa Q h/BP 0.75 = (1.18 x 0.00981)(1.42)(30.06) / BP BP = 0.6588 KW ep = wa Q hs/BP = (1.18 x 0.00981)(1.42)(21.52) / 0.6588 = 53.69% A fan is powered by a 0.5 hp motor and delivers air at a rate of 85 m3/min. Determine the highest value for the average velocity of air mobilized by the fan. The density of air to 1.18 kg/m3. A. 18.23 m/s *B. 21.12 m/s C. 25.34 m/s SOLUTION: P=wQh 0.50(0.746) = ( 1.18 x 0.00981)( 85 / 60) (h) h = 22.74 m v=

= 21.12 m/s

D. 32.23 m/s

A twin cylinder ammonia compressor with volume displacement of 14,726 cm3 operates at 300 rpm. Condenser and evaporator pressure are 1200 kPa and 227 kPa respectively. Specific volume of refrigerant at the entrance of compressor is 528.26 L/kg. Compression process is polytropic with n = 1.2 and clearance factor of compressor is 2 percent. Determine horsepower required. A. 60 hp B. 70 hp C. 80 hp D. 90 hp Consider 1 kg of air at 32 0C that expanded by a reversible polytropic process with n = 1.25 until the pressure is halved: Determine the heat transfer. Specific heat at constant volume for air is 0.1786 kJ/kg.K. A. 17.02 kJ heat rejected B. 17.02 kJ added C. 7.05 kJ heat rejected D. 7.05 kJ added One kilogram of air is compressed adiabatically and in a steady-flow manner. The compression efficiency is 80% and the work done on the air is 265kJ/kg. Compute the heat. A. 212 kJ/kg B. 100 kJ/kg C. 0 kJ/kg D. 331.25 kJ/kg An air compressor consumed 1200 kW-hr per day of energy. The electric motor driving the compressor has an efficiency of 80%. If indicated power of the compressor is 34 kW, Find the mechanical efficiency of the compressor. A. 117.65% B. 75% C. 85% D. 90% A 200 mm X 250 mm, 8 cylinder, 4-stroke diesel engine has a brake power of 150kW. The mechanical efficiency is 80%. If two of the cylinders were accidentally cut off, what will be the new friction power? A. 31.50 kW B. 33.50kW C. 35.5o kW D. 37.50 kW

An air compressor has a power of 40 kW at 4% clearance. If clearance will increase to 7%, what is the new power? A. 70 kW B. 40 kW C. 53 kW D. 60 kW A three stages air compressor compresses air from 100kPa to 1000 kPa. Find the intercooler pressure between the first and second stage. A. 505.44 kPa B. 108.44 kPa C. 316.23 kPa D. 215.44 kPa A 10-stages air compressor compresses air from 100 kPa to 800 kPa. Find the intercooler pressure between the first and second stage. A. 282.82 kPa B. 113.21 kPa C. 123.11 kPa D. 333.51 kPa A 3-stages air compressor compresses air from 1oo kPa to 700 kPa. Find the intercooler pressure between the 2nd and 3rd stage A. 365.88 kW B. 375.88 kW C. 385.88 kW D. 395.88 kW an air compressor has a power of 40 kw at 4 % clearance. If clearance will increase to 7 %, what is the new power? a. 70 kw b. 40 kw c. 53 kw d. 60 kw air compressed adiabatically from 30 to 100 c. if mass of air being compressed is 5 kg . find the change of entropy a. 1039 kj/kg b. 0.746 kj/kg

c. 0 kj/kg d. 1245kj/kg (pump problem) a 4 m3/ hr pump delivers water to a pressure tank. At a start, the gage reads 138 kpa until it reads 276 kpa and then the pump was shut off. The volume of the tank is 180 lit. 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. a. 31.20 lit b. 34.59 lit c. 16.87 lit d. 29.50 lit (fan problem) A 15 in. diameter fan operates at 1600 rpm and develops a head of 6 in. of water and delivers 120 cfm. What volumetric capacity for geometrically similar fan that will develop 6 in. of water at 1300 rpm? a. 147.70 cfm b. 181.8 cfm c. 97.5 cmf d. 79.2 cfm There are 1.25 kg of air at 140 kPaa stirred with internal paddles in an insulated rigid container, whose volume is 0.75 m3, until the pressure becomes 690 kPaa. Determine the initial temperature of air. a) 19.60 ˚C

𝑇=

b) 292.60 ˚C

𝑃1 𝑉1

=

c) 16.90 ˚C

d) 289.90 ˚C

(140 𝑘𝑃𝑎𝑎)(0.75𝑚3 )

Solution: 1 𝑚1 𝑅 (1.25 𝑘𝑔)(0.28708 𝑘𝐽 𝑘) 𝑘𝑔

=292.6 K

𝑇1 =292.6 – 273 = 19.6 ˚C

There are 1.25 kg of air at 140 kPaa stirred with internal paddles in an insulated rigid container, whose volume is 0.75 m3, until the pressure becomes 690 kPaa. Determine the final temperature. a) 1443.58 ˚C

b) 1170.58 ˚C

c) 1344.58 ˚C

d) 1710.58 ˚C

Air is compressed polytropically so that the pV1.4 = C. If 0.02 m3 of air at atmospheric pressure and 4 oC is compressed to a gage pressure of 405 kPa, determine the final temperature of the air in oC. a) 165.64 ˚C

b) 156.46 ˚C

c) 166.45 ˚C

d) 146.54 ˚C

A pump develops a total head of 50 ft of water under a given operating conditions. What pressure is the pump developing, in kPa? a) 194.284 b) 149.35 c) 189.294 d) 129.484 A fan observed to operate with pressure difference of 4 inches of water. What is the pressure difference in meter of water? a) 0.1016

b) 0.6101

c) 1.016 d) 0.1601

Determine the volume flow rate of water flowing at an average velocity of 2 m/s in a 2.45-m copper tubing.

a) 2.949 m3/s b) 9.429 m3/s c) 9.924 m3/s d) 4.299 m3/s What is the volume flow rate of air flowing at an average velocity of 4 m/s in a 0.30 m inside diameter duct? a) 0.2827 m3/s b) 0.2728 m3/s c) 0.2287 m3/s d) 0.7282 m3/s An adiabatic air compressor takes air at 100 kPaa and discharge to 600 kPaa. If the volume flow of discharge is 1200 lps, determine the capacity of air compressor, measured at the suction point, in m3/s. a) 4.315 lps

b) 4.315 m3/s c) 4.315 m3/min

d) 4.315 lpm

Air is compressed polytropically so that the pV1.4 = C. If 0.02 m3 of air at atmospheric pressure and 19 oC is compressed to a gage pressure of 405 kPa, determine the final temperature of the air in oC. a) 462.4 ˚C

b) 198.4 ˚C

c) 189.4 ˚C

d) 426.4 ˚C

In a piston-cylinder device the working substance is initially at 100 kPaa and 0.025 m3 then expands reversibly until the volume becomes 0.105 m3. The process is in accordance with pV1.25 = C. The work done during the process is: a. 1.03 kJ

c. 2.56 kW

c. 123.34 ft-lb d. 3.015 kJ

During an isothermal process at 88 oF, the pressure on 8 lbs of air drops from 80 psia to 5 psig. For an internally reversible process. Determine the non- flow work of the process, Btu. a. 421 b. 876 c. 543 d. 654 A pipe with a valve connects two unequal volume vessels A and B. Vessel A contains 0.142 m3 of air at 2758 kPaa and 93 oC. Vessel B of unknown volume contains air at 69 kPaa and 4 oC. The valve is opened, and when the properties have been determined it was found that pmixture = 1379 kPaa and tmixture = 43 oC. What is the volume of vessel B? a) 0.1094 m3

b) 0.4091 m3

c) 0.1904 m3

d) 0.1409 m3

A 20 cm x 25 cm reciprocating compressor has a 4 % clearance and operates at 550 rpm. The compressor receives air at 100 kPaa and 27 oC and discharges at 1850 kPaa. The compression and expansion are polytropic with n = 1.3. What is the volumetric efficiency? a) 66.26 %

b) 62.66 %

c) 76.27 %

d) 72.67 %

A two-stage compressor receives 0.20 kg/s of helium at 135 kPaa and 27 oC, and delivers it at 7000 kPaa. The compression is polytropic with n = 1.5. The intercooler is ideal. Determine the compressor power required, in kW. a) + 696.17 kW

b) – 696.17 kW

c) + 966.17 kW

d) – 669.17 kW

A 3-stage compressor delivers 0.23 kg/s of air. The suction pressure and temperature are 100 kPaa and 27 oC, respectively. The discharge pressure is 1380 kPaa. Intercooler is installed after each stage. Determine the compressor work. a) 59.07 kW

b) 55.07 kW

c) 57.35 kW

d) 55.73 kW

A two-stage compressor receives 0.20 kg/s of helium at 135 kPaa and 27 oC, and delivers it at 7000 kPaa. The compression is polytropic with n = 1.5. The intercooler is ideal. Determine the heat transfer in the intercooler, in kW. a) + 290.24 kW b) – 290.24 kW c) + 234.585 kWd) – 234.585 kW A 20 cm x 25 cm reciprocating compressor has a 4 % clearance and operates at 550 rpm. The compressor receives air at 100 kPaa and 27 oC and discharges at 1850 kPaa. The compression and expansion are polytropic with n = 1.3. Find the volume flow rate of air at inlet conditions a) 47.7 lps

b) 0.0477 m3/s c) 101 cfm

d) Both a, b, & c

Find the Hp of an industrial fan that delivers 25 m3/s of air through a 900 mm by 1200 mm outlet. Static pressure is 127 mm of water gage and air density is 1.18 kg/m3. a) 52.33 Hp

b) 25.33 Hp

c) 33.52 Hp

d) 53.32 Hp

The discharge pressure of an air compressor is 6 times the suction pressure. If volume flow rate at the suction is 0.8 m3/sec, what is the compressor power for n = 1.38 and suction pressure is 101 kPaa? a) 117 kW

b) 187 kW

c) 125 kW

d) 209 kW

A boiler requires 90 000 m3/hr of standard air. The mechanical efficiency of the fan to be installed is 65 %. Determine the size of driving motor assuming the fan can deliver a total pressure of 150 mm of water gage. a)55 kW

b) 60 kW

c) 65 kW

d) 70 kW

At 1.2 kg/m3 air density, the fan develops a brake power of 100 kW. If operates at 98 kPaa and 32 oC with the same speed, what is the new BP? a) 97.32 kW b) 93.27 kW c) 92.37 kW d) 92.37 kW Air is compressed polytropically so that the pV1.4 = C. If 0.02 m3 of air at atmospheric pressure and 19 oC is compressed to a gage pressure of 405 kPa, determine the final temperature of the air in oC. a) 462.4 oC

b) 198.4 oC

c) 189.4 oC

d) 426.4 oC

Air flow in a certain duct at 80 oF under a static pressure of 3 inches of water (gage), with the barometer at 29.4 inches Hg. The average velocity in the duct is 1500 fpm. Find the total pressure (head) in the duct. a)3.14 inches water

b) 13.4 inches water

c) 4.13 inches water

d) 1.34 inches water

During the polytropic process of an ideal gas, the state changes from 20 psia and 40 oF to 120 psia and 340 oF. Determine the value of n. a) 1.26

b) 1.63

c) 1.46

d) 1.36

A fuel pump is delivering 10 gpm of oil with a SG = 0.83. The total head is 9.14 m, find how much energy does the pump consumes, in kJ/hr. a) 168.89

b) 199.89

c) 189.89 d) 179.89

A pressure of 10 bar absolute is specified. What is the equivalent pressure in gauge units? a)3 bar g b) 11 bar g

c) 9 bar g

d) 12 bar g

A 15 kW motor running at 350 rpm is used to drive pump. If speed will be changed to 370 rpm, what is the increase in power? a) 2.72 kW

b) 7.22 kW

c) 3.73 kW

d) 7.33 kW

A pump discharges 300 kg/min of water whose density is 990 kg/m3. Determine the total time required to fill a spherical tank 2.75 meters in diameter. a)

35.94 minutes

b) 53.94 minutes

c) 39.54 minutes

d) 54.39 minutes

A single-acting reciprocating pump, with a diameter of 0.18 m and a stroke of 0.30 m, delivers water at a rate of 0.18 m3/min. What is the percentage slip it delivers at 25 rpm? a) 5.69 %

b) 6.59 %

c) 9.65 %

d) 6.95 %

A six-stage pump delivers 1500 gpm against a net pressure rise of 700 psi, what is the specific speed if its speed is 1750 rpm? a) 2010 rpm

b) 1200 rpm

c) 1020 rpm

d) 1002 rpm

An irrigation pump delivers water through a 15-cm horizontal pipe flowing full at the outlet, the jet striking the ground at a horizontal distance of 3.66 m and a vertical distance of 1.22 m from the end of the pipe. Find the capacity of the pump in lpm. a) 7982.5 lps

b) 7982.5 lpm

c) 9782.5 lps

d) 9782.5 lpm

A model centrifugal pump with a 3 inches diameter impeller delivers 600 gpm of water at a total head of 350 ft when operating at 1750 rpm. Find the diameter of a geometrically similar pump that will deliver 1000 gpm when operating 3500 rpm. a)

3.82 inches

b) 1.82 inches

c) 4.82 inches

d) 2.82 inches

A pump running at 100 rpm delivers water against a head of 30 m. If pump speed will be increased to 120 rpm, what is the increase in head? a) 13.2 m

b) 12.3 m

c) 21.3 m

d) 23.1 m

A centrifugal pump is designed for 1800 rpm and head of 61 m. Determine the head if impeller diameter is reduced from 305 mm to 254 mm. a) 24.13 m

b) 42.31 m

c) 34.21 m

d) 41.24 m

Find the Hp of an industrial fan that delivers 25 m3/s of air through a 900 mm by 1200 mm outlet. Static pressure is 127 mm of water gage and air density is 1.18 kg/m3. a) 52.33 Hp

b) 25.33 Hp

c) 33.52 Hp

d) 53.32 Hp

A boiler requires 90 000 m3/hr of standard air. The mechanical efficiency of the fan to be installed is 65 %. Determine the size of driving motor assuming the fan can deliver a total pressure of 150 mm of water gage. a)55 kW b) 60 kW

c) 65 kW

d) 70 kW

At 1.2 kg/m3 air density, the fan develops a brake power of 100 kW. If operates at 98 kPaa and 32 oC with the same speed, what is the new BP? a) 97.32 kW

b) 93.27 kW

c) 92.37 kW

d) 92.37 kW

A fan discharges 9320 cfm of air through a duct 36 inches in diameter against a static pressure of 9 inches of water gage. Barometric pressure is 730 mm Hg, the temperature of air is 85 oC and the gage fluid density is 62.11 lb/ft3. If the power input is 35.5 Hp, determine the fan static efficiency. a) 38 % b) 36 % c) 37 % d) 39 % A fan has a suction pressure of 30 mm water vacuum with air velocity of 3 m/s. The discharge has 150 mm of water gage and discharge velocity of 7 m/s. Determine the total head if air density is 1.2 kg/m3. a) 152 m b) 125 m c) 251 m d) 215 m