E8

MAPÚA UNIVERSITY Muralla St. Intramuros, Manila School of Mechanical and Manufacturing Engineering

EXPERIMENT NO. 8 HEAT EXCHANGER

12 MAHMUD, Ali R. 2015151413 ME144L – A1 Group No. 2

Date of Performance: September 28, 2018 Date of Submission: October 12, 2018

GRADE Engr. Teodulo A. Valle Instructor

TABLE OF CONTENTS

Objectives

Page 1

Theory and Principle

Page 1

List Of Apparatus

Page 9

Procedure

Page 12

Set-up of Apparatus

Page 14

Final Data Sheet

Page 17

Sample Computations

Page 18

Discussion of Result

Page 19

Questions and Answers

Page 20

Conclusion

Page 23

Reference

Page 24

Preliminary Data Sheet

Page 25

OBJECTIVES To determine the overall heat transfer coefficient of brass tubing in the heat exchanger operating at parallel and counter flow using steam as the heating medium. THEORY AND PRINCIPLE A heat exchanger is a device used to transfer heat between two or more fluids. The fluids can be single or two phase and, depending on the exchanger type, may be separated or in direct contact. Devices involving energy sources such as nuclear fuel pins or fired heaters are not normally regarded as heat exchangers although many of the principles involved in their design are the same. There are two approaches on describing heat exchanger. The first considers the flow configuration within the heat exchanger, while the second is based on the classification of equipment type primarily by construction. There are four basic flow configurations: •

Counter Flow: This type of flow arrangement allows the largest change in temperature of both

fluids and is therefore most efficient (where efficiency is the amount of actual heat transferred compared with the theoretical maximum amount of heat that can be transferred). •

Co-current Flow: In co-current flow heat exchangers, the streams flow parallel to each other

and in the same direction; also known as parallel flow. This is less efficient than countercurrent flow but does provide more uniform wall temperatures. •

Crossflow: Crossflow heat exchangers are intermediate in efficiency between countercurrent

flow and parallel flow exchangers. In these units, the streams flow at right angles to each other. •

Hybrids such as Cross Counter flow and Multi Pass Flow: In industrial heat exchangers,

hybrids of the above flow types are often found. Examples of these are combined crossflow/counter flow heat exchangers and multi pass flow heat exchangers.

Fig.1. Counter Flow Heat Exchanger 1

Fig.2. Parallel Flow Heat Exchanger

Fig.3. Crossflow Heat Exchanger

Fig.4. Hybrid Heat Exchanger

Heat exchangers were also classified based on construction. The first level of classification is to divide heat exchanger types into recuperative or regenerative. A Recuperative Heat Exchanger has separate flow paths for each fluid and fluids flow simultaneously through the exchanger exchanging heat across the wall separating the flow paths. A Regenerative Heat Exchanger has a single flow path, which the hot and cold fluids alternately pass through.

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In a regenerative heat exchanger, the flow path normally consists of a matrix, which is heated when the hot fluid passes through it (this is known as the "hot blow"). This heat is then released to the cold fluid when this flows through the matrix (the "cold blow"). Regenerative Heat Exchangers are sometimes known as Capacitive Heat Exchangers. Regenerators are mainly used in gas/gas heat recovery applications in power stations and other energy intensive industries. The two main types of regenerator are Static and Dynamic. Both types of regenerator are transient in operation and unless great care is taken in their design there is normally cross contamination of the hot and cold streams. However, the use of regenerators is likely to increase in the future as attempts are made to improve energy efficiency and recover lower grade heat. However, because regenerative heat exchangers tend to be used for specialist applications recuperative heat exchangers are more common. There are many types of recuperative exchangers, which can broadly be grouped into indirect contact, direct contact and specials. Indirect contact heat exchangers keep the fluids exchanging heat separate by the use of tubes or plates etc. Direct contact exchangers do not separate the fluids exchanging heat and in fact rely on the fluids being in close contact.

Fig.5. Classifications of Heat Exchangers In indirect contact heat exchanger, the steams are separated by a wall, usually metal. Examples of these are tubular exchangers.

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Tubular heat exchangers are very popular due to the flexibility the designer has to allow for a wide range of pressures and temperatures. Tubular heat exchangers can be subdivided into a number of categories, of which the shell and tube exchanger is the most common. A Shell and Tube Exchanger consists of a number of tubes mounted inside a cylindrical shell. Two fluids can exchange heat, one fluid flows over the outside of the tubes while the second fluid flows through the tubes. The fluids can be single or two phase and can flow in a parallel or a cross/counter flow arrangement. The shell and tube exchanger consists of four major parts: •

Front end–this is where the fluid enters the tube side of the exchanger.

•

Rear end–this is where the tube side fluid leaves the exchanger or where it is returned to the

front header in exchangers with multiple tube side passes. •

Tube bundle–this comprises of the tubes, tube sheets, baffles and tie rods etc. to hold the bundle

together. •

Shell—this contains the tube bundle. The popularity of shell and tube exchangers has resulted in a standard being developed for

their designation and use. This is the Tubular Exchanger Manufactures Association (TEMA) Standard. In general shell and tube exchangers are made of metal but for specialist applications (e.g., involving strong acids of pharmaceuticals) other materials such as graphite, plastic and glass may be used. It is also normal for the tubes to be straight but in some cryogenic applications helical or Hampson coils are used. A simple form of the shell and tube exchanger is the Double Pipe Exchanger. This exchanger consists of a one or more tubes contained within a larger pipe. In its most complex form there is little difference between a multi tube double pipe and a shell and tube exchanger. However, double pipe exchangers tend to be modular in construction and so several units can be bolted together to achieve the required duty. Other types of tubular exchanger include: •

Furnaces—the process fluid passes through the furnace in straight or helically wound tubes

and the heating is either by burners or electric heaters.

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•

Tubes in plate—these are mainly found in heat recovery and air conditioning applications. The

tubes are normally mounted in some form of duct and the plates act as supports and provide extra surface area in the form of fins. •

Electrically heated–in this case the fluid normally flows over the outside of electrically heated

tubes. •

Air Cooled Heat Exchangers consist of bundle of tubes, a fan system and supporting structure.

The tubes can have various type of fins in order to provide additional surface area on the air side. Air is either sucked up through the tubes by a fan mounted above the bundle (induced draught) or blown through the tubes by a fan mounted under the bundle (forced draught). They tend to be used in locations where there are problems in obtaining an adequate supply of cooling water. •

Heat Pipes, Agitated Vessels and Graphite Block Exchangers can be regarded as tubular or

could be placed under Recuperative "Specials". A heat pipe consists of a pipe, a wick material and a working fluid. The working fluid absorbs heat, evaporates and passes to the other end of the heat pipe were it condenses and releases heat. The fluid then returns by capillary action to the hot end of the heat pipe to re-evaporate. Agitated vessels are mainly used to heat viscous fluids. They consist of a vessel with tubes on the inside and an agitator such as a propeller or a helical ribbon impeller. The tubes carry the hot fluid and the agitator is introduced to ensure uniform heating of the cold fluid. Carbon block exchangers are normally used when corrosive fluids need to be heated or cooled. They consist of solid blocks of carbon which have holes drilled in them for the fluids to pass through. The blocks are then bolted together with headers to form the heat exchanger. Plate heat exchangers separate the fluids exchanging heat by the means of plates. These normally have enhanced surfaces such as fins or embossing and are either bolted together, brazed or welded. Plate heat exchangers are mainly found in the cryogenic and food processing industries. However, because of their high surface area to volume ratio, low inventory of fluids and their ability to handle more than two steams, they are also starting to be used in the chemical industry.

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Fig.6. Tubular Heat Exchanger Classification

Fig.7. Plate Exchanger Classification Plate and Frame Heat Exchangers consist of two rectangular end members which hold together a number of embossed rectangular plates with holes on the corner for the fluids to pass through. Each of the plates is separated by a gasket which seals the plates and arranges the flow of fluids between the plates. This type of exchanger is widely used in the food industry because it can easily be taken apart to clean. If leakage to the environment is a concern it is possible to weld two plate together to ensure that the fluid flowing between the welded plates cannot leak. However, as there are still some gaskets present it is still possible for leakage to occur. Brazed plate heat exchangers avoid the possibility of leakage by brazing all the plates together and then welding on the inlet and outlet ports. Plate Fin Exchangers consist of fins or spacers sandwiched between parallel plates. The fins can be arranged so as to allow any combination of crossflow or parallel flow between adjacent 6

plates. It is also possible to pass up to 12 fluid streams through a single exchanger by careful arrangement of headers. They are normally made of aluminum or stainless steel and brazed together. Their main use is in gas liquefaction due to their ability to operate with close temperature approaches. Lamella heat exchangers are similar in some respects to a shell and tube. Rectangular tubes with rounded corners are stacked close together to form a bundle, which is placed inside a shell. One fluid passes through the tubes while the fluid flows in parallel through the gaps between the tubes. They tend to be used in the pulp and paper industry where larger flow passages are required. Spiral plate exchangers are formed by winding two flat parallel plates together to form a coil. The ends are then sealed with gaskets or are welded. They are mainly used with viscous, heavily fouling fluids or fluids containing particles or fibers.

Fig.8. Shell and Tube Heat Exchanger

Fig.9. Plate and Frame Heat Exchanger

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In direct contact heat exchangers, it does not use a heat transfer surface, because of this, it is often cheaper than indirect heat exchangers. However, to use a direct contact heat exchanger with two fluids they must be immiscible or if a single fluid is to be used it must undergo a phase change. The most easily recognizable form of direct contact heat exchanger is the natural draught Cooling Tower found at many power stations. These units comprise of a large approximately cylindrical shell (usually over 100 m in height) and packing at the bottom to increase surface area. The water to be cooled is sprayed onto the packing from above while air flows in through the bottom of the packing and up through the tower by natural buoyancy. The main problem with this and other types of direct contact cooling tower is the continuous need to make up the cooling water supply due to evaporation. Direct contact condensers are sometimes used instead of tubular condensers because of their low capital and maintenance costs. There are many variations of direct contact condenser. In its simplest form a coolant is sprayed from the top of a vessel over vapor entering at the side of the vessel. The condensate and coolant are then collected at the bottom. The high surface area achieved by the spray ensures they are quite efficient heat exchangers. Steam injection is used for heating fluids in tanks or in pipelines. The steam promotes heat transfer by the turbulence created by injection and transfers heat by condensing. Normally no attempt is made to collect the condensate. In this experiment, the researcher will only focus on parallel and counter flow heat exchanger. Below are the formulae needed for the calculation of unknown variables. •

Solving for heat absorbed by the cold water: 𝑄𝑤 = 𝑚𝑤 𝑐𝑝 (𝑇𝑐,𝑜𝑢𝑡 − 𝑇𝑐,𝑖𝑛 ) = 𝜌𝑉𝑐𝑝 (𝑇𝑐,𝑜𝑢𝑡 − 𝑇𝑐,𝑖𝑛 ) Where: 𝑄𝑤 = heat absorbed by the cold water 𝑚𝑤 = 𝑚𝑎𝑠𝑠 𝑓𝑙𝑜𝑤 𝑟𝑎𝑡𝑒 𝑜𝑓 𝑤𝑎𝑡𝑒𝑟; 𝑉 = 𝑣𝑜𝑙𝑢𝑚𝑒 𝑓𝑙𝑜𝑤 𝑟𝑎𝑡𝑒 𝑜𝑓 𝑤𝑎𝑡𝑒𝑟 𝑐𝑝 = 𝑠𝑝𝑒𝑐𝑖𝑓𝑖𝑐 ℎ𝑒𝑎𝑡 𝑜𝑓 𝑤𝑎𝑡𝑒𝑟 𝑇𝑐,𝑜𝑢𝑡 = 𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 𝑜𝑓 𝑐𝑜𝑙𝑑 𝑤𝑎𝑡𝑒𝑟 𝑎𝑡 𝑑𝑖𝑠𝑐ℎ𝑎𝑟𝑔𝑒 𝑇𝑐,𝑖𝑛 = 𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 𝑜𝑓 𝑐𝑜𝑙𝑑 𝑤𝑎𝑡𝑒𝑟 𝑎𝑡 𝑠𝑢𝑐𝑡𝑖𝑜𝑛 8

Equation 1

•

Solving for LMTD:

𝐿𝑀𝑇𝐷 = •

∆𝑇𝑚𝑎𝑥 − ∆𝑇𝑚𝑖𝑛 ∆𝑇 𝑙𝑛 ( 𝑚𝑎𝑥 ) ∆𝑇𝑚𝑖𝑛

Solving for the lateral surface area: 𝐴 = 𝜋𝑑𝐿

•

Equation 2

Equation 3

Solving for overall heat transfer coefficient: 𝑈=

𝑄𝑤 𝐴 × 𝐿𝑀𝑇𝐷

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Equation 4

LIST OF APPARATUS 1. Heat Exchanger Piping system

2. Steam generator

3. Flow Meter

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4. Steel Tape

5. Stop Watch

6. Thermometer bulb (3 pcs)

7. Steel Drums

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8. Asbestos Gloves

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PROCEDURES A. Counter Flow 1. Set the heat exchanger piping system so that the counter flow will take effect.

2. Place the thermometer bulbs in their proper places for temperature readings.

3. Set the flow meter of the cooling water at 5GPM.

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4. After the system has been set-up, place the discharge hose of the cooling water inside the drum and time the trial for 2 minutes. 5. Measure the temperature readings after two minutes.

6. Repeat the same process for trial 2 but set the flow meter at 5.5 GPM.

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B. Parallel Flow 1. Set the piping system so that parallel flow will take effect.

2. Repeat steps 2 to 5. 3. Finalize the data and calculate the unknown variable using the formulas in the Theory and Principle Part.

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SET-UP OF APPARATUS

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FINAL DATA SHEET

Trial

U

Th is

Th out

Tc in

Tc out

Vw flow

Qw

LMTD

(˚C)

(˚C)

(˚C)

(˚C)

(gpm)

(KW)

(˚C)

Parallel

65

42

25.5

36

5

13.85

17.78

0.6282

Counter

62

40

25.5

38

5

16.48

18.85

0.7052

Parallel

61

39

25.5

36

5.25

14.55

13.15

0.8921

Counter

63

39

25.5

36

5.25

14.53

19.48

0.6015

Flow

(KW/m2˚C)

1

2

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SAMPLE COMPUTATIONS For Parallel Flow ΔTmax = 35.5 ˚C ΔTmin = 3 C

𝐿𝑀𝑇𝐷 =

ΔTmax−ΔTmin ΔTmax ) ΔTmin

ln(

=

35.5˚C−3˚C 35.5˚C ) 3˚C

ln(

= 13.1530 ˚C

ρ = 998.28 kg/m3

Heat Absorbed by Water 𝑄𝑤 = 𝑚𝑤 𝐶𝑝𝑤 (𝑇𝑐 𝑜𝑢𝑡 − 𝑇𝑐 𝑖𝑛 ) =

𝑄𝑤 = (998.28

ρv𝐶𝑝𝑤 (𝑇𝑐 𝑜𝑢𝑡 − 𝑇𝑐 𝑖𝑛 )

𝑘𝑔 7𝑔𝑎𝑙 1𝑚𝑖𝑛 3.7854𝐿 1𝑚3 𝑘𝐽 ) 𝑥 𝑥 𝑥 ) (36˚C − 25.5˚C) = 14.55𝐾𝑊 ( ) (4.187 3 𝑚 𝑚𝑖𝑛 60𝑠 1𝑔𝑎𝑙 1000𝐿 𝑘𝑔˚C

Thermal Transmittance 𝑈=

𝑄𝑤 14.55 𝑘𝑊 𝑘𝑊 = = 0.8921 2 𝐴 𝑥 𝐿𝑀𝑇𝐷 (1.24)(13.153 𝑚 ˚C

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DISCUSSION OF RESULT

Based on the data gathered by the researcher, two trials were performed and each trial, two different flow configuration was observed. The heat absorbed by cold water is higher when its volume flow rate was increased. Obviously, the amount of heat absorbed will increase since volume flow rate is directly proportional to the mass flow rate which also increases the amount of heat absorbed by cold water. The logarithmic mean temperature difference was used in order to determine the overall heat transfer coefficient. The temperature of the hot fluid was decreased after flowing from a hot temperature to a cold temperature since heat was absorbed by the cold water which gained a higher temperature compared to its starting point. In a parallel flow, the hot liquid flows parallel with its cooling medium which results to a high temperature gradient from the starting point and a very small temperature gradient at the end of heat transfer. In a counter flow, the hot liquid flows in a counter direction of the flow of its cooling medium which results to a low temperature gradient compared to parallel flow. LMTD were used in determining the overall heat transfer coefficient since there are no complications in the temperature gradient calculated by the researcher. In this problem occurs, AMTD must be used if one of the temperature gradient is zero.

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QUESTION AND ANSWERS 1. Hot gases at 280 degrees Celsius flow on one side of a metal plate of 50 mm thickness and air at 35 degrees Celsius flows on the other side. The heat transfer coefficient of the gases is 31.5 W/m2-K and that of the air is 32 W/m2-K. Calculate the over-all heat transfer coefficient if the value of thermal conductivity is 0.01. 1 1 𝑘12 1 1 0.01 1 0.0632 𝑚2 − 𝐾 𝑈= ; 𝑅𝑇 = + + = + + = 𝑅𝑇 ℎ1 𝑥12 ℎ2 31.5 50 32 𝑊 𝑈=

1 15.82𝑊 = 2 0.0632 𝑚 − 𝐾

2. A liquid to liquid counter flow heat exchanger is used to heat a cold fluid from 120 degrees Fahrenheit to 310 degrees Fahrenheit. Assuming that the hot fluid enters at 500 degrees Fahrenheit and leaves at 400 degrees Fahrenheit, calculate the logarithmic mean temperature difference for the heat exchanger. 𝐿𝑀𝑇𝐷 =

∆𝑇𝑚𝑎𝑥 − ∆𝑇𝑚𝑖𝑛 ∆𝑇 𝑙𝑛 (∆𝑇𝑚𝑎𝑥 ) 𝑚𝑖𝑛

∆𝑇𝑚𝑎𝑥 = 400℉ − 120℉ = 280℉ ∆𝑇𝑚𝑖𝑛 = 500 − ℉ − 310℉ = 190℉ 𝐿𝑀𝑇𝐷 =

280℉ − 190℉ = 232℉ 280℉ 𝑙𝑛 (190℉)

3. A turbo-generator, 16 cylinder, V-type diesel engine has an air consumption of 3000 kg/hr. per cylinder at rated load and speed. This air is drawn in thru a filter by a centrifugal compressor direct connected to the exhaust gas turbine. The temperature of the air from the compressor is 145 degrees Celsius and a counter flow air cooler reduces the air temperature to 45 degrees Celsius before it goes to the engine suction header. Cooling water enter air cooler at 30 degrees Celsius and leaves at 38 degrees Celsius. Calculate the arithmetic mean temperature difference. ∆𝑇𝑚𝑎𝑥 = 145℃ − 38℃ = 107℃ ∆𝑇𝑚𝑖𝑛 = 45℃ − 30℃ = 15℃ 20

𝐴𝑀𝑇𝐷 =

∆𝑇𝑚𝑎𝑥 + ∆𝑇𝑚𝑖𝑛 107℃ + 15℃ = = 61℃ 2 2

4. A surface condenser serving a 50,000 kW steam turbo-generator unit receives exhaust steam at the rate of 196,000 kg/hr. Vacuum in condenser is 702 mm Hg. Sea water for cooling enters at 29.5 degrees Celsius and leaves at 37.5 degrees Celsius. For steam turbine condenser, manufacturers consider 950 Btu/lb. of steam turbine condensed as heat given up to cooling water. Calculate the logarithmic mean temperature difference. 101.325𝑘𝑃𝑎 𝑃 = 101.325𝑘𝑃𝑎 − 702𝑚𝑚𝐻𝑔 ( ) = 7.733 𝑘𝑃𝑎 760𝑚𝑚𝐻𝑔 𝑆𝑎𝑡𝑢𝑟𝑎𝑡𝑖𝑜𝑛 𝑇𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 𝑎𝑡 7.733 𝑘𝑃𝑎 = 40.86℃ ∆𝑇𝑚𝑎𝑥 = 40.86℃ − 29.5℃ = 11.36℃ ∆𝑇𝑚𝑖𝑛 = 40.86℃ − 37.5℃ = 3.36℃ 𝐿𝑀𝑇𝐷 =

∆𝑇𝑚𝑎𝑥 − ∆𝑇𝑚𝑖𝑛 11.36℃ − 3.36℃ = = 6.57℃ 11.36℃ ∆𝑇𝑚𝑎𝑥 ln ( 3.36℃ ) 𝑙𝑛 (∆𝑇 ) 𝑚𝑖𝑛

5. The stack gas from a chemical operation contains noxious vapor that must be condensed by lowering its temperature from 315 degrees Celsius to 35 degrees Celsius. The gas flow rate is 0.70 m3/s. Water is available at 10 degrees Celsius at 1.26 kg/s. A two shell and 4 tube pass, counter flow heat exchanger will be used with a water flowing through the tubes. The gas has a specific heat of 1.10 kJ/kg-K and a gas constant of 0.26 kJ/kg-K. Calculate the logarithmic mean temperature difference. 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝑔𝑎𝑠 𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 =

𝐷𝑒𝑛𝑠𝑖𝑡𝑦 𝑜𝑓 𝐺𝑎𝑠, 𝜌 =

315 + 35 = 175℃ 2

𝑃 101.325 𝑘𝑔 = = 0.867 3 𝑅𝑇 (0.26)(175 + 273) 𝑚

𝑚3 𝑘𝑔 𝑘𝑔 𝑀𝑎𝑠 𝑓𝑙𝑜𝑤 𝑟𝑎𝑡𝑒 𝑜𝑓 𝑔𝑎𝑠, 𝑚𝑔 = (0.7 ) (0.867 3 ) = 0.607 𝑠 𝑚 𝑠 𝐻𝑒𝑎𝑡 𝑔𝑎𝑖𝑛𝑒𝑑 𝑏𝑦 𝑐𝑜𝑜𝑙𝑖𝑛𝑔 𝑤𝑎𝑡𝑒𝑟 = 𝐻𝑒𝑎𝑡 𝑙𝑜𝑠𝑡 𝑏𝑦 𝑔𝑎𝑠𝑒𝑠

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𝑚𝑤 𝑐𝑝𝑤 ∆𝑡𝑤 = 𝑚𝑔 𝑐𝑝𝑔 ∆𝑡𝑔 1.26(4.187)(𝑡 − 10) = 0.607(1.10)(315 − 35) → 𝑡 = 45.5℃ ∆𝑇𝑚𝑎𝑥 = 315℃ − 45.5℃ = 269.5℃ ∆𝑇𝑚𝑖𝑛 = 35℃ − 10℃ = 25℃ 𝐿𝑀𝑇𝐷 =

∆𝑇𝑚𝑎𝑥 − ∆𝑇𝑚𝑖𝑛 269.5℃ − 25℃ = = 102.8℃ ∆𝑇𝑚𝑎𝑥 269.5℃ 𝑙𝑛 (∆𝑇 ) ln ( ) 25℃ 𝑚𝑖𝑛

6. A counter flow heat exchanger is designed to heat fuel oil from 45 degrees Celsius to 100 degrees Celsius while the heating fluid enters at 150 degrees Celsius and leaves at 115 degrees Celsius. Calculate the arithmetic mean temperature difference. ∆𝑇𝑚𝑎𝑥 = 115℃ − 45℃ = 70℃ ∆𝑇𝑚𝑖𝑛 = 150℃ − 100℃ = 50℃ 𝐴𝑀𝑇𝐷 =

∆𝑇𝑚𝑎𝑥 + ∆𝑇𝑚𝑖𝑛 70℃ + 50℃ = = 60℃ 2 2

7. If the total resistance to heat flow of a composite wall is 3.0875 m2-K/W, what is the overall heat transfer coefficient of the wall? 𝑈=

1 1 𝑊 = = 0.324 2 2 𝑅𝑇 3.0875 𝑚 − 𝐾 𝑚 −𝐾 𝑊

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CONCLUSION The researcher was able to determine the overall heat transfer coefficient of brass tubing in the heat exchanger which was operated under parallel and counter flow using steam as the heating medium. Overall heat transfer coefficient was affected by variables such as heat absorbed by the cooling water, the lateral surface area of the pipe and the LMTD (logarithmic mean temperature difference). When the value of overall heat transfer coefficient of a material is high, the heat transfer is more effective since it increases the rate of heat transfer. If the pipe is huge and long and its LMTD is large, we expect a low value of overall heat transfer coefficient. Heat exchangers is important especially in power generating industries such as steam power plants. The purpose of a heat exchanger is to collect waste heat from a hot fluid which is cooled and the hot fluid becomes a working fluid with cold quantities which may be used as a refrigerant and for distillation for chemical processes. With that, latent heat is given up by the substance and transferred to the surrounding environment. In cars, the heat exchanger present is radiator. Radiator is installed in an internal combustion engine which collects heat from the hot engine and prevents over heating of an engine. The researcher was able to distinguish the two flow configurations of heat exchanger with the aid of a diagram illustrating the different temperature gradients. The principle of heat exchanger is essential for a mechanical engineer since it is used in related areas of the profession mentioned. Power generation, refrigeration, air conditioning, petrochemical plants, petroleum refineries, and sewage treatment are among the applications of heat exchanger so the researcher is obliged to learn the different types and principles of heat exchangers.

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REFERENCES

•

Heat Exchangers. (2018). Retrieved from http://www.thermopedia.com/content/832/

•

Logarithmic Mean Temperature Difference. (2018). Retrieved from https://memechanicalengineering.com/log-mean-temperature-difference-lmtd/

•

Arithmetic Mean Temperature Difference. (2018). Retrieved from https://www.vcalc.com/wiki/TeddyCamelus/Arithmetic+Mean+Temperature+Difference++AMTD

•

Difference between LMTD and AMTD. (2018). Retrieved from https://www.quora.com/What-is-the-difference-between-LMTD-and-AMTD

•

Overall Heat Transfer Coefficient. (2018). Retrieved from https://www.engineeringtoolbox.com/overall-heat-transfer-coefficient-d_434.html

•

Heat Exchanger Flows. (2018). Retrieved from https://www.brighthubengineering.com/hvac/62410-heat-exchanger-flow-patterns/

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