HEAT EXCHANGER

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1.0 Title

MEC 554-THERMALFLUIDS LAB

THERMODYNAMICS II LAB

CONCENTRIC TUBE HEAT

EXCHANGER

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2.0 Abstract

In this experiment, we investigate the effect of flow rate variation on the performance characteristics of a counter flow concentric tube exchanger and parallel flow tube heat exchanger. During this experiment, we need to record the temperature different by increased the volumetric flow rates of 2000, 3000 and 4000 cm3/min for both flow of heat exchanger. After that, we need to calculate the following heat exchanger performance factors: power emitted, power absorbed, power lost, efficiency, logarithmic mean temperature different and overall heat transfer coefficient. Generally it can be said that all factors that effects the heat exchanger performance which is power emitted, power absorbed, power lost efficiency (Ƞ), logarithmic mean temperature difference ( m), and overall heat transfer coefficient (U) were

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Table of Contents

3.0 Introduction and Applications ... 6

4.0 Objectives ... 8 5.0 Theory ... 9 6.0 Experimental Procedures ... 12 6.1 Apparatus/Experimental Setup ... 12 6.2 Procedure ... 14 7.0 Result ... 15 7.1 Data recorded ... 15 7.2 Sample calculation ... 16 7.3 Analysis result ... 19 8.0 Discussion ... 23 9.0 Conclusion ... 23 10.0 References ... 24 11.0 Appendices ... 25

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List of Symbols

A Area over which force (F) acts (m2) E Elastic modulus (GPa)

F Force (N)

( ) Initial dimension in direction i (mm) T Specimen thickness (m)

Rate of chart displacement (mm/min) Rate of sample displacement (mm/min)

w Specimen width (m)

Displacement of chart (mm) Displacement of sample (mm)

Strain

=0 Predicted strain at zero stress Normal strain in direction i

E Error in the predicted elastic modulus (GPa) F Error in the force (N)

Change in dimension in direction i (mm) t Error in the specimen thickness (m) w Error in the width (m)

=0 Error in the predicted strain at zero stress

Error in the predicted intercept of stress-stain data (MPa) Error in the stress (MPa)

Predicted intercept of stress-strain data (MPa) Engineering stress (MPa)

Yield point (MPa)

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List of figure

Figure 1: Space heater ... 7

Figure 2: Cara radiator ... 7

Figure 3: Packaged Annular-Space Pastuerizer and Sterilizer ... 7

Figure 4: Anaerobic Digestion ... 7

Figure 5: Recuparator ... 7

Figure 6: Heat exchanger temperature profiles and Fluid Flow Direction ... 9

Figure 7: Heat exchanger apparatus system diagram (schematic diagram) ... 12

Figure 8: Heat exchanger system ... 12

Figure 9: Temperature control ... 13

Figure 10: Cold fluid volumetric flow rate control ... 13

Figure 11: Valve diagram for parallel flow and counter flow ... 13

Figure 12: Hot fluid volumetric flow rate control ... 13

Figure 13: Graph 1... 20 Figure 14: Graph 2... 20 Figure 15: Graph 3... 21 Figure 16: Graph 4... 21 Figure 17: Graph 5... 22 Figure 18: Graph 6... 22

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3.0 Introduction and Applications

A heat exchanger is a specialized device that assists in transfer of heat from one fluid to the other. In some cases, a solid wall may separate the fluids and prevent them from mixing. In other designs, the fluids may be in direct contact with each other. In the most efficient heat exchangers, the surface area of the wall between the fluids is maximized while simultaneously minimizing the fluid flow resistance. Fins or corrugations are sometimes used with the wall in order to increase the surface area and induce turbulence.

The types of heat exchangers to be tested in this experiment are called parallel-flow and counter-flow concentric tube heat exchangers. In a parallel-flow heat exchanger, the working fluid flow in the same direction as it is for counter-flow but, at opposite direction. The figure below briefly explains the fluid flowing path from both heat exchangers.

There are some important variables or properties that influence the performance of a heat exchanger. Those variables include the physical properties, the mass flow rates, and the inlet temperature of the fluids, type of materials used, the configuration and area of the heat transfer surfaces, and the extent of scale or deposits on the heat transfer surfaces, and the ambient conditions.

The attempt to match the heat transfer hardware to the heat transfer requirements within the specified constraints has resulted in numerous types of innovative heat exchanger design. In the design of heat exchange equipment, heat transfer equations are applied to calculate this transfer of energy so as to carry it out efficiently and under controlled conditions. The equipment goes under many names, such as boilers, pasteurizers, jacketed pans, freezers, air heaters, cookers, ovens, space heaters and so on. The range is too great to list completely. Perhaps the most commonly known heat exchanger is a car radiator, which cools the hot radiator fluid by taking advantage of air flow over the surface of the radiator. Last but not least, Heat exchangers are found widely scattered throughout the food process industry.

Page | 7 Figure 2: Cara radiator _{Figure 1: Space heater}

Figure 4: Anaerobic Digestion Figure 3: Packaged Annular-Space Pastuerizer and Sterilizer

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4.0 Objectives

The purpose of this experiment is to:

1) To determine which configuration parallel or counter flow is more effective at transferring heat.

2) To demonstrate the effect of flow rate variation on the performance characteristics of a parallel-flow concentric tube heat exchanger and also on the counter-flow concentric tube heat exchanger.

3) To experience the concentric tube heat exchanger in practical.

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5.0 Theory

There are two types of flow that being investigated in this experiment which are parallel flow and counter flow. The figures below shows the differences between the two flow.

The simplest heat exchanger is one for which the hot and cold fluids move in the same or opposite directions in a concentric tube (or double-pipe) construction. In the parallel-flow arrangement, the hot and cold fluids enter at the same end, flow in the same direction, and leave at the same end. In the counter flow arrangement, the fluids enter at opposite ends, flow in opposite directions, and leave at opposite ends.

Page | 10 There are several important formulas or equations to calculate the performance characteristics for both parallel-flow and counter-flow concentric tube heat exchangers. The performance required are power emitted, power absorbed, power lost efficiency (Ƞ), logarithmic mean temperature difference ( m), and overall heat transfer coefficient (U). The

The Efficiency for the Cold Medium is:

The Efficiency for the Hot Medium is:

The Mean Temperature Efficiency is:

The Power Emitted is given below (where ̇h is the Volumetric Flow Rate of the hot

fluid):

̇ ( )

The Power Absorbed is given below (where ̇c is the Volumetric Flow Rate of the cold

fluid):

̇ ( )

The Power Lost is therefore:

The Overall Efficiency ( ) is:

Page | 11 The Logarithmic Mean Temperature Difference ( m) is:

[ ]

( ) ( ) [( ₍ )

)]

The Overall Heat Transfer Coefficient (U) is:

Where the Surface Area (As) for this heat exchanger is 0.067 m2

To obtain the value of Density for both hot water and cold water ( h & c) and Specific

Heat of Hot Water (Cph), the method of interpolation is required. As for the Specific Heat

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6.0 Experimental Procedures

6.1 Apparatus/Experimental Setup

Figure 8: Heat exchanger system Figure 7: Heat exchanger apparatus system diagram (schematic diagram)

Page | 13 Figure 9: Temperature control Figure 12: Hot fluid volumetric flow rate

control Figure 10: Cold fluid volumetric flow

rate control

Page | 14 6.2 Procedure

1. The experiment for counter-flow heat exchanger operation had been configure. The required hot water inlet temperature was set to Th,in = 60 ◦c with the decade switch. The cold water volumetric flow rate ( Vc ) also set to run at a constant 2000 cm3/min.

2. The hot fluid volumetric flow rate (Vh) was initially set to 1000 cm3/min. The six temperature readings in the following table was recorded. The readings for volumetric flow rates of 2000, 3000 and 4000 cm3/min was repeated.

3. Values for density ( and ) and constant pressure specific heat ( and )

for the cold fluids at a temperature of and for the hot fluids at a temperature of was discovered.

4. The following heat exchanger performance factors such as power emitted, power absorbed, power lost, efficiency (ŋ), logarithmic mean temperature difference (Δ ), and overall heat transfer coefficient (U) had been calculated and recorded in the tables by using the data.

5. The result was discussed by comparing the effect of changing the volumetric flow rate of the hot fluid on each of these heat exchanger performance factors.

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7.0 Result

7.1 Data recorded

A. Concentric Tube Heat Exchanger in Parallel Flow

Vh

(cm3/min) Th,in(

0

C) Th,mid(0C) Th,out(0C) Tc,in(0C) Tc,mid(0C) Tc,out(0C)

1000 60 47 46 28 31 33

2000 60 53 52 28 34 36

3000 60 53 54 28 34 37

4000 60 54 55 28 35 39

Table 1: Data for parallel flow From table A-9 ( Properties of saturated water )

At Tc,in = 28⁰C &Th,in = 60⁰C

Properties are:

ρc= 996.4 kg/m3 Cpc = 4178.8 J/kg.K

ρh= 983.3 kg/m3 Cph = 4185 J/kg.K

B. Concentric Tube Heat Exchanger in Counter Flow

Vh

(cm3/min) Th,in(

0

C) Th,mid(0C) Th,out(0C) Tc,in(0C) Tc,mid(0C) Tc,out(0C)

1000 60 51 48 27 30 34

2000 60 53 61 27 32 37

3000 60 53 53 27 33 38

4000 60 54 54 27 34 39

Table 2: Data for counter flow From table A-9 ( Properties of saturated water )

At Tc,in = 27⁰C &Th,in = 60⁰C.

Properties are:

ρc= 996.6 kg/m3 Cpc = 4179.2 J/kg.K

Page | 16 7.2 Sample calculation

A. Experiment A: [Example of parallel-flow at 2000 cm3/min (3.333 x 10-5m3/s)]

i. Power emitted

̇ ( )

( )

ii. Power absorbed

Power Absorbed = VcρcCpc(Tc,out– Tc,in)

= (3.333 x10-5 ) (996.4) (4178.8) (36 - 28) = 1110.25 W

iii. Power lost

Power lost = Power Emitted – Power Absorbed = (1097.25 – 1110.25) W = -13 W iv. Efficiency (η) % 101 % 100 1097.25 1110.25 % 100      ed PowerEmitt bed PowerAbsor 

Page | 17 v. Logarithmic mean temperature difference (∆Tm)

C T T T T T T T T T T T T T o out c out h in c in h out c out h in c in h m 08 . 23 16 32 ln 16 32 ) ( ) ( ln ) ( ) ( ln , , , , , , , , 2 1 2 1                                    

vi. Overall heat transfer coefficient (U)

) . /( 98 . 717 ) 08 . 23 )( 067 . 0 ( 1110.25 2 C m W T A bed PowerAbsor U o m s    

vii To calculate the efficiency for the cold medium, nc

viii To calculate the efficiency for the hot mecium, nh

= 18.75 %

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viii To calculate the mean temperature effieiency, nmean = 31.25 % B. Experiment B

 Calculate all heat exchanger performance factors which are power emitted, power absorbed, power lost, efficiency (ŋ), logarithmic mean temperature difference (Δ ), and overall heat transfer coefficient (U) exactly the same as experiment A.

Page | 19 7.3 Analysis result

A. Experiment A: Concentric Tube Heat Exchanger in Parallel Flow

Vh Power

Emitted

Power Absorbed

Power

Lost Efficiency ∆Tm U nc nh nmean

(cm3/min) _{(W) (W) (W) (η, %) (⁰C) W/(m}2 .0C) % % % 1000 614.72 693.89 -79.17 112.88 22.20 466.51 15.63 43.75 29.69 2000 1097.25 1110.25 -13 101 23.08 717.98 25 25 25 3000 1234.53 1110.22 124.31 89.93 24.47 677.17 28.13 18.75 23.44 4000 1372.69 1526.56 -153.87 111.21 23.87 954.52 34.38 15.63 25.01

B. Experiment B: Concentric Tube Heat Exchanger in Counter Flow

Vh Power

Emitted

Power Absorbed

Power

Lost Efficiency ∆Tm U nc nh nmean

(cm3/min) _{(W) (W) (W) (η, %) (⁰C) W/(m}2 .0C) % % % 1000 526.9 971.73 -44.3 184.42 23.41 619.54 21.21 36.36 28.79 2000 1234.41 1388.19 -153.78 112.46 28.14 736.29 30.30 -3.03 13.64 3000 1440.29 1527.01 -86.72 106.02 23.94 952.01 33.33 21.21 27.27 4000 1372.69 1665.83 -18.96 101.15 23.87 1041.61 36.36 18.18 27.27

Page | 20 0 200 400 600 800 1000 1200 1400 1600 0 500 1000 1500 2000 2500 3000 3500 4000 4500 Pow e r Em itt e d , (W)

Volumetric Flow Rate,(Vh), mᶟ/s

Graph of Power Emitted,(W) vs Volumetric Flow

Rate,(mᶟ/s)

Volumetric Flow Rate,(Vh), mᶟ/s

Graph of Power Absorbed,(W) vs Volumetric Flow

Rate,(mᶟ/s)

Parallel flow Counter flow Figure 13: Graph 1

Page | 21 -200 -150 -100 -50 0 50 100 150 0 500 1000 1500 2000 2500 3000 3500 4000 4500 Pow e r A b sor b e d , ( W)

Volumetric Flow Rate,(Vh), mᶟ/s

Graph of Power Absorbed,(W) vs Volumetric Flow

Rate,(mᶟ/s)

Volumetric Flow Rate,(Vh), mᶟ/s

Graph of Efficiency,(%) vs Volumetric Flow

Rate,(mᶟ/s)

Parallel flow Counter flow Figure 15: Graph 3

Page | 22 0 5 10 15 20 25 30 0 500 1000 1500 2000 2500 3000 3500 4000 4500 Lo gar it hm ic M ean T em pe rat ur e D if fe re nc e (∆ 𝑻m )

Volumetric Flow Rate,(Vh), mᶟ/s

Graph of Logarithmic Mean Temperature vs

Volumetric Flow Rate,(mᶟ/s)

Parallel flow Counter flow 0 200 400 600 800 1000 1200 0 500 1000 1500 2000 2500 3000 3500 4000 4500 Ov e ral l H e at Tr an sf e r Co e ff ic ie n t (U)

Volumetric Flow Rate,(Vh), mᶟ/s

Graph of Overall Heat Transfer Coefficient (U)

vs Volumetric Flow Rate,(mᶟ/s)

Parallel flow Counter flow Figure 17: Graph 5

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8.0 Discussion

This part of report is individually hand written. The result of each member is attched with this report.

9.0 Conclusion

This part of report is individually hand written. The result of each member is attched with this report.

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10.0 References

 Websites:

1) Car radiator diagram downloaded from :

http://www.northernradiators.co.uk/cms_media/images/250x250_fitbox-nrg_car_radiators2.jpg [Accessed 18/10/14]

2) Introduction for heat exchanger:

http://www.nzifst.org.nz/unitoperations/httrapps1.htm [Accessed 18/10/14] 3) Heat exchanger applications:

http://www.fivesgroup.com/FivesCryogenie/EN/Expertise/Products/HeatExchangerA pplications/Pages/Applicationsofheatexchangers.aspx [Accessed 18/10/14]

4) Space heater diagram:

http://sustainability.williams.edu/files/2010/02/space-heater.jpg [Accessed 18/10/14]

 Books:

1) Eastop & McConkey, Applied Thermodynamics for Engineering Technologists 5th Edition, Prentice Hall, 1993.

2) Yunus A. Vengeland Micheal A. Boles, Thermodynamics An Engineering Approach,7th edition in SI units, 2011 , The McGraw-Hill Companies.

3) Thermodynamics, An Engineering Approach Sixth Edition (SI Units), Yunus A. Cengel & Michael A. Boles).

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11.0 Appendices