HEAT EXCHANGER

THERMODYNAMICS II CONCENTRIC TUBE HEAT EXCHANGER EMD5M5A

1.0Title

MEC 554-THERMALFLUIDS LAB THERMODYNAMICS II LAB

CONCENTRIC TUBE HEAT EXCHANGER

LECTURER: SITI HAJAR BINTI MOHD YUSOP

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THERMODYNAMICS II CONCENTRIC TUBE HEAT EXCHANGER EMD5M5A

2.0Abstract 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

increased as hot fluid volumetric flow rate increased.

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THERMODYNAMICS II CONCENTRIC TUBE HEAT EXCHANGER EMD5M5A

Table of Contents 1.0

Title............................................................................................................................................. 1

2.0

Abstract...................................................................................................................................... 2

List of Symbols ........................................................................................................................................ 4 List of figure ......................................................................................................................................... 5 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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THERMODYNAMICS II CONCENTRIC TUBE HEAT EXCHANGER EMD5M5A

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) Ultimate strength (MPa)

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THERMODYNAMICS II CONCENTRIC TUBE HEAT EXCHANGER EMD5M5A

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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THERMODYNAMICS II CONCENTRIC TUBE HEAT EXCHANGER EMD5M5A

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.

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THERMODYNAMICS II CONCENTRIC TUBE HEAT EXCHANGER EMD5M5A

Figure 2: Cara radiator

Figure 4: Anaerobic Digestion

Figure 1: Space heater

Figure 3: Packaged Annular-Space Pastuerizer and Sterilizer

Figure 5: Recuparator

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THERMODYNAMICS II CONCENTRIC TUBE HEAT EXCHANGER EMD5M5A

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. 4) To gain more knowledge and understanding of the concentric tube heat exchanger.

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THERMODYNAMICS II CONCENTRIC TUBE HEAT EXCHANGER EMD5M5A

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.

Figure 6: Heat exchanger temperature profiles and Fluid Flow Direction

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.

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THERMODYNAMICS II CONCENTRIC TUBE HEAT EXCHANGER EMD5M5A

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:

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THERMODYNAMICS II CONCENTRIC TUBE HEAT EXCHANGER EMD5M5A

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 of Cold Water (Cpc), the value is given in the Property Tables.

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THERMODYNAMICS II CONCENTRIC TUBE HEAT EXCHANGER EMD5M5A

6.0 Experimental Procedures 6.1 Apparatus/Experimental Setup

Figure 8: Heat exchanger system

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

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THERMODYNAMICS II CONCENTRIC TUBE HEAT EXCHANGER EMD5M5A

Figure 10: Cold fluid volumetric flow rate control

Figure 12: Hot fluid volumetric flow rate control

Figure 9: Temperature control

Figure 11: Valve diagram for parallel flow and counter flow

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THERMODYNAMICS II CONCENTRIC TUBE HEAT EXCHANGER EMD5M5A

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 (

for the cold fluids at a temperature of temperature of

and

)

and for the hot fluids at a

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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THERMODYNAMICS II CONCENTRIC TUBE HEAT EXCHANGER EMD5M5A

7.0

Result 7.1 Data recorded A. Concentric Tube Heat Exchanger in Parallel Flow

Vh

Th,in(0C)

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

(cm3/min)

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

Th,in(0C)

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

3

(cm /min)

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

ρh= 983.3 kg/m3

Cph = 4185 J/kg.K

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THERMODYNAMICS II CONCENTRIC TUBE HEAT EXCHANGER EMD5M5A

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)

PowerAbsorbed  100% PowerEmitted 1110.25   100% 1097.25  101%



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THERMODYNAMICS II CONCENTRIC TUBE HEAT EXCHANGER EMD5M5A

v.

Logarithmic mean temperature difference (∆Tm) Tm 



T1  T2  T  ln  1   T2  (Th ,in  Tc ,in )  (Th ,out  Tc ,out )  (Th ,in  Tc ,in )  ln    (Th ,out  Tc ,out ) 

32  16  32  ln    16   23.08o C 

vi.

Overall heat transfer coefficient (U)

U 

PowerAbsorbed As Tm 1110.25 (0.067)(23.08)

 717.98W /(m 2 .o C )

vii

To calculate the efficiency for the cold medium, nc

=

25 %

viii To calculate the efficiency for the hot mecium, nh

= 18.75 % Page | 17

THERMODYNAMICS II CONCENTRIC TUBE HEAT EXCHANGER EMD5M5A

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.

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THERMODYNAMICS II CONCENTRIC TUBE HEAT EXCHANGER EMD5M5A

7.3 Analysis result A. Experiment A: Concentric Tube Heat Exchanger in Parallel Flow Power Emitted

Power Absorbed

Power Lost

Efficiency

∆Tm

U

nc

nh

nmean

(cm3/min)

(W)

(W)

(W)

(η, %)

(⁰C)

W/(m2.0C)

%

%

%

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

Vh

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

Power Emitted

Power Absorbed

Power Lost

Efficiency

∆Tm

U

nc

nh

nmean

(cm3/min)

(W)

(W)

(W)

(η, %)

(⁰C)

W/(m2.0C)

%

%

%

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

Vh

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THERMODYNAMICS II CONCENTRIC TUBE HEAT EXCHANGER EMD5M5A

Graph of Power Emitted,(W) vs Volumetric Flow Rate,(mᶟ/s) 1600

Power Emitted, (W)

1400 1200 1000 800

Parallel flow

600

Counter flow

400 200 0 0

500

1000

1500

2000

2500

3000

3500

4000

4500

Volumetric Flow Rate,(Vh), mᶟ/s Figure 13: Graph 1

Graph of Power Absorbed,(W) vs Volumetric Flow Rate,(mᶟ/s) 1800

Power Absorbed, (W)

1600 1400 1200 1000 800

Parallel flow

600

Counter flow

400 200 0 0

500

1000

1500

2000

2500

3000

3500

4000

4500

Volumetric Flow Rate,(Vh), mᶟ/s

Figure 14: Graph 2

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THERMODYNAMICS II CONCENTRIC TUBE HEAT EXCHANGER EMD5M5A

Graph of Power Absorbed,(W) vs Volumetric Flow Rate,(mᶟ/s) 150

Power Absorbed, (W)

100 50 0 -50

0

500

1000

1500

2000

2500

3000

3500

4000

4500

Parallel flow Counter flow

-100 -150 -200

Volumetric Flow Rate,(Vh), mᶟ/s Figure 15: Graph 3

Graph of Efficiency,(%) vs Volumetric Flow Rate,(mᶟ/s) 200 180 160 Efficiency,(%)

140 120 100

Parallel flow

80

Counter flow

60 40 20 0 0

500

1000

1500

2000

2500

3000

3500

4000

4500

Volumetric Flow Rate,(Vh), mᶟ/s

Figure 16: Graph 4

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THERMODYNAMICS II CONCENTRIC TUBE HEAT EXCHANGER EMD5M5A

Logarithmic Mean Temperature Difference (∆𝑻m)

Graph of Logarithmic Mean Temperature vs Volumetric Flow Rate,(mᶟ/s) 30 25 20 15

Parallel flow

10

Counter flow

5 0 0

500

1000

1500

2000

2500

3000

3500

4000

4500

Volumetric Flow Rate,(Vh), mᶟ/s

Figure 17: Graph 5

Overall Heat Transfer Coefficient (U)

Graph of Overall Heat Transfer Coefficient (U) vs Volumetric Flow Rate,(mᶟ/s) 1200 1000 800 600

Parallel flow

400

Counter flow

200 0 0

500

1000

1500

2000

2500

3000

3500

4000

4500

Volumetric Flow Rate,(Vh), mᶟ/s Figure 18: Graph 6

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THERMODYNAMICS II CONCENTRIC TUBE HEAT EXCHANGER EMD5M5A

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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THERMODYNAMICS II CONCENTRIC TUBE HEAT EXCHANGER EMD5M5A

10.0 References  Websites: 1) Car radiator diagram downloaded from : http://www.northernradiators.co.uk/cms_media/images/250x250_fitboxnrg_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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THERMODYNAMICS II CONCENTRIC TUBE HEAT EXCHANGER EMD5M5A

11.0 Appendices

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