1. The Fabrication and Testing of Heat Exchanger Experimental Test Rig
M. H. Rahman*, S. Z. Zahrin, N. Z. Kolan, M. A. Yusuff and A. B. A. Rahim
Faculty of Mechanical Engineering,
Universiti Malaysia Pahang,
26600 Pekan, Pahang, Malaysia.
*Email: mohdhelmyrahman92@gmail.com
Phone: +60183793352
ABSTRACT
This project focuses on designing and fabricating a heat exchanger test rig using a
designed tube counter flow heat exchanger. Aluminium sheet metal is used to fabricate a tank
to be filled with water as medium. Finite Element Analysis (FEA) is also done to the table
design in order to analyse the stress develop by actual weight experienced during the process.
The water in the tank will be heated by a heater to a temperature around 40°C to and a water
pump is used to produce a hot channel flow for the system. Tap water is used as the cold
channel for the heat exchanger system with inlet temperature around 29°C connected to the
system by a hose. The effectiveness-NTU method is used to calculate the theoretical hot
channel outlet value of the heat exchanger design and the heat transfer rate for the system.
The experimental temperature value obtained by thermocouple reading will be used to
calculate the percentage error between the experimental and theoretical values.
Keywords: Counter-flow tube heat exchanger; effectiveness-NTU method; heat transfer rate

2. INTRODUCTION
A heat exchanger is a piece of equipment built for efficient heat transfer from one
medium to another. The media may be separated by a solid wall to prevent mixing or they
may be in direct contact. They are widely used in space heating, refrigeration, air
conditioning, power plants, chemical plants, petrochemical plants, petroleum refineries,
natural gas processing, and sewage treatment. The classic example of a heat exchanger is
found in an internal combustion engine in which a circulating fluid known as engine coolant
flows through radiator coils and air flows past the coils, which cools the coolant and heats the
incoming air. Examples in practice in which flowing fluids exchange heat are air intercoolers
and preheaters, condensers and boilers in steam plant, condensers and evaporators in
refrigerator units, and many other industrial processes in which a liquid or gas is required to
be either cooled or heated (Eckert and Drakes, 1987).
In heat exchanger design, there are three types of flow arrangements; counter-flow,
parallel-flow, and cross-flow. In the counter-flow heat exchanger, both fluids entered the
exchanger from opposite sides. In the parallel-flow heat exchanger the fluids come in from
the same end and move parallel to each other as they flow to the other side. The crossflow
heat exchanger moves the fluids in a perpendicular fashion. Compare to other flow
arrangements counter–flow is the most efficient design because it transfers the greatest
amount of heat (Ankit R. Patel, 2013).
F. Joshua (2009), in his concentric tube heat exchanger (CHTX) design which
consists of a copper pipe of diameter 0.0127m that is enclosed by a bigger copper pipe of
diameter 0.0254m. The bigger pipe carries the cold water while the smaller copper pipe
conveys the hot water in a counter-current flow. He used the logarithmic mean temperature
difference (LMTD) to analyse the heat exchanger and found that the design was effective.

3. DESIGN CONSIDERATIONS
According to F. Joshua (2009), in designing heat exchangers, a number of factors that
need to be considered are:
1. Resistance to heat transfer should be minimized
2. The equipment should be sturdy.
3. Cost and material requirements should be kept low.
4. Corrosion should be avoided.
5. Pumping cost should be kept low.
6. Space required should be kept low.
7. Required weight should be kept low.
Design involves trade-off among factors not related to heat transfer. Meeting the
objective of minimized thermal resistance implies thin wall separating fluids. Thin walls may
not be compatible with sturdiness. Auxiliary steps may have to be taken, for instance, the use
of support plates for tubing, to realize sturdiness (Saunders, 1988). A heat exchanger
typically involves two flowing fluids separated by a solid wall. Heat is first transferred from
the hot fluid to the wall by convection through the wall by conduction and from the wall to
the cold fluid again by convection. Any radiation effects are usually included in the
convection heat transfer coefficients (Holman, 2002).
EFFECTIVENESS-NTU METHOD
One of the example of problem that occur in analysing the heat exchanger design is
the determination of heat transfer rate and the outlet temperature and inlet temperature of
both hot and cold fluids flow as the type and size of heat exchanger is prescribed. The log
mean temperature method (LMTD) which is commonly used in analysing the heat exchanger
can be used in this problem. However, the procedure on solving the problem will require

4. tedious iteration and therefore not practical. As a result, Kays and London (1984) came up
with the effectiveness-NTU method to simplify the analysis (Y. A. Cengel and A. J. Ghajar,
2011). They defined a dimensionless parameter called the heat exchanger effectiveness P
which is the ratio of actual heat transfer rate to the maximum possible heat transfer rate. For
the single-pass parallel-flow and counter-flow heat exchangers, P—NTU expressions are:
Where NTU = UA/Cmin is the number of transfer units, and C* = Cmin/Cmax is the
ratio of heat capacity rate of the fluid with the smaller heat capacity (hereafter, the minimum
fluid) to that of the fluid with the larger one (hereafter, the maximum fluid). P. Talukdar
(2011), state that the NTU method is mainly based on the dimensionless parameter called the
heat transfer effectiveness, ɛ, defined as below figure.
Figure 1: Effectiveness-NTU method calculation
Source: P. Talukdar (2011)

5. In order to determine the maximum heat transfer in a heat exchanger, the maximum
temperature difference that may occur must be considered. According to Y. A. Cengel and A.
J. Ghajar (2011), the heat exchanger will reach its maximum heat transfer rate if the outlet
temperature of the hot water channel is equal to the inlet temperature of the cold water
channel or anyway around.
Kays and London (1984), Shah and Sekulic (2003), and Shah and Pignotti (1992)
have presented effectiveness–NTU formulas for over 100 different heat exchanger flow
arrangements in the form of charts, tables and analytical closed-form P—NTU formulas. The
effectiveness–NTU method also offers advantages for the performance comparison between
various types of heat exchangers, that is from given value of NTU the goodness of the heat
exchanger can be easily identified from its value of P
PROJECT METHODOLOGY
In designing the heat exchanger test rig, several factor reviewed before need to be
considered in order to produce the lowest cost but effective design of heat exchanger. The
design of the heat exchanger is based on the situation taken from a swimming pool and a fish
pond during a hot sunny day or weather here in Malaysia. It was found that there might be an
increase of temperature to around 40°C due to the heat transfer from body source and the
surrounding temperature. Thus, an approach to design the simple and cost saving heat
exchanger is configured. The design of the heat exchanger test rig will consists of mainly two
parts which are:
1. Heat exchanger test rig table and tank
2. Heat exchanger flow and pipeline design
The design and analysis of these two parts will be conducted based on guidelines and
references from the previous study in order to maintain the reliability of the designs.

6. Figure 1: First design for table
Figure 2: Second design for table

7. Figure 3: Final design for table
Figure 4: Tank design

8. Figure 1: The square hollow bars are measured and cut according to size
Figure 2: Raw material that has been cut according to size

9. Figure 3: Cutting the square hollow bar according to the design
Figure 4: Cutting the sheet metal by using sheet metal machine cutter

10. Figure 5: The fabricated parts before installations
Figure 6: Welding process

11. Figure 7: Tank attached to the table by using MIG
Figure 8: Pump with pipe assembled in and out connection

12. Figure 9: Painted table and tank as coating for corrosion protection
Figure 10: A fully assembled heat exchanger

13. DESIGN AND SIMULATION
Figure 1: P& ID drawing
The above Figure 1 shows the P&ID drawing of the whole structure of heat exchanger
test rig. It shows 2D drawing of the components include in the system. The components
involve in the system includes 90 elbow, standard tee joint, flexible hose, pump, water
heater and thermocouple. The purpose of having 2D drawing of P&ID drawing is to get the
clear view on how the system will work.
In order to analyse the structural design of the table and tank, a 3D model is designed
using the Solidworks software in order perform the Finite Element Analysis (FEA) on the
structure. The design is as shown below:
: PUMP

14. Figure 1: Table and tank Solidworks design
In this design, the dimension of each components involved is based on the actual
dimension used for the project. Each part is connected by weldments and in this design; the
weldment beads are applied to every connected faces of the components in order to achieve
the precise analysis for the whole process. The material is applied for each part according to
the list of materials used in the project.
Solidworks Simulation is used to analyse the design. The bottom faces of the table are
treated as fixed point in order to create a stable part analysis. A total of 500N forces is
applied to the whole part by considering the weight of the pump, and the weight of the water
used by referring to the calculations:
ρwater = 1000 kg/m3
Actual volume of water used = 1/2 of tank
= (0.5m) x (0.5m) x (0.175m)
= 0.0437 m3
Mass of water = (1000 kg/m3
) x (0.0437 m3
)
= 43.75 kg

15. Mass of pump = 6 kg
Total mass = 49.75 kg
Weight/Force = (49.75 kg) x (9.81 m/s2
)
= 488.04 N ≈ 500 N
By applying the total forces, the analysis is created and run. The results obtained from
the analysis include the displacement results, strain and stress results. The obtained analysis
results are as shown below.
Figure 2: Displacement result
From the displacement result, the highest obtained value is 2.782e-002 mm. As we
can see, the area that experiences the most displacement is mostly at the centre of the table
where the vertices of the tank create most pressure to the unsupported middle part of the
table. But, the design is consider acceptable due to the value of the highest displacement is
relatively small.The statement is strengthening by analysing the strain result. By looking to
the result as shown in figure 3 below, we can say that the area of the unsupported vertices of
the tank at the middle experienced the most strain as said before at which the Equivalent
Strain value is around 2.537 e-005.

16. Figure 3: Strain result
Moving to the stress result as shown in figure 4 below, the highest obtained stress
result at the area mentioned before is around 9000 Kn/m2
. The design can be considered as
acceptable because as we can see, not all the parts experienced the highest stress in the
system and the area at which the stress occur does not react proportionally to the highest
stress value.
Figure 4: Stress result

17. RESULTS AND DISCUSSIONS
1. Heat Transfer Rate
The heat transfer in a heat exchanger will reach its maximum value when the cold
fluid is heated to the inlet temperature of the hot fluid or the hot fluid is cooled to the inlet
temperature of the cold fluid. In this project, will examine and compare the difference
between the calculated theory results and also the experimental results to determine the
percentage error that may occur in our design experiment. The outlet temperature will be
estimated theoretically and will be compare to the achieve value of the project.
Theoretical:
Hot water (Inlet)
Tin = 38C
 = 994.0kg/m3
k = 0.623W/Mk
 = 0.720x10-3
kg/ms
Cp = 4178J/kgK
Q = 5.833x10-4
m3
/s
𝑚̇ = (5.833x10-4
m3
/s)(994.0kg/m3
)
= 0.5798kg/s
Cold Water (Inlet)
Tin = 30C
= 998.0 kg/m3
k = 0.598W/Mk
 = 1.002x10-3
kg/ms
Cp = 4182J/kgK

18. Q = 1.5x10-4
m3
/s
𝑚̇ = (1.5x10-4
)(998)
= 0.1497kg/s
Ch = 𝑚̇ hCph
= (0.5789kg/s)(4.178kJ/kgK)
= 2422W/K
Cc = 𝑚̇ cCpc
= (0.1497kg/s)(4.182kJ/kgK)
= 626.05W/K
Therefore; Cmin = 626.05W/K
𝑄̇ = Cc (Tc,out – Tc,in)
Tc,out = Tc,in +
𝑄̇
𝐶𝑐
= 30 +
9390.75
626.05
= 45C
𝑄̇ = Ch (Th,in – Th,out)
Th,out = Th,in –
𝑄̇
𝐶ℎ
= 38C –
9390.75
2422
= 34C
2) Pipe friction loss
Pipe A (Hot Channel 38C):
1” ANSI schedule 40
Nominal diameter: 1 inch = 0.025 m
External diameter: 1.315 inch = 0.033 m
Internal diameter: 1.029 inch = 0.026 m
Area, A =
𝜋(𝐷𝑜2−𝐷𝑖2)
4
=
𝜋((0.033𝑚)2−(0.026𝑚)2)
4
= 3.244 x 10−4
𝑚2
Q = 5.833 x 10−4
𝑚3
/𝑠 (Pump flowrate
capacity)
V = Q / A
= (5.833 x 10−4
𝑚3
/𝑠) / (3.244 x 10−4
𝑚2
)
= 1.798 𝑚/𝑠
Total length: 1.867m
∆P =
𝜌𝑔𝐿𝑉2
𝐷2𝑔
=
(1000
𝑘𝑔
𝑚3)(9.81
𝑚
𝑠2)(1.867𝑚)(1.798 𝑚/𝑠)2
(0.026𝑚)2(9.81
𝑚
𝑠2)

19. = 8928.469Pa
Fittings:
Standard elbow 90 ̊ : k = 0.57
Standard Tee : k = 1.14
Pipe exit : k = 1.00
Pipe entrance: k = 0.78
h = kv2
/2g
h=
((2𝑥0.57)+(2𝑥1.14)+ (2𝑥1)+ 0.78) (1.798 𝑚/𝑠)2
2(9.81
𝑚
𝑠2)
= 0.568 m
∆P = 𝜌gh
= (1000
𝑘𝑔
𝑚3
) (9.81
𝑚
𝑠2
) (0.568 𝑚)
= 5573.8Pa
Total pressure loss :
∆P total = 8928.469Pa + 5573.8 Pa
= 8934.042Pa
Pipe B (Cold Channel 30C):
3/4” ANSI schedule 40
Nominal diameter: 3/4 inch = 0.019 m
External diameter: 1.050 inch = 0.027 m
Internal diameter: 0.804 inch = 0.020 m
Area, A =
𝜋(𝐷𝑜2−𝐷𝑖2)
4
=
𝜋((0.027𝑚)2−(0.020𝑚)2)
4
= 2.58 x 10−4
𝑚2
Q = 1.5 x 10−4
𝑚3
/𝑠 (estimation based on
average water flowrate in home supply)
V = Q / A
= (1.5 x 10−4
𝑚3
/𝑠) / (2.58 x 10−4
𝑚2
)
= 0.581 m/s
Total length: 1.08m
∆P =
𝜌𝑔𝐿𝑉2
𝐷2𝑔
=
(1000
𝑘𝑔
𝑚3)(9.81
𝑚
𝑠2)(1.08𝑚)(0.581 𝑚/𝑠)2
(0.020𝑚)2(9.81
𝑚
𝑠2)
= 911.415Pa

20. Fittings:
Pipe exit : k = 1.00
h = kv2
/2g
h =
( 1) (0.581𝑚/𝑠)2
2(9.81
𝑚
𝑠2)
= 0.0296 𝑚
∆P = 𝜌gh
= (1000
𝑘𝑔
𝑚3
) (9.81
𝑚
𝑠2
) (0.0296𝑚)
= 290.5 Pa
Experimental value:
Pipe A (Hot Channel):
Tin :37.6C
Tout: 37.3C
Percentage error:
𝑒𝑥𝑝𝑒𝑟𝑖𝑚𝑒𝑛𝑡𝑎𝑙 𝑣𝑎𝑙𝑢𝑒 − 𝑡ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙 𝑣𝑎𝑙𝑢𝑒
𝑡ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙 𝑣𝑎𝑙𝑢𝑒
Hot water (Inlet)

37.6 𝐶 − 38 𝐶
38 𝐶
 𝑥 100%
=1.05%
Hot water (Outlet)

37.3 𝐶 − 34 𝐶
34 𝐶
 𝑥 100%
=9.71%
The above calculations show the percentage error between experimental and
theoretical value is not big in difference. The percentage error for temperature of the hot
water inlet is about 1.05% while for the outlet is about 9.71%. The difference is might be due
to the heat release in any ways since the tank is not protected by any insulator.

21. CONCLUSION
In conclusion, there is a percentage error during the testing of the heat exchanger. In
order to prevent this error, controlling variable that can be controlled is by insulating the heat
exchanger with Styrofoam insulation sheets. The objective of this project is achieved. The
above calculations show the percentage error between experimental and theoretical value is
not big in difference. The percentage error for temperature of the hot water inlet is about
1.05% while for the outlet is about 9.71%. The difference is might be due to the heat release
in any ways since the tank is not protected by any insulator.
ACKNOWLEDGMENTS
The authors would like to say thanks to the lecturers and engineers in University
Malaysia Pahang (UMP) for guiding in completing this project and providing laboratory
facilities.

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