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HEAT Exchanger Experiment 218002346
Mechanical Engineering (University of Johannesburg)
Studocu is not sponsored or endorsed by any college or university
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DEPARTMENT OF MECHANICAL AND INDUSTRIAL ENGINEERING
FACULTY OF ENGINEERING AND BUILDENVIRONMENT
STUDENT NAME
: I.B. BABE
STUDENT NO
: 218002346
ASSIGMENT
: Experiment 1
MODULE
: THERMODYNAMICS A3
CODE
: TRDMIA3
DUE DATE
:19 April 2021
I confirm that this assignment is my own work, is not copied from any other person's work, and
has not previously submitted for assessment either at University of Johannesburg or elsewhere.
Signed………………………………………. Date ………………………………………….
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Table of Contents
Acknowledgement: ......................................................................................................................... 4
Statement of originality: ................................................................................................................. 5
Abstract: .......................................................................................................................................... 6
1.
Introduction: ............................................................................................................................ 7
2.
Aim: ......................................................................................................................................... 8
3.
Assumptions: ........................................................................................................................... 8
4.
Procedure: ................................................................................................................................ 9
5.
Results: .................................................................................................................................... 9
6.
Discussion:............................................................................................................................. 15
7.
Conclusion: ............................................................................................................................ 15
8.
References: ............................................................................................................................ 17
9.
Appendix: .............................................................................................................................. 18
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List of figures
Figure 1: Shell and tube heat exchanger ......................................................................................... 7
Figure 2: Counter Flow ................................................................................................................... 8
Figure 3: Parallel Flow.................................................................................................................... 9
Figure 4: heat exchanger for parallel flow .................................................................................... 18
Figure 5: Heat exchanger for counter flow ................................................................................... 18
Figure 6:Fluid flow direction for parallel and counter flow ......................................................... 18
List of tables:
Table 1: counter flow ...................................................................................................................... 9
Table 2: parallel flow .................................................................................................................... 10
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Acknowledgement:
My sincere appreciation goes to Mr Tlali for allowing us to perform the lab and was very patient
with us when we did not understand some concepts as he explained the procedure on how the lab
was conducted. I thank Mr Gqibani S who is our Thermodynamics lecture for helping us with the
analysis of the lab together with the tutor (Mr Dube). I also appreciate my family for helping me
with the data for research. And I want to thank the university for giving us the opportunity to go
to campus and be able to do our practical’s since we are facing difficult time due to Covid-19
pandemic.
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Statement of originality:
BABE. IB of Student no: 218002346 declare that this lab report is my own original work. All
secondary materials utilized, whether from the electronics or print sources, have been
acknowledged carefully and referenced in accordance with the referencing style used by the
Mechanical and Industrial Technology Department at the University of Johannesburg. I understand
that plagiarism is a serious offence, and necessary disciplinary actions will be taken. I have
comprehended all the plagiarism and policies regarding references as set out in the
Thermodynamics 3A Learner Guide.
Signature: BABE. IB Date: 19 April 2021
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Abstract:
The aim of the experiment was to demonstrate indirect heat or cooling by the heat transfer from
one fluid to another. Each heat exchanger was tested under two different flow arrangements:
parallel (co-current) flow and counter current flow. Aside from flow distribution cold mass flow
rates were varied to evaluate the effect on heat exchanger performance. From the results obtained,
the results shown that the cold water exit temperature of the counter flow is higher than the parallel
flow. Hence, the counter flow is much more efficiency than parallel flow. The results also shown
that the higher the flow rate will cause the rate of heat transfer increase. As a result, the counter
flow is more efficiency than parallel flow and are preferred to use in the transfer heat.
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1. Introduction:
A heat exchanger is a piece of process equipment in which heat exchange takes place between two
fluids that enter and exit at different temperatures. The primary design objective of the equipment
may be either to remove heat from a hot fluid or to add heat to a cold fluid. Depending upon the
relative direction of fluid motion, shell-and-tube heat exchangers are classified as parallel flow,
counter flow, cross flow. In parallel flow, the hot and cold fluids flow in the same direction and
therefore enter the exchanger on the same end and exit the exchanger on the same end. In counter
flow, the two fluids flow in opposite directions and thus enter the exchanger and exit the exchanger
from opposite ends. Cross flow heat exchangers will not be analyzed as a part of this laboratory
experiment (thermodynamics, n.d).
Figure 1: Shell and tube heat exchanger
Heat exchangers are deceiving that transfer energy from one fluid to another across a solid surface.
There are many different types of heat exchangers that are used in many different processes in the
chemical, electric utility, and aerospace industries. Also, in recent years, applications of heat
exchangers in the food processing and cryogenics industries have introduced many concerns when
it comes to control and the understanding of these systems3. These systems need to take into
consideration the type of heat transfer needed. The heat exchangers allow an operator to have
control over the dynamics of heat transfer between fluids. It is therefore very important to choose
the correct exchanger for the process that is being used as it can greatly affect the efficiencies of a
plant. A very common heat exchanger that is used to heat streams within a plant is the shell and
tube heat exchanger. This heat exchanger uses counter flow to heat up or cool down the desired
fluid. There are always hot and cold streams in the heat exchangers. Using the counter flow the
fluids have more opportunities to exchange heat than if a concurrent flow were to be used (Heat
exchanger control system, n.d).
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In indirect‐contact heat exchangers, the two flowing fluids are separated by a wall and heat
exchange between these two fluids occurs through this wall. As a separating wall hinders the heat
flow, these heat exchangers are less effective than the direct‐contact ones. However, these heat
exchangers are widely used because most of the practical cases fluids cannot be allowed to contact
or mix. Common examples of indirect‐contact exchangers are shell and tube, bayonet, concentric
tube, plate, spiral plate, radiator, storage or regenerators, and compact exchangers. On the other
hand, two fluids streams come into direct contact with each other and exchange heat before
separating (Murshed,2016).
2. Aim:
To demonstrate indirect heating or cooling by the heat transfer from one fluid to another.
3. Assumptions:
•
•
•
•
•
•
Steady state process
The mass flow rate is kept constant for hot and cold fluid.
The heat exchangers have only two streams.
Heat exchange with the surroundings is negligible.
There is a linear relationship between specific enthalpy and temperature for both streams
(i.e., constant specific heat capacities).
The overall heat transfer coefficient between the stream is constant throughout the heat
exchanger.
Apparatus:
Figure 2: Counter Flow
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Figure 3: Parallel Flow
4. Procedure:
➢ Set the machine to counter flow (see the picture for counter flow)
➢ Connect the water inlet pipe and supply cold water from pump.
➢ Turn the main switch and heater switch on.
➢ Set the hot water temperature controller to 60º C.
➢ Set the cold-water flow rate to (V cold) 15 g/ sec.
➢ Set the hot water flow rate to (V hot) 50 g/ sec.
➢ Monitor the stream temperatures and the hot and cold flow rates to ensure they remain
close to the original setting.
➢ Allow the conditions to stabilise and take measurements (T1 – T6)
➢ Adjust the cooling water flow to 30 g/ sec.
➢ Make sure the hot flow rate remains at 50g/sec.
➢ Allow the condition to stabilise and take measurements (T1 – T6) again
5. Results:
For counter flow
Table 1: counter flow
Sr. no
1
2
T1 º C
74.4
72.3
T5 º C
32.5
30.1
T2 º C
65.3
73.4
T3 º C
22
22.1
T6 º C
32.6
30.1
T4 º C
36.4
35.2
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V cold
15 g/s
30 g/s
V hot
50 g/s
50g/s
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For Parallel flow
Table 2: parallel flow
Sr. no
1
2
T1 º C
61.4
72.1
T5 º C
29.8
28.7
T2 º C
53.7
65.3
T3 º C
21.8
22
T6 º C
29.8
28.7
ρHot
= 0.9852 kg/litre
CPhot = 4.183 kJ/kg k
ρCold
= 0.9975 kg/litre
CPcold = 4.18 kJ/kg k
T4 º C
32.9
33.3
Calculations:
For counter flow:
Hot water inlet T1- 74.4 ⁰C
Hot water outlet T2- 65.3 ⁰C
Cold water inlet T3- 22 ⁰C
Cold water outlet T4- 36.4 ⁰C
𝑚𝑐𝑜𝑙𝑑 = 15 g/s or 15× 10−3 kg/sec
𝑚ℎ𝑜𝑡 = 50× 10−3 kg/sec
𝐶𝑝ℎ𝑜𝑡 = 4.183 kJ/kg k
𝐶𝑝𝑐𝑜𝑙𝑑 = 4.18 kJ/kg k
1. Reduction in hot fluid temperature:
∆T hot= T1-T2 = 74.4-65.3= 9.1 ⁰C
2. Increase in cold fluid temperature:
∆T cold= T4-T3= 36.4-22= 14.4 ⁰C
3. Temperature efficiency of hot stream:
𝑇1−𝑇2
𝜂ℎ𝑜𝑡 =
=
𝑇1−𝑇3
74.4−65.3
74.4−22
= 0.1736
4. Temperature efficiency of cold stream:
𝑇4−𝑇3
𝜂𝑐𝑜𝑙𝑑 =
𝑇1−𝑇3
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V cold
15 g/s
30 g/s
V hot
50 g/s
50 g/s
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36.4−22
= 0.2748
=
74.4−22
5. Mean temperature efficiency:
𝜂𝑚𝑒𝑎𝑛 =
=
𝜂ℎ𝑜𝑡 +𝜂𝑐𝑜𝑙𝑑
2
0.1736+0.2748
2
= 0.2242
6. Power emitted from hot stream (𝑄ℎ𝑜𝑡 ):
𝑄ℎ𝑜𝑡 = 𝑚ℎ𝑜𝑡 × 𝐶𝑝ℎ𝑜𝑡 (𝑇1 − 𝑇2)
= 50× 10−3 ×4.183(74.4-65.3)
= 1.903 kW
7. Power emitted from cold stream (𝑄𝑐𝑜𝑙𝑑 ):
𝑄𝑐𝑜𝑙𝑑 = 𝑚𝑐𝑜𝑙𝑑 × 𝐶𝑝𝑐𝑜𝑙𝑑 (𝑇4 − 𝑇3)
= 15× 10−3 ×4.18(36.4-22)
= 0.9028 kW
8. The logarithmic Mean Temperature difference (LMTD):
∆𝑇𝑖𝑛𝑙𝑒𝑡 =74.4-36.4= 38 ⁰C
∆𝑇𝑒𝑥𝑖𝑡 = 65.3-22= 43.3 ⁰C
LMTD=
=
𝑑𝑇𝑚𝑎𝑥−𝑑𝑇𝑚𝑖𝑛
𝑑𝑇𝑚𝑎𝑥
ln
𝑑𝑇𝑚𝑖𝑛
38−43.3
38
43.3
ln
=40.59 ⁰C
Experiment-2:
T1= 72.3 ⁰C
T2= 73.4 ⁰C
T3= 20.1 ⁰C
T4= 35.2 ⁰C
𝑚𝑐𝑜𝑙𝑑 = 30 × 10−3 kg/sec
𝑚ℎ𝑜𝑡 = 50× 10−3 kg/sec
1. ∆𝑇ℎ𝑜𝑡 = T1-T2= 72.3-73.4= -1.1 ⁰C
2. ∆𝑇𝐶𝑜𝑙𝑑 = T4-T3= 35.2-20.1= 15.1 ⁰C
𝑇1−𝑇2
3. 𝜂ℎ𝑜𝑡 =
=
𝑇1−𝑇3
1.1
= 0.0210 = 2.1%
52.2
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4. 𝜂𝑐𝑜𝑙𝑑 =
=
𝑇4−𝑇3
𝑇1−𝑇3
15.1
= 0.28927 =28.93%
52.2
𝜂ℎ𝑜𝑡 +𝜂𝑐𝑜𝑙𝑑
5. 𝜂𝑚𝑒𝑎𝑛 =
=
2
0.0210+0.28927
2
= 0.15513 =15.513%
6. 𝑄ℎ𝑜𝑡 = 𝑚ℎ𝑜𝑡 × 𝐶𝑝ℎ𝑜𝑡 (𝑇1 − 𝑇2)
= 50× 10−3 ×4.183× (-1.1)
= -0.23 kW
7. 𝑄𝑐𝑜𝑙𝑑 = 𝑚𝑐𝑜𝑙𝑑 × 𝐶𝑝𝑐𝑜𝑙𝑑 (𝑇4 − 𝑇3)
= 30 × 10−3 ×4.18× (15.1)
= 1.8935 kW
8. LMTD=
=
𝑑𝑇𝑚𝑎𝑥−𝑑𝑇𝑚𝑖𝑛
ln
𝑑𝑇𝑚𝑎𝑥
𝑑𝑇𝑚𝑖𝑛
(72.3−35.2)−(73.4−20.1)
37.1
53.3
ln
For parallel flow 1:
= 44.711 ⁰C
T1-61.4 ⁰C
T2-53.7 ⁰C
T3-21.8 ⁰C
T4-32.9 ⁰C
𝑚𝑐𝑜𝑙𝑑 = 15 × 10−3 kg/sec
𝑚ℎ𝑜𝑡 = 50 × 10−3 kg/sec
1. ∆𝑇ℎ𝑜𝑡 = T1-T2= 61.4-53.7= 7.7 ⁰C
2. ∆𝑇𝑐𝑜𝑙𝑑 = T4-T3= 32.9-21.8= 11.1 ⁰C
3. 𝜂ℎ𝑜𝑡 =
=
𝑇1−𝑇2
𝑇1−𝑇3
7.7
= 0.194 = 19.4%
𝑇1−𝑇3
11.1
= 0.280 = 28%
61.4−21.8
4. 𝜂𝑐𝑜𝑙𝑑 =
=
5. 𝜂𝑚𝑒𝑎𝑛 =
=
𝑇4−𝑇3
61.4−21.8
𝜂ℎ𝑜𝑡 +𝜂𝑐𝑜𝑙𝑑
2
0.194+0.280
2
= 0.237 =23.7%
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6.
7.
𝑄ℎ𝑜𝑡 = 𝑚ℎ𝑜𝑡 × 𝐶𝑝ℎ𝑜𝑡 (𝑇1 − 𝑇2)
= 50 × 10−3 ×4.183× (7.7)
= 1.610 kW
𝑄𝑐𝑜𝑙𝑑 = 𝑚𝑐𝑜𝑙𝑑 × 𝐶𝑝𝑐𝑜𝑙𝑑 (𝑇4 − 𝑇3)
= 15 × 10−3×4.18× (11.1)
= 0.69597 kW
∆𝑇𝑖𝑛 = T1-T3= 61.4-21.8= 39.6 ⁰C
∆𝑇𝐸𝑋𝑇 = T2-T4= 53.7-32.9 = 20.8 ⁰C
LMTD=
=
𝑑𝑇𝑚𝑎𝑥−𝑑𝑇𝑚𝑖𝑛
𝑑𝑇𝑚𝑎𝑥
ln
𝑑𝑇𝑚𝑖𝑛
36.6−20.8
= 29.19 ⁰C
39.6
20.8
ln
Experiment 2:
T1-72.1 ⁰C
T2-65.3 ⁰C
T3-22 ⁰C
T4-33.3 ⁰C
𝑚𝑐𝑜𝑙𝑑 = 30 × 10−3 kg/sec
𝑚ℎ𝑜𝑡 = 50 × 10−3 kg/sec
1. ∆𝑇ℎ𝑜𝑡 = T1-T2= 72.1-65.3= 6.8 ⁰C
2. ∆𝑇𝑐𝑜𝑙𝑑 = T4-T3= 33.3-22= 11.3 ⁰C
3. 𝜂ℎ𝑜𝑡 =
=
𝑇1−𝑇2
𝑇1−𝑇3
72.1−65.3
4. 𝜂𝑐𝑜𝑙𝑑 =
=
𝑇1−𝑇3
33.3−22
= 0.1357 =13.57%
= 0.2255 =22.55%
72.1−22
𝜂ℎ𝑜𝑡 +𝜂𝑐𝑜𝑙𝑑
5. 𝜂𝑚𝑒𝑎𝑛 =
=
6.
72.1−22
𝑇4−𝑇3
2
0.1357+0.2255
2
= 0.18035 =18.035%
𝑄ℎ𝑜𝑡 = 𝑚ℎ𝑜𝑡 × 𝐶𝑝ℎ𝑜𝑡 (𝑇1 − 𝑇2)
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7.
= 50 × 10−3 ×4.183× (6.8)
= 1.422 kW
𝑄𝑐𝑜𝑙𝑑 = 𝑚𝑐𝑜𝑙𝑑 × 𝐶𝑝𝑐𝑜𝑙𝑑 (𝑇4 − 𝑇3)
= 30 × 10−3 ×4.18× (11.3)
= 1.41702 kW
LMTD=
=
𝑑𝑇𝑚𝑎𝑥−𝑑𝑇𝑚𝑖𝑛
𝑑𝑇𝑚𝑎𝑥
𝑑𝑇𝑚𝑖𝑛
ln
(72.1−22)−(65.3−33.3)
ln
50.1
32
= 40.375 ⁰C
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6. Discussion:
From the results we can observe that the power emitted from the hot stream and the power absorbed
by the cold stream for counter flow are higher than of parallel flow
The increase in flow rate of one of the streams will results in an increase in the rate of heat transfer.
Theoretically, the amount of heat loss forms the hot water should be equal to the heat gain by the
cold water. However, this cannot be done practically. This may because of the heat loss to the
surrounding, the heat loss in counter flow is approximately 17% and the heat loss in parallel flow
is approximately 19% which is slightly higher. Based on the calculation done, we found out that
the values of LMTD for co-current flow is higher than the counter-current flow. But the overall
heat transfer coefficient for counter-current flow is higher than the co-current flow. This mean that
counter current flow heat exchanger has a higher effectiveness.
TheLMTDforparallelflow is higher than the counter flow. However, the overall heat transfer coef
ficient for counter flow is higher than the parallel flow. As a conclusion, counter flow configuration
of heat exchanger is more preferred for practical application. One of the applications of heat
exchanger is oil cooler.
The heat exchanger apparatus follows the basic laws of thermodynamics and this can be shown
experimentally. From all the parallel flow configurations, the exit temperature of the hot fluid is
always hotter than the exit temperature of the cold fluid. This supports the Clausius Statement in
which heat may not spontaneously transfer from a colder body to a hotter body. From the other
experiments that hold flow rates constant or vary the flow rates, the First Law of Thermodynamics
and conservation of energy applies to the heat exchanger apparatus. In practical application, the
counter flow configuration is preferred for its higher effectiveness. This experiment did show that
this configuration does in fact have a higher effectiveness than the parallel flow configuration.
Additionally, the counter flow configuration is also capable of have a cold fluid exit temperature
that is higher than the hot fluid exit temperature. This was not shown experimentally, however
from the data collected the flow rates were too high to achieve this desired result. If the experiment
were repeated with lower flow rates, it would be possible to demonstrate a situation where the exit
temperature of the cold fluid is hotter than the exit temperature of the hot fluid (heat exchanger lab
doc, n.d).
7. Conclusion:
From the results obtained, the results shown that the cold water exit temperature of the counter
flow is higher than the parallel flow. Hence, the counter flow is much more efficiency than
parallel flow. The results also shown that the higher the flow rate will cause the rate of heat
transfer increase. As a conclusion, the counter flow is more efficiency than parallel flow and are
preferred to use in the transfer heat. The hot fluid is always higher than the exit temperature of
the cold fluid. In counter flow configuration, the exit temperature of the hot fluid is also higher
than the exit temperature of the cold fluid. However, in counter flow configuration, the exit
temperature of the cold fluid is higher than the exit temperature of the cold fluid in parallel
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configuration. Hence, for heat exchanger, counter flow configuration has a higher effectiveness
than the parallel flow configuration. The experiment shows that when the flow rate of one of the
stream increases, the rate of heat transfer will also increase. The amount of heat loss forms the
hot water is not equal to the heat gain by the cold water due to the heat loss to the surrounding.
From the calculations done,
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8. References:
Heat exchanger lab doc. (n.d). available from:
file:///C:/Users/itemogeng%20babe/Downloads/23106551-Heat-Exchanger-Lab-Report.pdf .
Accessed date: 01 April 2021.
Thermodynamics. (n.d). “18.5 Heat Exchangers”. Available from:
https://web.mit.edu/16.unified/www/FALL/thermodynamics/notes/node131.html. Accessed date:
09 April 2021.
Heat exchanger control system. (n.d). “Heat Exchanger Control Systems”. Available from:
https://sites.google.com/site/heatexchangercontrolsystem/websitebuilder#:~:text=Heat%20exchangers%20are%20deceives%20that,another%20across%20a%20so
. Accessed date: 06 April 2021.
Murshed, S. (2016). “Introductory Chapter: An Overview of Design, Experiment and Numerical
Simulation of Heat Exchangers”. Available from: https://www.intechopen.com/books/heatexchangers-design-experiment-and-simulation/introductory-chapter-an-overview-of-designexperiment-and-numerical-simulation-of-heat-exchangers. Accessed date: 14 April 2021.
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9. Appendix:
Figure 4: heat exchanger for parallel flow
Figure 5: Heat exchanger for counter flow
Figure 6:Fluid flow direction for parallel and counter flow
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