Heat exchange characteristics between hot and cold water as well as cold air and hot water have been investigated in a finned tube heat exchanger. The exchanger was operated in both parallel and counter-flow modes. For water-water heat exchange, the tube side (hot water) fluid flow rate was varied to observe the effects on heating the cold water. Conversely, for air-water system, the shell side (cold air) flow rate was varied to evaluate the cooling effectiveness of air in the finned tube exchanger. COMSOL Multiphysics 5.6 was used to simulate the system in 3-D mode, and the temperature profiles along with heat flux and velocity streamlines were evaluated. The NTU and effectiveness for varying fluid flow rates for both water-water and air-water systems were calculated. NTU values were considerably higher for air-water heat exchange and showed a decreasing trend with increasing fluid flow rate. To ascertain the reliability of the simulation models, the experimental and simulated results were compared. To evaluate the performance of the fins, the fin efficiencies and effectivenesses were calculated and the values were notably higher in case of air-water system. This is consistent with established literature. Also, increasing shell-side fluid flow rate led to a reduction in fin efficiency and effectiveness, which is again consistent with literature.

2. 2
I. Objective
II. Literature Survey
III. Experimental Set-up
IV. Development of the Simulation Environment
— Simulation Geometry
— Generated Mesh Structure
V. Results & Discussion
— Preliminary Results
— Velocity & Temperature Streamlines
— Temperature Profile Samples
— Comparison of Experimental & Simulated Results
— NTU variation with cold-fluid Velocity
— Fin Performances : Fin Efficiency & Fin Effectiveness
— Dependence of Fin Parameters on Shell-side Fluid Flowrate
VI. Conclusion

3. 3

4. o To study the Heat Transfer Characteristics of Water-Water Heat Exchange in a Finned
Tube Exchanger in Parallel and Counter-Flow modes and Calculation of Heat Transfer
Coefficients.
o To study the Heat Transfer Characteristics of Air-Water Heat Exchange in a Finned Tube
Exchanger in Parallel and Counter-Flow modes and Calculation of Heat Transfer
Coefficients.
o To simulate the Temperature and Flow Profiles for both cases in COMSOL and study the
Effect of Laminarity and Turbulence on the Heat Transfer Coefficients.
o To compare the Fin Efficiency and Fin Effectiveness for Water-Water and Air-Water Heat
Exchange.
4

5. 5

6.  Gugulothu et al (2018) have conducted a numerical simulation of the heat transfer
characteristics in a Shell and Tube Heat Exchanger. They have observed that the Heat
Transfer Coefficient increases with decreasing Friction Factor.
 Du et al (2019) have studied the effect of Helical Baffles in a Shell and Tube Heat
Exchanger by CFD Simulation. The helical flow within the Heat Exchanger was associated
with significant leakage and by-pass and the Local Heat Transfer Coefficient was
observed to increase with back-flow.
 Petrik et al (2019) have studied the heating performance of a Finned Radiator,
considering 3D Turbulent flow of Air. They have found that the ratio of the Fin Pitch, Fin
Wall thickness and the number of Fins are the main factors which influence the Heat
Transfer characteristics.
 Zhang et al (2023) have investigated the effects of the Fin Tip thickness and the Fin Root
thickness on the Heat Transfer performance of Spiral Finned Tube bundles, specifically
the variation of Nusselt number and Euler number with these parameters were explored.
6

7.  Wei et al (2015) have modelled a Heat Recovery Unit (HRU) based on fluid-solid
coupling. The effects of Reynolds number on the outlet temperature, Nusselt number and
pressure drop were investigated. Larger Reynolds number was found to give better Heat
Transfer performance at expense of an increased pressure drop.
 D. Cruz et al (2022) have studied the effects of nanoparticle loading and Reynolds
number on the heat transfer coefficient, pressure drop and hydrodynamic characteristics
for Copper (II) Oxide – Water nanofluid flow in a shell and tube exchanger. Both particle
loading and Reynolds number were observed to have a positive effect on pressure drop
and heat transfer coefficient.
 Ravikumar et al (2017) have simulated the 3D cross-flow inside a smooth as well as a
finned tube exchanger for air-water heat exchange. Their results indicate that heat
transfer coefficient decreases with increasing fin thickness for Briggs and Young
correlation and the opposite happens with other correlations.
 Banu et al (2022) have used ANSYS Fluent for simulating the heat transfer performance
of a fin and tube exchanger and validated the simulation results with mathematical
simulation results from MATLAB Simulink. 7

8. 8

9. 9
Fig 1: Set-up for Water-Water Heat Exchange Fig 2: Set-up for Air-Water Heat Exchange

10. 10

11. 11
o A half section of the Finned Tube Exchanger was developed in COMSOL Multiphysics
5.6
o As a preliminary study, Water-Water and Air-Water heat exchange were investigated.
o The heat exchange experiments were conducted using both Parallel and Counter flow
modes at different volumetric flowrates. For Water-Water system, hot fluid flowrate was
varied from 3-4 LPM in the Tube, while for Air-Water system, cold fluid flowrate was
varied from 2-10 LPM in the Shell.
o In COMSOL, the simulation has been carried out using Laminar flow and Turbulent flow,
as applicable.

12. 12
The relevant equations that are used are as follows-
– for Laminar Flow physics
𝜌 𝑢 ∙ 𝛻 𝑢 = 𝛻 ∙ – 𝑝𝐼 + 𝐾 + 𝐹 ___ (1)
𝛻 ∙ 𝜌𝑢 = 0 ___ (2)
– for Heat Transfer in Fluids physics
𝜌Cpu ∙ 𝛻𝑇 + 𝛻 ∙ 𝑞 = Q + Qp + Qvd ___ (3)
𝑞 = – 𝑘𝛻𝑇 ___ (4)
o Equation 1, 2 and 4 represent the Navier-Stokes equation, Continuity equation and the
Heat Conduction equation respectively.
o Equation 3 represents the Heat Balance equation, where Qp represents work done by
pressure changes and Qvd represents the viscous heat dissipation. Q represents heat
sources other than viscous heat dissipation.

13. 13
We have analysed the Turbulent flow by k-ε Model-
– for Turbulent Kinetic Energy (TKE), k
𝜌 𝑢 ∙ 𝛻 𝑘 = 𝛻 ∙ 𝜇 +
μ𝑇
σ𝑘
+ 𝛻𝑘 + 𝑃𝑘 - 𝜌ε ___ (5)
– for Rate of Dissipation of TKE, ε
𝜌 𝑢 ∙ 𝛻 ε = 𝛻 ∙ 𝜇 +
μ𝑇
σε
+ 𝛻ε + 𝐶ε1
ε
𝑘
𝑃𝑘 - 𝐶ε2𝜌
ε2
𝑘
___ (6)
here, μ𝑇 = 𝜌𝐶μ
𝑘2
ε
𝑃𝑘 = μ𝑇 [𝛻u ∶ 𝛻u + (𝛻u )𝑇 )]
o μ𝑇 represents eddy viscosity, 𝑃𝑘 represents production of TKE due to mean velocity
shear, σ𝑘 & σε represents turbulent Prandtl number for k & ε, and 𝐶ε1, 𝐶ε2 & 𝐶μ are
model coefficients.

14. 14
Fig 3: Axial Half-section of the Finned Tube Exchanger

15. 15
Fig 4: Mesh Element Size- minimum 1.67 mm, maximum 5.59 mm

16. 16

17. 17
– Parallel flow
Time Hot Water (°C) Cold Water (°C)
(min) Inlet Outlet Inlet Outlet
0 66.1 62 38.3 45.6
10 66.6 62.6 39 46.5
20 67 62.7 36.6 45
30 67 62.7 36.6 45
– Counter flow
Time Hot Water (°C) Cold Water (°C)
(min) Inlet Outlet Inlet Outlet
0 66.7 61.9 32.8 42
10 66.8 62 32.7 42
20 67 62.1 32.6 41.9
30 67 62.3 32.7 41.9
 Air-Water Heat Exchange
 Water-Water Heat Exchange
– Parallel flow
Time Hot Water (°C) Cold Air (°C)
(min) Inlet Outlet Inlet Outlet
0 67.5 66.8 32.2 41.8
10 67.5 66.9 32.2 41.3
20 67.4 66.6 32.2 40.5
30 67.2 66.6 32.2 40.1
– Counter flow
Time Hot Water (°C) Cold Air (°C)
(min) Inlet Outlet Inlet Outlet
0 67.6 66.6 32 41.6
10 67.9 67 32.1 41.1
20 67.8 66.9 32.1 39.3
30 67.9 67 32.2 37.3
Set point= 70°C
Hot Fluid Flowrate= 4 LPM
Cold Fluid Flowrate= 2 LPM

18. 18
Fig 5: Velocity Streamlines for Cold Water Fig 6: Temperature Streamlines for Cold Water

19. 19
Fig 7: Velocity Streamlines for Air Fig 8: Temperature Streamlines for Air

20. 20
Fig 9: Parallel Flow Fig 10: Counter Flow

21. 21
Fig 11: Parallel Flow Fig 12: Counter Flow

22. 22
 Water-Water Heat Exchange
 Air-Water Heat Exchange
Cold Water Hot Water Experimental Value Simulated Value % Error Experimental Value Simulated Value % Error
Parallel 2 3 311.28 308.95 0.75 324.53 323.31 0.38
Counter 2 3 311.53 308.79 0.89 324.13 323.41 0.22
Parallel 2 4 318.55 314.98 1.13 335.55 334 0.46
Counter 2 4 315 310.91 1.32 335.15 333.28 0.56
Shell-side Outlet Temperature (K) Tube-side Outlet Temperature (K)
Volumetric Flowrate (LPM)
Air Hot Water Experimental Value Simulated Value % Error Experimental Value Simulated Value % Error
Parallel 2 4 314.68 327.13 3.81 339.73 330.65 2.75
Counter 2 4 311.47 327.62 4.93 339.87 330.54 2.82
Parallel 4 4 326.8 316.48 3.26 337.58 322.27 4.75
Counter 4 4 325.48 316.69 2.78 336.42 321.31 4.70
Parallel 6 4 328.62 312.49 5.16 336.22 318.88 5.44
Counter 6 4 325.63 312.52 4.19 336.13 318.03 5.69
Parallel 8 4 330.78 309.98 6.71 338.95 317.74 6.68
Counter 8 4 330.03 309.82 6.52 338.75 316.53 7.02
Parallel 10 4 332.17 311.11 6.77 338.55 318.22 6.39
Counter 10 4 329.5 310.98 5.96 338.03 317.24 6.55
Shell-side Outlet Temperature (K) Tube-side Outlet Temperature (K)
Volumetric Flowrate (LPM)

23. 23
Fig 13: NTU vs. Air Velocity

24. 24
 Water-Water Heat Exchange
Shell-side Fluid Volumetric Flowrate
(LPM)
Fin Efficiency Fin Effectiveness
2 0.0767 2.980
2 0.0766 2.975
 Air-Water Heat Exchange
Shell-side Fluid Volumetric Flowrate
(LPM)
Fin Efficiency Fin Effectiveness
2 0.1765 6.854
4 0.1579 6.131
6 0.1479 5.742
8 0.1410 5.474
10 0.1364 5.297

25. 25
Fig 14: Fin Efficiency vs. Volumetric Flowrate of Air Fig 15: Fin Effectiveness vs. Volumetric Flowrate of Air

26. 26

27. 27
o Heat exchange characteristics were investigated in a finned tube heat exchanger for hot and cold
water, and cold air and hot water, operating in both parallel and counter-flow modes.
o For Water-Water system, the tube-side flow rate (hot water) was varied to observe its effect on
heating cold water, while for Air-water system, the shell-side flow rate (cold air) was varied to
assess the cooling effectiveness of air in the finned tube exchanger.
o COMSOL Multiphysics 5.6 was used to simulate the system in 3-D mode, and the temperature
profiles along with heat flux and velocity streamlines were evaluated.
o NTU and Heat Exchanger Effectiveness were calculated for varying fluid flow rates in both water-
water and air-water systems, with NTU values notably higher for air-water heat exchange,
exhibiting a decreasing trend with increasing fluid flow rate.
o The reliability of simulation models was assessed by comparing experimental and simulated results,
revealing percentage errors ranging from 0.38%-1.32% for the Water-Water system and from
2.75%-7.02% for the Air-Water system.
o The evaluation of fin performance involved calculating fin efficiencies and effectivenesses, notably
higher in the air-water system, consistent with established literature. Additionally, increasing shell-
side fluid flow rate resulted in reduced fin efficiency and effectiveness, aligning with existing
literature.

28. 28
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Baffles (2019). Front. Eng. Manag. 6, p 70-77. https://doi.org/10.1007/s42524-019-0005-8
• Gugulothu R, Sanke N, Gupta, A.V.S.S.K.S. Numerical Study of Heat Transfer Characteristics in Shell-and-Tube Heat
Exchanger (2019). In: Srinivasacharya, D., Reddy, K. (eds) Numerical Heat Transfer and Fluid Flow. Lecture Notes in
Mechanical Engineering. Springer, Singapore. https://doi.org/10.1007/978-981-13-1903-7_43
• Petrik M, Szepesi, G Jármai, K (2019). CFD Analysis and Heat Transfer Characteristics of Finned Tube Heat
Exchangers. Pollack Periodica Pollack Periodica 14(3), p 165-176. https://doi.org/10.1556/606.2019.14.3.16
• Wei L, Zhu G, Jin Z. Numerical Simulation of Heat Transfer in Finned Tube of Heat Recovery Unit Using Fluid-Solid
Coupled Method (2015). Advances in Mechanical Engineering 7(1). https://doi.org/10.1155/2014/127815
• Zhang D, Wu W, Zhao L, Dong H. Mathematical Investigation of Heat Transfer Characteristics and Parameter
Optimization of Integral Rolled Spiral Finned Tube Bundle Heat Exchangers (2023). Processes 11, p 2192.
https://doi.org/10.3390/pr11072192
• D Cruz P A, Yamat E J, Nuqui J P E, Soriano A N. Computational Fluid Dynamics (CFD) analysis of the heat transfer
and fluid flow of copper (II) oxide-water nanofluid in a shell and tube heat exchanger (2022). Digital Chemical
Engineering. 3. p 100014. https://doi.org/10.1016/j.dche.2022.100014
• Ravikumar K, Naga Raju Ch, Saheb M. CFD Analysis of a Cross-flow Heat Exchanger with Different fin thickness
(2017). International Journal of Dynamics of Fluids. 13(2), p 345-362. ISSN 0973-1784.
• Arshi Banu, P S; Ramesh Lohith, D N S; Kalyan, M P et al. Materials Today Proceedings. 2022, 66 (3), 1471-1476.

29. 29