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GRD Journals- Global Research and Development Journal for Engineering | Volume 2 | Issue 6 | May 2017

ISSN: 2455-5703

CFD Analysis on Finned Tube Heat Exchanger


using Alumina Nanofluid As Coolant
Edwin Cyriac
PG Scholar
Department of Mechanical Engineering
Mar Athanasius College of Engineering

Reji Mathew Aneesh K Johny


Professor PG Scholar
Department of Mechanical Engineering Department of Mechanical Engineering
Mar Athanasius College of Engineering Mar Athanasius College of Engineering

Sunny K George Issac Thamban


Professor Professor
Department of Mechanical Engineering, Department of Mechanical Engineering
Mar Athanasius College of Engineering Mar Athanasius College of Engineering

Abstract
Finned tube heat exchanger are used for heat transfer between air, gas and liquids or steam. Heat exchanger with finned heating
surfaces, so-called finned tube heat exchanger, offer the possibility of heat transfer between gases and liquids significantly space-
saving and is more efficient to implement than it is possible with straight tubes. Finned tube heat exchangers are designed to
transfer heat from clean air and gases with high efficiency on liquids or vapors, and vice versa. In this way the media can be heated,
cooled or condensed, in a closely space. Finned tube heat exchangers can be used for different applications and in a variety of
designs. In this work a model of finned tube heat exchanger was made and by using ANSYS fluent and used Al2O3 nanofluid as
cooant for heat transfer enhancement and the analysis was carried out. CFD simulations are done for different concentration of
Al2O3 at different flow speed. Temperature contours in all the cases can be plotted by using CFD.by this we can clearly understand
the heat transfer enhancement role of small concentration of nano particle on base fluid.
Keywords- Nanofluid, CFD, Al2O3, Finned Tube Heat Exchanger, Industrial Chiller

I. INTRODUCTION
Finned tube heat exchanger are mainly used for heat transfer between liguid and gasius working medium, for example, between
air and water, steam and water etc. Heat exchanger with finned heating surfaces, so-called finned tube heat exchanger, offer the
possibility of heat transfer between gases and liquids significantly space-saving and is more efficient to implement than it is
possible with straight tubes. Finned tube heat exchangers are designed to transfer heat from clean air and gases with high efficiency
on liquids or vapors, and vice versa. In this way the media can be heated, cooled or condensed, in a closely space. Finned tube heat
exchangers can be used for different applications and in a variety of designs. The problem of non-Newtonian fluid flow has been
under a lot of attention in recent years because of its various applications in different fields of engineering specially the interest in
heat transfer problems of non-Newtonian fluid flow, such as hot rolling, lubrication, cooling problems and drag reduction.

II. LITERATURE BACKGROUND


Madrood, M. R. K., Etemad S. G., Bagheri R. [1] Natural convection heat transfer of non-Newtonian nanofluids(dispersion of
Al2O3 and TiO2) in 0.5 wt% aqueous solution of carboxy methyl cellulose) in a vertical cylinder uniformly heated from below and
cooled from top was investigated experimentally. They showed that the heat transfer performance of nanofluids is significantly
enhanced at low particle concentrations and that increasing nanoparticle concentration has a contrary effect on the heat transfer of
nanofluids.
Cheng (2012). [2] studied the free convection heat transfer over a truncated cone embedded in a porous medium saturated
by a non-Newtonian power-law nanofluid with constant wall temperature and constant wall nanoparticle volume fraction and
reported that increasing the thermophoresis parameter or the Brownian parameter tends to decrease the reduced Nusselt number.
Moraveji et al. [3] numnerically investigated forced convective heat transfer effect on the non-Newtonian nanofluid containing
Al2O3 and xanthan aqueous solution as a liquid single phase in the horizontal tube with constant heat flux. M. Hojjat, S. et al. [4]
investigated the forced convective heat transfer of these nano-fluids through a uniformly heated circular tube under turbulent flow

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CFD Analysis on Finned Tube Heat Exchanger using Alumina Nanofluid As Coolant
(GRDJE/ Volume 2 / Issue 6 / 032)

conditions. Results reveal that the local and average heat transfer coefficients of nanofluids are larger than that of the base fluid.
Heat transfer enhancement of nanofluids increases with an increase in nanoparticle concentration. Similar trend are demonstrated
for Nusselt number of nano fluids. For a given nanop article concentration and Peclet numb er, the local heat transfer coefficient
of the base fluid and that of the nanofluids decreases with the axial distance from the tube inlet.
Mohammad Hojjat et al.[5] Forced convection heat transfer of non-Newtonian nanofluids in a circular tube with constant
wall temperature under turbulent flow conditions was investigated experimentally Al2O3,TiO2and CuO nanoparticles into the
base fluid(CMC) Results indicate that the convectiveheat transfer coefficient of nanofluids is higher than that of the base fluid.
The enhancement of the convective heat transfer coefficient increases with an increase in the Peclet number and the nanoparticle
concentration. The increase in the convective heat transfer coefficient of nanofluids is greater than the increase that would be
observed considering strictly the increase in the effective thermal conductivity of nanofluids. Mahmoud Reza et al. [6] Al2O3,
TiO2 nanoparticles in a 0.5 wt. % CMC. Natural convection heat transfer of non-Newtonian nanofluids in a vertical cylinder
uniformly heated from below and cooled from top was investigated experimentally. Results show that the heat transfer performance
of nano fluids is significantly enhanced at low particle concentrations. Increasing nanoparticle concentration has a contrary effect
on the heat transfer of nanofluids, so at concentrations greater than 1 vol. % of nanoparticles the heat transfer coefficient of nano
fluids is less than that of the base fluid
R. Kamali , A.R. Binesh[7] numerically investigated convective heat transfer of multi-wall carbon nanotube (MWCNT)-
based nano fluids in a straight tube under constant wall heat flux condition. The objectives of this research are to provide detailed
information of non-Newtonian behavior of CNT nanofluids, comparison of the numerical simulation predictions to the
experimental measurements and investigation of non-Newtonian effects on the local heat trans fer of the CNT nano fluid and
compare the thermal performance of the CNT nanofluids and convent ional fluids. Putra et al.[8] presented a study of the natural
convection of nanofluids (Al2O3water, CuOwater with w = 14%) using a horizontal cylinder test section with one end heated
and the other cooled. The time to reach the steady state was much lesser even at relatively high particle concentrations, due to the
non-agglomera-tive and mono-dispersive nature of the nanofluids. The heat transfer coefficient was found to be higher at the hot
wall than at the cold wall. The natural convective heat transfer is higher for the CuOwater than the Al2O3water nanofluid.
Wen and Ding [9] conducted experiments on nanofluids (TiO2water with w =01%) using two horizontally positioned
aluminum discs separated by a 10 mm gap filled with nanofluid. The lower disc was heated at the bottom surface and the upper
surface was open to the atmosphere.The temperature rose smoothly without any initial temperature oscillations as compared to
micro-sized particles. The time to reach the steady state was also shorter and the heating surface temperature was found to increase
with nanoparticle concentra-tions. The temperature difference between the walls increased with the volume fraction and reached
2.3 K for a w = 0.57% compared to 1.5 K for pure liquid. Hwang et al.[10] theoretically presented the effects of the volume fraction,
the size of nanofluids (Al2O3water),and the average temperature of nanofluids on natural convective heat transfer characteristics
in a rectangular cavity heated from the bottom.

III. METHODOLOGY

A. Designing of Finned Tube Heat Exchanger


The figure 1 shows the finned tube heat exchanger made in solidworks software and finnes are arranged in the tubes. There is one
inlet and one outlet. The inlet is where the hot fluid comes in and out let is where the hot fluid goes out. The air is the cooling
medium in these kinds of heat exchangers and heat will transfer from hot fluid to air through fluid convection. Finned tube heat
exchanger offer the possibility of heat transfer between gases and liquids. Heat exchanger with finned heating surfaces used for
heat transfer between air, gas and liquids or steam. It is space-saving and is more efficient to implement than it is possible with
straight tubes. The effectiveness of the heat transfer will be improved by using finns.Finned tube heat exchangers are designed to
transfer heat from clean air and gases with high efficiency on liquids or vapours, and vice versa. In this way the media can be
heated, cooled or condensed, in a closely space. Finned tube heat exchangers can be used for different applications and in a variety
of designs.
Table 1: Geometric details
Part ID Dimensions

Overall dimensions (LxBxH) 850 x 520 x 620

Tube dia OD 20 mm ID 15 mm

Fin dia 40 mm

Fin thickness 1.5 mm

Pitch 15 mm

No. of tubes per system 144 nos.

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CFD Analysis on Finned Tube Heat Exchanger using Alumina Nanofluid As Coolant
(GRDJE/ Volume 2 / Issue 6 / 032)

Fig. 1: The CAD drawing of the heat exchanger

B. CFD Analysis of Finned Tube Heat Exchanger


Geometric model is generated in SOLIDWORKS which is very popular modeling software. The generated model is exported
to the further process in the form of .IGES as it is a third party format which can be taken in to any other tools. Extracting the
fluid region is the next step in which all the surfaces which are in the contact of fluid are taken alone and all other surfaces are
removed completely. To keep the domain air /water tight some extra surfaces are created. This clean up is done in ANSA meshing
tool which is very robust meshing .After cleaning up the geometry surface mesh is generated in ANSA tool itself. All the surfaces
are discritized using tri surface mesh element .

1) Meshing Details
Table 2: Meshing Details
Mesh Count Quality

SURFACE MESH 1625780 0.6


VOLUME MESH 9254845 0.81

Fig. 2: Meshed Model

2) Solver Setup and Cell Zone Conditions


Ansys-fluent is used as the solver for this case. Fluid is assumed to be 3-D, turbulent Turbulence model is by K- Realizable model
with Energy ON and Simple algorithm is used to solve the problem Segregated solver is used for pressure-velocity coupling Fin
side fluid is air ,Tube side fluid is water, water + 0.1% Al 2O3 and water + 0.05% Al2O3.Heat exchanger material Aluminum

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CFD Analysis on Finned Tube Heat Exchanger using Alumina Nanofluid As Coolant
(GRDJE/ Volume 2 / Issue 6 / 032)

3) Property of Fluid
Table 3: Properties of Fluid
Parameter Water Water + 0.05% Al2O3 Water + 0.1% Al2O3
Desnsity () Kg/m3 998.2 992.25 1038
Specific Heat (Cp)j/kg-k 4182 4157 4182
Thermal conductivity (w/m.K) 0.6 0.651 0.72
Viscosity ()kg/m.s 0.001003 0.000786 0.000950

4) Boundary Conditions
Table 4: Boundary Conditions
Part ID Parameter
Tube side fluid
Mass flow rate 0.25, 0.5 and 0.75 Kg/s
Inlet Temperature 360 K
Air
Velocity 5 m/s
Inlet Temeprature 300 K

IV. RESULT AND DISCUSSION


The performance of the heat exchanger is determined by the effectiveness of heat transfer process. The performance of the heat
exchanger relies on the fin profiles, type of coolant used and arrangement of pipes etc. In the present work, the working fluid is
mixed nanoparticles based additives to enhance the heat transfer process. Numerical analysis is carried out to examine the effect
of different volume fraction of additives added with the hot liquid. In the below section CFD results are plotted for different flow
rates are tabulated.
Table 5: The tabulation of results from CFD analysis
Mass flow rate of hot fluid Velocity of cold fluid (Air) Cold fluid Hot fluid

Inlet Outlet Inlet Outlet


Kg/s m/s K K
WATER SYSTEM
0.25 5 300 305.1 360 357.92
0.5 5 300 305.33 360 358.94
0.75 5 300 305.2 360 359.28
0.05% Al2O3-WATER SYSTEM
0.25 5 300 305.28 360 356
0.5 5 300 305.1 360 357.5
0.75 5 300 304.2 360 358.05
0.1% Al2O3-WATER SYSTEM
0.25 5 300 305.22 360 355
0.5 5 300 305.26 360 356.5
0.75 5 300 305.3 360 357.37

V. CONCLUSIONS
The CFD analysis was conducted on a finned tube heat exchanger for different flow rates by using three different fluids First water
is used as hot fluid and then 0.05 Volume fraction of Al 2O3 water solution and after that the analysis with 0.1Volume fraction of
Al2O3-water solution is done And found that the heat transfer rate will increase when we substitute water with a Al 2O3 water
nanofluid And also when the concentration of nanoparticle increases the total heat transfer rate also increases.

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CFD Analysis on Finned Tube Heat Exchanger using Alumina Nanofluid As Coolant
(GRDJE/ Volume 2 / Issue 6 / 032)

ACKNOWLEDGMENT
The authors would like to thank benny paul Professor in Department of Mechanical engineering for granting permission to conduct
CFD ANALYSIS in the CFD Laboratory, mar athanetious college kothamangalam.. The authors would like to thank the reviewers
for their suggestions, which improved the quality of the paper substantially.

REFERENCES
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Heat and Mass Transfer, Vol. 39, No. 9, 1348-1353
[3] M.K. Moraveji, S.M.H. Haddad, M. Darabi(2012).Modelling of convective heat transfer of a non-Newtonian fluid in the horizontal tube under constant heat
flux with computational fluid dynamics, International Communications in Heat and Mass Transfer, Vol. 39, No. 7, 995-999
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[8] Putra N, Roetzel W, Das SK. (2003) Natural convection of nano-fluids. International Journal of Heat and Mass Transfer; 39:77584.
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