Int. J. Engg. Res. & Sci. & Tech. 2014
Kuber Dwivedi and Nilesh Mohan, 2014
ISSN 2319-5991 www.ijerst.com
Vol. 3, No. 4, November 2014
© 2014 IJERST. All Rights Reserved
Research Paper
INFLUENCE OF GEOMETRICAL PARAMETERS OF
MPFHS WITH FOUR FIN GEOMETRY (SQUARE,
TRIANGULAR, CIRCULAR AND DIAMOND) ON
THE THERMO HYDRAULIC CHARACTERISTICS
Kuber Dwivedi1* and Nilesh Mohan1
*Corresponding Author: Kuber Dwivedi  [email protected]
Computational studies were carried out by using the ANSYS FLUENT 14.0 to find the effects of
various fin geometries (square, triangular, circular and diamond) with constant surface area on
heat transfer and pressure drop in a finned micro channel heat sink. Simulation was performed
with the Reynolds number in a range from 100 to 500 at constant boundary condition when
Ag-water Nano fluid is used as a coolant, Boussines q approximation was used to get the
buoyancy effect and N-S equations were used to solve for the fluid flow. From the studied it is
illustrated that, diamond fins is dissipating more amount of heat after circular fins. It was also
found that diamond fins gives minimum pressure drop compared to other finned heat sink and
both triangular and square finned heat sink is having approximate same performance in thermal
and hydraulic characteristics.
Keywords: Heat Transfer, Fins, Nano Fluid, Computational Fluid Dynamic
INTRODUCTION
(thermal and hydraulic) . Now the recent days for
optimum performance in thermal point of view,
Nano fluid is also used as a coolant in which Nano
particle of metal or metal oxide are unvaryingly
deferred into the base fluid for escalation in
thermal conductivity of fluid. There are numerous
investigators having their prime deliberation in the
field of micro-electro-mechanical system to
enhance the performance in respect of coolant,
geometry of fins, configuration of fins, and shape
of MCHS, etc. An experiment has been already
Rapid growth in electronic world, Micro-pin-fin
heat sink is used for dissipating the heat from
microelectronic chips, therefore provide larger
heat transfer surface area in compact size for
avoid the overheating problem. But due to small
size of product, we need liquid forced convection
mechanism for better heat transfer, but it also
leads the pressure drop so geometry of fins is
also imperative aspect for analysis because it
plays a vital role in both the characteristics
1
Scope College of Engineering, Bhopal, India.
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Int. J. Engg. Res. & Sci. & Tech. 2014
Kuber Dwivedi and Nilesh Mohan, 2014
of Nano particles and Reynolds number, but it
cause to increase the pressure drop and also it
is noticed that decreasing the diameter of Nano
particle enhances the nusselt number forAl2O3water Nano fluid while the trend is reverse for
CuO-water Nano fluid John et al. (2010) they are
performed the numerical analysis for the influence
of thermal resistance and pressure drop of a
micro pin-fin heat sink with single phase liquid
flow and different pin-fin geometries (square
shaped pin-fins and circular pin-fins) when
subjected to several factors and concluded that
with square pin-fins. The change in the axial pitch
between the pin-fin structures show negligible
effects on both the thermal and hydraulic behavior
but for heat sinks with circular pins the thermal
resistance of the device decreases as the axial
pitch is decreased at the cost of increased
pressure drop. Ricci and Montelpare (2006) they
did examined experimentally the pin fin heat sink
with fins in different shapes (circular, square,
triangular and rhomboidal) arranged in-line with
constant heat flux boundary condition and they
found that, the triangular geometry is on an
average the best with respect to the others.
Soodphakdee et al. (2001) they investigated that
the heat transfer performance of heat sink with
commonly used fin geometries (round, elliptical
and square) also the plate fins in staggered and
inline arrangement. They found that, in all cases,
staggered geometries perform better than inline,
also at lower values of pressure drop and
pumping power, elliptical fins work best.
performed for analysis of thermo-hydraulic
behaviour of circular finned micro heat sink with
Ag-H2o and Al2O3-water Nano fluid and founded
that Ag-H2o Nano fluid perform better then Al2O3water Nano fluid (Kuber et al., 2014). Mushtaq
Ismael Hasan (2014) he has numerically
deliberate the MPFHS with three fin geometries
(square, triangular and circular) same in hydraulic
diameter and boundary condition with two types
of Nano-fluid (diamond-water and Al2O3-water)
with (1-4)% volumetric concentration and founded
that diamond-water Nano fluid is better than Al2O3water from heat transfer point of view and circular
fins give the higher heat transfer rate also square
fins caused of higher pressure drop compared
with other fin geometries. Alfaryjat et al. (2010)
they are numerically investigated that influence
of the geometrical parameters on the thermohydraulic behavior of the MCHS with three different
channel shapes (hexagonal, circular, and
rhombus) at the similar boundary condition and
founded that the highest value of the top wall
temperature, f riction factor and thermal
resistance are found with the use of rhombus
cross-section MCHS. And the smallest hydraulic
diameter of the hexagonal cross-section MCHS
has the highest pressure drop and heat transfer
coefficient among other shapes. Paisarn Naphon
and Lursukd Nakharintr (2013) they are
deliberated the thermal behaviour of TiO2-water
Nano fluids cooling in the small-rectangular heat
sink with three different channel heights. And they
found that average heat transfer rates for Nano
Hamid Reza Seyfand Morteza Feizbakhshi (2012)
At higher values, round pin fin offer highest
performance.
they observed from his experiment Nano fluid
Relation Involved in Study
enhance the heat transfer instead of pure water
Following relationship has been used for
analysis.
fluids as a coolant are higher than those for water.
and it is intensified with increase in volume fraction
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Int. J. Engg. Res. & Sci. & Tech. 2014
Kuber Dwivedi and Nilesh Mohan, 2014
For calculating the properties of Nano fluid
specimens have been used for analysis. The
nomenclatures and dimensions of the specimens
are given in the Table 1.
Thermal Conductivity:
K nf
Kf

K p   SH  1 K f   SH  1 c  K f  K p 
Material Parameter: Ag-water Nano fluid at 4%
volumetric concentration are used as coolant and
for heat sink and pin fins aluminium metal is
considered. Following values of thermo physical
properties of Nano fluid which is calculated by
Equations 1, 2, 3 and 4, heat sink and fin, at the
ambient temperature are taken for computational
fluid dynamic analysis is shown in Table 2.
K p  SH  1 K f  c  K f  K p 
...(1)
For spherical particle considered (SH=3)
Viscosity :
 nf
 1  2.5c
f
...(2)
Density :  nf  c  p  1  c  p f
Table 2: Material Parameter
...(3)
Specific heat : c pnf  cC p p  1  c  C p f
...(4)
For calculating the velocity of flow
wi 
Re 
 dh
...(5)
4a
dh 
p
...(6)
Material
( )
(kg/m3)
(Cp)
(J/kg-k)
(K)
(W/m-k)
( )
(kg/m-s)
Pure water
(c=0%)
981.3
4189
0.643
0.000598
Ag
10500
235
429
-
Ag-water
(c=4%)
1362.048
4030.89
0.723
0.000657
Aluminium
2719
871
202.4
-
where , Cp, K and  are density, specific heat,
thermal conductivity and dynamic viscosity,
respectively.
Geometrical and Material Parameters
Geometrical Parameter: In this study five
OBJECTIVE OF THE THESIS
Table 1: Geometric Parameter
Name of the
Specimens
Geometrical
parameter
1
Base plate (heat sink)
Length = 11.5 mm,
Width = 6 mm,
Thickness = 1mm
2
Square fins
Width = 0.41 mm,
Height = 0.5 mm
3
Triangular fins
Width = 0.564 mm,
Height = 0.5 mm
The present study approaches to examine the
thermo-hydraulic behavior of micro pin fin heat
sink with some more different shape of pin fins
(square, triangular, circular and diamond) with
constant surface area with Ag-H2O Nano fluids
at 4% volumetric concentration at similar
boundary condition and the range Reynolds
number is 100 to 500 for further optimization of
its performance.
4
Circular fins
Diameter = 0.5 mm,
Height = 0.5 mm
METHODOLOGY
5
Diamond fins
Diagonal Length = 0.81X0.3mm,
Height = 0.5 mm
S. No.
Modelling
The geometry is modelled in NX 7.5. It is
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Int. J. Engg. Res. & Sci. & Tech. 2014
Kuber Dwivedi and Nilesh Mohan, 2014
consisting of 50 number of 3D micro pin fins of
four shapes (square, triangular, circular,
diamond) which are fixed in heat sink as shown
in Figure 1. The pitch distance between the fins
is 1 mm and these are arranged in staggered
configuration which is better than inline
configuration. From the heat transfer point of view
as it is used by many references. Aluminium (Al)
is used as material having thermal conductivity
(K=202.4 w/m-k).
programmable controlled meshing is generated
with growth rate as 1.2, relevance and span angle
center is kept fine. Edge sizing is done for fluid
domain with bios factor is 7.
Meshing
further it was imported in fluent solver, where all
Meshing of the specimen is generated by
Meshing software of Ansys (Figure 2), it plays the
important role in simulation. For the specimen
the boundary conditions have defined for
Simulation
To analyze the thermal behavior and other
characteristics of Nano fluid and heat sink with
different shapes of pin fins, after meshing of the
all the specimen, output file has been created and
simulation. In this analysis one open domain has
been created for fluid flow.
Figure 1: Isometric View of Heat Sink with Different Profile of Pin Fins
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Int. J. Engg. Res. & Sci. & Tech. 2014
Kuber Dwivedi and Nilesh Mohan, 2014
Figure 2: Mesh of Different Profile of Pin Fins with Heat Sink
Flow analysis: Here domain properties and
boundary condition are defined. The realizable
laminar model was applied to all the simulations
because of its numerical stability for analysis of
fluid flow. Energy model is also used for analysis
of heat flow. Viscosity and density of fluid is
considered to be constant, i.e., the Nano fluid is
Newtonian and incompressible.
surface of the heat sink the constant wall
temperature boundary condition is used (T =
373 K) and velocity is w = win, u = v = 0 which
is calculated by eq. (5).
• Outlet boundary: At the outlet the flow is
assumed to be fully developed, hence gauge
pressure is taken zero at outlet.
RESULTS AND DISCUSSION
Boundary conditions: The two types of boundary
condition are defined at inlet and outlet, at normal
atmospheric operating condition.
Solver solves the given problem and creates a
result file, which has been analyzed in CFD-Post.
Here temperature contour pattern and velocity
contour pattern, etc., has been analyzed. The
• Inlet boundary: At the inlet the finite values of
velocity and temperature was used at the lower
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Int. J. Engg. Res. & Sci. & Tech. 2014
Kuber Dwivedi and Nilesh Mohan, 2014
values of heat transfer rate and pressure are
predicted at different surfaces.
respectively. It is inferred that the temperature is
increasing along the flow direction due to heat
transfer from lower wall with constant
temperature.
Temperature Distribution of different Heat
Sink with Ag-H2O Nano Fluid with Reynolds
Number (Re=500)
Velocity Distribution of different Heat Sink
with Ag-H 2 O Nano Fluid with Reynolds
Number (Re=500)
Figure 3 shows the temperature contour on
longitudinal (x-y) plan at z = 0.0002165 m for heat
sink with four fin geometries (square, triangular,
circular and diamond) with Ag-water Nano-fluid
with volumetric concentration (c=4%) at 500
Figure 4, shows the velocity profile on longitudinal
(x-y) plan at z = 0.0002165 m for micro heat sink
with four fin geometries (square, triangular,
Figure 3: Temp. Contour of HS with Different Shape of pin fins with (Ag-water)
Nano fluid (Re=500)
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Int. J. Engg. Res. & Sci. & Tech. 2014
Kuber Dwivedi and Nilesh Mohan, 2014
Figure 4: Velocity Contour of HS with Different Shape of pin fins with (Ag-water)
Nano fluid (Re=500)
circular and diamond) with Ag-water Nano fluid
with volumetric concentration (c=4%) at Re = 500
respectively From the figure it can be observed
that, velocity increases at side of wall along the
flow and also it has seen that the shape of flow
differ for every geometry and here circular finned
heat sink gives the better mixing compared to
other geometry.
From this figure it can be seen that, the value of
present model and data of Kuber et al. (2014) is
very near to close. The slightly difference in
parameter (pressure drop) due to the difference
in mesh and solving control method. Therefore
the present numerical model is reliable and can
be used to study the effect of geometry of fins
and using of Nano fluid.
Validation of Result of Presented Model with
(Kuber et al., 2014) For Pressure Drop and
Heat Transfer Rate
Graphical Representation of Comparison of
Heat Transfer Rate with Different Nano-fluid
for Different Heat Sink
Figure 5 shows the comparison between result
of presented numerical model and the data of
Kuber et al. (2014) for pressure drop of circularfinned heat with Ag-water Nano-fluid respectively.
Figure 6 shows the comparison of pressure drop
with Reynolds number of different profile of heat
sink with Ag-water Nano-fluid. From the figure, it
has been illustrated that the triangular and square
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Int. J. Engg. Res. & Sci. & Tech. 2014
Kuber Dwivedi and Nilesh Mohan, 2014
finned-heat sink gives approximate same and
maximum pressure drop with Ag-water Nano fluid
and it is also observed that diamond finned heat
sink is having the low pressure drop for both the
Nano-fluid comparison with others profile.
Figure 5: Comparison of Pressure
Drop Between the Presented Model
and Result of [4]
Figure 7 shows the comparison of heat
transfer with Reynolds number of different profile
of heat sink with Ag-water Nano-fluid. From the
figure, it has been illustrated that the circular
finned-heat sink gives maximum heat transfer
rate due to create better mixing of fluid and after
circular, diamond performs better in comparison
with others.
Figure 6: Comparison of Pressure
Drop with Re of Different Heat Sink with
Ag-water Nano-fluid
CONCLUSION AND FUTURE
SCOPE
Following points are worth observing from the
present exploration.
• At the same boundary condition and constant
heat transfer surface area, circular finned-heat
sink gives the higher cooling rate compared
to others finned heat sink for all values of
Reynolds number..
• After circular, diamond finned heat sink perform
better in heat transfer point of view compared
to others.
Figure 7: Comparison of Heat Transfer Rate
with Re of Different Heat Sink with
Ag-water Nano-fluid
• Diamond finned heat sink gives minimum
pressure drop at all values of Reynolds number
and at same thermal boundary condition
compared to others.
• Square and triangular finned heat sink
approximately has same performance in heat
transfer and pressure drop.
SUGGESTIONS FOR THE
FUTURE WORK
In the present investigation work and on the basis
of literature review, it was assumed that the rate
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Int. J. Engg. Res. & Sci. & Tech. 2014
Kuber Dwivedi and Nilesh Mohan, 2014
of will increase by considering the use of heat
transfer fins and Nano-fluid as a coolant. Further
from the computational analysis it was understood
that the rate of heat transfer is increased by using
the Nano-fluid but the pressure drop also
increases, which is important parameter for pump
work. The computational analysis did not indicate
any particular shape of fins, which would give
maximum heat transfer.
enhancement of micro-pin-fin heat sinks”,
International Journal of Thermal Sciences,
Vol. 58, pp. 168-179.
It was only our presumption of considering
only the commonly available shapes like square,
triangular, circular and diamond. Although the
current investigative study reveals that maximum
heat transfer is gives by the circular fins and after
it diamond fins performs better and also diamond
fins gives the low pressure drop compared to
others. Probably there would be other shapes of
fins for which the rate of heat transfer would be
maximum and pressure drop would be minimum.
Current study also helped in finding the
performance of Nano-fluid. In future study a
similar exhaustive investigation may be
performed for optimizing the result with respect
to concentration of Nano-fluid, spacing between
the fins and using different kind of Nano-fluid and
shape of fins.
REFERENCES
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Alfaryjat A A, Mohammed H A, Nor Mariah
Adam M K A, Ariffin M I and Najafabadi (2014),
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channel heat sinks on the thermo hydraulic
characteristics”
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Communications in Heat and Mass
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Hamid Reza Seyf and Morteza Feizbakhshi
(2012), “Computational analysis of nanofluid
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John T J, Mathew B and Hegab H (2010),
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Kuber Dwivedi, Rupesh Kumar Malviya and
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