Location via proxy:   [ UP ]  
[Report a bug]   [Manage cookies]                
SlideShare a Scribd company logo
International Journal of Research in Advent Technology, Vol.2, No.8, August 2014 
E-ISSN: 2321-9637 
Heat Transfer Simulation of Impinging Jet with Finned 
110 
Heat Sink 
Shivakumar H1, Krishnamurthy K N2, Akashdeep B.N3 
Department of Thermal power Engineering, M.Tech student1, Assistant professor2, VTU P G Centre Mysore, 
Karnataka, India 1, 2. 
Department of Mechanical Engineering Assistant Professor KSSEM Bangalore Karnataka, India3. 
Email: shivu_bec@hotmail.com1, murthykrishnakn@gmail.com 2,bndeep@gmail.com3 
Abstract- This study examines numerically details of the flow and temperature fields of heat sinks with short 
plate fins cooled by impinging jet. The main focus is on the effect of fin spacing, fin material and jet velocities 
on the heat sink performance. Conjugate heat transfer between airflow convection and conduction inside the fin 
and base is considered. Three different fin spacing (2 mm, 3 mm, 4 mm), fin material (Aluminum, copper and 
steel) and jet velocity of (5 m/s,10 m/s and 15 m/s ) are the parameters under study. Detailed temperature 
contours, velocity vector, pressure drop are presented and compared. In this current work the effect of fin 
material is observed that heat transfer rate varies in accordance with thermal conductivity of fin material. For the 
considered geometry there was increase of 0.2 W and 0.7804 W heat transfer rate for copper fin material, when 
it is compared to Aluminum and steel respectively for 15 m/s jet velocity. The effect of fin spacing on rate of 
heat transfer rate for the considered geometry it is observed that there is increase of 19% and 48% heat transfer 
rate for decrease of fin spacing of 2 mm and 3 mm respectively at 15 m/s jet velocity. Pressure drop is also 
sensitive to fin spacing in all the combinations, as fin spacing decreases pressure drop increases. For the 
considered geometry it is observed that pressure drop of 100 Pa, 120Pa and 140Pa for 4 mm, 3 mm, and 2 mm 
fin spacing respectively for jet velocity of 15 m/s. In overall pressure drop and heat transfer rate are 
contradicting with respect to fin spacing. However use of copper material makes heat sink heavier and 
expensive. Hence it can be concluded that for considered geometry of fin spacing 2 mm at 15 m/s of jet velocity 
for Aluminum fin material the numerical result was found to be optimum. The results of this can help in design 
of heat sinks with jet impingement, which are commonly used in electronic cooling systems. 
Index Terms: Jet impingement, heat sink, plate fin. 
1. INTRODUCTION 
The relentless trend of ever increasing 
integrated circuit chip functionality and decreasing 
chip dimensions for miniaturization of products have 
led to the need to develop new thermal management 
techniques to handle intense heat generation rate in IC 
chips. The need for effective cooling of chips at an 
acceptable cost is an urgent issue Extended surfaces 
(fins) and impinging jets have commonly been used to 
enhance heat transfer in many applications, for 
example, electronic cooling and gas turbine cooling. 
In electronic thermal management, heat sinks are 
designed to take advantage of the combined effect of 
fins and jet impingement such as jets impinging on an 
array of pin fins or plate fins. Significant studies have 
been focused on the thermal resistance, pressure drop, 
and the parametric effect of Reynolds number, fin 
thickness, density and height. Different correlations 
based on one-dimensional heat conduction and 
experimental data are developed to predict the heat 
sink performance. Efforts to optimize the heat sink 
design have also been made by using both 
experimental and numerical methods. 
2. CURRENT STUDY 
This study applies numerical simulation to 
examine the details of flow and temperature fields of 
plate fin heat sinks with jet impingement. Based on 
the literature review few studies have been done on 
the effect of fin spacing, fin material and jet velocity. 
Therefore, the main focus of this study is on the effect 
of fin spacing of (2 mm, 3 mm and 4 mm), fin 
material Aluminum, copper and steel, jet velocity of 
(5 m/s, 10 m/s and 15 m/s) on the heat sink 
performance. The characteristics of 3D temperature 
field inside the fins and solid base are also explored. It 
is observed that the fin spacing affects largely both 
the heat transfer and pressure drop, fin material and 
jet velocity effects on heat transfer rate especially of 
the short fin cases .The results of this paper can help 
in design of heat sinks with jet impingement. 
2.1 Objectives: 
1. This concerns the familiarization with the 
methods and materials. This involves literature 
reviews on the different methods of cooling 
employed in electronic equipment’s. 
2. This involves choosing the parameter on which 
analysis should be carried out. In this work the 
parameters selected are fin material (Aluminum, 
copper and steel), fin spacing (2 mm, 3 mm, 4 
mm), and velocity of jet (5 m/s, 10 m/s and 15 
m/s). 
3. The selection of geometry for the CAD model 
was selected from literature [10] and the physical
International Journal of Research in Advent Technology, Vol.2, No.8, August 2014 
E-ISSN: 2321-9637 
111 
arrangement of fin is modeled using hyper mesh 
V10 software. 
4. Mesh generation of the modeled geometry 
was carried out using hyper mesh V10 
software. 
5. The boundary conditions for the fluid flow 
analysis were imposed and the solution was 
obtained through the analysis software 
FLUENT 6.3.26. 
6. The analysis was carried out to obtain heat 
transfer rate, pressure drop and contours of 
temperature, Velocity vector are drawn 
. 
3. PROBLEM UNDER CONSIDERATION 
There are generally two types of heat sinks 
with jet impingement. One is with parallel plate fins, 
and the other is with pin fins. In this study the plate 
fin heat sink is considered. Figure 1 shows the 
geometric schemes of this type of heat sink. The slot 
jet impinges from the top to the plate fins and exits 
from two sides into the surroundings. The sink base is 
connected to the electronic modules to dissipate the 
heat to the cooling airflow. The top can be either open 
or confined, which is considered as confined in this 
study. The performance depends on the jet velocity, 
fin height, fin width, number of fins, and the base 
thickness. In practice, there usually is a small gap 
between the fin tip and jet plate 
Fig 1 Geometric scheme of a heat sink of parallel 
plate fins cooled by an impinging jet 
The heat sink in Fig 1 is symmetric in both 
the x- and z directions unless the flow or thermal 
boundary conditions are applied differently. Figure 2 
shows the symbolic dimension of the cases under 
study. The fin shape considered is rectangular fins. 
All the fins share the same height and base width, 
which leads to a slightly different surface area and 
thus different volume or weight. The total height in 
the y-direction is H, and heights for the fin and base 
are h1 and h2, respectively. The fin has a thickness of 
b, and the distance between the fins is B1.The the 
impinging slot jet has a width of( l1) and the rest of 
the top surface is the confined wall (l2).In this study, 
the air jet with constant properties impinges on the 
heat sink vertically with a uniform inlet velocity and 
temperature. Constant temperature is applied to the 
heat sink bottom surface for simplification. The 
considered dimensions and thermal Properties of fin 
materials are presented in table 1 and 2 respectively. 
b 
H h1 
B 
h 
2 
B1 
2 
Fig. 2 shows the symbolic dimension of the cases 
under study 
Table 1 Dimensions of Fin geometry 
Fin height( h1) 0.006 m 
Base height( h2) 0.002 m 
Total height (H) 0.01 m 
Fin width (b) 0.002 m 
Distance between the 
fins(B1) 
0.002 m, 0.003 m and 
0.004 m 
Jet width( l1) 0.01 m 
Confined wall 
length( l2) 
0.015 m 
Table 2 Thermal properties Fin materials 
Material Density 
(kg/m3) 
Thermal 
conductivity 
(W/m-K) 
Specific 
heat 
(J/kg-K) 
Copper 8978 387.6 381 
Aluminum 2719 202.4 871 
Steel 8030 16.3 502.5 
4. NUMERICAL METHADOLOGY 
In CFD calculations, there are three main steps. 
 Pre-Processing 
 Solver Execution 
 Post-Processing 
Pre-Processing is the step where the modeling 
goals are determined and computational grid is 
created. In the second step numerical models and 
boundary conditions are set to start up the solver. 
Solver runs until the convergence is reached. When 
solver is terminated, the results are examined which is 
the post -processing. 
4.1 Pre-Processing 
In this study, the aim is to investigate the 
cooling characteristics of different fins. So, an 
adequate numerical model is to be created. Pre-
International Journal of Research in Advent Technology, Vol.2, No.8, August 2014 
E-ISSN: 2321-9637 
112 
processing is the most time consuming and least 
knowledge requiring part. There are two important 
points here. The first one is the size of the domain, 
and the second one is the density and quality of the 
computational grid. Model size is the computational 
domain where the solution is done. It is important to 
build it as small as possible to prevent the model to be 
computationally expensive. On the other hand it 
should be large enough to resolve all the fluid and 
energy flow affecting the heat transfer around the Fin. 
In this problem, domain is selected to be the two fins 
The model of the present problem is created 
using hyper mesh 10 software major commands used 
for creation are nodes; line .The obtained model is 
meshed using the HYPERMESH 10 software. In 
meshing first 2D meshing is done using the quad 
elements it is because the model is in regular shape as 
shown in Fig 3 to Fig 5. 
Fig. 3 Meshed diagram of 2mm spacing 
Fig 4 Meshed diagram of 3mm spacing 
. Fig 5 Meshed diagram of 4mm spacing 
4.2 Symmetry Condition 
Symmetry boundary conditions are used 
when the physical geometry of interest, and the 
expected pattern of the flow/thermal solution, has 
mirror symmetry. These can also be used to model 
zero-shear slip walls in viscous flows. In the present 
case single fin is considered and applying symmetry 
boundary condition at one face it can obtain two fins. 
The symmetry grid display is shown in Fig 6. 
Fig 6 symmetry grid display 
5. SOLVER SET UP 
The solver set up is very important in any of 
the fluid flow problem; the solver setting indicates the 
method and also a procedure for solving (analysis) the 
problem. The flow analysis has studied using ANSYS 
FLUENT (6.3.26) [17] 
5.1 Turbulence Modeling 
The turbulence model used for this work is 
standard k-epsilon. The 3D space pressure based 
solver is used and implicit formulation is used for 
solution scheme. Solution controls uses flow and 
turbulence equations. The simple algorithm is used for 
pressure velocity coupling and for discretization 
second order scheme is used [9]. The convergence 
criteria for all case studies are taken as 0.001. 
5.2 Governing Equations to be solved 
Time independent flow equations with 
turbulence are to be solved. The viscous dissipation 
term will be omitted. Therefore the governing 
equations for the fluid flow, Above Equation are 
modified as follows:
International Journal of Research in Advent Technology, Vol.2, No.8, August 2014 
E-ISSN: 2321-9637 
113 
Mass 
X momentum (ρu ) = 
Ymomentum: (ρv )= 
Zmomentum: (ρ )= 
Energy: ( ) = -p + + 
Equation of state: p= 
5.3. BOUNDARY CONDITIONS 
The boundary conditions are the important 
values for the mathematical model. The boundary 
condition is applied to different zones. There are 
different kinds of boundary conditions for the fluid 
flow to enter and exit the domain. The boundary 
condition is depending on type of fluid use for the 
analysis. The fluid used for this analysis is 
incompressible hence velocity inlet condition applies. 
Inlet velocity profile was assumed, slip condition 
assigned to all surfaces. The boundary conditions used 
for the analysis are listed in table 3 
Table 3 Boundary conditions used in CFD analysis. 
Sl no Quantities Condition/value 
1 Working fluid Air 
2 Gauge pressure 0 Pa 
3 Inlet velocity 5m/s,10m/s and 15m/s 
4 Fin material Aluminum, copper and 
steel 
6. RESULTS AND DISCUSSION 
In this study two rectangular fin geometry is 
considered. The parameters like fin material 
(Aluminum, copper and steel) are considered and fin 
spacing varied as (2 mm, 3 mm, 4 mm) and jet 
velocity of (5 m/s, 10 m/s and 15 m/s) are considered. 
The detailed effect of these parameters are analysed as 
shown below Simulation technique is used in the 
present work which involves selection of geometry 
from the literature, modeling and meshing of the 
geometry was performed using HYPERMESH10 
software. The physical boundary conditions were 
applied to meshed model by importing meshed model 
to FLUENT 6.3.26 and analysis is carried out using 
CFD solver. The different graphs of heat transfer rate, 
pressure drop and temperature distribution, velocity 
vectors for varied combinations of fin material, fin 
spacing and jet velocity (27 combinations) were 
analyzed in detail. 
6.1 Convergence 
Only a well converged simulation can give 
reliable results. Convergence is determined by the 
order of magnitude residuals drop the convergence of 
simulation is required to get the parameters of the fin. 
It also gives accurate value of parameters for the 
requirement of heat transfer rate, pressure drop. 
Continuity, X-velocity, Y-velocity, Z-velocity, 
energy, k, epsilon are the part of scaled residual which 
have to converge in a specific region. For the 
continuity residuals set are 10-3, X velocity, Y 
velocity, Z-velocity, k, epsilon should be less than 
10-5 and the energy should be less than 10-6. If all 
values in same manner then solution will be 
converged. For the considered problem convergence 
is obtained at 500 iterations. 
6.2 Heat transfer rate in impinging jet with finned 
heat sink: 
Heat transfer rate is defined as the amount 
heat transferred from the fin and base to the 
surrounding fluid. The effect of velocity and fin 
material is examined and tabulated in table 4, table 5 
and table 6 for 2 mm, 3 mm and 4 mm fin spacing 
respectively. 
Table 4 Heat transfer rates for 2mm spacing between 
the fins. 
Sl no Material Velocity 
5m/s 
Velocity 
10m/s 
Velocity 
15m/s 
Heat transfer rate in watts 
1 Copper 1.4189 2.2440 2.9054 
2 Aluminum 1.3076 2.0990 2.7054 
3 Steel 1.1969 1.7456 2.1250 
Fig 7 variation of heat transfer rate at 2mm spacing 
Table 5 Heat transfer rates for 3mm spacing between 
the fins 
Sl 
no 
Material Velocity 
5m/s 
Velocity 
10m/s 
Velocity 
15m/s 
Heat transfer rate in watts 
1 Copper 1.3351 2.124 2.7084 
2 Aluminum 1.3224 2.005 2.6615
International Journal of Research in Advent Technology, Vol.2, No.8, August 2014 
E-ISSN: 2321-9637 
114 
3 steel 1.1674 1.6225 1.9434 
Fig 8 variation of heat transfer rate at 3mm spacing 
Table 6 Heat transfer rates for 4mm spacing between 
the fins 
Sl 
no 
Material Velocity 
5m/s 
Velocity 
10m/s 
Velocity 
15m/s 
Heat transfer rate in watts 
1 Copper 1.2927 1.9200 2.4190 
2 Aluminum 1.1999 1.8050 2.3900 
3 steel 1.1307 1.5928 1.785 
Fig 9 variation of heat transfer rate at 4mm spacing 
Heat transfer rate is the important parameter 
to judge performance of a fin. The variation of heat 
transfer rate for Aluminum, copper and steel is 
tabulated and variation is plotted in Fig 7, Fig 8 and 
Fig 9. In all these cases heat transfer rate is increasing 
as the velocity increases and also heat transfer rate is 
high for the copper, than Aluminum and lowest for 
the steel .The variation of heat transfer rate depend on 
fin material, jet velocity and fin spacing. Heat transfer 
rate increases with increase in thermal conductivity of 
fin material and also with increase in jet velocity. But 
increase in fin spacing there was decrease in heat 
transfer rate for all the cases of fin material and jet 
velocity. For 2 mm spacing of copper material at 
15m/s there was increase of 0.4864 W of heat transfer 
rate when compared to 4 mm spacing at 15 m/s jet 
velocity. It is due to decrease in fin spacing, velocity 
loss will be less and also volume flow rate of fluid 
particles will be higher between the two fins. Due to 
which there is increase in heat transfer rate at 2 mm 
fin spacing. 
From the CFD analyses the obtained graphs 
shows that when the steel is used as fin material there 
will be a drastic reduction in heat transfer rate for all 
the cases of fin spacing and jet velocity. When 
aluminum is used as fin material there was increase in 
heat transfer rate when compared to steel but slightly 
less when copper is used as fin material. For 2 mm 
spacing of aluminum material at 15 m/s there was 
0.5804 W of heat transfer rate increase with respect to 
steel, but 0.2 W of heat transfer rate decrease when 
compared to copper fin material. From the above 
obtained graphs it can be concluded that for 2mm 
spacing at 15 m/s when copper is used as fin material 
heat transfer rate will be maximum for the considered 
geometry when compared to other materials and fin 
spacing 
6.3 Temperature Distributions in Fins 
For the considered geometry, the temperature 
distribution is mainly dependent on fin material used 
and inlet jet velocity, But it is invariant with fin 
spacing so temperature distribution is presented for 
fin material of copper ,aluminum and steel for varying 
inlet velocity 15 m/s for only 2 mm spacing. Fig 10, 
Fig 11 and Fig 12 shows temperature contour for 
copper, aluminum and steel at 15 m/s jet velocity 
. 
Fig 10 Temperature contour for copper 2 mm fin 
spacing @15 m/s 
Fig 11 Temperature contour for Al 2 mm fin spacing 
@15 m/s
International Journal of Research in Advent Technology, Vol.2, No.8, August 2014 
E-ISSN: 2321-9637 
115 
Fig 12 Temperature contour for steel 2mm fin spacing 
@ 15 m/s 
It is reasonable to see that the temperature in 
the region close to the fin tip and jet inlet is lowest. It 
is observed that the temperature gradient for the fin 
base and tip of the fin for copper and aluminum is 
around 2 K to 3 K but for steel it is around 10 K it is 
because the Thermal conductivity for copper and 
aluminum is high as compared to steel. The 
conduction heat transfer takes place from bottom 
surface of the base to the top surface of the fin .The 
temperature in region close to the fin tip and jet inlet 
is lowest, because as the jet inlet velocity is maximum 
at the inlet and also heat transfer coefficient increases 
with increase in the Reynolds number due to which 
heat transfer rate is maximum at the inlet of the jet 
corresponding to fin tip. So it is observed that 
minimum temperature will be at the inlet of the jet. 
From this there will be effective heat transfer 
takes place when the impinging jet technique is used 
for heat sink in an electronic cooling purpose. 
6.5 Velocity Analysis 
Velocity of jet around the fin and between 
the fins is predominant factor for rate of heat transfer 
by the heat sink. The variation of velocity from inlet 
to the outlet is presented by plotting velocity vectors 
since the velocity variation is mainly depends on inlet 
velocity of the jet and it is invariant with fin material 
so for the considered geometry velocity variation for 
copper material is presented. Fig 13, Fig14 and Fig15 
shows the velocity variation for inlet jet velocity of 
5m/s for copper material at 2 mm, 3 mm and 3 mm 
spacing respectively. 
Fig 13 Velocity vector for cu at 5m/s for 2mm fin 
spacing 
Fig 14 Velocity vector for cu at 5m/s for 3mm fin 
spacing 
Fig 15 Velocity vector for cu at 5m/s for 4mm fin 
spacing 
It is observed from velocity vectors for all the 
cases of varying inlet velocity the outlet velocity close 
to the base is higher due to the impinging effect. For 
the considered geometry for inlet velocity of 5 m/s, 
10 m/s and 15 m/s the outlet velocity close to the base 
is around 13 m/s, 25 m/s and 38 m/s respectively. 
For the decrease in fin spacing it is observed 
from velocity vectors there was increase in average 
channel velocity of jet. As the fin spacing decreases 
the pressure drop increases which results in increase 
of velocity. Since the velocity variation is mainly 
depends on fin spacing and inlet velocity but it is 
invariant of fin material so only for copper material 
velocity variation is presented in this work but 
velocity variation for aluminum and steel is also 
analyzed. 
6.6 Pressure drop analysis 
Pressure drop is the resistance to the air 
movement and it is related with flow cross sectional 
area, fin spacing and fin length. The heat sink should 
be designed so as to yield a smaller pressure drop than 
the static pressure of the fan. In general, the total heat 
sink pressure drop depends on four major factors the 
friction factors, the heat sink geometry, the approach 
velocity and the heat sink channel velocity. The 
friction factors arise from the airflow entering and 
exiting heat sink channel are known as the contraction 
loss coefficient and expansion loss coefficient 
respectively, whereas the friction factor that due to the
International Journal of Research in Advent Technology, Vol.2, No.8, August 2014 
E-ISSN: 2321-9637 
116 
transition of airflow from developing flow to fully 
developed flow is called the apparent friction. 
Pressure drop values were tabulated in table 7, table 8 
and table 9 for 2mm, 3mm and 4mm fin spacing 
respectively. 
Table 7 pressure drop for 2 mm spacing between the 
fins 
Sl 
Velocity 
Velocity 
Velocity 
Material 
no 
5m/s 
10m/s 
15m/s 
Pressure drop in (Pascal) 
1 Copper 140 520 1200 
2 Aluminum 140 520 1200 
3 Steel 140 520 1200 
Table 8 pressure drop for 3 mm spacing between the 
fins 
Sl 
no 
Material 
Velocity 
5m/s 
Velocity 
10m/s 
Velocity 
15m/s 
Pressure drop in (Pascal) 
1 Copper 120 450 1000 
2 Aluminum 120 450 1000 
3 Steel 120 450 1000 
Table 9 pressure drop for 4mm spacing between the 
fins 
Sl 
no 
Material 
Velocity 
5m/s 
Velocity 
10m/s 
Velocity 
15m/s 
Pressure drop in (Pascal) 
1 Copper 100 300 800 
2 Aluminum 100 300 800 
3 steel 100 300 800 
Fig 16 pressure drop variation with fin spacing 
Since from the table 7 table 8 and table 9. It 
is observed that pressure drop is invariant with fin 
material so pressure drop along the fin is presented 
with the variation of fin spacing only. From Fig 16 It 
can be observed that as the fin spacing decreases 
pressure drop increases. With the decrease in fin 
spacing flow between the fin spacing is fully 
developed because due to high Reynolds number 
friction Factor will be very much greater for minimum 
fin spacing this affects heat transfer rate. Increase in 
pressure drop affects the fluid flow particles 
movement over the fin material. 
Sometimes negative pressure will be 
developed at inlet with respect to exit. Due to which 
the flow will be reversed which affects performance 
of the heat sink. For the considered geometry it is 
observed increase in pressure drop as the decrease in 
fin spacing but not less than static pressure. 
7. CONCLUSIONS 
The analytical model is developed for high 
Reynolds number turbulent flow and heat transfer in 
inter fin channels of impingement flow plate fin heat 
sink. The simple model is suitable for heat sink 
parametric design study. From the obtained numerical 
results the following conclusions can be drawn. 
1. From the obtained numerical analysis maximum 
heat transfer rate was for copper fin material at 2 
mm spacing for 15 m/s jet velocity. The results 
shows that there was increase in 0.2 W and 
0.7804 W heat transfer rate compared to 
aluminum and steel respectively at 2mm fin 
spacing and 15m/s. 
When aluminum is used as fin material and 
compared with respect to copper and steel. The 
rate of heat transfer was maximum compared to 
steel but there was slight reduction in rate of heat 
transfer compared to copper at all fin spacing (2 
mm, 3 mm and 4mm ) and at all jet velocity (5 
m/s ,10 m/s). 
In overall copper fin material showed good 
results but the use of copper as fin material makes 
heat sink heavier and expensive so aluminum can 
be selected as fin material for thermal heat sink 
which gives optimum result compared to copper. 
2. For all combinations it is observed as the fin 
spacing decreases there is an increase in heat 
transfer rate. For the considered geometry 2mm 
fin spacing gives optimum heat transfer. 
3. Pressure drop plays vital role with respect to fin 
spacing. With decrease in fin spacing for the 
considered geometry pressure drop increases 
which affects the rate of heat transfer. But for 
considered geometry the effect of pressure drop is 
negligible. But when higher dimensions are 
considered with impinging jet the rate of heat 
transfer decreases with increase in pressure drop 
for the reduced fin spacing. 
4. From the velocity vectors it was observed that 
there was an increase in jet velocity as the fluid 
flows from inlet to exit. It is because of the 
impinging effect and reduced fin spacing. This
International Journal of Research in Advent Technology, Vol.2, No.8, August 2014 
E-ISSN: 2321-9637 
117 
results in increase of heat transfer rate when 
compared to parallel flow arrangement. 
5. From the temperature contours it can be 
concluded that temperature close to the fin tip at 
inlet of the jet is observed minimum. This 
indicates maximum temperature difference 
resulting in high heat transfer rate at the inlet. 
6. In overall for the considered geometry and 
boundary conditions it can be concluded that fin 
material of aluminum with 2 mm fin spacing at 
15 m/s jet velocity gives the optimum result for 
electronic cooling systems. 
REFERENCES 
[1] Clemens, J. M. Lasance and Robert E. Simons, 
Advances In High-Performance Cooling For 
Electronics, Philips Research Laboratories 
IBM Corporation, 2005 
[2] Thyrum, G., Critical Aspects of Modeling Heat 
Pipe Assisted Heat Sinks, 2002 
[3] Duan, Z. and Muzychka, Y.S., “Experimental 
investigation of heat transfer in impingement 
air cooled plate fin heat sinks,” ASME J. of 
Electronic Packaging, v 128, pp. 412-418, 
2006 
[4] Zhipeng Duan; Muzychka, Yu.S., 
Impingement air cooled plate fin heat sinks. 
Part I - Pressure drop model, Thermal and 
Thermomechanical Phenomena in Electronic 
Systems, 2004. ITHERM '04. The Ninth 
Intersociety Conference on , vol., no., 
pp.429,435 Vol.1, 1-4 June 2004 doi: 
10.1109/ITHERM.2004.1319206 
[5] Zhipeng Duan; Mzychka, Y.S., Impingement 
air cooled plate fin heat sinks. Part II Thermal 
resistance model, Thermal and 
Thermomechanical Phenomena in Electronic 
Systems, 2004. ITHERM '04. The Ninth 
Intersociety Conference on, vol., no., pp.436, 
443 Vol.1, 1-4 June 2004 doi: 
10.1109/ITHERM.2004.1319207 
[6] Weilin Qu, Issam Mudawar “Experimental and 
numerical study of pressure drop and heat 
transfer in a single-phase micro-channel heat 
sink”international journal of heat and mass 
transfer (45)2002 2549-2565 
[7] Biber, C.R., “Pressure drop and heat transfer in 
an isothermal channel with impinging flow,” 
IEEE Transactions, Components, Packaging, 
and Manufacturing Technology, Part A, v. 20, 
pp. 458 – 462, 1997 
[8] Wu, M.C., Lee, C.Y., Peng, C.H., Fang, C.J., 
and Hung, Y.H., “Cooling performance of 
plain-plate-fin heat sinks with slot jet 
impingement,” ASME Int. Mechanical 
Engineering Congress and Exposition, 
IMECE2006, Chicago, IL, United States, Nov 
5-10, 2006. 
[9] Li, H.-Y. and Chen, K.-Y., “Thermal 
performance of plate-fin heat sinks under 
confined impinging jet conditions,” Int. J. of 
Heat and Mass Transfer, v. 50, pp. 1963-1970, 
2007 
[10] 
Li, X. C., Conjugate heat transfer of jet 
impingement on short fins with different 
shapes, Thermal and Thermo mechanical 
Phenomena in Electronic Systems, 2008. 
ITHERM 2008. 11th Intersociety Conference 
on, vol., no., pp.49,56, 28-31 May 2008 
doi: 10.1109/ITHERM.2008.4544253 
[11] Bhopte, S., Alshuqairi, M. S. Agonafer, D., and 
Refai- Ahmed, G. “Mixed convection of 
impinging air cooling over heat sink in telecom 
system application,” ASME J. of Electronic 
Packaging, v. 126, pp. 519-523, 2004 
[12] Md. Farhad Ismail “Numerical simulation of 
turbulent heat transfer from perforated plate-fin 
heat sinks” Heat Mass Transfer (2014) 
50:509–519 
[13] Chougule N K “CFD Analysis of Multi-jet Air 
Impingement on Flat Plate” Proceedings of the 
World Congress on Engineering 2011 Vol III 
WCE 2011, July 6 - 8, 2011, London, U.K 
[14] Rajesh kumar Panda “conjugate heat transfer 
from a flat plate with shower head impinging 
jets” Frontiers in Heat and Mass Transfer 
(FHMT), 2, 013008 (2011) DOI: 
10.5098/hmt.v2.1.3008 
[15] Arularasan R. “CFD analysis in a heat sink for 
cooling of electronic devices” International 
Journal of The Computer, the Internet and 
Management Vol. 16.No.3 (September- 
December, 2008) pp 1-11 
[16] M. Beriache “Numerical study on hydraulic 
and thermal characteristics of a minichannel 
heat sinks with impinging air flow” ISSN 1392 
- 1207. MECHANIKA. 2011. 17(2): 156-161 
[17] FLUENT 6.3.26 Users Guide, Fluent, Inc, 
2006

More Related Content

Paper id 28201451

  • 1. International Journal of Research in Advent Technology, Vol.2, No.8, August 2014 E-ISSN: 2321-9637 Heat Transfer Simulation of Impinging Jet with Finned 110 Heat Sink Shivakumar H1, Krishnamurthy K N2, Akashdeep B.N3 Department of Thermal power Engineering, M.Tech student1, Assistant professor2, VTU P G Centre Mysore, Karnataka, India 1, 2. Department of Mechanical Engineering Assistant Professor KSSEM Bangalore Karnataka, India3. Email: shivu_bec@hotmail.com1, murthykrishnakn@gmail.com 2,bndeep@gmail.com3 Abstract- This study examines numerically details of the flow and temperature fields of heat sinks with short plate fins cooled by impinging jet. The main focus is on the effect of fin spacing, fin material and jet velocities on the heat sink performance. Conjugate heat transfer between airflow convection and conduction inside the fin and base is considered. Three different fin spacing (2 mm, 3 mm, 4 mm), fin material (Aluminum, copper and steel) and jet velocity of (5 m/s,10 m/s and 15 m/s ) are the parameters under study. Detailed temperature contours, velocity vector, pressure drop are presented and compared. In this current work the effect of fin material is observed that heat transfer rate varies in accordance with thermal conductivity of fin material. For the considered geometry there was increase of 0.2 W and 0.7804 W heat transfer rate for copper fin material, when it is compared to Aluminum and steel respectively for 15 m/s jet velocity. The effect of fin spacing on rate of heat transfer rate for the considered geometry it is observed that there is increase of 19% and 48% heat transfer rate for decrease of fin spacing of 2 mm and 3 mm respectively at 15 m/s jet velocity. Pressure drop is also sensitive to fin spacing in all the combinations, as fin spacing decreases pressure drop increases. For the considered geometry it is observed that pressure drop of 100 Pa, 120Pa and 140Pa for 4 mm, 3 mm, and 2 mm fin spacing respectively for jet velocity of 15 m/s. In overall pressure drop and heat transfer rate are contradicting with respect to fin spacing. However use of copper material makes heat sink heavier and expensive. Hence it can be concluded that for considered geometry of fin spacing 2 mm at 15 m/s of jet velocity for Aluminum fin material the numerical result was found to be optimum. The results of this can help in design of heat sinks with jet impingement, which are commonly used in electronic cooling systems. Index Terms: Jet impingement, heat sink, plate fin. 1. INTRODUCTION The relentless trend of ever increasing integrated circuit chip functionality and decreasing chip dimensions for miniaturization of products have led to the need to develop new thermal management techniques to handle intense heat generation rate in IC chips. The need for effective cooling of chips at an acceptable cost is an urgent issue Extended surfaces (fins) and impinging jets have commonly been used to enhance heat transfer in many applications, for example, electronic cooling and gas turbine cooling. In electronic thermal management, heat sinks are designed to take advantage of the combined effect of fins and jet impingement such as jets impinging on an array of pin fins or plate fins. Significant studies have been focused on the thermal resistance, pressure drop, and the parametric effect of Reynolds number, fin thickness, density and height. Different correlations based on one-dimensional heat conduction and experimental data are developed to predict the heat sink performance. Efforts to optimize the heat sink design have also been made by using both experimental and numerical methods. 2. CURRENT STUDY This study applies numerical simulation to examine the details of flow and temperature fields of plate fin heat sinks with jet impingement. Based on the literature review few studies have been done on the effect of fin spacing, fin material and jet velocity. Therefore, the main focus of this study is on the effect of fin spacing of (2 mm, 3 mm and 4 mm), fin material Aluminum, copper and steel, jet velocity of (5 m/s, 10 m/s and 15 m/s) on the heat sink performance. The characteristics of 3D temperature field inside the fins and solid base are also explored. It is observed that the fin spacing affects largely both the heat transfer and pressure drop, fin material and jet velocity effects on heat transfer rate especially of the short fin cases .The results of this paper can help in design of heat sinks with jet impingement. 2.1 Objectives: 1. This concerns the familiarization with the methods and materials. This involves literature reviews on the different methods of cooling employed in electronic equipment’s. 2. This involves choosing the parameter on which analysis should be carried out. In this work the parameters selected are fin material (Aluminum, copper and steel), fin spacing (2 mm, 3 mm, 4 mm), and velocity of jet (5 m/s, 10 m/s and 15 m/s). 3. The selection of geometry for the CAD model was selected from literature [10] and the physical
  • 2. International Journal of Research in Advent Technology, Vol.2, No.8, August 2014 E-ISSN: 2321-9637 111 arrangement of fin is modeled using hyper mesh V10 software. 4. Mesh generation of the modeled geometry was carried out using hyper mesh V10 software. 5. The boundary conditions for the fluid flow analysis were imposed and the solution was obtained through the analysis software FLUENT 6.3.26. 6. The analysis was carried out to obtain heat transfer rate, pressure drop and contours of temperature, Velocity vector are drawn . 3. PROBLEM UNDER CONSIDERATION There are generally two types of heat sinks with jet impingement. One is with parallel plate fins, and the other is with pin fins. In this study the plate fin heat sink is considered. Figure 1 shows the geometric schemes of this type of heat sink. The slot jet impinges from the top to the plate fins and exits from two sides into the surroundings. The sink base is connected to the electronic modules to dissipate the heat to the cooling airflow. The top can be either open or confined, which is considered as confined in this study. The performance depends on the jet velocity, fin height, fin width, number of fins, and the base thickness. In practice, there usually is a small gap between the fin tip and jet plate Fig 1 Geometric scheme of a heat sink of parallel plate fins cooled by an impinging jet The heat sink in Fig 1 is symmetric in both the x- and z directions unless the flow or thermal boundary conditions are applied differently. Figure 2 shows the symbolic dimension of the cases under study. The fin shape considered is rectangular fins. All the fins share the same height and base width, which leads to a slightly different surface area and thus different volume or weight. The total height in the y-direction is H, and heights for the fin and base are h1 and h2, respectively. The fin has a thickness of b, and the distance between the fins is B1.The the impinging slot jet has a width of( l1) and the rest of the top surface is the confined wall (l2).In this study, the air jet with constant properties impinges on the heat sink vertically with a uniform inlet velocity and temperature. Constant temperature is applied to the heat sink bottom surface for simplification. The considered dimensions and thermal Properties of fin materials are presented in table 1 and 2 respectively. b H h1 B h 2 B1 2 Fig. 2 shows the symbolic dimension of the cases under study Table 1 Dimensions of Fin geometry Fin height( h1) 0.006 m Base height( h2) 0.002 m Total height (H) 0.01 m Fin width (b) 0.002 m Distance between the fins(B1) 0.002 m, 0.003 m and 0.004 m Jet width( l1) 0.01 m Confined wall length( l2) 0.015 m Table 2 Thermal properties Fin materials Material Density (kg/m3) Thermal conductivity (W/m-K) Specific heat (J/kg-K) Copper 8978 387.6 381 Aluminum 2719 202.4 871 Steel 8030 16.3 502.5 4. NUMERICAL METHADOLOGY In CFD calculations, there are three main steps. Pre-Processing Solver Execution Post-Processing Pre-Processing is the step where the modeling goals are determined and computational grid is created. In the second step numerical models and boundary conditions are set to start up the solver. Solver runs until the convergence is reached. When solver is terminated, the results are examined which is the post -processing. 4.1 Pre-Processing In this study, the aim is to investigate the cooling characteristics of different fins. So, an adequate numerical model is to be created. Pre-
  • 3. International Journal of Research in Advent Technology, Vol.2, No.8, August 2014 E-ISSN: 2321-9637 112 processing is the most time consuming and least knowledge requiring part. There are two important points here. The first one is the size of the domain, and the second one is the density and quality of the computational grid. Model size is the computational domain where the solution is done. It is important to build it as small as possible to prevent the model to be computationally expensive. On the other hand it should be large enough to resolve all the fluid and energy flow affecting the heat transfer around the Fin. In this problem, domain is selected to be the two fins The model of the present problem is created using hyper mesh 10 software major commands used for creation are nodes; line .The obtained model is meshed using the HYPERMESH 10 software. In meshing first 2D meshing is done using the quad elements it is because the model is in regular shape as shown in Fig 3 to Fig 5. Fig. 3 Meshed diagram of 2mm spacing Fig 4 Meshed diagram of 3mm spacing . Fig 5 Meshed diagram of 4mm spacing 4.2 Symmetry Condition Symmetry boundary conditions are used when the physical geometry of interest, and the expected pattern of the flow/thermal solution, has mirror symmetry. These can also be used to model zero-shear slip walls in viscous flows. In the present case single fin is considered and applying symmetry boundary condition at one face it can obtain two fins. The symmetry grid display is shown in Fig 6. Fig 6 symmetry grid display 5. SOLVER SET UP The solver set up is very important in any of the fluid flow problem; the solver setting indicates the method and also a procedure for solving (analysis) the problem. The flow analysis has studied using ANSYS FLUENT (6.3.26) [17] 5.1 Turbulence Modeling The turbulence model used for this work is standard k-epsilon. The 3D space pressure based solver is used and implicit formulation is used for solution scheme. Solution controls uses flow and turbulence equations. The simple algorithm is used for pressure velocity coupling and for discretization second order scheme is used [9]. The convergence criteria for all case studies are taken as 0.001. 5.2 Governing Equations to be solved Time independent flow equations with turbulence are to be solved. The viscous dissipation term will be omitted. Therefore the governing equations for the fluid flow, Above Equation are modified as follows:
  • 4. International Journal of Research in Advent Technology, Vol.2, No.8, August 2014 E-ISSN: 2321-9637 113 Mass X momentum (ρu ) = Ymomentum: (ρv )= Zmomentum: (ρ )= Energy: ( ) = -p + + Equation of state: p= 5.3. BOUNDARY CONDITIONS The boundary conditions are the important values for the mathematical model. The boundary condition is applied to different zones. There are different kinds of boundary conditions for the fluid flow to enter and exit the domain. The boundary condition is depending on type of fluid use for the analysis. The fluid used for this analysis is incompressible hence velocity inlet condition applies. Inlet velocity profile was assumed, slip condition assigned to all surfaces. The boundary conditions used for the analysis are listed in table 3 Table 3 Boundary conditions used in CFD analysis. Sl no Quantities Condition/value 1 Working fluid Air 2 Gauge pressure 0 Pa 3 Inlet velocity 5m/s,10m/s and 15m/s 4 Fin material Aluminum, copper and steel 6. RESULTS AND DISCUSSION In this study two rectangular fin geometry is considered. The parameters like fin material (Aluminum, copper and steel) are considered and fin spacing varied as (2 mm, 3 mm, 4 mm) and jet velocity of (5 m/s, 10 m/s and 15 m/s) are considered. The detailed effect of these parameters are analysed as shown below Simulation technique is used in the present work which involves selection of geometry from the literature, modeling and meshing of the geometry was performed using HYPERMESH10 software. The physical boundary conditions were applied to meshed model by importing meshed model to FLUENT 6.3.26 and analysis is carried out using CFD solver. The different graphs of heat transfer rate, pressure drop and temperature distribution, velocity vectors for varied combinations of fin material, fin spacing and jet velocity (27 combinations) were analyzed in detail. 6.1 Convergence Only a well converged simulation can give reliable results. Convergence is determined by the order of magnitude residuals drop the convergence of simulation is required to get the parameters of the fin. It also gives accurate value of parameters for the requirement of heat transfer rate, pressure drop. Continuity, X-velocity, Y-velocity, Z-velocity, energy, k, epsilon are the part of scaled residual which have to converge in a specific region. For the continuity residuals set are 10-3, X velocity, Y velocity, Z-velocity, k, epsilon should be less than 10-5 and the energy should be less than 10-6. If all values in same manner then solution will be converged. For the considered problem convergence is obtained at 500 iterations. 6.2 Heat transfer rate in impinging jet with finned heat sink: Heat transfer rate is defined as the amount heat transferred from the fin and base to the surrounding fluid. The effect of velocity and fin material is examined and tabulated in table 4, table 5 and table 6 for 2 mm, 3 mm and 4 mm fin spacing respectively. Table 4 Heat transfer rates for 2mm spacing between the fins. Sl no Material Velocity 5m/s Velocity 10m/s Velocity 15m/s Heat transfer rate in watts 1 Copper 1.4189 2.2440 2.9054 2 Aluminum 1.3076 2.0990 2.7054 3 Steel 1.1969 1.7456 2.1250 Fig 7 variation of heat transfer rate at 2mm spacing Table 5 Heat transfer rates for 3mm spacing between the fins Sl no Material Velocity 5m/s Velocity 10m/s Velocity 15m/s Heat transfer rate in watts 1 Copper 1.3351 2.124 2.7084 2 Aluminum 1.3224 2.005 2.6615
  • 5. International Journal of Research in Advent Technology, Vol.2, No.8, August 2014 E-ISSN: 2321-9637 114 3 steel 1.1674 1.6225 1.9434 Fig 8 variation of heat transfer rate at 3mm spacing Table 6 Heat transfer rates for 4mm spacing between the fins Sl no Material Velocity 5m/s Velocity 10m/s Velocity 15m/s Heat transfer rate in watts 1 Copper 1.2927 1.9200 2.4190 2 Aluminum 1.1999 1.8050 2.3900 3 steel 1.1307 1.5928 1.785 Fig 9 variation of heat transfer rate at 4mm spacing Heat transfer rate is the important parameter to judge performance of a fin. The variation of heat transfer rate for Aluminum, copper and steel is tabulated and variation is plotted in Fig 7, Fig 8 and Fig 9. In all these cases heat transfer rate is increasing as the velocity increases and also heat transfer rate is high for the copper, than Aluminum and lowest for the steel .The variation of heat transfer rate depend on fin material, jet velocity and fin spacing. Heat transfer rate increases with increase in thermal conductivity of fin material and also with increase in jet velocity. But increase in fin spacing there was decrease in heat transfer rate for all the cases of fin material and jet velocity. For 2 mm spacing of copper material at 15m/s there was increase of 0.4864 W of heat transfer rate when compared to 4 mm spacing at 15 m/s jet velocity. It is due to decrease in fin spacing, velocity loss will be less and also volume flow rate of fluid particles will be higher between the two fins. Due to which there is increase in heat transfer rate at 2 mm fin spacing. From the CFD analyses the obtained graphs shows that when the steel is used as fin material there will be a drastic reduction in heat transfer rate for all the cases of fin spacing and jet velocity. When aluminum is used as fin material there was increase in heat transfer rate when compared to steel but slightly less when copper is used as fin material. For 2 mm spacing of aluminum material at 15 m/s there was 0.5804 W of heat transfer rate increase with respect to steel, but 0.2 W of heat transfer rate decrease when compared to copper fin material. From the above obtained graphs it can be concluded that for 2mm spacing at 15 m/s when copper is used as fin material heat transfer rate will be maximum for the considered geometry when compared to other materials and fin spacing 6.3 Temperature Distributions in Fins For the considered geometry, the temperature distribution is mainly dependent on fin material used and inlet jet velocity, But it is invariant with fin spacing so temperature distribution is presented for fin material of copper ,aluminum and steel for varying inlet velocity 15 m/s for only 2 mm spacing. Fig 10, Fig 11 and Fig 12 shows temperature contour for copper, aluminum and steel at 15 m/s jet velocity . Fig 10 Temperature contour for copper 2 mm fin spacing @15 m/s Fig 11 Temperature contour for Al 2 mm fin spacing @15 m/s
  • 6. International Journal of Research in Advent Technology, Vol.2, No.8, August 2014 E-ISSN: 2321-9637 115 Fig 12 Temperature contour for steel 2mm fin spacing @ 15 m/s It is reasonable to see that the temperature in the region close to the fin tip and jet inlet is lowest. It is observed that the temperature gradient for the fin base and tip of the fin for copper and aluminum is around 2 K to 3 K but for steel it is around 10 K it is because the Thermal conductivity for copper and aluminum is high as compared to steel. The conduction heat transfer takes place from bottom surface of the base to the top surface of the fin .The temperature in region close to the fin tip and jet inlet is lowest, because as the jet inlet velocity is maximum at the inlet and also heat transfer coefficient increases with increase in the Reynolds number due to which heat transfer rate is maximum at the inlet of the jet corresponding to fin tip. So it is observed that minimum temperature will be at the inlet of the jet. From this there will be effective heat transfer takes place when the impinging jet technique is used for heat sink in an electronic cooling purpose. 6.5 Velocity Analysis Velocity of jet around the fin and between the fins is predominant factor for rate of heat transfer by the heat sink. The variation of velocity from inlet to the outlet is presented by plotting velocity vectors since the velocity variation is mainly depends on inlet velocity of the jet and it is invariant with fin material so for the considered geometry velocity variation for copper material is presented. Fig 13, Fig14 and Fig15 shows the velocity variation for inlet jet velocity of 5m/s for copper material at 2 mm, 3 mm and 3 mm spacing respectively. Fig 13 Velocity vector for cu at 5m/s for 2mm fin spacing Fig 14 Velocity vector for cu at 5m/s for 3mm fin spacing Fig 15 Velocity vector for cu at 5m/s for 4mm fin spacing It is observed from velocity vectors for all the cases of varying inlet velocity the outlet velocity close to the base is higher due to the impinging effect. For the considered geometry for inlet velocity of 5 m/s, 10 m/s and 15 m/s the outlet velocity close to the base is around 13 m/s, 25 m/s and 38 m/s respectively. For the decrease in fin spacing it is observed from velocity vectors there was increase in average channel velocity of jet. As the fin spacing decreases the pressure drop increases which results in increase of velocity. Since the velocity variation is mainly depends on fin spacing and inlet velocity but it is invariant of fin material so only for copper material velocity variation is presented in this work but velocity variation for aluminum and steel is also analyzed. 6.6 Pressure drop analysis Pressure drop is the resistance to the air movement and it is related with flow cross sectional area, fin spacing and fin length. The heat sink should be designed so as to yield a smaller pressure drop than the static pressure of the fan. In general, the total heat sink pressure drop depends on four major factors the friction factors, the heat sink geometry, the approach velocity and the heat sink channel velocity. The friction factors arise from the airflow entering and exiting heat sink channel are known as the contraction loss coefficient and expansion loss coefficient respectively, whereas the friction factor that due to the
  • 7. International Journal of Research in Advent Technology, Vol.2, No.8, August 2014 E-ISSN: 2321-9637 116 transition of airflow from developing flow to fully developed flow is called the apparent friction. Pressure drop values were tabulated in table 7, table 8 and table 9 for 2mm, 3mm and 4mm fin spacing respectively. Table 7 pressure drop for 2 mm spacing between the fins Sl Velocity Velocity Velocity Material no 5m/s 10m/s 15m/s Pressure drop in (Pascal) 1 Copper 140 520 1200 2 Aluminum 140 520 1200 3 Steel 140 520 1200 Table 8 pressure drop for 3 mm spacing between the fins Sl no Material Velocity 5m/s Velocity 10m/s Velocity 15m/s Pressure drop in (Pascal) 1 Copper 120 450 1000 2 Aluminum 120 450 1000 3 Steel 120 450 1000 Table 9 pressure drop for 4mm spacing between the fins Sl no Material Velocity 5m/s Velocity 10m/s Velocity 15m/s Pressure drop in (Pascal) 1 Copper 100 300 800 2 Aluminum 100 300 800 3 steel 100 300 800 Fig 16 pressure drop variation with fin spacing Since from the table 7 table 8 and table 9. It is observed that pressure drop is invariant with fin material so pressure drop along the fin is presented with the variation of fin spacing only. From Fig 16 It can be observed that as the fin spacing decreases pressure drop increases. With the decrease in fin spacing flow between the fin spacing is fully developed because due to high Reynolds number friction Factor will be very much greater for minimum fin spacing this affects heat transfer rate. Increase in pressure drop affects the fluid flow particles movement over the fin material. Sometimes negative pressure will be developed at inlet with respect to exit. Due to which the flow will be reversed which affects performance of the heat sink. For the considered geometry it is observed increase in pressure drop as the decrease in fin spacing but not less than static pressure. 7. CONCLUSIONS The analytical model is developed for high Reynolds number turbulent flow and heat transfer in inter fin channels of impingement flow plate fin heat sink. The simple model is suitable for heat sink parametric design study. From the obtained numerical results the following conclusions can be drawn. 1. From the obtained numerical analysis maximum heat transfer rate was for copper fin material at 2 mm spacing for 15 m/s jet velocity. The results shows that there was increase in 0.2 W and 0.7804 W heat transfer rate compared to aluminum and steel respectively at 2mm fin spacing and 15m/s. When aluminum is used as fin material and compared with respect to copper and steel. The rate of heat transfer was maximum compared to steel but there was slight reduction in rate of heat transfer compared to copper at all fin spacing (2 mm, 3 mm and 4mm ) and at all jet velocity (5 m/s ,10 m/s). In overall copper fin material showed good results but the use of copper as fin material makes heat sink heavier and expensive so aluminum can be selected as fin material for thermal heat sink which gives optimum result compared to copper. 2. For all combinations it is observed as the fin spacing decreases there is an increase in heat transfer rate. For the considered geometry 2mm fin spacing gives optimum heat transfer. 3. Pressure drop plays vital role with respect to fin spacing. With decrease in fin spacing for the considered geometry pressure drop increases which affects the rate of heat transfer. But for considered geometry the effect of pressure drop is negligible. But when higher dimensions are considered with impinging jet the rate of heat transfer decreases with increase in pressure drop for the reduced fin spacing. 4. From the velocity vectors it was observed that there was an increase in jet velocity as the fluid flows from inlet to exit. It is because of the impinging effect and reduced fin spacing. This
  • 8. International Journal of Research in Advent Technology, Vol.2, No.8, August 2014 E-ISSN: 2321-9637 117 results in increase of heat transfer rate when compared to parallel flow arrangement. 5. From the temperature contours it can be concluded that temperature close to the fin tip at inlet of the jet is observed minimum. This indicates maximum temperature difference resulting in high heat transfer rate at the inlet. 6. In overall for the considered geometry and boundary conditions it can be concluded that fin material of aluminum with 2 mm fin spacing at 15 m/s jet velocity gives the optimum result for electronic cooling systems. REFERENCES [1] Clemens, J. M. Lasance and Robert E. Simons, Advances In High-Performance Cooling For Electronics, Philips Research Laboratories IBM Corporation, 2005 [2] Thyrum, G., Critical Aspects of Modeling Heat Pipe Assisted Heat Sinks, 2002 [3] Duan, Z. and Muzychka, Y.S., “Experimental investigation of heat transfer in impingement air cooled plate fin heat sinks,” ASME J. of Electronic Packaging, v 128, pp. 412-418, 2006 [4] Zhipeng Duan; Muzychka, Yu.S., Impingement air cooled plate fin heat sinks. Part I - Pressure drop model, Thermal and Thermomechanical Phenomena in Electronic Systems, 2004. ITHERM '04. The Ninth Intersociety Conference on , vol., no., pp.429,435 Vol.1, 1-4 June 2004 doi: 10.1109/ITHERM.2004.1319206 [5] Zhipeng Duan; Mzychka, Y.S., Impingement air cooled plate fin heat sinks. Part II Thermal resistance model, Thermal and Thermomechanical Phenomena in Electronic Systems, 2004. ITHERM '04. The Ninth Intersociety Conference on, vol., no., pp.436, 443 Vol.1, 1-4 June 2004 doi: 10.1109/ITHERM.2004.1319207 [6] Weilin Qu, Issam Mudawar “Experimental and numerical study of pressure drop and heat transfer in a single-phase micro-channel heat sink”international journal of heat and mass transfer (45)2002 2549-2565 [7] Biber, C.R., “Pressure drop and heat transfer in an isothermal channel with impinging flow,” IEEE Transactions, Components, Packaging, and Manufacturing Technology, Part A, v. 20, pp. 458 – 462, 1997 [8] Wu, M.C., Lee, C.Y., Peng, C.H., Fang, C.J., and Hung, Y.H., “Cooling performance of plain-plate-fin heat sinks with slot jet impingement,” ASME Int. Mechanical Engineering Congress and Exposition, IMECE2006, Chicago, IL, United States, Nov 5-10, 2006. [9] Li, H.-Y. and Chen, K.-Y., “Thermal performance of plate-fin heat sinks under confined impinging jet conditions,” Int. J. of Heat and Mass Transfer, v. 50, pp. 1963-1970, 2007 [10] Li, X. C., Conjugate heat transfer of jet impingement on short fins with different shapes, Thermal and Thermo mechanical Phenomena in Electronic Systems, 2008. ITHERM 2008. 11th Intersociety Conference on, vol., no., pp.49,56, 28-31 May 2008 doi: 10.1109/ITHERM.2008.4544253 [11] Bhopte, S., Alshuqairi, M. S. Agonafer, D., and Refai- Ahmed, G. “Mixed convection of impinging air cooling over heat sink in telecom system application,” ASME J. of Electronic Packaging, v. 126, pp. 519-523, 2004 [12] Md. Farhad Ismail “Numerical simulation of turbulent heat transfer from perforated plate-fin heat sinks” Heat Mass Transfer (2014) 50:509–519 [13] Chougule N K “CFD Analysis of Multi-jet Air Impingement on Flat Plate” Proceedings of the World Congress on Engineering 2011 Vol III WCE 2011, July 6 - 8, 2011, London, U.K [14] Rajesh kumar Panda “conjugate heat transfer from a flat plate with shower head impinging jets” Frontiers in Heat and Mass Transfer (FHMT), 2, 013008 (2011) DOI: 10.5098/hmt.v2.1.3008 [15] Arularasan R. “CFD analysis in a heat sink for cooling of electronic devices” International Journal of The Computer, the Internet and Management Vol. 16.No.3 (September- December, 2008) pp 1-11 [16] M. Beriache “Numerical study on hydraulic and thermal characteristics of a minichannel heat sinks with impinging air flow” ISSN 1392 - 1207. MECHANIKA. 2011. 17(2): 156-161 [17] FLUENT 6.3.26 Users Guide, Fluent, Inc, 2006