20120140507005

1. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 7, July (2014), pp. 47-56 © IAEME
47
ANALYSIS OF ELECTRONIC CHIPS MICROCHANNEL BY USING ANSYS
SOFTWARE
Ali Salah Ameen*, Dr. Ajeet Kumar Rai**
*Directorate of Telecommunications & post kirkuk, Iraqi Telecommunication& post company
Ministry of Communications, Republic of Iraq
**Department of Mechanical Engineering SSET, SHIATS- DU Allahabad (U.P) India
ABSTRACT
In this present work a three-dimensional fluid flow and heat transfer in a rectangular micro-
channel heat sink are analyzed numerically with the help of commercial CFD - ANSYS-FLUENT
14.0. The micro-heat sink model consists of a 10 mm long substrate material with rectangular micro
channels, 57µm wide and 180µm height, fabricated along the entire length. Two different materials
(silicon, copper) for rectangular micro channels are taken for our study. Water at 293K is taken as
working fluid. A comparison of heat transfer characteristics of liquid coolant is made in forced
convection cooling at a heat flux of 90W/cm2
in micro-heat sink with different pressure drops
(30kpa, 50kpa).
Keywords: Electronic Chips Cooling, Ansys, Micro Channel Heat Sink.
INTRODUCTION
Advance in micromachining technology in recent years has enabled the design and
development of miniaturized systems, which opens a promising field of applications, particularly in
the medical science and electronic-/bioengineering. Micro-channel cooling technology was first put
forward by Tuckerman, D.B. and Pease(1983) introduced a kind of water-cooled heat sink made of
silicon, used in very-large-scale integrated circuits (VLSI). The micro-channels were fabricated with
a 50 µm width and a 300 µm height so that heat fluxes as high as 790 W/cm2 could be removed with
the maximum temperature difference between substrate and inlet water of 71 K and the pressure drop
across the micro-channels of 31 Pa. The thermal performance is much better than presented by
conventional thermal dissipation technologies. After that, many researchers focused on such new
kind of chip cooling technology. Roy W. Knight (1992) The equations governing the fluid dynamics
and combined conduction/convection heat transfer in a heat sink are presented in dimensionless form
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2. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
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48
for both laminar and turbulent flow. A scheme presented for solving these equations enables the
determination of heat sink dimensions that display the lowest thermal resistance between the hottest
portion of the heat sink and the incoming fluid.Judy. (2002) did pressure drop experiments on both
round and square microchannels with hydraulic diameters ranging from 15 to 150 µm. They tested
distilled water, methanol and iso-propanol over a Reynolds number range of 8 to2300. Their results
showed no distinguishable deviation from laminar flow theory for each case. Weilin Qu, Issam
Mudawar (2004) study, the three-dimensional fluid flow and heat transfer in a rectangular micro-
channel heat sink are analyzed numerically using water as the cooling fluid. The heat sink consists of
a 1-cm2 silicon wafer. The micro-channels have a width of 57 lm and a depth of 180 lm, and are
separated by a 43 lm wall. A numerical code based on the finite difference method and the SIMPLE
algorithm is developed to solve the governing equations. Harshal R. Upadhye , Satish G. Kandlikar
(2004) Direct cooling of an electronic chip of 25mm × 25mm in size is analyzed as a function of
channel geometry for single-phase flow of water through small hydraulic diameters. Fully developed
laminar flow is considered with both constant wall temperature and constant channel wall heat flux
boundary conditions. The effect of channel dimensions on the pressure drop, the outlet temperature
of the cooling fluid and the heat transfer rate are presented. J. Li , G.P. Peterson , P. Cheng (2004)
numerically simulated a forced convection heat transfer occurring in silicon based micro channel
heat sinks has been conducted using a simplified three-dimensional conjugate heat transfer model
(2D fluid flow and 3D heat transfer) consists of a 10 mm long silicon substrate, with rectangular
micro channel, 57 µm wide and 180 µm deep, fabricated along entire length with hydraulic diameter
86 µm. The influence of the geometric parameters of the channel and thermo physical properties of
the fluid on the flow and the heat transfer, are investigated using temperature dependent thermo
physical property method..Poh-Seng Lee, Suresh V. Garimella (2006) Three-dimensional numerical
simulations were performed for laminar thermally developing flow in micro channels of different
aspect ratios. Based on the temperature and heat flux distributions obtained, both the local and
average Nusselt numbers are presented graphically as a function of the dimensionless axial distance
and channel aspect ratio. J. Li, G.P. Peterson(2007) (3D) conjugate heat transfer model has been
developed to simulate the heat transfer performance of siliconbased, parallel micro channel heat
sinks. A semi-normalized 3-dimensional heat transfer model has been developed, validated and used
to optimize the geometric structure of these types of microheat sinks by the model were a pitch of
100 lm, a channel width of 60 lm and a channel depth of about 700 lm. Afzal Husain and Kwang-
Yong Kim A numerical(2013) investigation of 3-D fluid flow and heat transfer in a rectangular
micro-channel has been carried out using water as a cooling fluid in a silicon substrate. Navier–
Stokes and energy equations for laminar flow and conjugate heat transfer are solved using a finite
volume solver. Nivesh Agrawal1 (2013) he is study the comparison of heat transfer characteristics
of liquid coolants in forced convection cooling in a micro-heat sink with different pressure drops
such as (35, 50 and 65kPa).The heat transfer characteristics of water and Propylene Glyco.l
Numerical results of a fluid flow micro-heat sink are obtained using commercial CFD software
ANSYS-CFX.
MATHEMATICAL FORMULATION
The micro- channels heat sink model modeling in ANSYS FLUENT 14.0 its consists of a 10
mm long and dimension of rectangular single micro-channel have a width of 57 µm and a depth of
180 µm as shown in Fig(1). The heat sink substrate is (silicon, copper) and water is used as the
cooling fluid. The electronic component is idealized as a constant heat flux boundary condition at the
heat sink bottom wall. Heat transport in the unit cell is a conjugate problem which combines heat
conduction in the solid and convective heat transfer to the coolant (water). Here we consider a

3. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 7, July (2014), pp. 47-56 © IAEME
49
rectangular channel of dimension (900µx100µmx10mm) applied constant heat flux of 90 W/cm2
from bottom.
Fig(1):Modeling Structure of a rectangle micro-channels heat sink and Computational domain of
single micro-channel heat sink and the unit with a constant heat flux in ANSYS FLUENT 14.0
Governing Equations
The governing equations are continuity, momentum and energy equations, which are derived from
fundamental principles of heat and fluid flow. The equations are posed to implement SIMPLE
(Semi-Implicit Method for Pressure Linked equation) algorithm.
length required to fully developed laminar flow entrance length = 0.057Re× Dh (1)
= (0.057× 106.8× 86.58) µm= 527.064 µm it is less than 10 mm So fully developed laminar flow is
valid.

4. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 7, July (2014), pp. 47-56 © IAEME
50
Continuity Equation
(2)
Momentum Equation (Navier-stokes Equation)
X-momentum equation
(3)
Y-momentum equation
(4)
Z-momentum equation
(5)
Energy Equation
(6)
The hydrodynamic boundary condition can be stated as at the inner bottom wall surface of
channel (no-slip condition)
(7)
(7.1)
(7.2)

5. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 7, July (2014), pp. 47-56 © IAEME
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(7.3)
(8)
(9)
Table (1): Thermophysical Properties of fluid
Fluid
liquid
ƿ f
kg/m3
cp
j/ kg-k
µ f
kg/m-s
Kf
W/m-K
T
k
P
kpa
water 998.2 4182 0.001003 0.6 293 30-50
Table (2): Geometric dimensions of the single microchannel
H
(µm)
h
(µm)
W
(µm)
w
(µm)
St
(µm)
Sb
(µm)
t
(µm)
L
(mm)
900 180 100 57 450 270 21.5 10
Table (3): Thermo physical Properties of solid
Table (4): Relaxation factors- Solution controls
Pressure 0.3
Density 1
Momentum 0.7
Body force 1
RESULT AND DISCUSSION
This present numerical simulation and mishing has been done using ANSYS FLUENT-CFD
14.0 after putting Table (1,2,3,4) the boundary conditions and flow conditions in micro-channel
Fig(2), iteration will be start. The model of the micro-channel heat sink has been converged in 100
iteration. Fig(3).
Solid ƿ s
Kg/m3
c p
J/Kg-K
k s
W/m-K
Silicon 2330 712 148
copper 8978 381 387.6

6. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 7, July (2014), pp. 47-56 © IAEME
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Fig (2): The boundary names and meshing Optimum grid system for single micro channel heat sink
in ANSYS FLUENT 14.0
Fig (3): Convergence graph
Simulation of Single Micro channel
The fluid is entered through the micro channel made of (silicon, copper) at pressure 50
kPa,30kpa with constant inlet temperature 293k. After passing through the channel, the fluid
discharged to the atmosphere. A constant heat flux q"=90 W/cm2
is applied at the bottom wall of heat
sink. Fig(4).

7. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 7, July (2014), pp. 47-56 © IAEME
53
Fig (4): Pressure contours of channel for ∆ p = 50 kPa, 30kpa and q"=90 W/cm2
The temperature of fluid at the inlet is initially uniform (293k). The temperature Profiles
shown is due to the assumption of hydrodynamic fully developed Flow. The temperature rise along
the flow direction in the solid and fluid regions of the micro channel heat sink. Fig(5,6,7,8)
Fig (5):Temperature contours inside channel of heat sink (silicon, copper) for inlet and outlet for
∆ p = 30 kPa q"=90 W/cm2

8. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 7, July (2014), pp. 47-56 © IAEME
54
Fig (6): Temperature contours inside channel of heat sink (silicon, copper) for inlet and outlet for
∆ p = 50 kPa q"=90 W/cm2
Fig (7): Temperature contours inner wall channel of heat sink (silicon, copper) for inlet and outlet
for ∆ p = 30 kPa q"=90 W/cm2
Fig(8): Temperature contours along channel of heat sink (silicon, copper) for inlet and outlet for
∆ p = 50 kPa q"=90 W/cm2

9. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 7, July (2014), pp. 47-56 © IAEME
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Fig(9): Velocity vectors at outlet of channel for ∆ p = 30 kPa, 50kPa, q"=90 W/cm2
Fig(10): Comparison of temperature difference (silicon, copper) based of micro channel heat sink for
different pressure drop q"= 90 W/cm2
Fig (11): Average heat transfer coefficient and Average Nusselt number distributions inside the
channel for different pressure drop at q"=90 W/cm2
290
295
300
305
310
315
320
325
0 2 4 6 8 10 12
50 kpa - cu
50 kpa - si
30 kpa- cu
30 kpa- si
Z - (mm)
T
(k)
0
10000
20000
30000
40000
50000
60000
70000
80000
90000
100000
0 2 4 6
30 kpa- si
30 kpa- cu
50 kpa- cu
50 kpa- si
Z- (mm)
Havg
(w/m2.k)
0
2
4
6
8
10
12
14
16
18
0 2 4 6
30 kpa- cu
50 kpa- cu
50 kpa- si
30 kpa- si
Z- (mm)
Nuavge

10. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 7, July (2014), pp. 47-56 © IAEME
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CONCLUSION
In the present study it has been observed that the temperature of cooling fluid at the outlet of
micro channel is maximum when the pressure drop is 30 kPa. It is further observed that the water
temperature is maximum at the outlet when substrate Silicon is used. The outlet temperature of water
when substrate copper is used is observed to be 316 K and 305 K for respective pressure drop of 30
kPa and 50 kPa. Whereas it is 321 K and 310 K for respective pressure drop of 30 kPa and 50 kPa.
REFERENCES
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[5] Harshal R. Upadhye , Satish G. Kandlikar (2004), Optimization of Microchannel
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