comsol heat sink
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heat sink problem analysis using comsolTRANSCRIPT
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Heat sink analysis using COMSOL Solver. (A tutorial guide)
Kaleeswaran.B
M.Tech (CFD); Dept. of Aerospace.
University of Petroleum Energy Studies
Dehradun, India
Abstract—In this paper COMSOL multiphysics analysis of
heat sink in an aluminum material is shown. Various steps
involved in it are explained and diagrammatic version of it is also
explained.
Keywords: COMSOL, Multiphysics,
I. INTRODUCTION.
In COMSOL multiphysics analysis involves three steps;
1. Sequencing – the methods done are saved in a step
wise tree method. Thus, during every part of the
training the step can be viewed and can be changed if
on wishes.
2. Selection of materials: in this the material one wishes
to add, could be added and its properties could be
studied.
3. Use of selections: to define the boundaries, initial
conditions and other steps of the modeling process.
The modeled system consists of an aluminum heat sink for
cooling of components in electronic circuits mounted inside a
channel of rectangular cross section. Such a set-up is used in
order to measure the cooling capacity of heat sinks. Air enters
the channel at the inlet and exits the channel at the outlet. The
base surface of the heat sink is kept at a constant temperature
through an external heat source. All other external faces are
thermally insulated.
Figure1: Model of the heat sink with the boundaries.
II.ABOUT THE MODEL.
The cooling ability of the heat sink is determined by the
power required to keep the base of the surface at a constant
temperature. The model solves the concept of thermal
balance.Actually,the thermal energy is transported through the
conduction, convection in the heat aluminum sinks. The
temperature field is made continuous throughout the model.
The temperature is set at the inlet of the channel and at the
base of the heat sink. The layer can also be sliced to view the
model in layers.. In such case, you have to define a heat
transfer coefficient for the adhesive layer and then set the
temperature at the heater side of the layer. The transport of
thermal energy at the outlet is dominated by convection.
The flow conditions are solved by taking momentum and
mass conservation equations. The flow field is obtained by
solving one momentum balance for each space coordinate (x,
y, and z) and a mass balance. The inlet velocity is defined by a
parabolic velocity profile for fully developed laminar flow. At
the outlet, a constant pressure is combined the assumption that
there are no viscous stresses in the direction perpendicular to
the outlet. At all solid surfaces, the velocity is set to zero in all
three spatial directions. The thermal conductivity of
aluminum, the thermal conductivity of air, the heat capacity of
air, and the air density are all temperature-dependent material
properties.
III.PROCESS/METHODS
i. First step involves click on MODEL WIZARD. In
model wizard click add physics tree> click on the Heat
transfer>conjugate heat transfer>laminar flow (nitf).In the
studies click preset studies>stationery>OK (finish).
ii. Second step click on the GLOBAL DEFINITIONS.
The global definitions are located in the model builder
window. GLOBAL DEFINITIONS > click on the
SETTINGS in the parameter window and enter the
following settings;
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S.no Name Expression Description
1 L channel 7 Channel length
2 W channel 3 Channel width
3 UO 5 Inlet velocity
4 H channel 1.5 Channel height
Table: 1.Global settings parameters
iii. Third step involves defining the GEOMETRY.
Right click on the model I> GEOMETRY I and IMPORT.
Go to settings window> browse and click import HEAT
SINK model and click on the build selected button.(actually
strictly speaking U can use this import facility only when U
install the COMSOL setup. The import model is already a
finished CAD model stored in the COMsol setup).
Figure: 2.Model selected with domain as air.
IV. Now, right click on the Geometry I and then click
WORKPLANE I. Now, under the work plane I > click on
the geometry and then click RECTANGLE. Now, go to
settings window for rectangle.
Width of the rectangle = L channel.
Height of the rectangle = W channel.
Position section of the rectangle along X axis = 4.5e-02.
Position section of the rectangle in Y axis = W channel/2.
Figure:3.Model selected with inner domain aluminum
V. In the Model Builder window, right-click Work
Plane and choose Extrude. Right-click Extrude and choose
Go to Default 3D View. Go to the Settings window for
Extrude. Locate the Distances from Work Plane section. In
the table, enter the following settings:
Enter the Distance as H channel
Click the Build Selected button.
VI. MATERIALS:
In the Model Builder window, right-click Model
1>Materials and choose Open Material Browser. Go to the
Material Browser window, locate the Materials section. In
the Materials tree, select Built-In>Air. Right-click and
choose Add Material to Model from the menu. Air By
default, the first material you add applies to all domains.
Typically, you can leave this setting and add other materials
that override the default material where applicable. In this
example, specify aluminum for Domain 2.Use Aluminum
AH 3003-H18.
VII.CONJUGATE HEAT TRANSFER:
In the Model Builder window, right-click Model
1>Conjugate Heat Transfer and choose Fluid. Select
Domain 1 only.
Figure :4.Conjugate heat model.
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1. In the Model Builder window, right-click Conjugate Heat
Transfer and choose Laminar Flow>Inlet.
2. Select Boundary 115 only. Go to the Settings window for
Inlet. Locate the Boundary Condition section. From the
Boundary condition list, select laminar inflow.
Figure: 5.Inlet condition chosen model
3. In the U (average velocity) field edit field, type U0. In the
Model Builder window, right-click Conjugate Heat Transfer
and choose Laminar Flow>Outlet.
4. Select Boundary 1 only. In the Model Builder window,
right-click Conjugate Heat Transfer and choose Heat
Transfer>Temperature.
5. Select Boundary 115 only. In the Model Builder window,
right-click Conjugate Heat Transfer and choose Heat
Transfer>Temperature.
6. In the Model Builder window, right-click Conjugate Heat
Transfer and choose Heat Transfer>Temperature.
7. Select Boundary 8 only. Go to the Settings window for
Temperature. Locate the Temperature section. In the T0 edit
field, type 393.15 K.
8. In the Model Builder window, right-click Conjugate Heat
Transfer and choose Heat Transfer>Outflow. Select
Boundary 1 only.
VII.MESH:
1. In the Model Builder window, right-click Model 1>Mesh
and choose Free Tetrahedral. In the Model Builder window,
right-click Study and choose Compute.
2. Create a selection to use for defining a data set in the
Results branch. In the Model Builder window, right-click
Mesh 1>Free Tetrahedral 1 and choose Size.
Figure :6.Fine tetrahedral mesh
3. Go to the Settings window for Size. Locate the Geometric
Scope section. From the Geometric entity level list, select
Domain.
4. Select Domains 1 only. 5 Locate the Element Size
section. From the Predefined list, select Finer. 6 Click the
Build All button.
IX. Study Definitions:
1. In the Model Builder window, right-click Model
1>Definitions and choose Selection.
2. Go to the Settings window for Selection. Locate the
Geometric Scope section. From the Geometric entity level
list, select Boundary.
3. Right-click Selection 1 and choose Select Box.Select
Boundaries 3 and 5–114 only.
X.RESULTS:
1. Data Sets, in the Model Builder window, right-click
Results>Data Sets>Solution and choose Add Selection.
2. Go to the Settings window for Selection. Locate the
Geometric Scope section. From the Geometric entity level
list, select Boundary.
3. From the Selection list, select walls. 3D Plot Group .In
the Model Builder window, click Surface .Go to the Settings
window for Surface. Locate the Coloring and Style section.
From the Color table list, select Thermal.
4. In the Model Builder window, right-click 3D Plot Group
1 and choose Arrow Volume. Go to the Settings window for
Arrow Volume. In the upper-right corner of the Expression
section, click Replace Expression.
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5. From the menu, choose Conjugate Heat Transfer
(Laminar Flow)>Velocity field (u, v, w). Locate the Arrow
Positioning section. Find the x grid points subsection. In the
Points edit field, type 40.
6. Find the y grid points subsection. In the Points edit field,
type 20.
Figure: 7.Heated vector-temp plots over the heat sink
7. In the Coordinates edit field, type 5e-3. Right-click Arrow
Volume 1 and choose Color Expression. Go to the Settings
window for Color Expression. In the upper-right corner of the
Expression section, click Replace Expression. From the menu,
choose Conjugate Heat Transfer (Laminar Flow)>Velocity
magnitude. Click the Plot button.
This will produce th required vector plots and the much
required contour plots of the heat sink model.
Figure 9.Sliced model of the temperature plot.
Figure 10.Zoomed view of the sliced model.
Figure: 8.Zoomed view of the temperature vector plots Figure 11.Top view of the heat sink model.
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XI.CONCLUSION:
Figure 7 shows the temperature vector plot of velocity over
the model. A region of high temperature can be seen near to
the model. After crossing the model the temperature of the
high velocity air reduces. A zoomed view of the vector plot is
also shown, in that a region of circulation occurs near to the
model. This causes the pressure to reduce and thus reducing
the temperature increment also.
Figure 9, 10 Sliced view models shows that the temperature
plots near and far from the models. It shows that there occurs a
region of high temperature before the model and near to the
model. After the model the heating effect of the air reduces
much.Thus,the model really acts as a heat sink