11 Desing and Analysis of Heat Sink

Design of heat sink Chapter 4

CHAPTER 4

NUMERICAL ANALYSIS OF HEAT SINK

4.1 MODELING OF FIN

The design of Heat sink includes the following steps

Profile of fin

Fin length

Fin Thickness

Number of fin

Space between the fin

4.1.1 SELECTION FIN OF PROFILE

There are various types of fin profiles are available, in that fin Rectangular ,

Radial fin, Pin fin, Taper fin are important fin. For this analysis Rectangular fin and

Taper fin are been selected for design. These fin are simple to manufacture and

used for most of the automobile, electric and electronic components. In performance

also these fin have high efficiency and effectiveness compared to other fins.

1) RECTANGULAR FN 2) TAPER FIN

Fig.4.1 Profile of Rectangular and Taper Fin

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4.1.3 MODEL DESCRIPTION

MODELING SOFTWARE:

The fin with various extensions are design with the help of design

software Solidworks 2013 by using the Solidworks 2D and 3D commands like as 2D

commands polyline, arc, circle, mirror , pattern ,& 3D commands extrude, extrude cut. The

angle is measured in anti-clock direction starting from the first quadrant. There are 18

different heat sink models are been created using Solidworks.

SPECIFICATION OF THE EXTENTION:

a) Rectangular extension b) Trapezium extension

c) Triangular extension d) circular extension

Fig.4.2 Types of Extensions

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4.2 RECTANGULAR FIN PROFILES

In this study three types of Rectangular fin are to be model using solidworks.

They are listed below:

1) Plain Rectangular Fin

2) Fin with Extension

a) Triangular Extension

b) Trapezium Extension

c) Circular Extension

d) Rectangular Extension

3) Perforated fin

a) With dia 18

b) With dia 20

c) With dia 22

d) With dia 24

4.2.1 PLAIN RECTANGULAR FIN WITH DIMENSIONS

Plain rectangular fin

Fig.4.3 Dimension of Plain Rectangular Fin

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4.2.2 RECTANGULAR FIN WITH EXTENSION AND DIMENSIONS

a) Rectangular Extension

Fig.4.4 Dimension of Fin with Rectangular Extension

b) Triangular Extension

Fig.4.5 Dimension of Fin with Triangular Extension

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c) Trapezium Extension

Fig.4.6 Dimension of Fin with Trapezium Extension

d) Circular Extension

Fig.4.7 Dimension of Fin with Circular Extension

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4.2.3 RECTANGULAR FIN WITH PERFORATED

In the perforated fin the most of the profiles are in same dimension and only

the perforated hole diameter changes to 18mm, 20mm, 22mm, 24mm.

1

)

FIN TYPE: RECTANGULAR

NO. OF FIN: 3

HOLE DIA : 18 MM

NO. OF HOLE: 15

2

)


NO. OF FIN: 3

HOLE DIA : 20 MM

NO. OF HOLE: 15

3

)


NO. OF FIN: 3

HOLE DIA : 22 MM

NO. OF HOLE: 15

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4

)


NO. OF FIN: 3

HOLE DIA : 24MM

NO. OF HOLE: 15

ISOMETRIC VIEW OF RECTANGULAR FIN WITH EXTENTION

1

)


NO. OF FIN: 3

EXTENTION: TRIANGULAR

NO. OF EXTENTION: 30

2

)


NO. OF FIN: 3

EXTENTION: CIRCULAR


3

)


NO. OF FIN: 3

EXTENTION:

RECTANGULAR


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4

)


NO. OF FIN: 3

EXTENTION: TRAPEZIUM


4.3 TAPER FIN PROFILES

In this study three types of Taper fin are to be model using solidworks.

They are listed below:

1) Plain Taper Fin

2) Fin with Extension

a) Triangular Extension

b) Trapezium Extension

c) Circular Extension

d) Rectangular Extension

3) Perforated fin

a) With dia 18

b) With dia 20

c) With dia 22

d) With dia 24

4.3.1 PLAIN TAPER FIN WITH DIMENTIONS

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Plain Taper fin

Fig.4.8 Dimension of Taper Fin

4.3.2 TARER FIN WITH EXTENTION AND DIMENSIONS

a) Rectangular Extension

Fig.4.9 Dimension of Taper Fin with Rectangular Extension

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b) Triangular Extension

Fig.4.10 Dimension of Taper Fin with Triangular Extension

c) Trapezium Extension

Fig.4.11 Dimension of Taper Fin with Trapezium Extension

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d) Circular Extension

Fig.4.12 Dimension of Taper Fin with Circular Extension

1)FIN TYPE: TAPER

NO. OF FIN: 3

EXTENTION: TRIANGULAR


2) FIN TYPE: TAPER

NO. OF FIN: 3

EXTENTION: CIRULAR


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3) FIN TYPE: TAPER

NO. OF FIN: 3

EXTENTION:

RECTANGULAR


4) FIN TYPE: TAPER

NO. OF FIN: 3

EXTENTION:TRAPEZIUM


ISOMETRIC VIEW OF RECTANGULAR FIN WITH EXTENSION

4.3.3 TAPER FIN WITH PERFORATED

In the perforated fin the most of the profiles are in same dimension and only the perforated

hole diameter changes to 18mm, 20mm, 22mm, 24mm.

1)FIN TYPE: TAPER

NO. OF FIN: 3

HOLE DIA : 18 MM

NO. OF HOLE: 15

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2) FIN TYPE: TAPER

NO. OF FIN: 3

HOLE DIA : 20 MM

NO. OF HOLE: 15

3) FIN TYPE: TAPER

NO. OF FIN: 3

HOLE DIA : 22 MM

NO. OF HOLE: 15

4) FIN TYPE: TAPER

NO. OF FIN: 3

HOLE DIA : 24MM

NO. OF HOLE: 15

4.4 ANALYSIS OF HEAT SINK USING FEA

4.4.1 IMPORT THE GEOMETRY

After the creation of design the next process is to analysis the fin for heat

transfer by using software Ansys Workbench. The important factor is while saving the

model in solidworks it should be in “.igs” file format. So it can access through the FEA

software.

Now, select the type of analysis as thermal analysis for steady-state heat transfer

process. Assign unit system as customization length in mm, temperature in °C .

4.4.2 GENERATING THE MESH

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Now from the 3D mesh setting set mesh size towards fine the high in smooth

and fast in transition. Select the model and generate the mesh for the design

Fig.4.13 PLAIN RECTANGULAR FIN MESH

Fig.4.13 shows that a sample meshing of the model. The meshing result shows

that the solid mesh surface part having 14880 elements created, final mesh size is 3.7636

mm and surface mesh contains 72397 nodes. The mesh type is mix of brick, wedges,

pyramids and tetrahedra.

4.4.3 ASSIGNING MATERIAL TO THE MODEL

Aluminium (AL 6061 T6) has selected for the model due light weight and high heat

transfer rate and heat dissipation in this material. The manufacturing process also simple in

the aluminium and cost wise it is an economic.

S.NO. PROPERTIES VALUES

1) Density 2770 kg m^-3

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2) Coefficient of Thermal Expansion 2.3e-005 C^-1

3) Specific Heat 875 J kg^-1 C^-1

4) Thermal Conductivity 167 W/ m^-1 C^-1

5) Compressive Yield Strength Pa 2.8e+008

6) Tensile Yield Strength Pa 2.8e+008

7) Young's Modulus Pa 7.1e+010

8) Bulk Modulus Pa 6.9608e+010

PROPERTIES OF AL6061 T6

4.4.4 ASSIGNING LOAD AND CONSTRAINTS TO THE MESHED MODEL

In this assign the material having thermal conductivity, convection coefficient of heat

transfer for fluid, temperature of surface and ambient temperature as:

1) Thermal conductivity, k = 167 W/m °C = 0.167 J/(s mm °C)

2) Convection coefficient of heat transfer, h = 83 W/m2 °C = 0.00083 J/(s mm2°C)

3) Temperature of wall surface at which fin attached, to = 55 °C

4) Ambient temperature, ta = 30 °C

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Fig.4.14 Load Assign for Plain Rectangular Fin

A – Surface contact with atmosphere

B – Wall Temperature

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11 Desing and Analysis of Heat Sink