1. Heat sink analysis: analytically and via ANSYS
ME 340 Final Project - Dr. Soloviev - Fall 2010 by
Mathew Marshal & Kevin Hoopes

2. Problem definition
Intel core i7 processors can dissipate up to 130W under full load
They must be kept below 373 K to prevent hardware damage
We are given a certain rectangular fin, integral heat sink
Find the required convection coefficient to keep the base below 373 K.

3. Boundary Conditions Base exposed to constant heat input of 130W
Sides of base are adiabatic
Sides and tops of fins are exposed to convective heat transfer to surrounding atmosphere at 298 K
Heat sink is solid Aluminum

4. ANSYS Solution
Define Geometry
Apply boundary conditions
Mesh
Solve

5. ANSYS Solution Results obtained for initial guess for h
Iterated until base temperature reached approximately 373 K
h value found to be 37.6 W*K/m^2

6. Analytical Solution
h = 39.8 W*K/m^2

7. Summary
ANSYS Solution – 37.5
Analytical Solution – 39.8

8. Appendix
Analytical Solution
ANSYS Log file

10. *SET,_REMOTE_VIS_ID,'39'
/SOL
FITEM,2,-6
WPSTYLE,,,,,,,,0
FITEM,2,82
/PREP7
FITEM,2,-83
!DEFINE THE BLOCK
!DEFINE ELEMENT TYPE
BLC4,0,0,0.042,0.001,0.045
ET,1,SOLID70
FLST,2,1,5,ORDE,1
!MAKE A FIN
ET,2,SOLID70
FITEM,2,3
BLC4,0,0.001,0.0021,0.055,0.045
MPTEMP,,,,,,,,
!COPY THE FINS
MPTEMP,1,0
!DEFINE HEAT FLUX ON BOTTOM OF HEAT SINK
FLST,3,1,6,ORDE,1
!DEFINE CONDUCTION COEFICIENT
SFA,P51X,1,HFLUX,68783
FITEM,3,2
MPDATA,KXX,1,,250
VGEN,2,P51X, , , , , , ,0
FLST,2,59,5,ORDE,23
FITEM,2,10
FITEM,3,3
FITEM,2,12
/POST1
FITEM,2,-14
FITEM,2,16
FITEM,3,4
FITEM,2,-20
SMRT,6
FITEM,2,22
SMRT,2
FITEM,2,-26
SMRT,1
FITEM,3,5
FITEM,2,28
MSHAPE,1,3D
FITEM,2,-32
MSHKEY,0
FITEM,2,34
CM,_Y,VOLU
FITEM,3,6
FITEM,2,-38
VSEL, , , ,
FITEM,2,40
CM,_Y1,VOLU
FITEM,2,-44
CHKMSH,'VOLU'
FITEM,3,7
FITEM,2,46
CMSEL,S,_Y
FITEM,2,-50
VMESH,_Y1
FITEM,2,52
CMDELE,_Y
FITEM,3,8
FITEM,2,-56
CMDELE,_Y1
FITEM,2,58
CMDELE,_Y2
FITEM,2,-60
FITEM,3,9
FITEM,2,64
FITEM,2,-65
SOLVE
FITEM,2,67
FITEM,3,10
FITEM,2,-81
/GO
FLST,2,11,6,ORDE,2
!DEFINE CONVECTION COEFICIENT, THIS IS ITERATED TO OBTAIN THIS SOLUTION
FITEM,2,1
FITEM,2,-11
SFA,P51X,1,CONV,37.60,298
VADD,P51X
FLST,2,4,5,ORDE,4
FINISH
FITEM,2,5