Transcript Heat sink analysis: analytically and via ANSYS by

Heat sink analysis:
analytically and via ANSYS
ME 340 Final Project - Dr. Soloviev - Fall 2010
by
Mathew Marshal & Kevin Hoopes
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.
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
ANSYS Solution
•Define Geometry
•Apply boundary conditions
•Mesh
•Solve
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
Analytical Solution
•h = 39.8 W*K/m^2
300
250
q(w)
200
q with fins
150
q with no fins
Linear (q with fins)
100
Linear (q with no fins)
50
0
0
20
40
60
80
h(w/m^2*K)
100
120
300
250
Summary
q(w)
•ANSYS Solution – 37.5
•Analytical Solution – 39.8
200
q with fins
150
q with no fins
Linear (q with fins)
100
Linear (q with no fins)
50
0
0
20
40
60
80
h(w/m^2*K)
100
120
Appendix
Analytical Solution
ANSYS Log file
*SET,_REMOTE_VIS_ID,'39'
WPSTYLE,,,,,,,,0
/PREP7
!DEFINE THE BLOCK
BLC4,0,0,0.042,0.001,0.045
!MAKE A FIN
BLC4,0,0.001,0.0021,0.055,0.045
!COPY THE FINS
FLST,3,1,6,ORDE,1
FITEM,3,2
VGEN,2,P51X, , ,0.004433333, , , ,0
FLST,3,1,6,ORDE,1
FITEM,3,3
VGEN,2,P51X, , ,0.004433333, , , ,0
FLST,3,1,6,ORDE,1
FITEM,3,4
VGEN,2,P51X, , ,0.004433333, , , ,0
FLST,3,1,6,ORDE,1
FITEM,3,5
VGEN,2,P51X, , ,0.004433333, , , ,0
FLST,3,1,6,ORDE,1
FITEM,3,6
VGEN,2,P51X, , ,0.004433333, , , ,0
FLST,3,1,6,ORDE,1
FITEM,3,7
VGEN,2,P51X, , ,0.004433333, , , ,0
FLST,3,1,6,ORDE,1
FITEM,3,8
VGEN,2,P51X, , ,0.004433333, , , ,0
FLST,3,1,6,ORDE,1
FITEM,3,9
VGEN,2,P51X, , ,0.004433333, , , ,0
FLST,3,1,6,ORDE,1
FITEM,3,10
VGEN,2,P51X, , ,0.004433333, , , ,0
FLST,2,11,6,ORDE,2
FITEM,2,1
FITEM,2,-11
VADD,P51X
FINISH
/SOL
FINISH
/PREP7
!DEFINE ELEMENT TYPE
ET,1,SOLID70
ET,2,SOLID70
MPTEMP,,,,,,,,
MPTEMP,1,0
!DEFINE CONDUCTION COEFICIENT
MPDATA,KXX,1,,250
FLST,2,59,5,ORDE,23
FITEM,2,10
FITEM,2,12
FITEM,2,-14
FITEM,2,16
FITEM,2,-20
FITEM,2,22
FITEM,2,-26
FITEM,2,28
FITEM,2,-32
FITEM,2,34
FITEM,2,-38
FITEM,2,40
FITEM,2,-44
FITEM,2,46
FITEM,2,-50
FITEM,2,52
FITEM,2,-56
FITEM,2,58
FITEM,2,-60
FITEM,2,64
FITEM,2,-65
FITEM,2,67
FITEM,2,-81
/GO
!DEFINE CONVECTION COEFICIENT, THIS IS
ITERATED TO OBTAIN THIS SOLUTION
SFA,P51X,1,CONV,37.60,298
FLST,2,4,5,ORDE,4
FITEM,2,5
FITEM,2,-6
FITEM,2,82
FITEM,2,-83
/GO
FLST,2,1,5,ORDE,1
FITEM,2,3
/GO
!DEFINE HEAT FLUX ON BOTTOM OF HEAT SINK
SFA,P51X,1,HFLUX,68783
FINISH
/SOL
FINISH
/POST1
FINISH
/PREP7
SMRT,6
SMRT,2
SMRT,1
MSHAPE,1,3D
MSHKEY,0
CM,_Y,VOLU
VSEL, , , , 12
CM,_Y1,VOLU
CHKMSH,'VOLU'
CMSEL,S,_Y
VMESH,_Y1
CMDELE,_Y
CMDELE,_Y1
CMDELE,_Y2
FINISH
/SOL
SOLVE
FINISH