METBD 452 HW-6

Prof. Dave Johnson, dhj1@psu.edu

Penn State - Erie, The Behrend College

Reference:  ANSYS Heat Transfer Training Manual

Chapter 8: Radiation from a Finned Aluminum Heat Sink

  Follow the procedure for Chapter 8: steady-state heat transfer of heat dissipated by a finned aluminum heat sink.
  Do CASE 1: convection only
  Do CASE 2: adding radiation using the "hidden" method
  Do NOT do CASE 3 (the "non-hidden" method technique)
Model the radiation using a radiation matrix and model the surface convection using surface effect finite elements.  Use different nodes as the "space node" for radiation and the "extra node" for convection.

SOLVE the nonlinear radiation model, using (10%) tighter than default heat flow convergence tolerance (CNVTOL,HEAT,...).  This setting is not needed for the Case 1 solution, only for Case 2.  (Solution > Nonlinear > Convergence Criteria)

Turn in:

• model geometry plot(s) showing ALL thermal loads and boundary conditions
• for the radiation model, a plot of ONLY the radiation surface "skin" with element coordinate systems (ESYS) showing proper radiation directions
• a results contour plot of the temperature on the model for both cases
• compare the total heat loss by convection (Case 1) to the total heat loss by radiation (Case 2) and compare to the totals reported in the text
• Include the annotated log file, showing the model generation and solution for both cases.  (The final log file should show both solutions).

THE SOLID MODEL GEOMETRY IS GIVEN:

finish
/clear

*SET,base,0.15   ! thickness of heatsink base (in.)
*SET,hgt,1.0     ! overall height of heatsink (in.)
*SET,ttop,0.05   ! width of fin tip (in.)
*SET,tbot,0.15   ! width of fin at base (in.)
*SET,fspc,0.4    ! fin spacing at center (in.)

/PREP7 
!* 
ET,1,PLANE55     ! 2D solid quad. element type
!* 
KEYOPT,1,1,0
KEYOPT,1,3,0     ! plane behavior
KEYOPT,1,4,0
KEYOPT,1,8,0
KEYOPT,1,9,0
!* 
ET,2,SURF151      ! 2D surface effect element type
!* 
KEYOPT,2,3,0
KEYOPT,2,4,1      ! exclude mid-side nodes
KEYOPT,2,5,1      ! include extra node
KEYOPT,2,6,0
KEYOPT,2,7,0
KEYOPT,2,8,2      ! convection: Hf at avg. T
KEYOPT,2,9,0      ! exclude radiation
!* 
MPTEMP,,,,,,,, 
MPTEMP,1,0 
MPDATA,KXX,1,,8.5 ! themal conductivity of Al (BTU/hr-in-F)

K,1,0,,,          ! Bottom-Up modeling
K,2,0,base,,
K,3,0,hgt,, 
K,4,tbot/2,0,, 
K,5,tbot/2,base,, 
K,6,ttop/2,hgt,,
K,7,fspc/2,0,, 
K,8,fspc/2,base,, 
A,1,4,5,2         ! Make 3 "regular" areas
A,2,5,6,3 
A,4,7,8,5 
!* 
LOCAL,11,0,0.2,0,0, , , ,1,1, 
ARSYM,X,all       ! reflect area pattern
CSYS,0            ! activate global Cartesian CSYS
NUMMRG,KP ! merge common edges

AGEN,5,all,,,fspc ! copy area pattern

LOCAL,11,0,2,0,0, , , ,1,1, 
ARSYM,X,28,30,1   ! reflect final area pattern
NUMMRG,KP         ! merge common edges

CSYS,0            ! activate global Cartesian CSYS
ESHAPE,2          ! mapped mesh
ESIZE,ttop*0.5    ! global element size
AMESH,all