Icepak - Low Temperatures on model with Radiation
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Imagine a unit modeled in free air on 5 sides. unit sitting on an adiabatic surface. Unit is a vented box containing a PCB + components Sides of box are made of plates - bottom surface left as cabinet Radiation from all->all + default values for the load tolerance and display tolerance. PCB is slightly above base of unit - view factors from the pcb's bottom surface may be calculated to other sides of chassis of unit, but maybe very small - below load tolerance. So Icepak indicates that displayable view factors are only available for max y side of PCB. To me this suggests that no view factors were generated for the low y face so everything should be ok. But, in reality the surface will radiate with vf very close to 1 to the radiation ref temp - hence results maybe artifically low. NOTE: if you export the view factors again only those displayed will be exported. 1) Set load min to be 0.0 and then re-load, this will show where view factors have actually been calculated. Now miny surface of PCB does appear. 2) Add in a wall to mimic bottom of unit - and include in radiation calc then vf from PCB -> wall very close to 1 so no radiation to reference temp. Leave wall as is in all other respects. |
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