If you were calculating the force on an air lock door, then an absolute pressure differential would work ok. However, for thermal analysis, the air properties are very important. I would recommend not using that approach.
I'm actually having trouble getting the thermal analysis to run at all. Anyone know of a good tutorial? What do you need to have specified in order for it to run? I have the material, a boundary condition for ambient temp, and a heat load.
Also, do I need a heat load (i want to simulate a hot liquid) or can I just specify another boundary condition as a constant temperature for the liquid since i'm not sure what the heat transfer rate is for the heat load (I'm trying to simulate the heat transfer for a liquid in a thermos).
Thank you to all who gave applicable help (which would of course exclude Mr. boydt). As for my dating life, if your sister's been released from her institution I'd love to take her out, give her a couple strong drinks, and have her drive home.
Seriously Mr. Dougr, would applying an external pressure of 14.7 psi would simulate a vacuum for THERMAL analysis?? How is pressure to do anything with the conductivity? The conductivity for vacuum is supposed to be zero except that thermal heat transfer is only through radiation... no conduction.