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# Vacuum

#### amoncur

##### New member
Does anyone know how to simulate a vacuum while doing a thermal analysis in Mechanica?

Thanks,

Aaron

Duh... Nope! But I'll definitly think about it!

Aaron,

Since in reality what most people call a vacuum is actually differential pressure, apply pressure loads on the surfaces in the opposite direction. Will this work in Thermal?

Best regards,

Matthew Ian Loew

Luck is the residue of design.

Branch Rickey

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.

But how to actually do it... don't know

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).

Thanks,

Aaron

Does anyone know how to simulate a vacuum while doing a thermal analysis in Mechanica?

Apply an external pressure of 14.7 psi.

I think what amoncur is referring to is radiation heat transfer across a vacuum. There is an article in the PTC knowlege base about how to get mechanica to do radiation heat transfer. I'd look there

I'm trying to simulate the heat transfer for a liquid in a thermos

You must have a thermos fetish! Aaron! we need to get you a date and fast. Next thing I know we will be seeing renderings of heat vapors coming from your 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.

Thanks again,

Aaron

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.

-Rishi