Why is Emissivity in Boundary Condition

[Benjamin Brannon]

I'm new to Therm, so I hope this question isn't too simple, but I can't understand why an emissivity needs to be defined for a boundary condition.  It's already a material property, as it should be.  Why would it also change based upon the boundary condition?

[Alessandro Marzi]

Hi Benjamin,

I think is due to the fact that you can choose to assign different values to the internal or the external surface of a material. The most common case is aluminium that has an internal face not painted and the external one painted.

Anyway, if you check my last post, I noticed that each time you change that property, when you open a second time the boundary condition after assigning a value (or the cavity to which you change it), you'll find the original value and this can bring to lose control of your operations.

Alessandro

[Robin Mitchell/LBNL]

See my previous answer about the fix in THERM 7.6 so that now the changes to emissivities are saved.

Robin