radiation heat transfer

Hi Ivar,

Since you are the expert in radiation heat transfer, I wonder if you can help with some problem in radiation heat transfer.

I am running a 3D case with surface-to-surface radiation heat transfer. The element number is around 0.18M, but it requires a large memory (virtual memory is >70GB), so I select the segregated solver, and still COMSOL is running very slowly. Is this normal based on your experience, I mean large memory requirment or very slow calculation speed?

Another question is that: my current case is surface-to-surface radiation heat transfer between solid surfaces. And I do not define any domain between the two solid bodies involving surface-to-surface radiation heat transfer. So it means the surface-to-surface radiation heat transfer in vacuum. Is this OK? The reason I ask this quesiton is from my previous experience of using some other softcase, such as ANSYS Fluent. In Fluent, the domain between two solid bodies has to be defined even though it is not anticipating radiation heat transfer. So I wonder if it is correct without defining anything between two solid bodies in COMSOL.

Thanks very much for your time.

Best regards.