Problems using radiative heat transfer in Comsol

[curros38]

Hi everyone. I am starting using Comsol modeling the temperature field of a buried cable installed into a PVC duct (2D problem). I have already solved the problem considering heat transfer by conduction. To do this, I have used the Electro-Thermal Interaction Application Mode (Perpendicular induction heating: Steady-state) included in the AC/DC Module. However, when I try to implement radiation I have this message:

Error: 6253
Complex number found in irradiation expression.
- Expression: J
- Geometry: 1
- Boundaries: 5,6,7,8,13,14,17,18
Failed to evaluate expression.
- Expression: d(((dVolbnd_htgh*epsilon_htgh*(Gm_htgh+Famb_htgh*sigma_htgh*Tamb_htgh^4-sigma_htgh*T^4)*test(T))-(0))*(dvol),{test@0})

I think the problem is that in this application mode the variable T has become a complex number (I don´t know why, but it´s true. When I click on the T surface plot I get this: Value: 341.171896-6.440595e-6i [K], Expression: T, Position: (-0.013275,-0.006)).

Could this behaviour be a program bug? or Should I have to change anything in my model to make variable T a real number again?
I hope someone can help me.

Thank you for your suggestions.

 

[snorky]

Dear Curros,

Please reevaluate your material parameters.

Example: if your temperature is relative (as on overtemperature with respect to ambient) then it is possible to be 0.

COMSOL evaluates the properties with the absolute temperature (ambient+relative for the given example), so if your model has 0 in reality should be Tambient+T.
I hope you get the idea.