Somebody help me about Microwave heating boundary condition

Hi all friend,
Somebody can help me about how to solution the equation of heat transfer in microwave heating in cavity.I would like to know how to specific the boundary condition and how to solution it. If you have the tutorial or easy sample to understand it are well.And who have the MATLAB code in this field also need.I need to learn it step by step.Anyone can suggestion me step by step.

Thanks and Best Regards,
Vincent
My thesis not have any update if I can not understand this part.