Do anyone have such experience to change the cell type during calcultation? For example, in transit problem, some cell type is considered as solid first, then after certain time, the cell is changed to fluid and the calculation restart with the previous output file as restart file and the initial condition of changed fluid cell is mannually set?

Dynamically changing cell types of different materials would be difficult - with the solid cells, you are running Conjugate heat transfer - that is the heat transfers from one room to another throught solid material. This is an interesting setup because most applications would have assume the door is thin enough to be treated as conducting baffle. Indeed if you treat it as baffle with some sort of resistance, then the problem may be solved with advanced transient setup. At first load step: treat baffle as solid wall. and then the baffle can be turned into porous baffle in the second load step. Just an idea.

Thanks. It works!