The following picture shows two different situations with solar radiation to a plate. Heat leaving the plate through radiation, convection and conduction in plate. Under the plate there is a boundary layer. In both cases gravity acts downward and there is no forced wind blowing.
In first situation the plate is located on the boundary layer, which means that the plate is isolated from the buttom.
In the other case the plate is liftet.
I want to find the temperatures in those two cases. But it seems that i cannot isolate the plate completely, In the situation with no space heat is being transfered through the boundary layer, see figure below. I have tried the following; real wall with 0 heat transfer coefficient. Ideal wall. Choosing rockwool with a thickness, nothing works. Heat is being transfered through the wall as you see.
So my question is; how can i isolate heat transfer completely from a boundary??
the top layer is supposed to be ordinary material, and the buttom layer is suppose to represent a bounday layer