solar radiation no convection
 

Hi,

I am a very beginner in Ansys Fluent. I hope someone can help me with my problem:
I want to calculate how much the interior space heats up in one winter day using the solar modul.
I modelled a room, including a sun grabber (glass on the upper side) that catches the sun rays. Inside I have a layer of copper that should heat up and transfer the heat to the interior space. In addition there is also a window above the sun grabber for additional heat. Inside the room we have 18C.

Image 1: As as cell zone for copper layer I gave fluid. In that case the material heats up and becomes hotter, but there is no natural convection to the surrounding air. And I don't even understand why the material gets hot with fluid.

Image 2: As a cell zone for copper I gave solid. In this case the geometry acts like there is nothing there and thus the sunlight goes through it without any interaction and heats the bottom of the sun grabber (red)

Can someone explain me why is it like that and maybe help me to solve this problem?
I would really appreciate it!

Thank you in advance,
Ivan