Hi @39001194,
Thanks for posting your question!
One of the ways to simulate closed windows in CHT is using wall boundary condition enabling radiation, then you will be able to consider the external wall heat flux, ambient temperature, thermal conductivity of the windows (e.g.: if it is made of glass, etc). In this tutorial you have closed windows, so please take a look:
About natural convection inlet/outlet, we provide this detailed page on that:
best,