Hi @gcleite96, so although the inlet-outlet will not be driving the flow, they still need to be defined to tell the simulation where air can naturally come in and out, otherwise, as you have experienced, air will circulate within the domain, continuously increasing in temperature. I would define a pressure inlet and pressure outlet, without applying a pressure difference, this will result in a natural flow due to buoyancy from the inlet to the outlet.
Let me know how it goes!
Darren