Hi, i have to solve a natural convection problem in a box with an inlet and outlet and a heated floor. but it seems if i just model the box, the inlet doesnt work. it seems that the air does not come in, and the problem is i dont know the value of the incoming air, it should take so much air like the heated floor needs. Does anyone know which specific boundary conditions i set best to the inlet (pressure inlet, velocity inlet etc) and outlet? or do i have to model a big box around the heated small box? i hope anyone can help me.

I assume that your box is open at the top, so cooler air can enter the model from above and are heated by the floor can exit. If this s the case, you can use a pressure inlet and specify the temperature of the air beyond the model boundary. If this is not your condition, you'll need to provide a better physical description.

Thank you very much for your help, a first short test shows quite good results!