Reply To: radiatiom

[peteroznewman]

Convection doesn't work the way you think it does. You added a hole to provide "ventilation" and applied a convection boundary condition thinking that would blow cool air into the box. It doesn't work that way in a Steady State Thermal analysis. The way convection works is that heat can be carried away from any surface that touches a large and free flowing body of cooler 25 C air. Therefore, all the external surfaces of the box except for the surface on the floor would get the convection boundary condition. I suggest you take the free course on Convection Heat Transfer.

Radiation doesn't work the way you think it does either. If the box was in a room and the temperature of the walls of the room was 35 C and there was no direct sunlight, then what you have in the model is correct, but that represents a tiny amount of heat transfer.  Also, how is it possible that the walls of the room are at 35 C when the air is at 25 C?  That doesn't make sense.  But you said the box is in direct sunlight. That can be modelled using Radiation.  I suggest you take the free course on Radiation Heat Transfer.