Velocity within domain

Andre

Thank you for taking interest in my question,

I'm trying to simulate the transient thermal behavior of an air flow in an enclosure (imagine a box), with a heat exchanger placed on one face. Hence, the air flow is interior, both inlet and outlet don't exist.

I'm using a wall boundary condition with imposed heat flux for the heat exchanger, but then I can't simulate the air moviment (im interested in a rough approximation only) caused by the fan of the heat exchanger.

In summary, I cannot impose both heat flux and air velocity.

Can anybody suggest required zones and respective BC?