i was performing a flow simulation for a plate of size 250x206.5x10. I applied a load of 30 W on one side(i.e., on of the faces) and tried solving the simulation by applying the boundary conditions. 1st I selected environmental pressure on all the other faces and then on the next run i selected real wall as the boundary condition. It was giving more appropriate results with real wall. can someone please explain this.The ambient temperature was 20.05 deg Celcius and material of plate was aluminium. Plate was kept vertically in computational domain with heat conduction in solids and radiation option on (not considering solar radiations). Flow type was laminar. surrounding fluid being air. and the wall type was a black body.