Please follow the guidelines given in the following tutorial:
This should be enough to get you up to speed with boundary conditions and general setup. If you have more questions after following the tutorial and trying to apply the principles to your case, please come back and let us know.
thanks for the reply. I have tried the tutorial but there is some difference between to the inlet and outlet as for my case, the exhaust fan is place within the enclosure (before the outlet).
So in this case, do I need to create a MRF for my exhaust fan or there is another way to work around it?