Your power supply should be have a good enough fan to keep it cool enough to function. You could try adding an extra fan in the case. Do you have a specific problem? like is your CPU overheating? try a better fan on the CPU.
Your PSU should not make too much heat, and it should have a fan blowing all the hot air outside the case. I also do not know what you are going to do to get the PSU outside the case.