The unit consists of a single, long rectangular chamber. On the inside is a moving wall. On one side of the wall is a vacuum, and the other side is room-temperature air. The moving wall starts much closer to the side with the air and moves slowly in the vacuum direction. As this happens, air particles that make contact with the moving wall will lose kinetic energy, and thus the temperature inside will be lowered. I just realized as I'm writing this that I don't have a good way to bring the machine back to its starting state, but maybe one of you can come up with a method. Anyway, is this entire line of thinking silly? Would such a device cool the air significantly? I'm only a first year university student so go easy on me.