Hello everybody, I am working on some tests on materials and structures in a vacuum chamber. I noted that during the final moments of the pressure rising (when I open the valve to let the air in), temperature sensors installed in the chamber record the temperature rising more than ten degrees celsius above the previous constant temperature, before dropping to the previous equilibrium values. The same, but reverse, applies when the pump is activated to extract the air inside, and it happens in the first minutes of operations, while the pump is extracting the major part of the molecules inside the chamber. I found a thread here about the Joule-Thompson expansion for real gas. Is this the case? Can the air extraction from a vacuum chamber be thought as a free expansion of the real gas inside?