We are doing some testing on pressure relief valve for pressurized oil. Our test engineer reported the heating of the PRV during operation. I am surprised since there should be cooling during the release of the pressurized oil. As the process is very fast and we assume it is adiabatic it is a case of adiabatic cooling. Isn't it?

Your explanation will help me to understand the process.

Thanks

I assume the pressurized oil is (almost) incompressible. So there is no real cooling as with a compressible gas undergoing an adiabatic expansion. When the oil contains dissolved gas which is released during depressurization this will have a slight cooling effect. But when dealing with an incompressible fluid you will get heating due to friction.

Thanks Bart for the explanation. I will dig into it further.