tank depressurization through a valve

Hello guys,

I want to study the temperature evolution of a gas in a vessel from 200 bar to 20 bar. I made the assumption the expansion is isentropic. However I have some trouble to represent the heat exchange between the wall and the gas. I used the energy conservation (transfer from a fluid to another through a wall) but I don't know if it's clearly what I need to use. Can someone help me to define the heat transfer? I found a topic talking about This but nothing was explain.


http://www.physicsforums.com/showthr...ic+isenthalpic

Another question, when the gas from the vessel at 200 bar flows through a valve and the circuit is at the atmospheric pressure, is there a temperature evolution? I don't think so but if We use the relation PV = nRT the circuit pressure rise so the temperature rise too.

Thanks for your help.

Hybro