[yaserbm]

please i'm seeking your help to help me in this issue,
lets say that we have liquid stream of propylene that has tempreature of 37 C and pressure of 13 barg, if we introduce this stream to low pressure vessel of 4 barg, the result of this will be flushing of propylene, as its pressure drop from 13 to 4, as result of this the tempreature also will dropped because propylene approch new equilibrium, my question is what makes this drop in tempreature what force the tempreature to drop, i knew its due to the new equilibrium approcah, but what drives this temp to drop if we approach the new equilibrium.
 please help me to understand this phenomena.