# Ideal Hampson-Linde Cycle: a constant enthalpy device

1. Aug 2, 2011

### JFuld

1. The problem statement, all variables and given/known data
consider an ideal hampson-linde cycle in which no heat is lost to the environment. Argue that the combination of the throttling valve and the heat exchanger is a constant enthalpy device, so that the total enthalpy of the fluid coming in this combination is the same as the enthalpy of the fluid coming out.

2. Relevant equations

deltaH=deltaU+PdeltaV
deltaU=Q-PdeltaV +work(other)

3. The attempt at a solution

when fluid goes through the heat exchanger towards the throttle, H is changed by the amount -Q, during the throttling process no heat is transferred and (U+PV)initial = (U+PV)final so the change is enthalpy is zero. When the fluid goes through the heat exchanger a second time after leaving the throttle, enthalpy changes by the amount +Q. Thus the total enthalpy is unchanged.

I am certain that enthalpy doesnt change during the throttling process, but am I missing something about the enthalpy change during the heat exchange processes?