Looking at a simple TXV system. Lets assume after the TXV we seperate the gas down one pipe and the liquid down another. The question is how do we assign the correct thermodynamic properties to each fluid when it gets to end of its pipe.

The gas we want to do work on like heat it or compress it but before we can see where it ends up and predict its temperature and pressure we need to know from where we started? So do we move the gas out of the middle of the bell on a PH diagram to its edge and similarly do we move the liquid back to the saturated liquid line to gets its new properties?

Simply jumping out of the bell interior means that the enthalpy and entropy both make huge changes without any process being done. Hmmm

Your thoughts welcome

Chef