I understand that valves in two-phase vapour / liquid were sometimes sized by considering the required vapour and liquid flow rates separately, and then adding the results together. But this is now considered an outdated practice.
I have also heard of the homogeneous equilibrium model (HEM), but I am under the impression that there are a number of other accepted sizing techniques.
My primary question is: what are the currently accepted practices / standards for sizing relief devices with two-phase vapour / liquid flow?
Otherwise, if the older techniques are still valid, under what conditions or assumptions behind each technique are they still valid?