two-phase psv sizing with direct integration HEM Homogeneous Equilibrium Model

[cbadia]

for a two phase discharge I am sizing a relief valve with the isentropic Nozzle unit available in Prode Properties,
the procedure allows to specificy the HEM (Homogeneous Equilibrium Model) and NHNE (Non-Homogeneous Non-Equilibrium Model) for isentropic flow.
While the HEM model gives results consistent with those calculated by Excel page nozzle.xls distributed with the program the NHNE model requires specific settings and may give results quite different.
Which is the best option (HEM or NHNE) for modeling a PSV discahrge ?

[carlo.stenali]

I think it depends from several factors as for example the size of the valve and the physical properties of the fluid,
my version of Prode Properties has three models
HEM (Homogeneous Equilibrium Model)
HNE-DS (Homogeneous Non Equilibrium, simplified model)
NHNE Non Homogeneous Non Equilibrium)
the last two require a specific parameter which for HNE-DS is available in several papers while for NHNE you have to estimate the value, generally I select HEM and I do a test with HNE-DS