Incoherent phase identification

[GZALAT]

Property "Phase" is returning neither the same nor a correct result if calculated by Temperature - Density or Temperature - Pressure. This occurs when called from Excel (see attached Refprop Phase issue.xlsx) or Python with the code

import os
from ctREFPROP.ctREFPROP import REFPROPFunctionLibrary
RP = REFPROPFunctionLibrary(os.environ['RPPREFIX'])
RP.SETPATHdll(os.environ['RPPREFIX'])
US = RP.GETENUMdll(0,"MASS BASE SI").iEnum
FLD = "Oxygen;Nitrogen"
Comp = [0.2,0.8]
T = 160 #K
P = 60e5 #Pa
D = RP.REFPROPdll(FLD,"TP","D",US, 0,0,T,P,Comp).Output[0] #kg/m3
Phase_TP = RP.REFPROPdll(FLD,"TP","PHASE",US, 0,0,T,P,Comp).hUnits # Returns incorrect but acceptable "Superheated gas"
Phase_TD = RP.REFPROPdll(FLD,"TD","PHASE",US, 0,0,T,D,Comp).hUnits # Returns incorrect "Subcooled liquid"
print (f"Phase calculated from T,P is {Phase_TP} and calculated from T,D is {Phase_TD}")

When using the Refprop GUI the Phase always correctly solves to "Supercritical" from both "TP" and "TD"

[ianhbell]

@EricLemmon this looks like a bug, or is this expected behavior? How does the GUI handle this to get the right answer always?

[TMercerP]

I don't think that the (T,P) input pair is independent for saturated states and may not produce meaningful results for Quality/Phase. The independent pairs are (P,H), (P,S), (P,D), (T,S), (T,D), (H,D), and (S,D), right?

[GZALAT]

I don't think that the (T,P) input pair is independent for saturated states and may not produce meaningful results for Quality/Phase. The independent pairs are (P,H), (P,S), (P,D), (T,S), (T,D), (H,D), and (S,D), right?

I do not really agree as we are in unsaturated monophase here, but this question is about the different results in GUI and Python/Excel, and additionally, the result (T,D) is providing is even more off than the (T,P) one...

[GZALAT]

Any news on this issue? thank you