Patches PropsSI imposed phase for backends other than HEOS

[henningjp]

Patches #1660. Mods to StripPhase() in CoolProp.cpp to handle (or reject) backends that don't have phase functions like calc_phase() and specify_phase(). Specifically REFPROP and INCOMP and IF97 backends were affected. Tests should all pass now.

Error message was something like:

In [1]: PropsSI('C','T',500,'P',101325,'INCOMP::DowQ')
ValueError: This backend does not implement calc_phase function : PropsSI("C","T",500,"P",101325,"INCOMP::DowQ")

With the patch, these backends are all passing tests:

In [4]: PropsSI('C','T',500,'P',101325,'INCOMP::DowQ')
Out[4]: 2288.1643758645673

In [7]: PropsSI("D","P",101325,"T",375,"REFPROP::Water")
Out[7]: 0.5944246707421037

In [8]: PropsSI("D","P",101325,"T|gas",375,"REFPROP::Water")
Out[8]: 0.5944246707421037

In [9]: PropsSI("D","P",101325,"T|liquid",375,"REFPROP::Water")
Out[9]: 957.0103405813556

In [10]: PropsSI("D","P",101325,"T",375,"SRK::Water")
Out[10]: 709.0245321521222

In [13]: PropsSI("D","P|gas",101325,"T",375,"SRK::Water")
Out[13]: 0.5903825428777025

In [14]: PropsSI("D","P|liquid",101325,"T",375,"SRK::Water")
Out[14]: 709.0245321521222

In [15]: PropsSI("D","P",101325,"T",375,"IF97::Water")
Out[15]: 0.5943926157152021

[ibell]

I'm going to merge this so that we can make the users/buildslaves happy again.

A question though: why do you worry about getting the phase at all? If you are talking about the high-level interface, won't the phase ALWAYS be the default phase? If my understanding is wrong, it would in any case better to just wrap the call in a try-except block, so you don't need to specialize manually. That's usually not the right solution, though it is called for in some special cases.

[henningjp]

Yeah, I wasn't sure. I think my initial thought was if it was already set by the first parameter, but setting anything on the second parameter will get tossed anyway.

I don't get phase() now, I just initialize the temp variable to iphase_not_imposed. Then if there's any way for it to fall through the phase checking process, the State phase will just get set to iphase_not_imposed again.

[henningjp]

I also put checks in to throw errors if the user tries to enter an imposed phase on the backends where phase shouldn't be imposed.