Compressible mixture support?

[bilderbuchi]

It was not clear to me how far compressible Coolprop mixtures or mixtures using Cubic EoS are supported in ExternalMedia.

E.g. can we already do substanceNames = {"CO2[0.99]&Methane[0.01]"} and expect that to work? If not, how much effort would it be to add that (e.g. for the binary pairs known to Coolprop)? There are some mentions in source code here or there (e.g. fractions are apparently being set), but it does not look like this is supposed to work OOTB.

[thorade]

Azeotropic mixtures (no unmixing, no temperature glide, the R5xx series) should work already today, as they behave like pure fluids.
https://en.wikipedia.org/wiki/Azeotrope
Multi-component mixtures in single phase might also work, as long as you do not cross the phase boundary and it all stays single phase.

But to my understanding, the Modelica Media interface does not support multi-phase multi-component mixtures, like oil&gas mixtures, or water-alcohol in a distiallation column. So as long as ExternalMedia follows the MSL media interface, this is not possible.

[bilderbuchi]

Multi-component mixtures in single phase might also work, as long as you do not cross the phase boundary and it all stays single phase.

That sounds like a reasonable restriction, and would work for my use case (I'm staying in the gaseous regime).