Excel problem with Mixture

[Clifford Bradford]

New user in Excel and I'm trying to calculate properties of an air water vapor mixture using PropsSI. I've already run some cases with HAPropsSI but I may need properties at temps above the validity of HAPropsSI. WHenI try to run a case with an air & water mixture I get an error.

I've entered this formula in a cell

=PropsSI("CPMASS","T",CONVERT($A4,"C","K"),"P",CONVERT($B4,"atm","Pa"),"HEOS::"&MixtureString($S$2:$S$3,AD12:AD13))

where: 

A4 = 15

B4 = 1

S2:s3 = "Air":"Water"

AD12:AD13 = .985:.185

I get the following error:

Initialize failed for backend: "HEOS", fluid: "Air&Water" fractions "[ 0.9855880381, 0.0144119619 ]"; error: Could not match the binary pair [7732-18-5,AIR.PPF] - for now this is an error. : PropsSI("CPMASS","T",288.15,"P",101325,"HEOS::Air[.985588038076329]&Water[1.44119619236714E-02]")

[Ian Bell]

That won't work because "air" is a pseudo-pure fluid that can only be used as a "pure" fluid. You could put in the components of the air yourself if you wanted.

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[Clifford Bradford]

Yes, that's what I eventually figured out. I tried it by breaking down air into N2, O2, Argon, CO2 and then adding the moisture and that worked. I assume that the state of the water will be appropriately calculated based on the temperature and partial pressure (if I remember my thermo right)? Do you have a feel for which is more accurate between this approach and the HAPropsSI? I t probably doesn't matter because it'd probably make sense to use the same approach and HAPropsSI doesn't go high enough in temperature for me.

Thanks,

Cliff