Try FluidProp for Free!
With more than 1.000 downloads per year, it is probably one of the most popular software packages for thermodynamic calculations.
There are free versions available for the MS-Windows, MacOS and Linux platforms and you can try the many features of FluidProp for an indefinite period of time. The free Windows version is the same as the Basic version for Windows, the free macOS and Linux versions are also functionally identical to their corresponding Basic version but contain a limited set of fluids. Various add-ons are available for modeling more challenging situations and many additional fluids. For complete information about FluidProp, check out the FluidProp main page. The fluids that are available in the Basic version and in the various add-ons of FluidProp are listed in fluids_overview.pdf.
The free versions of FluidProp offer the following thermodynamic models:
GasMix implements the ideal gas model for fluids and mixtures. It is very fast, but obviously has all the limitations of the ideal gas model: it cannot compute properties for liquids and cannot deal with phase changes. It can be used to model any mixture, but obviously with limited accuracy as the interaction between the consituents are not taken into account.
IF97 (Industrial Formulation) calculates the thermodynamic and transport properties of water and steam according to International Association for the Properties of Water and Steam (IAPWS-IF97). It is the reference calculation for industrial applications of water and steam.
FreeStanMix implements the PRSV equation of state, which is one of the most accurate cubic equations of state to predict the properties of non-ideal gases and fluids. In particular, it gives good results for the estimation of saturation properties. It is particularly useful for fluids for which RefProp is not available, as it requires only a single parameter to model a fluid. Also, it is faster than RefProp. A more accurate version of FreeStanMix is available in the StanMix add-on.
For mixtures, FreeStanMix uses the Wong and Sandler mixing rules which are suitable for the modeling of highly non-ideal mixtures.
One of the nice properties of the FreeStanMix model is that we can add extra fluids to those that are already supported relatively easily. So, even if your particular fluid is not yet supported, it will not cost you much to get it in the library.
TPSI implements accurate thermodynamic models for a number of fluids as described in: Reynolds, W.C., Thermodynamic properties in S.I., Department of Mechanical Engineering - Stanford University, Stanford, CA, 1979.