CoolProp is an open source C++ library of thermophysical properties for pure fluids, pseudo-pure fluids, and humid air. Ian Bell has recently developed a wrapper for Maple (get the wrapper and library at Github). Compiling CoolProp gives a library (a DLL on Windows) you can call in Maple via define_external().
I started exploring CoolProp a few days ago, and here's a few simple examples of what you can do
The saturation pressure (in kPa) of the refrigerant R134a at 253 K
The pressure (in kPa) of the refrigerant R22 that produces a two-phase mixture of quality 0.3 with an enthalpy of 300 kJ/kg
And since I'm a fan of engineering visualization, here's a refrigeration cycle on a P-h-T chart, generated in Maple with CoolProp.
Here's a Maple application that uses CoolProp to analyze a refrigeration cycle (together with a CoolProp DLL for 64-bit Windows).
I'd like to encourage anyone with an interest in thermophysical modeling to download CoolProp and explore its functionality. It's certainly opened up a new field of applications for me.