Fees fund the continued updates of fluid property libraries. How to Get RefProp (The Right Way)
Excellent for students learning the interface or testing basic thermodynamic cycles. Legitimate Free Alternatives to RefProp
A free, open-source chemical process simulator. It includes its own property packages and can integrate with CoolProp to provide RefProp-like functionality within a full plant simulation environment. A Note on "Free" Downloads
It only includes a few fluids (like water, nitrogen, and R134a).