: If you already own a previous version (like 9.0), you may be eligible for a discounted upgrade to the latest version. REFPROP-Lite : NIST offers a free "Lite" version
Employs Helmhotz-energy-based equations of state, which represent the highest level of accuracy available for fluid property modeling.
The Thermodynamic Foundation of Modern Living: Analyzing NIST REFPROP 9.1