: 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
NIST REFPROP 9.1: Comprehensive Download and Usage Guide (REFerence Fluid PROPerties) is a gold-standard software tool developed by the National Institute of Standards and Technology (NIST) . It provides highly accurate thermodynamic and transport properties for industrially important fluids and their mixtures. nist refprop 91 download hot
It implemented high-accuracy equations of state, primarily based on the Helmholtz energy form , designed to match underlying experimental data as closely as possible. : If you already own a previous version (like 9