| Feature | REFPROP 9 (Legacy) | REFPROP 10 / 10.0 (Current) | | :--- | :--- | :--- | | | ~147 | 200+ (including carbon capture solvents and new low-GWP refrigerants) | | Mixture Model | GERG-2008 (excellent for natural gas) | GERG-2012 (improved for CO2-rich mixtures) | | Transport Properties | Stable, mature correlations | Novel models for ionic liquids and nanorefrigerants | | User Interface | Classic, simple Windows GUI | Modernized with live plotting and tabular exports | | Programming | 32-bit and 64-bit DLL | 64-bit only; Python wrappers improved | | License Cost | No longer for sale (legacy users only) | Active sales; academic discounts available |
In the world of chemical engineering, HVAC design, natural gas processing, and academic research, the accuracy of thermodynamic data is not just a convenience—it is a necessity. Errors in fluid properties can lead to catastrophic pipeline failures, inefficient power plants, or pharmaceutical batches that fail quality control. For over three decades, the National Institute of Standards and Technology (NIST) has provided the solution to this challenge. The flagship software, NIST REFPROP 9 (Version 9 of the REFerence fluid PROPerties program), remains one of the most widely cited and trusted tools for calculating the thermophysical properties of pure fluids and mixtures. nist refprop 9
This article provides a comprehensive deep dive into NIST REFPROP 9: its core features, the science behind it, its practical applications, and how it compares to its successors (REFPROP 10 and 10.0). NIST REFPROP 9 is a software program that implements the most accurate equations of state (EOS) available for a wide range of fluids. Unlike simple lookup tables or ideal gas laws, REFPROP uses complex Helmholtz energy formulations to predict properties across a broad spectrum of temperatures and pressures—including the critical region, two-phase conditions, and cryogenic temperatures. | Feature | REFPROP 9 (Legacy) | REFPROP 10 / 10