Nist Refprop 9 Official
NIST REFPROP 9 — Overview and Practical Guide
What it is
REFPROP (Reference Fluid Thermodynamic and Transport Properties) is a NIST-maintained software library and database that provides high-accuracy thermophysical property models for pure fluids and mixtures. Version 9 is a widely used release that implements equations of state, transport property correlations, and mixture models intended for engineering and research applications where precision matters (HVAC, refrigeration, power cycles, cryogenics, process simulation, and scientific studies).
⚠️ Limitations
- Not free/open source
- No built-in cycle modeling (pure property calculation only)
- User interface is functional but dated
The Tolerances
REFPROP 9 is not a simulation guess; it is a reference standard. Typical uncertainties are:
- Density: 0.01% to 0.1% (in calibrated ranges)
- Speed of sound: 0.01% to 0.1%
- Heat capacity: 0.1% to 1% (depending on the fluid)
- Viscosity & Thermal Conductivity: 1% to 5% (still industry-leading for transport properties)
What is NIST REFPROP?
Developed by the National Institute of Standards and Technology (NIST), REFPROP is a computer program that provides tables and plots of thermodynamic and transport properties for a wide variety of fluids and fluid mixtures. nist refprop 9
It doesn't rely on simple, "back-of-the-napkin" calculations. Instead, it utilizes the most accurate physical models currently available, primarily the Helgerud-Mixon Equation of State (EOS) for pure fluids. This ensures that the data you pull—whether it's density, heat capacity, or surface tension—is as close to the experimental reality as physically possible.
What’s New in REFPROP 9 (vs. Version 8)
| Feature | REFPROP 8 | REFPROP 9 | |--------|-----------|-----------| | Fluids | ~105 | 120+ | | Mixture model | Mostly mixing rules | GERG-2008 added | | GUI | Basic | Improved interface | | HFOs | Few | R1234yf, R1234ze(E) | | Transport props | Limited | Expanded models | | 64-bit support | No | Yes | NIST REFPROP 9 — Overview and Practical Guide
Note: REFPROP 10.0 is now available (2023+), but version 9 remains widely used due to licensing and compatibility in legacy systems.
3. Equation of State (EOS) Methods
REFPROP 9 uses high-accuracy equations:
- Helmholtz energy formulations (most pure fluids)
- GERG-2008 (for natural gas mixtures)
- Peng-Robinson and other cubic EOS for some hydrocarbons
- Extended corresponding states for viscosity and conductivity
5. Working with Mixtures
Mixtures require GERG-2008 (or simpler mixing rules).
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