REFPROP

REFPROP, short for Reference Fluid Properties, is a thermophysical property database and equation-of-state library developed by the National Institute of Standards and Technology (NIST). It provides accurate properties for a large number of pure fluids and fluid mixtures over wide ranges of temperature, pressure, and composition, making it a widely used tool in engineering, research, and education.

REFPROP employs a Helmholtz-energy based equation of state to model the behavior of fluids and mixtures. It can compute a broad set of properties including density, pressure, temperature, enthalpy, entropy, internal energy, and specific heats (Cp and Cv), as well as the speed of sound, viscosity, and thermal conductivity. It also provides saturated liquid and vapor properties, phase equilibria, critical properties, and comprehensive P–v–T data. For mixtures, REFPROP uses mixing rules and interaction parameters to derive properties from component data.

Availability and interfaces: REFPROP is distributed by NIST as a software package with a Windows graphical interface and as a callable library for Fortran, C, and C++, along with wrappers for other languages and environments. It is used in HVAC and refrigeration system design, power cycle and thermal-fluid simulations, chemical process design, and academic research.

Data coverage and licensing: the database includes hundreds of fluids and many mixtures, including refrigerants, hydrocarbons, water, air, and specialty fluids. New fluids and updates are periodically released, and full access requires a license.

Limitations: while REFPROP provides high accuracy within its validated ranges, extrapolation beyond those ranges should be avoided, and mixture properties rely on models and interaction parameters that introduce uncertainty.