The following paragraphs were reproduced from the User's Guide for REFPROP NIST Standard Reference Database 23

1.1 Objectives and Scope of the Database

REFPROP is an acronym for REFerence fluid PROPerties. This program, developed by the National Institute of Standards and Technology (NIST), provides tables and plots of the thermodynamic and transport properties of industrially important fluids and their mixtures with an emphasis on refrigerants and hydrocarbons, especially natural gas systems.

REFPROP is based on the most accurate pure fluid and mixture models currently available. It implements three models for the thermodynamic properties of pure fluids: equations of state explicit in Helmholtz energy, the modified Benedict-Webb-Rubin equation of state, and an extended corresponding states (ECS) model. Mixture calculations employ a model that applies mixing rules to the Helmholtz energy of the mixture components; it uses a departure function to account for the departure from ideal mixing. Viscosity and thermal conductivity are modeled with either fluid-specific correlations, an ECS method, or in some cases the friction theory method.

These models are implemented in a suite of FORTRAN subroutines. They are written in a structured format, are internally documented with extensive comments, and have been tested on a variety of compilers. Routines are provided to calculate thermodynamic and transport properties at a given (T,rho,x) state. Iterative routines provide saturation properties for a specified (T,x) or (P,x) state. Flash calculations describe single- or two-phase states given a wide variety of input combinations [(P,h,x), (P,T,x), etc].

A separate graphical user interface, designed for the Windows operating system, provides a convenient means of accessing the models. It generates tables and plots for user-specified mixtures or a number of predefined mixtures (air and the commercially available refrigerant blends). A help system provides information on how to use the program. Information screens that display fluid constants and documentation for the property models can be called up at any time. Numerous options to customize the output are available as well as capabilities to copy and paste to and from other applications.

The property models can also be accessed by other applications (such as spreadsheets) through use of a dynamic link library (DLL). (Note: This is how the models are accessed within TDE.)


Properties of many pure components included in the REFPROP Database are used in TDE to speed evaluation of properties for mixtures and reactions. For pure-component evaluations, properties are evaluated dynamically by TDE and comparisons with the REFPROP equation of state are possible through the EOS Menu on the Main Form.

Properties for 105 compounds are taken from the NIST REFPROP Database (Version 9.0) and used in TDE to speed evaluations for mixtures and reactions.

Complete list of compounds from the REFPROP Database that are used in TDE