In the thermodynamic module also REFPROP is used by CONVAL^®

This program, developed by the National Institute of Standards and Technology (NIST), calculates the thermodynamic and transport properties of industrially important fluids and their mixtures. REFPROP is a Program, not a Database Containing Measurements. The REFPROP "database" is actually a program and does not contain any experimental information, aside from the critical and triple points of the pure fluids. The program uses equations for the thermodynamic and transport properties to calculate the state points of the fluid or mixture. These equations are the most accurate equations available worldwide. Their high accuracy is obtained through many coefficients in the equations, and thus the calculation speed will be slower than other equations such as the Peng-Robinson cubic equations. The equations are generally valid over the entire vapor and liquid regions of the fluid, including supercritical states; the upper temperature limit is usually near the point of decomposition of the fluid, and the upper pressure (or density) limit is defined by the melting line of the substance.

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. 

Fluids and mixtures which are embedded in REFPROP database together with their range of validity: