Accurate representation of thermodynamic properties near the critical point

Abstract

The singularities in the thermodynamic functions of fluids at their critical points cannot be described by the analytic equations used for preparing tables of these functions. They can be described by scaling equations, but these are accurate only close to the critical point. It is shown that Schofield's parametric version of the scaling equations can be combined with an analytic equation in such a way as to permit the accurate representation of the thermodynamic functions for all values of density and temperature. The method is demonstrated for carbon dioxide and methane.