A Simple Semiempirical Method for Predicting the Temperature–Entropy Saturation Curve of Pure Fluids

Abstract

In this work we propose an approximate analytical method to obtain the liquid–vapor saturation curve in a Tr–s* diagram, with Tr = T/Tc, s* = (s – sc)/R, Tc the critical temperature, s the molar entropy, sc the critical molar entropy, and R the gas constant, for a given fluid. The method uses a modified rectilinear diameter law for the saturated liquid and vapor entropies and an extended corresponding states equation for the entropy of vaporization. From this method, two approximations are derived. The first approximation requires the use of data obtained from RefProp or a similar program. The second approximation only needs Tc, the critical molar volume, vc, and the acentric factor, ω, of the fluid as input data. For most fluids, both approximations yield very good predictions.