On "tuning" the CCOR equation parameters to the saturation curve

Abstract

Ćirić, G. and Paunović, R., 1994. On "tuning" the CCOR equation parameters to the saturation curve. Fluid Phase Equilibria 93; 177-192. We analyze the possibility of obtaining a better representation of pure fluid VL coexistence curves by the cubic chain-of-rotators (CCOR) equation of state which in the original form, has two temperature dependent parameters α and γ. Introducing separate γ parameters for liquid and vapor phases, while retaining the common α parameter has enabled description of saturation pressures and densities of coexisting phases with a high degree of accuracy. As one may expect, this improvement extends also to predictions of superheated vapor densities and subcooled liquid densities at low pressures. However, it has been shown that "tuning" the equation parameters to the saturation curve up to the critical point leads to a thermodynamically inconsistent description of compressed liquid at high pressures as well as to a dramatic increase of enthalpy prediction errors in the critical region. Three common substances CO2, NH3 and H2O, are taken for illustration. © 1994.