A four-parameter corresponding-states method for the prediction of thermodynamic properties of polar and nonpolar fluids

Abstract

A four-parameter corresponding-states correlation has been developed for the prediction of thermodynamic properties of polar and nonpolar fluids. Required input constants include the critical temperature, the critical pressure, the radius of gyration (to account for geometrical deviations from simple corresponding states), and a liquid density at any known conditions from which a fourth constant (to account for polar and association effects) is calculated. The fluid property is written as a Taylor's series expansion about the simple fluid at the same reduced conditions, thereby separating deviations from simple corresponding states into geometric and polar contributions. Three fixed reference fluids are used to evaluate the deviation terms. Nonpolar results were equivalent to those obtained by the Lee-Kesler three-parameter method; polar results were substantially better than obtainable from any other currently available method. Average errors for calculated compressibility factors of polar fluids were 1.9 and 1.6% for the vapor and liquid phases, respectively, while those for enthalpy departure functions were 250 and 422 J·mol−1, respectively.