NONCUBIC EQUATION OF STATE FOR PHASE-EQUILIBRIUM CALCULATIONS

A new non-cubic equation of state is proposed for calculation of the thermodynamic properties of nonpolar and polar fluids and their mixtures, including saturated vapor pressure, saturated liquid volume, saturated vapor volume, heats of vaporization and vapor-liquid equilibria. The new equation is derived from the generalized van der Waals partition function in which the repulsion terms are expressed with the Carnahan and Starting equation for hard spheres, and the attractive terms are made up of the dispersive energy and the chemical association energy. The rules of dependence of parameters alpha and sigma and on temperature are considered broadly so that the new equation yields good agreement with experimental saturated properties of 20 nonpolar and 27 polar fluids in the range of reduced temperatures of 0.5 to 1.O. The new equation with parameters group contributed generally satisfactory predictions on saturated properties. Correlations of vapor-liquid equilibrium data for alcohol containing systems by using van der Waals one-fluid mixing rides prove that the new equation is superior to the M-PR equation of state.