A cubic equation of state for vapor-liquid equilibrium calculations of nonpolar and polar fluids

A cubic perturbed hard body (CPHB) equation of state (EOS) was developed and applied for vapor-liquid equilibrium (VLE) calculations in this study. The repulsive part of this EOS was investigated in our previous work. It is a simplified expression of hard body equation which yielded satisfactory agreement to the molecular simulation data of hard molecules from a single sphere to long chain fluids. An empirical attractive term was combined with the repulsive contribution, and the total EOS was written in a cubic form. This EOS has three parameters for each real pure fluid. Pure fluid parameters were regressed in this study for nonpolar and polar fluids. Satisfactory calculated results of the saturated properties of pure fluids were obtained. The accuracy of the CPHB EOS is better than that of other two- or three-parameter cubic MSRK, CCOR, PT or PRSV2 EOSs. VLE calculations on fluid mixtures were also investigated using the van der Waals mixing rules. The CPHB EOS again gave good results, which are comparable to those from other cubic EOSs.