Coordination number models and equations of state for square-well pure and mixture fluids, Part II: Equations of state

Abstract

Equations of state (EOSs) for square-well (SW) pure and mixture fluids were derived based on the coordination number models (CNM) proposed in the preceding paper ( Cao & Wang, 1999, Chemical Engineering Science). The EOS proposed for the SW pure fluid is compared with previous CNM EOS and three theoretical perturbation theory EOS with respect to the capability of estimating the compressibility and critical point, covering wide density range and variable well width. The results indicate that the new EOS gives better accuracy than the other CNM EOSs, and is comparable with the first-order, but less accurate than the second-order perturbation theory EOSs. More importantly, the new EOS for the SW mixture fluids is a remarkable improvement over the other two feasible CNM EOSs at high densities, in particular. Consequently, the EOSs proposed in this work lead to a reasonable framework for the development of practical EOSs, in which the SW fluid is a reference system.