A COMPARISON BETWEEN ANDERKOS MODEL WITH COMPOSITION-DEPENDENT PHYSICAL INTERACTION PARAMETERS AND SRK-BASED HEXAMER MODEL FOR HFC AND HF SYSTEMS

A new composition-dependent mixing rule in physical contribution term of AEOS by Anderko [A. Anderko, Phase equilibria in aqueous systems fr om an equation of state based on the chemical approach. Fluid Phase Eq uilibria, 1991, 65, 89.] was introduced to predict the phase behavior for HFC-134a + HF and HFC-32 + HF binary systems. The approach develop ed in this work gives better results for systems containing strongly a ssociating compounds in the vapor phase such as hydrogen fluoride than the SRK-based hexamer model developed by Twu et al. [C.H. Twu. J.E. G oon, J.R. Cunningham, A new cubic equation of state for hydrogen fluor ide, Fluid Phase Equilibria 1993, 86, 47.] with fewer binary adjustabl e parameters. The equation of Peng and Robinson [D.Y. Peng, D.B. Robin son, A new two-constant equation of state. Ind. Eng. Chem. Fundam., 19 76, 15, 59.] is used to describe the physical interactions. The van de r Waals mixing rule was replaced by composition-dependent mixing rules to improve the predictability of this model. This study shows more ac curate results for VLE phase behavior for HFC and HF systems than the SRK-based hexamer model or any other activity coefficient-based hexame r models developed so far. (C) 1998 Elsevier Science B.V.