Modeling Vapor Liquid Phase Equilibrium for C_xH_y + C_xH_yF_z Using Peng-Robinson and Perturbed-Chain SAFT

Modeling the vapor liquid phase equilibrium of mixed refrigerants is the essential precondition for the calculation of refrigeration system. In this work, the study on 48 pure substances and 58 binary systems consisting of C_xH_y and C_xH_yF_z was performed. Both Peng-Robinson (PR) and perturbed-chain SAFT (PCSAFT) were investigated. The relationship between the parameters in PR and PCSAFT was exhibited. Strong linear function of the volume parameter mσ³ in PCSAFT with covolume parameter b in PR were found, as well as the energy parameter mε² in PCSAFT with energy parameter a/b in PR. This correlated characteristic provides an idea for regressing pure substance parameters and a criterion whether the regressed parameters are reasonable or not. The interaction parameters in PR-VDW and PCSAFT show consistent tendency, and both are limited to a very narrow range. The simple predictive method was proposed by using the average value 0.146 for PR-VDW and 0.093 for PCSAFT. The internal correlated behaviors result that the PCSAFT equation is no better than PR equation on the VLE description of C_xH_y + C_xH_yF_z systems.