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Prediction of critical points for carbon dioxide-based binary mixtures by the Heidemann-Khalil approach
Rui Sun, Hua Tian and Gequn Shu
Prediction of critical point is of great interest for CO2-based binary mixture being the working fluid of power cycle. Compared with empirical correlation, the critical point of mixture can be calculated based on its rigorous thermodynamic criteria, with limited binary interaction parameters and consistency on vapor-liquid equilibrium and other thermodynamic properties. In this study, the critical points of CO2-based binary mixture, applicable for being working fluid of power cycle, including hydrocarbons, fluorocarbons, dimethyl ether, methanol, water and xenon, were studied based on the Peng-Robinson equation of state (PREOS) with van der Waals (vdW) mixing rule, according to the Heidemann-Khalil approach. By comparing the predicted results with the experimental data in the literature, the applicability of this method to various mixtures is discussed. The characteristics of critical lines, type of phase diagram, and binary interaction parameters of each mixture were analyzed and discussed, and the results show that the Heidemann-Khalil approach is efficient for critical point calculation and prediction of CO2-based binary mixture.
Keywords: Carbon dioxide, binary mixture, critical point, equations of state, vapor–liquid equilibrium