Critical points calculation of CO2-based binary mixture working fluids: evaluation of PC-SAFT equation of state

Abstract

Critical point is basic and important thermophysical property of CO2 mixtures, which determines the parameter design of power cycle and the optimization of its operating conditions. In this work, the perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state is used to calculate the critical point of CO2 mixture working fluids of the power cycle. To tackle the challenge of the original PC-SAFT in quantitatively representing of critical point of pure substance, the deviation between calculation results and experimental data was reduced by using the refitted pure-component parameters, so as to realize the effective increase of accuracy and representation the critical loci of the CO2 mixtures. By comparing with the classical cubic equation of state (Peng-Robinson and Soave-Redlich-Kwong), the results of PC-SAFT are effectively improved with relative deviation close to that of the cubic equation of state. The results show that the refitting of pure-component parameters can effectively help the accurate calculation of the critical point of CO2 mixtures, especially for the mixture containing hydrofluoroolefins with more complex molecular structure. This work provides an important reference for predicting the critical point of other potential CO2 mixtures.