An improved crossover SRK EOS for more accurate assessment of thermodynamic properties of CO₂+pentane binary system

The CO₂ transcritical power cycles in medium-high temperature areas are gaining attention for industrial heat recovery. At present, increasing studies focus on CO₂-based mixtures, particularly the CO₂+pentane binary mixture, due to its high thermal efficiency and low operating pressure. Based on this, high-precision calculation of thermodynamic properties is essential. In this study, the crossover SRK (CSRK) equation of state (EoS) based on Kiselev's crossover method is established, then the phase equilibrium properties, second-order thermodynamic properties, and single-phase region density for pentane and CO₂+pentane binary system are investigated using CSRK. Our research reveals that CSRK can accurately describe the thermodynamic properties of working fluids in near-critical region, precisely explore the change law of critical region density, and improve calculation accuracy of thermodynamic properties in far-critical region, which is suitable for engineering application. The CSRK significantly improves the calculation accuracy on liquid density, reducing the average absolute relative deviation (AARD) by more than half to 1.89 % compared with multi-parameter EoS. Additionally, a new phase equilibrium iterative solution method of binary mixtures is proposed, which has higher calculation efficiency and faster evaluation of the response of system to different disturbances, providing important support for future dynamic analysis.