Experimental Measurement and Thermodynamic Modeling of Isobaric Specific Heat Capacity for Supercritical CO2/Propane Mixtures

Adjusting the critical point of CO2 by adding propane is an effective method to enhance the performance of the supercritical CO2 Brayton cycle under high-temperature conditions. This study measured the isobaric specific heat capacity of CO2, propane, and their mixtures within the temperature range of 323–473 K and pressure range of 8–12 MPa using a flow calorimeter. We optimized the parameters of the GERG-2008 model for the CO2/propane mixture system. Results indicate that the isobaric specific heat capacity of CO2 and propane, as well as their mixtures, exhibits sensitivity to temperature and pressure variations in the pseudocritical region, with the sensitivity becoming increasingly gradual when moving away from this region. The isobaric specific heat capacity of the mixture increases with rising propane content. The average absolute relative deviation (AARD) between experimental values and GERG-2008 model calculations for pure CO2, propane, and mixtures was 0.79%, 0.86%, and 1.25%, respectively. The GERG-2008 model, optimized using literature and experimental data, significantly improved the calculation accuracy of isobaric specific heat capacity for CO2/propane mixtures, reducing the AARD to 0.93%.