Theoretical model of transcritical CO2 ejector with non-equilibrium phase change correlation

A theoretical model of an ejector was proposed for a transcritical carbon dioxide ejector-expansion refrigeration system capable of predicting the mass flow rates of both primary and secondary flows. A non-equilibrium correlation in the energy-conservation equation was proposed and validated using 130 cases obtained from three different ejector configurations. The differences in the predicted primary mass flow rates between the cases with and without the correlation were insignificant when the liquid mass fraction at the nozzle throat xt was less than 0.65. However, the prediction error increases dramatically when the correlation was not used for xt > 0.65. The Mach number in the CO2 ejector is lower than 1.5 and the “double choking” phenomenon will not happen in the CO2 ejector. Finally, a correlation was fitted for the primary flow pressure at the nozzle throat, which can be used to replace iterative solving in the model calculation.