The ejector is key to the performance of the transcritical CO2 ejector refrigeration system. Considering the complex processes

such as metastable phase change

supersonic flow

and choking phenomena et al.

in the CO2 two-phase ejector

a 1D distributed model was built in this paper and the delayed equilibrium theory was employed to analyze metastable phenomena in the motive nozzle. After the comparison with the relevant experiments data

the model was validated to be reliable to predict ejector performance. Compared with the homogeneous equilibrium model (HEM)

the proposed model presented a 12.39%~25.30% lower critical mass flow rate. Meanwhile

the comparison results showed that the metastable phenomena would slow down the expansion process causing higher nozzle outlet pressure than that of the HEM simulation results. Moreover

the model is used to study the effect of the dimensions on the ejector performance and the results revealed that under a certain operating condition

an optimal mixing section diameter existed for both high entrainment ratio and pressure lift. Besides

a longer mixing section with a fixed mixing section diameter would increase the pressure lift ratio.