Performance of two-phase ejector in compression/ejection refrigeration cycle

Taking into account of the phenomena of choking in entrained flow and condensation shock in mixing chamber, a thermodynamic model of two-phase ejector was established by using mass, momentum and energy balances. In the simulation, the mixing area in the mixing chamber is constant. With R141b as refrigerant, the pressure change in the ejector at various mixing pressures was studied, and the effects of mixing pressure on the performance of compression/ejection cycle, the entrainment ratio and exit pressure of ejector were analyzed. The variations of optimum suction chamber pressure drop, the corresponding ejector entrainment ratio, the system optimum performance coefficient and the corresponding performance improvement ratio with condensation temperature and evaporation temperature were presented. The results show that under the operation conditions in this study, no condensation shock occurs in the mixing chamber of two-phase ejector. The constant area model for mixing chamber is more appropriate than constant pressure model. It is important to choose appropriate mixing pressure for optimizing the system performance, and the optimum mixing pressure, at which the ejector has the highest entrainment ratio, is slightly lower than the pressure of entrained flow but far larger than the critical pressure entrained flow.