Experimental study on the improvement of CO2 air conditioning system performance using an ejector

Several preceding researches have evidenced that the transcritical air conditioning system using CO2 as a refrigerant has an inherent inefficiency resulting in degraded steady-state system performance of a CO2 air conditioning system compared with that of a conventional air conditioning system. As a practical improvement, two-phase ejector was considered in place of expansion device in this study. The two-phase ejector for CO2 air conditioning system was designed and developed considering the non-equilibrium state for evaluating the sonic velocity and the critical mass flux. The experiments of performance with respect to variation of ejector geometry such as the motive nozzle throat diameter, mixing section diameter and the distance between motive nozzle and diffuser were carried out. There exist optimum design parameters in each test. Experiments showed that the coefficient of performance of the system using an ejector was about 15% higher than that of the conventional system.