Study of ejector efficiencies in refrigeration cycles

This paper presents a method of determining internal ejector component efficiencies using a two-phase flow ejector model. The measured performance data external to the ejector in conjunction with the ejector model were used to determine the isentropic efficiencies of the motive and suction nozzles, and the efficiency of mixing section. It was found that ejector component efficiencies vary with ejector geometries and operating conditions, which are different from the constant efficiencies assumed by previous researchers. The efficiencies of the controllable ejector motive nozzle, suction nozzle and mixing section range from 0.50 to 0.93, from 0.37 to 0.90, and 0.50 to 1.00, respectively, in CO2 refrigeration cycles under different operating conditions. Empirical correlations were established and incorporated into a CO2 air conditioning system model to estimate ejector component efficiencies at different ejector geometries and operating conditions.