Influence of liquid volume fraction on ejector performance: A numerical study

Abstract

In ejector-based refrigeration systems, the fluid phase state plays a key role in improving the ejector performance. In this study, the effects of liquid volume fraction on ejector performance were investigated by computational fluid dynamics simulations. The ejector was applied in a multi-evaporator refrigeration system used for refrigerated trucks with refrigerant R134a superheated gas and gas-liquid two-phase mixture. Under three operating modes (air-conditioning – freezing, refrigerating – freezing, and air-conditioning – refrigerating modes) of the ejector, by varying liquid volume fraction of the two inlets of the ejector in the range of 0–0.1, the variation trends of primary mass flow rate, secondary mass flow rate and entrainment ratio were obtained. The results indicated that: (1) when secondary fluid is superheated gas, with the increase of primary flow liquid volume fraction, the ejector performance degrades greatly, even reflux occurs; (2) primary mass flow rate is not affected by secondary flow liquid volume fraction; (3) when secondary flow liquid volume fraction reaches a certain value, secondary mass flow rate increases with the increasing of primary flow liquid volume fraction; and (4) for three modes, the entrainment ratio change is the greatest when liquid volume fraction increases from 0 to 0.02. The novelty of this study is that the effects of different liquid volume fraction in the primary inlet and secondary inlet on the ejector performance are identified.