Investigation on the effects of water steam ejector geometry in the refrigeration systems using entropy generation assessment

Abstract

Steam ejector, as a heat pump, plays a key role in ejector refrigeration system which operates with water vapor as an available, economic and environmentally friendly refrigerant. In this research, supersonic steam flow through the ejector is simulated by CFD methods to investigate effects of ejector geometry on its performance. Basic design criteria are entrainment ratio (ER) and critical compression ratio so that the former affects COP of the refrigeration system and the latter changes the temperature at which condenser is operated. For more accurate design, we also investigate the effect of ejector geometry (non-dimensional parameters consist of D/L and d/D) on the entropy generation rate as a design criterion. In fact, increase in ER and COP and decrease in the entropy generation rate are desirable changes in the present work. Among all geometric parameters which affect the entropy generation, the diameter of the throat of the primary nozzle is more effective than the rest. Finally, the ejector geometry has been proposed that make improvement in the ejector ER and COP of the refrigeration cycle up to 32% and 38%, respectively, and reduction of 28% in total entropy generation rate.