Performance of a two-stage ejector with varying liquid fraction at its inlet

Abstract

Liquid volume fraction (LVF) in a two-phase flow has a certain effect on the flow performance. In this paper, a two-stage ejector applied to a multi-evaporator refrigeration system was proposed by the authors, in which, the refrigerant of R134a is used and then the effects of different LVF in the two-stage ejector inlet on the two-stage performance were studied by using CFD simulation, which is the novelty of this study. One of the main contributions is that the reason for the changed performance of each stage was explained by analyzing the volume flow rates, density and mass flow rates of the two-phase mixture when the LVF of one, two or three inlets varied. The results show that: (1) when the LVF of one inlet increases, the two-phase mass flow rate can be increased evidently due to the significant increase of the density of the mixture; (2) if one inlet fluid is in two-phase, the improvement of the LVF in the first-stage secondary flow, the performance of the first-stage as well as the second-stage can be improved; (3) if two inlet flows are in two-phase, the increase of the LVF of the two inlet flows of the first-stage with the same proportion can offer the best performance to both stages; and (4) when the LVF of three inlet flows increase from 0.04 to 0.12 with the same proportion, the ER of both stages can be increased evidently.