Numerical Investigation of the Effects of Primary Nozzle Diverging Portion on Performance of the Supersonic Ejector of an Ejector Refrigeration Cycle

Abstract

A supersonic ejector with desirable performance characteristics reduces the energy consumption rate of an ejector refrigeration system and increases its coefficient of performance (COP). In this paper, the effects of using different primary nozzles on the performance of a supersonic ejector of an ejector refrigeration system have been numerically studied, while the working fluid is steam. To this end, conical, Rao and parallel-flow primary nozzles with identical converging portions and equal exit area to throat area ratios have been tested. The diverging portion curves for the parallel-flow and Rao nozzles were derived using the method of characteristics. Using the Rao nozzle, the critical entrainment ratio and the critical back pressure were increased compared to the conical nozzle by 6.3% and 2.08%, respectively. It was also found that the physics of the internal flow of the ejector was changed by changing the diverging curve of the primary nozzle.

Optimization of VD/VOD multi-stage serial steam ejectors based on CFD

“…This decrease in values is because the collision of flow vortices to the wall of the mixing chamber in the early stages increases the mechanical energy loss and reduces the effective cross-section for the passage of secondary fluid flow [16]. It is important to note that the internal flow physics of an ejector changes by changing the divergence curve of the primary nozzle [18]. Another crucial geometric factor affecting the performance of the ejector, which directly affects the entrainment ratio and critical outlet pressure, is the place of the primary nozzle outlet.…”