Numerical simulation and performance evaluation of ejector refrigeration systems: comparative analysis of single-stage, two-stage, and three-stage ejectors

Abstract

This paper concerns with numerical performance evaluation of a refrigeration cycle with one, two and three-stage ejectors with an integrated ejector structure. The main innovation of this study lies in the integration of the stages in two-stage and three-stage ejectors into a single unified structure, and the numerical investigation of its impact on overall ejector performance compared to a conventional single-stage ejector. This approach simplifies the system, reduces manufacturing costs, enables operation at low absolute pressures, makes better use of the generator, and allows the system to be used under various evaporator operating conditions. Moreover, a comprehensive parametric study has been conducted on the influence of key geometrical parameters—including throat length, throat diameter, convergence angle, and mixing chamber length and area ratio in the second stage—on the performance of the two-stage ejector, which exhibited the highest coefficient of performance. Evaluation of Mach number and pressure variations along the ejector axes reveals that a two-stage ejector significantly enhances the performance of high-capacity refrigeration systems with low condenser pressure, achieving a 53.6% increase in the coefficient of performance. However, in the case of the three-stage ejector, high-pressure gradients at the inlets lead to increased pressure drops and irreversibility, resulting in a 26% decrease in performance compared to the single-stage ejector. © The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering 2025.