Study on the key ejector structures of the waste heat-driven ejector air conditioning system with R236fa as working fluid

► R236fa is suggested to improve the ejector performance and system feasibility. ► R236fa makes the heat exchangers easy to build on safety and economic considerations. ► The optimized main geometries were drawn and the entrainment ratio can reach 0.24. ► It was found that the experimental results agreed well with the CFD results. The ejector performance is numerically and experimentally studied using R236fa as working fluid to analyze the influence of the key geometries of ejector. The computational fluid dynamics (CFD) was employed to predict the flow process and performance of the ejector. A case study was provided in this paper, in which the angles of nozzle outlet were 8°, 10° and 14°, the distance of nozzle exit to mixing chamber was varied as 23 and 33mm and the length of diffuser was varied as 88 and 103mm. The CFD results were verified with an experiment. It can be concluded that, the ejector with the nozzle outlet angle of 8°, the distance of nozzle exit to mixing chamber of 23mm and the diffuser length of 88mm has the best performance.