Parametric Effects of Mixing Channel Geometry on Entrainment Characteristics of Ejector in R410A Heat Pump Systems

The two-phase ejector has gained prominence in heat pump systems as a device that effectively mitigates throttling losses through expansion work recovery. This investigation employs three-dimensional computational fluid dynamics (CFD) simulations to analyze the parametric effects of the mixing channel geometry on the entrainment characteristics in an R410A ejector. After validating the model according to the experimental data, the parameter analysis was carried out, and four key geometric parameters were changed within a certain range: the nozzle exit position (NXP = 13–19 mm), the pre-mixing channel convergent angle (CA = 20–60°), the diameter ratio (DDR = 5.0–7.1), and the length-to-diameter ratio (LDR = 8.9–12.4). Multi-variable optimization studies revealed optimal geometric configurations at NXP = 17 mm (about 3.5Dmix), CA = 30°, DR = 6.4, and LDR = 11.1, yielding an optimized mass entrainment ratio enhancement of 23.6% compared to baseline designs. This research provides actionable guidelines for the design of high-efficiency ejector components for heat pump applications.