CFD-Based Optimization of the Supersonic Nozzle Used in Ejector Refrigeration Systems

This research optimizes the design of supersonic nozzles for ejector refrigeration systems using computational fluid dynamics (CFD) simulations with ANSYS Fluent 2024. The study investigates the effects of nozzle exit diameters (5.48 mm, 6.48 mm, and 7.48 mm) on system performance. Ejector parameters include a mixing chamber with a 1.67° inlet angle, a 15.96 mm throat length, and a 6° subsonic diffuser angle. Simulations were performed under generator saturation temperatures of 85°C–95°C, evaporator temperatures of 5°C–10°C, and a constant condenser temperature of 28°C, using refrigerants R1233zd and R1224yd. The results indicate that the 6.48 mm nozzle diameter provides the highest Mach number (2.85) and mass entrainment ratio (0.570) at an evaporator temperature of 6°C. As the evaporator temperature increases to 8°C–10°C, the optimal nozzle diameter changes to 5.48 mm, with the highest mass entrainment ratio of 0.72. Additionally, R1233zd outperforms R1224yd in terms of sound speed and mass flow ratios across all conditions. These findings suggest that nozzle size and refrigerant type significantly impact the performance of ejector refrigeration systems.