Design and numerical investigation of an adaptive nozzle exit position ejector in multi-effect distillation desalination system

•An adaptive nozzle exit position (ANXP) ejector was proposed for the first time.•An ejector simulation model was established and validated by experimental data.•An optimum NXP range was obtained for the highest performance of ejector.•An optimum NXP correlation was developed to design the ANXP ejector.

Few investigations have been conducted on an ejector that has an auto-tuning capability to regulate the performance of a multi-effect distillation-thermal vapour compression (MED-TVC) desalination system with the variation of operating conditions. In this study, an adaptive nozzle exit position (ANXP) ejector was first proposed to enhance ejector performance by self-adjusting the position of the primary nozzle with the change of primary pressure. A computational fluid dynamics (CFD) model was established and validated using experimental data. Simulation results indicate that there is an optimum NXP range of 43 mm-70 mm for an ejector to achieve its highest performance. The maximum increase of the entrainment ratio is 35.8% compared to that at an NXP of −30 mm. The secondary flow rate first increases and then decreases while the primary flow rate remains unchanged with the increase of the NXP in fixed working conditions. Furthermore, a correlation between optimum NXP and primary pressure was developed to provide designing parameters for the ANXP ejector.