Effect of water nano-droplet injection on steam ejector performance based on non-equilibrium spontaneous condensation: A droplet number study

Abstract

Condensation and evaporation processes in high velocity flowing steam within ejectors profoundly influence the performance of these devices. In the current study, the effects of water droplet injection in the inlet of the primary nozzle on the condensation and evaporation processes are investigated through the wet steam model. The findings reveal that the existence of liquid droplets in the steam related to the inlet of the primary nozzle has effects on the two-phase parameters, shock waves intensity, entrainment ratio, mixing layer growth and two-phase heat, such that these parameters are minimized or maximized for a specific number of droplets. The inlet wetness in the primary nozzle provides a delay in the condensation shock, and the maximum delay happens in the wetness 0.4%. In the case of using 2.0×1017 droplets with 17.5 nm radius (wetness 0.4%), in comparison with the case of without the droplets at the inlet, the entrainment ratio, primary mass flow rate, and secondary mass flow rate reduce by 2.79%, 0.8%, and 3.72%, respectively. The novelty of this study is displaying the effects of water droplet injection in the inlet of the primary nozzle on the ejector performance.