Effect of droplets in the primary flow on ejector performance of MED-TVC systems

Abstract

The performance of an ejector, as a crucial component that determines the operating efficiency of the multi-effect distillation system, is closely related to the state of the motive steam. However, the motive steam may be accompanied by droplets during system operation, which decreases the dryness of the motive steam. Nine wet-steam numerical models with different droplet mass fractions and numbers were established to investigate the influence of droplets in the primary flow on the performance and condensation phenomenon of the ejector. The results showed that as the droplet mass fraction of the primary flow increased from 0 to 0.12, the entrainment ratio (ER) of the ejector decreased by 9.15%, and the condensation intensity at the throat of the primary nozzle and the outlet of the primary nozzle decreased by 2.9% and increased by 201%, respectively. In addition, as the droplet number increased from 6 to 14, the ER of the ejector and condensation intensity at the throat of the primary nozzle varied merely between 1.5% and 1.8%, whereas the condensation intensity at the outlet of the primary nozzle fluctuated by 50%. Therefore, the presence of droplets in the primary flow of the ejector cannot be ignored. Some steam–water separation measures must be adopted to ensure efficient operation of the ejector.