Study on evolution law of non-equilibrium phase transition flow and performance improvement of steam ejector for MED-TVC desalination system

Non-equilibrium phase transition flow is prevalent and of great irreversible loss during the transonic mixing process of steam ejector, but its complex evolution law is thus far unclear. In this study, a considerate two-phase ejector model was developed to investigate the non-equilibrium phase transition flow characteristics by means of CFD numerical simulation, including how, where and to what extent the phase transition occurs. Additionally, the quantitative analysis of the operating parameters influences on the phase transition flow and ejector's entrainment performance were conducted. Results showed that the evolution law of condensate is highly consistent with the pressure fluctuation of shock wave. Non-equilibrium condensation is to be intensified as the primary fluid pressure increases, and the entrainment performance thus worsens. For raising the secondary fluid pressure, the case is opposite, the entrainment ratio ω increases by 17.8 %. Superheating the working fluids can restrain the droplet development, and more small-sized droplets therefore emerge, but ω only raises by a maximum of 3.53 %. However, it is hard to restrain the condensate generation in primary jet flow by superheating the secondary fluid, both suction pressure and ω decrease. This study provides meaningful guidance for reducing the irreversibility loss from non-equilibrium phase transition flow.