Impact of inlet steam state on ejector internal flow and performance considering non-equilibrium condensation

Abstract

Most of the numerical studies adopted dry gas model to predict transonic and supersonic flow in steam ejectors, but it cannot accurately reflect flow characteristics in ejectors, since the condensation and evaporation of wet steam is ignored. The current work develops and validates a CFD model describing spontaneous condensation to simulate complicated flow behaviors and phase transition inside an ejector, and illustrates the impact of initial state of primary fluid including wet, saturated and superheated state on flow characteristics, mass and heat exchange and ejector performance. It is found that the initial steam wetness obviously impacts the average liquid fraction in the ejector. Both the superheated and wet initial primary steam suppress the process of mass and heat exchange during nucleation, and the position and intensity of nucleation are influenced by the inlet steam state. Compared with the case of dry saturated inlet steam, the superheated inlet steam improves entrainment ratio by 3.7%, and decreases compression ratio by 2.5%.