Visualization experimental study of the condensing flow regime in the transonic mixing process of desalination-oriented steam ejector

Abstract

There are few available related studies about condensing flow regime in the transonic mixing process of steam ejector due to its extreme complexity, although it is of great importance for improving ejector entrainment performance and broadening its application. In this paper, a visualization experimental platform of desalination-oriented steam ejector is designed, and the condensing flow regimes under various entrainment pressures pH are captured from multiple perspectives, by means of direct photography approach. The results reveal that the supersonic jet flow is full with massive amounts of condensation droplets whose particle size distribution is not uniform at various vertical positions, and some easily lose their dynamic equilibrium. There exists a slant reverse condensing flow cross-section at the mixing chamber end, which moves upstream as pH rises and where great numbers of condensation droplets constantly generate around. The condensate quantity of each observation surface is different and increases with pH. The reverse condensing flow regime formed is very complex and accompanied by flexible swirls, clockwise circumferential flow and condensate dynamic accumulation. Then the generated condensate significantly reduces after multiple evaporations downstream the reverse cross-section. It is also found that the flow regime is similar at a same field of view, but diverse at the different fields of view. These meaningful results could serve as a good start point for reducing internal irreversible losses and tailoring ejector design, as well as refining and evaluating physical and mathematical two-phase flow ejector models.