Study on evolution laws of two-phase choking flow and entrainment performance of steam ejector oriented towards MED-TVC desalination system

Abstract

In this study, a visualizable experimental platform of steam ejector oriented towards MED-TVC desalination system is constructed, and the evolution laws of two-phase choking flow and ejector's entrainment performance under various operating parameters are obtained. Further, a matching double-choking theory with consideration of the condensing flow is developed to explain the inherent reason behind these evolution laws. Key results revealed that the formed two-phase choking flows have great effects on ejector's entrainment performance. The primary jet flow choking area linearly increases as the primary steam pressure raises, and the entrainment choking area experiences a small reduction, while the extended flow area marginally increases. Accordingly, the entrainment ratio significantly decreases, while the choking cross-section is slightly shifted upstream. In addition, the primary jet flow choking area considerably decreases with increasing entrainment pressure, but the entrainment choking area is nearly unchanged and the extended flow area increases by more than 8 times. As a result, the entrainment ratio remarkably increases, the choking cross-section migration distances are much larger than that in the case of primary steam pressure varies. A meaningful guide evolves from fact that priority should be given to restrain the condensing flow for achieving a higher energy efficiency of ejector.