Vapor Overproduction Condition Monitoring in a Liquid–Vapor Ejector

Abstract

We consider the influence of vapor content in the mixed flow leaving a liquid-vapor ejector on the energy efficiency of a vacuum unit. As shown by numerical studies of liquid-vapor ejectors, this issue is important as vapor overproduction, which accompanies the process of secondary flow ejection, directly impacts the efficiency of the working process of both the liquid-vapor ejector and the vacuum unit as a whole. The greater the degree of vapor overproduction, the greater the load on the vapor phase of the separator, which is part of the vacuum unit. In addition, the liquid phase must be returned to the cycle to ensure the constancy of the mass flow rate of the working fluid of the primary flow. Our numerical study results revealed the rational value of the degree of vapor overproduction at which the efficiency of the liquid–vapor ejector was maximized, and the amount of additional working fluid that needed to enter the cycle of the vacuum unit was minimal. Experimental condition monitoring studies on the liquid–vapor ejector were carried out on plane-parallel transparent models with different flow path geometries. Through experimental studies, we confirmed and adjusted the values of the achievable efficiency of the working process of a liquid–vapor ejector, depending on the degree of vapor overproduction. Using a comparative analysis of liquid–vapor ejectors with different flow path geometries, differences were revealed in their working processes, which consisted of the degree of completion of the mixing of the working media of primary and secondary flows. To determine the feasibility of using liquid–vapor ejectors with different flow path geometries, exergy analysis was performed, resulting in achievable efficiency indicators.