Development of ejector performance map for predicting fixed-geometry two-phase ejector performance for wide range of operating conditions

Recent studies have expanded the operational envelope of ejector by utilizing both pressure recovery and liquid recirculation mechanisms. This necessitates finding a consistent representation of fixed-geometry ejector performance data using only operational variables for predicting ejector performance. Taking inspiration from the compressor performance maps, the study explores the appropriate motive, performance, and characterization variable for representing ejector performance while conducting experiments on a transcritical CO₂ ejector system. The existing ejector efficiency is revisited by conducting ejector power analysis. Two possible motive variables, along with a new ejector efficiency is introduced. The trends of existing and new ejector efficiencies are studied in controlled motive variable experiments while changing suction flow conditions. The ejector performance can be represented with the help of a single curve, termed as ejector performance map, using the new ejector efficiency as performance variable and the volumetric entrainment ratio as characterization variable. The prediction accuracy for both the single-phase and the two-phase suction inlet conditions are evaluated while developing performance map using only the single-phase suction inlet data points. The methodology can predict 89.3% of the data within 20% accuracy. The applicability of the methodology is assessed for other datasets involving different refrigerants, cycle architectures, and applications. The proposed ejector performance map can be utilized in numerical ejector system analysis for investigating new cycle architectures based on ejector experimental data, thus, improving system model fidelity. It can also help system design engineers in making ejector system selection decisions after thorough system performance analysis.