Experimental comparison of critical performance for variable geometry ejectors with different mixer structures

Abstract

To further optimize the performance of Solar-driven Ejector Refrigeration system under variable driving conditions, ejectors design using conical-cylindrical mixers are more effective than using cylindrical mixers were elucidated. The effects of the nozzle exit position (NXP), area ratio (Ar), and expansion ratio (E) on the performance of the conical-cylindrical mixer ejector (CCME) and the cylindrical mixer ejector (CME) were investigated. It was revealed that compared with the performance of the CME at the optimal nozzle exit position, the variable geometry CCME exists a NXP range where both the critical entrainment ratio (Ercri) and critical compression ratio (Ccri) are larger. This NXP range can be widened by appropriately reducing the NXP or Ar of the CCME under a specified expansion ratio. Besides, under variable expansion ratios, the expansion ratio range in which both Ercri and Ccri of the CCME are better than those of the CME can be widened by appropriately reducing the NXP or Ar of the CCME. The results demonstrated that the CCME is more suitable for variable expansion ratios than the CME. This implies that using the variable geometry CCME has a higher energy utilization efficiency in a Solar-driven Ejector Refrigeration system than that of using the CME. This work provides a promising guide for achieving higher energy efficiency of an ejector refrigeration system under variable driving conditions.