heat driven ejector refrigeration system, hybrid ejector refrigeration system, vapor compression heat pump system, efficiency analysis, ejector numerical model
Recently, the utilization of low-grade thermal energy has gained increased attention as an attractive opportunity to save energy. Heat driven ejector refrigeration systems are among a number of promising solutions for utilizing thermal energy from waste heat. However, the main drawbacks of this system are low efficiency at off-design conditions and difficult controllability. Hybrid ejector refrigeration system is a promising solution for overcoming these drawbacks. In this system, a booster compressor is installed in order to improve the efficiency for a wide range of conditions and substantially improve controllability. In this study, a numerical efficiency analysis for hybrid refrigeration ejector system is performed and compared with conventional ejector system and vapor compression system. The investigations are focused on chilled water supply conditions (evaporation temperature is 5 °C) at various ambient temperature conditions ranging from 15 °C to 35°C. The seasonal performances in Tokyo and Los Angeles for each system are compared. R1234ze(E), which is a promising low-GWP refrigerant, is used in the system. The calculation results show that the hybrid system performance is 142 % higher than ejector system, 16 % higher than vapor compression system in Tokyo, and 86 % higher than ejector system, 21 % higher than vapor compression system in Los Angeles at summer conditions. Therefore, this study clearly demonstrates the potential of the hybrid ejector system.