Performance analysis and energy saving potential of an ejector-enhanced CO₂ refrigeration system for supermarkets.

To improve the usability of the CO2 supermarket refrigeration system in warmer zones, two types of ejectorenhanced CO2 refrigeration systems (ECRS, DECRS) combining ejectors and subcooling to improve the system efficiency by subcooling and replacing the expansion valve are proposed as solutions. Three representative cities in China are selected and discussed in detail in energy, exergy and energy saving evaluation. The energy results illustrate that the ejectors significantly improve the system performance, and the higher the ambient temperature, the greater the performance improvement. At the ambient temperature of 45 ◦C, the maximum coefficient of performance (COPmax) of ECRS and DECRS is increased by 21.6 % and 26.3 %, compared to basic CO2 refrigeration system (BCRS). Using subcooling as well as further replacement of the expansion valve with ejector lead to a remarkable reduction of the irreversible loss of the system. In the transcritical zone, the exergy efficiency of ECRS and DECRS improves 11.9 % to 30.5 % and 13.7 % to 31.3 %, compared with BCRS. The energy saving evaluation demonstrates that compared with the annual performance factor of BCRS, in Guangzhou, ECRS can be increased by 5.1 %, and DECRS even reaches 7.1 %, which provides a solution and a certain theoretical basis for the use of ejector systems in supermarket system in warmer zones.