Performance evaluation of CO2 ejector system with parallel compressor for supermarket application
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Evolution in modifications for CO2 system configuration came across from the last two decades has proven to hold the potential in order to improve the overall performance of the CO2 cooling system for various applications. However, performance of the CO2 system at high ambient context is not promising and comparable with popular conventional refrigerants. Due to its unique properties, the CO2 system possesses substantial losses at high ambient temperature due to the throttling process. System configuration with parallel compressor is proven as the most popular and efficient configuration for high ambient temperature (up to 46 °C). In this study performance evaluation of a CO2 multi-ejector based supermarket cooling system of 33 kW cooling capacity with compressor configuration is experimentally evaluated at high ambient temperature (up to 46 °C). Test facility is equipped with two-phase multi-ejector resulting in pressure lift due to the expansion work recovery. Removed flashes in flash gas tank or separator after passing through two-phase ejector, are further compressed with the help of auxiliary compressor configured in parallel but with an additional possession of low compression ratio. High stability with high gascooler pressure and CO2 system consistency at high gascooler outlet temperature is observed. Maximum reduction in the AUX compressor energy consumption observed is 8% for 46 bar & 10.7% for 48 bar receiver pressure at 36 ºC gascooler outlet temperature. Also, the Exergy efficiency of the system observed is 0.315 corresponding to 3.2 PIR at 46 ºC gascooler outlet temperature.