EXPERIENCE WITH R744 REFRIGERATING SYSTEMS AND IMPLEMENTED MULTI EJECTORS AND LIQUID OVERFEED

摘要

Two CO_2 refrigerating systems with parallel compression and ejectors have been designed, installed andrncommissioned in 2014 in a Swiss supermarket. Additional components and measuring instruments arerninstalled, so that different operation modes and control strategies can be investigated. Recorded data fromrnthe first year of operation are analyzed.rnSince the end of 2014, the systems are running in the ejector operation mode. The ejectors recoverrnexpansion work which normally is lost. The recovered work is applied to return liquid and vapour from thernMT suction accumulator downstream of the MT evaporators back to the medium pressure receiver. Due tornthe liquid ejectors and the MT suction accumulators, the MT suction pressure of system A was raised fromrn-8℃ up to -2℃ and of system B from -8℃ up to -3℃. Further, the systems are equipped with an LTrnsuction accumulator and two internal heat exchangers. Thereby, the LT suction pressure of system A andrnB was raised from -33℃ up to -26℃. Switching from booster operation mode to ejector operation mode,rnthe energy consumption of the systems has been reduced by 15 to 20%. Depending on the application,rnclimatic region and the demand of the heat recovery, the annual energy efficiency improvement of ejectorrnsupported CO_2 refrigerating systems compared to ordinary CO_2 systems with parallel compression isrnbetween 15 to 25%.