R744 EJECTOR SUPPORTED PARALLEL VAPOUR COMPRESSION SYSTEM

摘要

The average energy use of European supermarkets is in the range of 300 to 600 kWh/m~2 (Energy star, 2008;rnArias, 2005). Around 50% of the energy is used to the refrigeration equipment which provides cooling andrnfreezing capacity for the display cabinets and the cold / freezing storage rooms. Most of the currentrnrefrigeration systems are applying HFC 404A as the working fluid. In Accordance to the survey in the latestrnIPCC/TEAP Special Report (2007), the average annual leakage rates of existing European HFC supermarketrnunits are between 15 and 20 % of the total refrigerant charge. On a global perspective the commercialrnrefrigeration leakage rates are around 30 %, while HCFC 22 is the most common refrigerant. Therefore,rneffort should be given to identify alternative refrigerants which are able to improve the energy efficiencyrncompared to current HFC solutions. Preference should be given to natural working fluids, since their longrnterm environmental impact can be foreseen and they minimize the direct GWP contribution.rnCurrently there are more than 2000 commercial refrigeration system, applying carbon dioxide (R744), manlyrnlocated in Central- and Northern Europe. The efficiency challenge related to ordinary R744 booster systemsrnoperated at high ambient temperatures (Finckh, 2011) can be overcome by an improved system design asrndescribed in this paper. As one possible example, an enhanced R744 commercial refrigeration system withrnparallel compressor technology and ejector support is described, as implemented in a large supermarket inrnthe region of Fribourg (Switzerland) during summer 2013. First measurement results are analysed andrnevaluated.