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7th European Thermal-Sciences Conference (Eurotherm2016) Journal of Physics: Conference Series 745 (2016) 032157 1st ) 2nd ) IOP Publishing doi:10.1088/1742-6596/745/3/032157 3rd ) Figure 2. Principle circuit architecture of 1st , 2nd and 3rd generation all-CO2 supermarket refrigeration systems Based on the experimental investigations in laboratories and field tests of the CO2 supermarket systems a seasonal energy efficiency improvement of 10% is obtained between the first and second generation. At high ambient temperature operation, another 20% improvement is achievable when adding the multi-ejector technology to a well-designed CO2 parallel compression system. For a successful and rapid implementation of CO2 refrigeration also outside Central and Northern Europe, an acceptable total cost of ownership for the end-users is important. The 2nd and 3rd generation of CO2 supermarket refrigeration systems enable a cost and energy efficient integration of other necessary functions needed in the supermarket, as air-conditioning at correct pressure levels enabled with the parallel compressor and hot water production, as shown in figure 2. As described by Girotto [5], direct heating and AC devices, not requiring water as a secondary fluid should be considered in the future, to further reduce the total cost of ownership for the end-users. When applying hot water production, the drawback of applying CO2 having an increased exergy loss due to transcritical heat rejection compared to conventional condensers, is turned into a benefit. Conventional working fluids do have a challenge to produce 80-90°C water without auxiliary heating, which is not at all a problem for a CO2 unit (see next chapter). Heat recovery for space heating, where needed, has been and will always be an integrated part of the refrigeration systems. This means that in the future the end-user and their service teams just need to maintain one single refrigeration system, applying only CO2 as working fluid. Asia: The typical refrigeration capacity of a condensing unit is in the range of 1 to 20 kW. Several display cabinets and/or AC indoor units are connected to these units, which explain their global popularity for small shops and convenience stores. Currently H(C)FC refrigerants are dominating this market segment, supported by the Asian manufactures of these units. However, there are no technical barriers which would exclude CO2 refrigeration units to become an alternative working fluid for condensing units, In Japan, more than 1000 small supermarkets are successfully converted from HFC’s to CO2 during the past years, as described by Uto [24]. Energy savings of up the 27 % are reported by the end-users. A successful technology transfer has also taken place from Japan to Indonesia ([21], [24]). 12 pilot stores are equipped with the same CO2 technology as in Japan, and their energy saving at these locations, very close the equator, are in the region of 20%, compared the conventional HFC systems. The stores in Indonesia had a 15 % higher turnover after the refurbishment 5PDF Image | R744 ejector technology
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