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7th European Thermal-Sciences Conference (Eurotherm2016) IOP Publishing Journal of Physics: Conference Series 745 (2016) 032157 doi:10.1088/1742-6596/745/3/032157 R744 ejector technology future perspectives Armin Hafner1 and Krzysztof Banasiak2 1 NTNU (Norwegian University of Science and Technology), 7491 Trondheim, Norway E-mail: Armin.Hafner@ntnu.no 2SINTEF Energy Research, 7465 Trondheim, Norway E-mail: Krzysztof.Banasiak@sintef.no ABSTRACT Carbon Dioxide, CO2 (R744) was one of the first commonly applied working fluids in the infancy of refrigeration more than 100 years ago. In contrast to ammonia it mainly disappeared after the first generation of synthetic refrigerants have been introduced to the market after 1930. One reason was that the transition from low-rpm belt driven compressors towards the direct electrical motor driven compressors (50-60 Hz) was not performed for CO2 compressors before the revival introduced by Gustav Lorentzen in the 90is of last century. Since 1988 an enormous R & D effort has been made to further develop CO2 refrigeration technology in spite of the opposition from the chemical industry. Today CO2 refrigeration and heat pumping technologies are accepted as viable and sustainable alternatives for several applications like commercial refrigeration, transport refrigeration, vehicle air conditioning & heat pumping, domestic hot water heat pumps and industrial applications. For some applications, the current threshold to introduce R744 technology can be overcome when the system design takes into account the advantage of the thermo dynamical- and fluid properties of CO2. I.e. the system is designed for transcritical operation with all it pros and cons and takes into consideration how to minimize the losses, and to apply the normally lost expansion work. Shortcut-designs, i.e. drop in solutions, just replacing the H(C)FC refrigeration unit with an CO2 systems adapted for higher system pressures will not result in energy efficient products. CO2 systems do offer the advantage of enabling flooded evaporators supported with adapted ejector technology. These units offer high system performances at low temperature differences and show low temperature air mal-distributions across evaporators. This work gives an overview for the development possibilities for several applications during the next years. Resulting in a further market share increase of CO2 refrigeration and heat pump systems, as energy efficient alternatives to current systems not applying natural working fluids. 1. Introduction Globally, the number of heat pumping equipment in operation is growing and its energy demand, due to rising living standards across the world. Currently about 15% of the global electric is used by heat pumping devices. These units are vital means to realize fundamental needs of humans regarding thermal comfort, water heating, food security & conservation, and healthcare. The European F-gas regulation EU 517/2014 will boost the uptake of sustainable refrigeration and heat pumping technology applying natural working fluids (NWF). Vendors within this industrial sector, able to introduce high energy efficient refrigeration and heat pumping systems utilizing NWFs, will have a significant competitive advantage on the European and global markets. As indicated earlier by Lorentzen [15] there is always a risk of creating harmful effects to the environment when synthetic refrigerants are lost to the atmosphere. Humans do have a long record list with new chemicals believed to be a benefit to mankind turned out to be environmentally unacceptable; examples are DDT, PCB, Pb, CFC's, HCFC's and nowadays HFC's. As mentioned by Lorentzen [15], in this situation, when Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Published under licence by IOP Publishing Ltd 1PDF Image | R744 ejector technology
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