2020 PERSPECTIVES FOR CO2 REFRIGERATION AND HEAT PUMP SYSTEMS

摘要

Carbon Dioxide, CO_2, was one of the first commonly applied working fluids in the infancy of refrigerationmore than 100 years ago. In contrast to ammonia it mainly disappeared after the first generation of syntheticrefrigerants have been introduced to the market after 1930. One reason was that the transition from low-rpmbelt driven compressors towards the direct electrical motor driven compressors (50-60 Hz) was notperformed for CO_2 compressors before the revival introduced by Gustav Lorentzen in the 90is of lastcentury. Since 1988 an enormous R & D effort has been made to further develop CO_2 refrigerationtechnology in spite of the opposition from the chemical industry.Today CO_2 refrigeration and heat pumping technologies are accepted as viable and sustainable alternativesfor several applications like commercial refrigeration, transport refrigeration, vehicle air conditioning & heatpumping, domestic hot water heat pumps and industrial applications. For some applications the currentthreshold to introduce CO_2 technology can be overcome when the system design is taking into account andadvantage of the thermo dynamical- and fluid properties of CO_2. I.a the system is designed for transcriticaloperation with all it pros and cons and takes into consideration how to minimize the losses and to apply thenormally lost expansion work. Shortcut-designs, i.e. drop in solutions, just replacing the H(C)FCrefrigeration unit with an CO_2 systems adapted for higher system pressures will not result in energy efficientproducts. CO_2 systems do offer the advantage of enabling flooded evaporators supported with adaptedejector technology which offer high system performances at low temperature differences and lowtemperature air mal-distributions across evaporators.The paper gives an overview for the development possibilities for several applications during the next yearsto further increase the market share of CO_2 refrigeration and heat pump systems.