RECENT INSTALLATIONS OF CO_2 SUPERMARKET REFRIGERATION SYSTEM FOR WARM CLIMATES: DATA FROM THE FIELD

摘要

CO_2 is a viable solution for supermarket refrigeration in north and central Europe. However, under the pressurernof a wide-spread environmental friendly attitude as well as tighter incoming EU regulations, there is a need tornmake CO_2 systems attractive also in warmer areas, such as Italy and Spain. Improved systems have beenrninstalled so far, mainly using economized cycle with auxiliary compressors. At the same time a large debate isrntaking place amongst researchers to evaluate the possibility of using two-phase ejectors in place of expansionrnvalves to recover expansion work and improve energy efficiency. In the very last months, some plants have beenrninstalled where ejectors are used. In these plants, ejectors can re-circulate liquid through evaporators, thusrnoverfeeding them and improving the overall system energy efficiency by allowing higher evaporationrntemperature, or pre-compress vapour before compressors, thus reducing their work. Liquid recirculation, vapourrnpre-compression and economizer have also been combined according to a specific design.rnIn this paper some innovative installations are presented and data from the field are evaluated, thus showing thatrnimproved design may be efficient as well as technically feasible.