SELF CONTAINED WATER CONDENSED REFRIGERATED DISPLAY CABINET: EXPERIMENTAL DATA ANALYSIS OF A CARBON DIOXIDE UNIT, WITH COMPARISON OF SYSTEM PERFORMANCE EFFICIENCY AND ENVIRONMENTAL IMPACT

Recently, a number of supermarket applications were realized, in which refrigerated display cabinets are equipped with variable speed compressor unit connected to a water loop. The water loop connection allows to remove the heat from the cabinet, and to either reject it in the external environment or to re-use it in a heating demanding side of the plant. The rotational speed of the compressor and the evaporation temperature of each unit are dynamically adapted to the current real field condition faced by the cabinet. By doing so, the performance of the cabinet was optimized throughout the daily and seasonal conditions of the indoor environment. The water loop can include an additional water chiller, which may be used either as a heat pump during the winter or promoting efficiency during the summer. This generates various application scenarios in a commercial building, depending on the size and type of building thermal loads. The first examples of such systems were based on R410A, but environmental concerns arising with the existing regulation in Europe are pushing towards the creation of alternative refrigerant. One valid alternative in this sense is represented by carbon dioxide. We realized a unit running on carbon dioxide tested on vertical cabinets. In this paper we report our experimental results, presented together with an analysis of the performances in terms of technological potential, environmental impact, and energy consumption compared with similar unit developed with R410A.