High-efficiency, low-cost glass door merchandisers using transcritical carbon dioxide.

Glass door merchandisers are used in grocery and convenience stores to display chilled beverages or refrigerated foods. Among other possible choices for this application, carbon dioxide (R744, CO2) is seen as a promising low global warming potential (GWP) refrigerant alternative that is non-flammable and non-toxic. This study demonstrates that it is possible to design high-performance transcritical R744 glass door merchandiser systems that deliver cooling capacities and energy efficiencies that are comparable to results obtained with an R134a baseline system. In the present case, pull down time of the improved R744 system was slightly lower (97%), while energy efficiency was almost equal (103%) for tests conducted at an elevated ambient temperature of 32°C and 65% relative humidity. The most important observation is that these promising system results were obtained with low-cost technology, which was very comparable to what was used in the R134a system.