Performance improvements of R744 glass door merchandiser using low-cost two-phase ejector.

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. Earlier studies demonstrated 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 this present study, the performance of the R744 refrigeration system has been further improved by implementing a very small-scale ejector, a device that uses the expansion of a high-pressure fluid to provide a pumping effect to a low pressure fluid. A low-cost design has been devised and implemented. Performance of the improved system is compared against the baseline without ejector in terms of energy consumption and production pull-down times.