Abstract
The share of the energy consumption of supermarkets in the total national consumption cannot be neglected, since it reaches up to 5%. In addition, the electricity used for the refrigeration, and heating, ventilation and air conditioning (HVAC) systems is the highest share of the total energy demand of the supermarket. Therefore, any enhancement of the performance of these systems will have an environmental and cost impact both on the supermarket sector and on the country itself. R744 appears as the preferred solution for centralized commercial refrigeration systems, however, it is crucial to improve their efficiency to eliminate previous geographical limits of applying these refrigerant and to make these units competitive in warmer climates. Therefore, it would wise to implement components such as ejectors and a parallel compression suction group in the R744 refrigeration units, and to meet and integrate all the different demands of a supermarket; refrigeration, HVAC and domestic hot water (DHW), with a single unit. This new concept of integrated R744 ejector supported parallel compression racks needs to be further studied, since it involves many control and optimisation issues never approached before, such as the floating pressure of the receiver, the air conditioning (AC) ejectors with pressure lift control, the use of compressors with pivoting suction group connections, etc. This study is part of the SuperSmart-Rack project, funded by the Norwegian Research Council and industrial partners. In this paper the optimization of operation conditions is approached with steady state simulations using a numerical model based on boundary conditions of the experimental facility available in the laboratory of NTNU/SINTEF in Trondheim.