Multi-ejector concept for R-744 supermarket refrigeration

• A calculation method to identify energy savings for different supermarket layouts is presented.
• Models for supermarket refrigeration and heat recovery systems with ejector are implemented.
• Measurements on a R-744 ejector prototype show an averaged ejector efficiency of about 20%.
• The multi-ejector system shows significant COP increase for both cooling and heating mode.

Supermarkets are commercial buildings with major energy consumption and relatively large contribution to direct emissions of greenhouse gases through refrigerant emissions of the refrigeration and air condition system. The majority of the European systems are applying HFC-404A as working fluid. Average annual leakage rates in Europe are in the range of 15–20% of the total charge. Worldwide the figure is about 30% and HCFC-22 being the main refrigerant in use. Systems applying R-744 as the only refrigerant have been developed and more than 2000 supermarkets exists in Europe, mainly in northern and mid-European countries. However, the systems still have large potential in development with respect to energy efficiency, heat recovery and cost efficiency. In this paper efficiencies and capacities for an R-744 supermarket system layout with ejectors and heat recovery have been compared for different climate conditions. First results show relevant improvements in system efficiency of up to 30%.