Multi-ejector R744 booster refrigerating plant and air conditioning system integration – A theoretical evaluation of energy benefits for supermarket applications

The multi-ejector rack is the most promising technology to push the so-called “CO2 equator” further south and improve the global energy efficiency of R744 supermarket refrigeration systems. This paper theoretically compares the energy consumption of a CO2 refrigerating plant equipped with a multiejector unit with that of a R404A direct expansion system (DXS), of a conventional CO2 booster configuration and of two CO2 solutions using parallel compression. The energy benefits related to the adoption of low temperature (LT) overfed display cabinets were also assessed. Furthermore, various scenarios involving different sizes of the supermarket, integration and capacity of the air conditioning (AC) system and efficiency of the parallel compressors were investigated. The evaluations were carried out by considering different locations in Southern Europe. The results showed that, as a function of the selected boundary conditions, energy savings ranging from 15.6% to 27.3% could be accomplished with the multi-ejector concept over DXS.