Energy evaluation of a CO2 refrigeration plant equipped with ejector on the medium temperature suction line liquid separator

Abstract

The EJ installation as a method to reduce energy consumption in commercial refrigeration plants with CO₂ refrigerant has been successfully used by the whole industry in recent years. However, the heat transfer surface of the EV, both on LT and MT consumers, could not be utilized at the maximum capacity because it could not operate at all the time flooded, due to the possibility of liquid droplets entering the compressor’s crankcase. No studies have been found so far in the specialized literature on improving the energy consumption of transcritical CO₂ refrigeration systems in supermarkets that use an EJ on the suction line of the medium-temperature liquid separator. In this paper, the authors analysed a new booster transcritical refrigeration system with EJ and droplet separators, on both cooling circuits, installed in southern Romania, and compare it with standard CO₂ booster refrigeration system. Taking advantage of the experimental measurements, the mathematical model is validated and allows the prediction of the annual performance of the installation under field operating conditions. The model considers how indoor and outdoor conditions impact energy efficiency.  The results showed a significant reduction of energy consumption by 18.3% at the compressor rack level, and by 6.3% at the entire plant, compared to the standard CO₂ transcritical booster system. The new system was also analysed regarding the overall exergy efficiency, and the results indicated an improved efficiency between 7 and 10%, depending on the exterior temperature variance. Knowledge of these performance data from actual installation, equipped with EJ on the medium temperature suction line liquid separator gives the entire industry the opportunity to promote this type of plant for future installations.