Subcooling systems in transcritical CO2 refrigeration cycles. Experimental evaluation of energy improvement

Abstract

The F-Gas regulation regulates or prohibits the use of certain refrigerants in refrigeration installations in order to reduce greenhouse gasses emissions and mitigate global warming. This leaves CO2 as the best solution to implement in centralized commercial refrigeration facilities. The problem arises especially in hot climates, where simple CO2 cycles are not very efficient. To improve the efficiency of such systems two cycles have been designed: dedicated mechanical subcooling (DMS) and integrated mechanical subcooling (IMS). The theoretical and experimental study of these systems has allowed determining their operating and improvement limits. The main experimental results show that the IMS provides increases in COP of 4.1% at 25.0ºC, 7.2% at 30.4ºC and 9.5% at 35.1ºC and the DMS of 7.8%, 13.7% and 17.5% respectively, when compared to the use of the parallel compressor for an evaporation level of -10ºC.