Experimental evaluation of a CO2 transcritical refrigeration plant with dedicated mechanical subcooling

CO₂ transcritical refrigeration cycles require optimization to reach the performance of conventional solutions at high ambient temperatures. Theoretical studies demonstrated that the combination of a transcritical cycle with a mechanical subcooling cycle improves its performance; however, any experimentation with CO₂ has been found. This work presents the energy improvements of the use of a mechanical subcooling cycle in combination with a CO₂ transcritical refrigeration plant, experimentally. It tested the combination of a R1234yf single-stage refrigeration cycle with a semihermetic compressor for the mechanical subcooling cycle, with a single-stage CO₂ transcritical refrigeration plant with a semihermetic compressor. The combination is evaluated at two evaporating levels of the CO₂ cycle (0 and ?10 °C) and three heat rejection temperatures (24, 30 and 40 °C). The optimum operating conditions and capacity and COP improvements are analysed with maximum increments on capacity of 55.7% and 30.3% on COP.