A test rig of the R134a/CO2 cascade supermarket refrigeration system has been built up to get a comprehensive understanding of its performance. The results show that the maximum COP of the system occurred when the condensing temperature of the CO2 cycle was about -2℃

the condensing temperature of R134a and the evaporating temperature of CO2 was settled at 48℃ and -30℃ respectively with a temperature difference of 3℃. Moreover

the COP remained stable while the condensing temperature varied within a certain range of ±5℃. Results also show that the maximum deviation of the compressor adiabatic efficiency is within 4%

the main factor affecting the system cooling capacity is the compressor volumetric efficiency. And the performance of the cascade system could be 3% higher compared with that of conventional R404a refrigeration system at the same condition.