Numerical Study and Experimental Comparison of CO2 Reciprocating Compressors for Small Cooling and/or Freezing Capacity Applications

The present paper is a numerical and experimental comparative study of hermetic and semi-hermetic reciprocating compressors working with carbon dioxide as fluid refrigerant against the conventional R134a hermetic compressors.When cooling conditions for one-stage compressor type (i.e., evaporation temperatures between 7.2ºC and -10ºC) have been considered, the numerical and experimental results obtained have shown a reasonable good agreement, while the comparative global values have indicated very similar efficiencies between the carbon dioxide compressor and the conventional ones.In all these cases the CO 2 semi-hermetic compressor presents higher mass flow rate and better efficiency than the CO 2 hermetic compressor.However, when freezing conditions are analysed (i.e., evaporation temperature between -10ºC and -40ºC) the onestage CO 2 compressor shows lower COPs in comparison with R134a conventional compressor.In these cases a numerical study of the availability of two-stage semi-hermetic reciprocating compressors is presented in order to obtain comparative or even better efficiencies against conventional hermetic reciprocating compressors.