Experimental study on the performance of a twin-screw CO₂ compressor in NH₃/CO₂ cascade refrigeration system

A twin-screw compressor with CO₂ as the working fluid is investigated experimentally for using it inNH₃/CO₂ cascade refrigeration system. Experimental measurement was conducted for the CO ₂ low-temperature cycle in the cascade system. The analysis of the compressor efficiencies and power consumption is performed. Mathematical expressions of the volumetric efficiency and isentropic efficiency are obtained with a regression method. The absolute values of the maximum deviations between the results using the regression correlations and the experiment data in this study are lower than 8 per cent. The effect of oil injection pressure on the compressor performance is also studied. It is indicated that the oil injection pressure of the compressor should not be too high to enhance the compressor efficiencies and decrease the power consumption on the premise of fulfilling the compressor works.