Experimental Performance of a Prototype Carbon Dioxide Compressor

Implementing carbon dioxide (CO2) as a natural refrigerant in heating and cooling applications is becoming a technology of increasing importance. This report discusses the performance of a CO2 prototype compressor and compares the results with its predecessor prototype and other prototype compressors. The compressor tested was a semi-hermetic, single-stage, axial configuration with an estimated cooling capacity of 10-14 kW. Testing was performed utilizing a hot-gas bypass test apparatus. While operating at steady-state conditions, parameters such as suction pressure, suction temperature, discharge pressure, discharge temperature, refrigerant mass flow rate, and compressor power consumption were measured and recorded. Thermodynamic properties and performance measures were calculated from the experimental data using software programs such as REFPROP and Engineering Equation Solver. The results of the testing indicated volumetric efficiencies ranging from 67-75%; isentropic efficiencies ranging from 49-73%; and overall isentropic efficiencies of 38-59%. Significant improvements were seen relative to the predecessor prototype compressor. When compared to other carbon dioxide compressors tested, this prototype also demonstrated competitive performance marks.