Reciprocating Compressors, Carbon Dioxide, Hot Gas Cycle
This paper presents the performance measurements of carbon dioxide two-stage reciprocating compressors using a hot-gas load stand.Â The data is used to characterize the compressorsâ€™ performances and evaluate the oil management between the two compressors. A compressor load stand has been redesigned to conduct the compressor performance tests. Two hermetic reciprocating compressors, including two oil separators, two intercooling fans and safety control valves, are connected to the load stand. A membrane tank filled with the working fluid is connected to the load stand, using an appropriate back pressure on the membrane to ensure a fixed intermediate pressure as the anchor point of the hot gas cycle. The first series of compressor tests was conducted for varying suction pressures and varying discharge pressures with different pressure ratios. In a second series, the running time was varied and the suction pressure was kept constant. Based on these measurements, the compressor performance indices, such as the volumetric and overall isentropic efficiencies, have been determined. Furthermore, compressor initial clearance factor can be calculated, based on available compressor maps, which is useful tool for future carbon dioxide system modeling. Also, a simulation model to predict the compressor performance has been developed. The entire process can be simulated to provide the compressor performance data for different working conditions. Finally, the compressor performance measurements are used to validate the model predictions.