Performance prediction of centrifugal compressor for drop-in testing using low global warming potential alternative refrigerants and performance test codes

As environmental regulations to stall global warming are strengthened around the world, studies using newly developed low global warming potential (GWP) alternative refrigerants are increasing. In this study, substitute refrigerants, R-1234ze (E) and R-1233zd (E), were used in the centrifugal compressor of an R-134a 2-stage centrifugal chiller with a fixed rotational speed. Performance predictions and thermodynamic analyses of the centrifugal compressor for drop-in testing were performed. A performance prediction method based on the existing ASME PTC-10 performance test code was proposed. The proposed method yielded the expected operating area and operating point of the centrifugal compressor with alternative refrigerants. The thermodynamic performance of the first and second stages of the centrifugal compressor was calculated as the polytropic state. To verify the suitability of the proposed method, the drop-in test results of the two alternative refrigerants were compared. The predicted operating range based on the permissible deviation of ASME PTC-10 confirmed that the temperature difference was very small at the same efficiency. Because the drop-in test of R-1234ze (E) was performed within the expected operating range, the centrifugal compressor using R-1234ze (E) is considered well predicted. However, the predictions of the operating point and operating range of R-1233zd (E) were lower than those of the drop-in test. The proposed performance prediction method will assist in understanding thermodynamic performance at the expected operating point and operating area of a centrifugal compressor using alternative gases based on limited design and structure information.