Real gas effects on the aerodynamic design and modelling for high-temperature heat pump centrifugal compressors

High-temperature heat pump (HTHP) technology holds significant potential for low-grade waste heat recovery and industrial heat supply, and it is advancing towards higher heating capacities and temperature lifts. The centrifugal compressor is a key component in HTHP and needs to meet the requirements for high pressure ratio, high temperature, and high efficiency. For HTHPs, organic fluids such as R245fa and R1233zd(E) exhibit real gas characteristics, which significantly influence the aerodynamic performance of the compressor, thereby limiting the accuracy of performance prediction. Practical experience indicates that impellers designed using conventional commercial software often exhibit poor performance and significant deviations between the calculation results and the experimental data. This study accounts for the real gas effects of organic fluids and corrects the traditional performance prediction model for centrifugal compressors. The key novelty of the proposed model are the explicit velocity-driven real-gas total-to-static isentropic formulation, and an improved slip factor model that incorporates a blade turning term and Reynolds number. Experimental data were collected by conducting centrifugal compressor tests under various operating conditions on an HTHP test loop. A comparison between the experimental data and the model prediction results shows that the proposed model reduces the pressure ratio error to ±2.0% and the isentropic efficiency error to ±3.5%, effectively improving the accuracy of the performance prediction model, indicating that real gas thermal properties are critical for accurate performance prediction of compressors using organic fluids. Therefore, this study offers a reliable method for performance prediction and preliminary design of centrifugal compressors for HTHP.