A holistic design framework of centrifugal compressors for high temperature heat pumps considering wet compression prevention and global optimization

Centrifugal compressors are an attractive option for high temperature heat pumps (HTHPs) due to advantages such as high efficiency, large capacity, and oil-free operation. Proper design of centrifugal compressors is crucial to realizing the desired HTHP performance. Apart from the strong interactions between different cycle components, there are also complex nonlinear correlations between compressor performance and design parameters. Moreover, the wet compression of dry fluids presents an additional challenge for centrifugal compressors operating at high temperature lifts, further complicating the design of centrifugal compressors for HTHPs. This study proposed a holistic design framework of centrifugal compressors for HTHPs based on the mean-line approach. Real fluid properties and generic design parameters are adopted, considering the flow non-ideality and effective utilization of domain knowledge. A wet compression prevention strategy is introduced to ensure a dry compression by identifying the stage component fluid conditions. Furthermore, a global optimization technique integrated with cycle conceptual design is presented to obtain the optimal compressor design. A case study is performed based on the proposed framework. The influence of design and cycle operating parameters is discussed. A comprehensive comparative assessment on the resultant designs is conducted. Moreover, the corresponding loss distributions are investigated. The case study reveals a clear negative correlation between temperature lift and compressor performance, and diffuser losses exhibit a rapid growth as the condensation temperature increases. This work can provide valuable guidelines for the development of HTHPs with centrifugal compressors.