Comprehensive study of high temperature heat pump configurations: A framework of performance and application

High temperature heat pumps (HTHPs) are essential technology for the electrification of industrial thermal processes. However, their widespread deployment is conditioned by the development of a framework for selecting the optimal HTHP configuration and refrigerant. In this paper, thermodynamic models are developed for estimating the performance of various HTHP configurations: single-stage, two-stage, cascade, Joule-Brayton, mechanical vapor re/compression HTHPs working with low-GWP refrigerants. The results are used to construct a new map of HTHP performance and selection. This represents a systematic, concise, and visual framework to guide the selection of the appropriate HTHP configuration that achieves a high COP for a given temperature lift and of the refrigerant that maximizes the COP. The map illustrates the influence of temperature conditions and the limitations imposed by compressors and refrigerants. Joint evaluation of HTHP configuration, refrigerant, and compressor technology extends achievable temperatures (evaporation temperature between 10 °C and 90 °C, condensation temperature up to 250 °C for closed vapor compression cycles, and up to 350 °C for open vapor compression cycles, and maximum temperature above 500 °C for gas compression cycles). Additionally, centrifugal compressors are shown to be applicable in HTHPs, considering the limitations in impeller peripheral speed (for refrigerants with small molecular mass) and fluid flow Mach number (for refrigerants with large molecular mass), as well as their implications on the achievable temperature lift. This indicates that high heating capacity HTHPs can be realized. An original system design diagram of industrial multi-energy systems shows the appropriate application of different HTHP configurations across suitable temperature levels.