Operating characterization and performance optimization of high-temperature heat pumps: A comparative energy, economic and environmental analysis

Abstract

The high-temperature heat pump (HTHP) operates under severe conditions and there is a need for further research into its operating characteristics and performance optimization. In this study, the effect of three optimization strategies, namely vapor injection, subcooling and cascade type, on the system characteristics of the HTHP at varying ambient temperatures (Tam) was investigated. Subsequently, a comparative analysis focusing on energy, economy and environment was conducted. As the result shows: The introduction of vapor injection creates the presence of an optimal intermediate pressure and greatly improves the COP of HTHP by a range of 14.7 %-52.6 %, while the application of an economizer further elevates the COP by 0.6 %-7.0 %; The cascade cycle exists an optimal intermediate temperature and has operating performance advantages at lower Tam. As the condensing temperature increases from 120 °C to 130 °C to 140 °C, the turning Tam rises from 54 °C to 63 °C to 71 °C, respectively; HTHP requires a certain level of Tam to maintain a higher level of system performance to meet economic and environmental requirements. In the research framework, HTHP begins to show economic advantages at a Tam of 10 °C, while it can only generate benefits of emission reduction at a Tam of 65 °C or higher.