Characteristic analysis and performance optimization of a transcritical CO2 heat pump for high-temperature heating: An experimental study

Abstract

Based on the improved experiment, a study on the characterization and optimization of transcritical CO2 heat pumps for high-temperature heating is conducted through the combined analysis perspective of thermal quality and heat capacity, as well as the proposed indicator. The result shows that: In the heat transfer process of the gas cooler, the thermal quality of CO2 is closely related to the variation of discharge pressure and compression ratio, and the temperature rise of water shows a corresponding three stages; An increase in the heating temperature (th) requires a higher level of thermal quality on the CO2 side, which exacerbates the heat capacity mismatch in the gas cooler; The elevated compressor speed (ncom) can effectively alleviate this mismatch, but an excessive ncom can instead cause a reduction in system COP; In the study, the COP of the system is improved by up to 26.12 % by optimizing the throttle opening benchmark, and it is further enhanced by up to 19.91 % through the synergistic control strategy optimization; Consequently, the optimized COP can be obtained 2.204 when the required th is 100 °C; Furthermore, the introduction of IHX significantly benefits the high-temperature heating performance of the system and the COP lifting studied ranges 3.70%–14.12 %.