期刊
APPLIED THERMAL ENGINEERING
卷 124, 期 -, 页码 1457-1470出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.applthermaleng.2017.06.014
关键词
Transcritical CO2 cycle; Cascade heat pump; Combined heat pump; Space heating; Performance
资金
- National Natural Science Foundations of China [51576152]
- science and technology process of Jiangsu province [BA2016051]
In this study, comparison between combined and cascade CO2/R134a heat pump systems were investigated theoretically. The characteristics of the R134a and CO2 cycles in both combined and cascade systems were studied under different working conditions. The evaporation temperature in the R134a cycle and the discharge pressure in the CO2 cycle were first evaluated in the combined and cascade systems. Results showed that the change of the R134a evaporation temperature in the cascade system was much larger than that in the combined system as the hot water supply temperature increased from 55 to 75 degrees C. The CO2 discharge pressures in the cascade system were much lower than those in the combined system under all working conditions. The heating capacity in the two cycles was then examined in the two systems. The results showed that the CO2 cycle played the major role in the combined system while the R134a cycle played the major role in the cascade system. The system COP comparison showed that the cascade system performed better under relatively low ambient and hot water supply temperatures whilst the combined system performed better under high hot water supply temperatures. The compressor displacement ratio comparison results showed that the combined system would be much more environmentally friendly in comparison to the cascade system. (C) 2017 Elsevier Ltd. All rights reserved.
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