Theoretical investigation on the combined and cascade CO2/R134a heat pump systems for space heating
Theoretical investigation on the combined and cascade CO2/R134a heat pump systems for space heating
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DOI：
10.1016/j.applthermaleng.2017.06.014
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发表时间：
2017-09
影响因子：
6.4
通讯作者：
Yulong Song;Dongzhe Li;F. Cao;Xiaolin Wang
中科院分区：
文献类型：
--
作者：
Yulong Song;Dongzhe Li;F. Cao;Xiaolin Wang
本文对CO2/R134 a热泵系统与CO2/R134 a热泵系统进行了理论比较。研究了不同工况下R134 a和CO2联合循环和复叠循环的特性。首先对R134 a循环中的蒸发温度和CO2循环中的排放压力进行了评估。结果表明，当热水供应温度从55 ° C升高到75 °C时，复叠式系统中R134 a蒸发温度的变化幅度远大于组合式系统。在所有工况下，复叠系统的CO2排放压力均远低于组合系统。然后在两个系统中检查两个循环中的加热能力。结果表明，在联合系统中，CO2循环起主要作用，而在复叠系统中，R134 a循环起主要作用。系统性能系数比较表明，级联系统表现较好，在相对较低的环境温度和热水供应温度，而组合系统表现较好，在高热水供应温度。压缩机排量比的比较结果表明，与级联系统相比，组合系统将更加环保。
In this study, comparison between combined and cascade CO2/R134a heat pump systems were investigated theoretically. The characteristics of the R134a and CO2cycles 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 CO2cycle 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 °C. The CO2discharge 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 CO2cycle 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.