Modeling and simulation of the transcritical CO 2 heat pump system

Kai Hsiang Lin, Cheng Shu Kuo, Wen Der Hsieh, Chi-Chuan Wang*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


In this study, a CO 2 transcritical cycle model without imposing any excessive constraints such as fixed discharge pressure and suction pressure is developed. The detailed geometrical variation of the gas cooler and the evaporator have been taken into account. The model is validated with the experimental measurements. Parametric influences on the CO 2 system with regard to the effect of dry bulb temperature, relative humidity, inlet water temperature, compressor speed, and the capillary tube length are reported. The COP increases with the dry bulb temperature or the inlet relative humidity of the evaporator. Despite the refrigerant mass flowrate may be increased with the inlet water temperature, the COP declines considerably with it. Increasing the compressor speed leads to a higher heating capacity and to a much lower COP. Unlike those of the conventional sub-critical refrigerant, the COP of the transcritical CO 2 cycle does not reveal a maximum value against the capillary tube length.

Original languageEnglish
Pages (from-to)2048-2064
Number of pages17
JournalInternational Journal of Refrigeration
Issue number8
StatePublished - 1 Dec 2013


  • Carbon dioxide
  • COP
  • Gas cooler
  • System modeling
  • Transcritical

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