Experimental study on the heating performance of a variable speed CO 2 heat pump with a variation of operating conditions

Honghyun Cho, Ho Sung Lee, Yonghee Jang, Yongchan Kim

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2 Citations (Scopus)


The applications of a transcritical CO2 cycle into water heaters show advantages over conventional systems in the respect of power consumption and heating efficiency because the CO2 cycle has a high compressor discharge temperature. Besides, the heating performance of the transcritical CO2 cycle can be improved by optimizing operating conditions. In this study, the heating performance of a variable speed CO2 heat pump was measured and analyzed by varying refrigerant charge amount, EEV opening, compressor frequency and outdoor temperature. As a result, the optimum normalized charge for heating was 0.226. The COPs at the compressor frequencies of 40, 50 and 60 Hz were 2.94, 2.75 and 2.25, respectively. The heating performance of the CO2 cycle with charge amount was more sensitive than the cooling performance. Moreover, the heating performance was improved significantly by optimizing of compressor frequency and EEV opening.

Original languageEnglish
Pages (from-to)694-701
Number of pages8
JournalTransactions of the Korean Society of Mechanical Engineers, B
Issue number8
Publication statusPublished - 2007 Aug 1



  • Carbon dioxide
  • Coefficient of performance
  • Heating performance
  • Transcritical cycle

ASJC Scopus subject areas

  • Mechanical Engineering

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