Cooling and heating performances of a CO2 heat pump with the variations of operating conditions

Honghyun Cho, Changhyun Baek, Eungchan Lee, Hun Kang, Yongchan Kim

Research output: Contribution to journalArticlepeer-review


Since operating conditions are significantly different for heating and cooling mode operations in a CO2 heat pump system, it is difficult to optimize the performance of the CO2 cycle. In addition, the performance of a CO2 heat pump is very sensitive to outdoor temperature and gascooler pressure. In this study, the cooling and heating performances of a variable speed CO2 heat pump with a twin-rotary compressor were measured and analyzed with the variations of EEV opening and compressor frequency. As a result, the cooling and heating COPs were 2.3 and 3.0, respectively, when the EEV opening was 22%. When the optimal EEV openings for heating and cooling were 28% and 16%, the cooling and heating COPs increased by 3.3% and 3.9%, respectively, over the COPs at the EEV opening of 22%. Beside, the heating performance was more sensitive to EEV opening than the cooling performance. As the compressor speed decreased by 5 Hz, the cooling COP increased by 2%, while the heating COP decreased by 8%.

Original languageEnglish
Pages (from-to)454-462
Number of pages9
JournalTransactions of the Korean Society of Mechanical Engineers, B
Issue number6
Publication statusPublished - 2008 Jun


  • Carbon dioxide
  • Coefficient of performance(COP)
  • Electronic expansion valve(EEV)
  • Transcritical cycle

ASJC Scopus subject areas

  • Mechanical Engineering


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