Control optimisation of CO2 cycles for medium temperature retail food refrigeration systems

Y. T. Ge*, S. A. Tassou

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

28 Citations (Scopus)


This paper describes a detailed procedure into the investigation of optimised control strategies for CO2 cycles in medium temperature retail food refrigeration systems. To achieve this objective, an integrated model was developed composing of a detailed condenser/gas cooler model, a simplified compressor model, an isenthalpic expansion process and constant evaporating temperature and superheating. The CO2 system can operate subcritically or transcritically depending on the ambient temperature. For a transcritical operation, a prediction can be made for optimised refrigerant discharge pressures from thermodynamic cycle calculations. When the system operates in the subcritical cycle, a floating discharge pressure control strategy is employed and the effect of different transitional ambient temperatures separating subcritical and transcritical cycles on system performance is investigated. The control strategy assumes variable compressor speed and adjustable air flow for the gas cooler/condenser to be modulated to achieve the constant cooling load requirement at different ambient conditions.

Original languageEnglish
Pages (from-to)1376-1388
Number of pages13
JournalInternational Journal of Refrigeration
Issue number6
Publication statusPublished - 1 Sept 2009
Externally publishedYes


  • Carbon dioxide
  • Commercial application
  • Control
  • Modelling
  • Optimization
  • Performance
  • Refrigeration system
  • Transcritical cycle


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