A DDC-based capacity controller of a direct expansion (DX) air conditioning (A/C) unit for simultaneous indoor air temperature and humidity control - Part II: Further development of the controller to improve control sensitivity

Zheng Li, Shiming Deng

Research output: Journal article publicationJournal articleAcademic researchpeer-review

36 Citations (Scopus)


The development of the novel direct digital control (DDC)-based capacity controller for a direct expansion (DX) air conditioning (A/C) unit having variable-speed compressor and supply fan to simultaneously control indoor air temperature and relative humidity (RH) in a conditioned space served by the DX A/C unit has been reported in Part I of the two-part series. The results of preliminary controllability tests for the novel capacity controller presented in Part I, however, suggested that the controller developed was operational, with acceptable control accuracy but rooms for improvement with respect to control sensitivity. This paper, the second part of the two-part series, reports on the further development of the controller to improve its control sensitivity and the associated controllability test results. Both control accuracy and reasonable control sensitivity were achieved by incorporating a traditional Proportional-integral (PI) controller into the DDC-based capacity controller.
Original languageEnglish
Pages (from-to)124-133
Number of pages10
JournalInternational Journal of Refrigeration
Issue number1
Publication statusPublished - 1 Jan 2007


  • Air conditioning
  • Capacity reduction
  • Compression system
  • Design
  • Experiment
  • Improvement
  • Refrigeration system
  • Regulation
  • Variable speed

ASJC Scopus subject areas

  • Food Science
  • Mechanical Engineering

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