Research on a novel DDC-based capacity controller for the direct-expansion variable-air-volume A/C system

Wu Chen, Shiming Deng

Research output: Journal article publicationJournal articleAcademic researchpeer-review

6 Citations (Scopus)


A direct-expansion (DX) variable-air-volume (VAV) air-conditioning (A/C) system consists of a VAV air-distribution sub-system and a DX refrigeration plant. This paper reports in detail on a novel capacity controller developed for the DX VAV A/C system to regulate its compressor speed and hence its cooling capacity. The capacity controller consisted of both a numerical calculation algorithm (NCA), which was fundamentally based on the principle of energy balance using a number of real-time measured system's operating parameters, and a dead-band for decoupling the control actions from both the capacity controller and a conventional PI feedback controller for regulating the opening of an electronic expansion valve (EEV) in the refrigeration plant. To study the feasibility of the capacity controller, an experimental rig for the DX VAV A/C system having two conditioned spaces was built and experimental tests were carried out. The test results showed that using the capacity controller, the cooling capacity of the system's refrigeration plant can be accurately and continuously regulated and the supply air temperature well maintained at its desired value. The desirable independent zoning-control for space air temperatures can be successfully achieved by the DX VAV A/C system and the control performance for air temperatures in the conditioned space was highly satisfactory.
Original languageEnglish
Pages (from-to)1-8
Number of pages8
JournalEnergy Conversion and Management
Issue number1
Publication statusPublished - 1 Jan 2010


  • Capacity controller
  • DX VAV A/C system
  • Experimental tests
  • Variable-frequency compressor

ASJC Scopus subject areas

  • Energy Engineering and Power Technology
  • Fuel Technology
  • Nuclear Energy and Engineering
  • Renewable Energy, Sustainability and the Environment


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