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A DDC-based capacity controller of a direct expansion (DX) air-conditioning unit for simultaneous indoor air temperature and humidity control. I. Control algorithms and preliminary controllability tests.

Author(s) : LI Z., DENG S.

Type of article: Article, IJR article

Summary

For residential buildings located in the subtropics, direct expansion (DX) air conditioning (A/C) units are commonly used. Most DX A/C units are currently equipped with single-speed compressors and supply fans, relying on on-off cycling compressors as a low-cost approach to maintain only indoor air dry-bulb temperature, resulting in either space overcooling or an uncontrolled equilibrium indoor relative humidity (RH) level. With the rapid development of A/C industry, the use of variable-speed compressor and supply fan has become more and more prevalent and practical. This paper, the first part of a two-part series, reports on the development of a novel direct digital control (DDC)-based capacity controller for a DX A/C unit having variable-speed compressor and supply fan to simultaneously control indoor air temperature and RH in a conditioned space served by the DX A/C unit. The controller is the first of its kind as a composite parameter, sensible heat ratio (SHR), is used as a controlled parameter. The core element of the capacity controller, a numerical calculation algorithm (NCA) is firstly presented. This is followed by reporting the results of preliminary controllability tests of the DDC-based capacity controller, which suggested that the controller developed could achieve a reasonable control accuracy, but with room for improvement with respect to control sensitivity. Part II of the two-part series reports on the further development of the controller to improve its control sensitivity, and the results of associated controllability tests. (See this Bulletin, reference 2006-3123).

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Pages: 113-123

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Details

  • Original title: A DDC-based capacity controller of a direct expansion (DX) air-conditioning unit for simultaneous indoor air temperature and humidity control. I. Control algorithms and preliminary controllability tests.
  • Record ID : 2006-3122
  • Languages: English
  • Source: International Journal of Refrigeration - Revue Internationale du Froid - vol. 30 - n. 1
  • Publication date: 2007/01

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