Thermodynamic-behaviour model for air-cooled screw chillers with a variable set-point condensing temperature

K.T. Chan and F.W. Yu

Applied Energy, 2006, vol. 83, issue 3, 265-279

Abstract: This paper presents a thermodynamic model to evaluate the coefficient of performance (COP) of an air-cooled screw chiller under various operating conditions. The model accounts for the real process phenomena, including the capacity control of screw compressors and variations in the heat-transfer coefficients of an evaporator and a condenser at part load. It also contains an algorithm to determine how the condenser fans are staged in response to a set-point condensing temperature. The model parameters are identified, based on the performance data of chiller specifications. The chiller model is validated using a wide range of operating data of an air-cooled screw chiller. The difference between the measured and modelled COPs is within ±10% for 86% of the data points. The chiller's COP can increase by up to 115% when the set-point condensing temperature is adjusted, based on any given outdoor temperature. Having identified the variation in the chiller's COP, a suitable strategy is proposed for air-cooled screw chillers to operate at maximum efficiency as much as possible when they have to satisfy a building's cooling-load.

Keywords: Air-cooled; chillers; Coefficient; of; performance; Condensing; temperature; Screw; compressors (search for similar items in EconPapers)
Date: 2006
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Citations: View citations in EconPapers (6)

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