Performance analysis and improvement of air-to-water chiller for application in wide ambient temperature range

Some air-to-water chillers can work well in summer but meet problems in low temperature ambience. When the ambient temperature decreases into a certain level, the cooling capacity of the chiller drops rapidly or in severe situation the compressor stops running. In order to expand the applicable condition, performance variation of an air-to-water chiller in a wide range of ambient temperature is analyzed based on simulation, and a new type air-to-water chiller is presented, in which an auxiliary capillary tube is installed parallel to the thermostatic expansion valve (TEV) as well as variable number condenser fans are used. A suitable control strategy of the chiller is proposed, and the performance of the chiller across an assorted range of ambient temperature range is also predicted. The operation of the capillary tube and the cooling fans are found to be a function of the coolant temperatures and the unique chiller operation has been tested for a period of more than a year. (C) 2004 Elsevier Ltd. All rights reserved.