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Airedale pushes the boundaries of free-cooling chillers
Published: February 2012
Airedale’s OptiChill FreeCool large-capacity chillers maximise the use of free cooling to save more that half of the energy used by a conventional chiller. For up to 30% of the year these chillers can operate purely in free-cooling mode with an EER of up to 75 (15°C return water, 20% ethylene glycol, 3°C ambient and based on total input power to the fans). Some free cooling is available for 95% of annual operating hours (in London). The range has models with cooling capacities from 750 to 1300 kW. There are four case sizes, two free-cooling variants (two and three rows of coils). three fan variants (including EC fans and two sound-level variants in each range. In all, there are over 200 model permutations. The refrigerant is R134a with new modulating screw compressors to achieve a 12.5 K increase in the operating evaporating temperature range. Increasing the temperature of the supply water by 1 K can increase chiller efficiency by 10%. The compressors offer eight stages across dual refrigerant circuits. When applying interactive head-pressure setpoint management, the control strategy modulates the fans to maximise EER for any ambient temperature. Chilled-water pumps can be inverter controlled to achieve significant energy savings. Up to eight chillers can be integrated into a single operating system. For more information on this story, click here: Feb 2012, 167 Related articles: 
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