Designing Cooling &
Heating Systems

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24/7 operation saves 30% in energy costs per year

The soft drinks factory based in South Wales saves 30% in energy costs per year. The business operated a pasteurizer supplied with coolants from two separate pumped chilled water circuits. Both were filled with different fluids and were separated to avoid mixing propylene glycol with water. Clearly this situation added considerable operational complexity and three aging refrigerant chillers lacked cooling capacity during summer to meet factory demands.

The proposed phased replacement of the HCFC chillers was agreed to change to a single unit of 800kW cooling capacity with an HFC refrigerant alternative.

As the required water temperature was to be about 11OC, a two-circuit design was proposed to cool a large tank of water providing a ‘buffer’ between the supply and (much) warmer returning water when commencing the pasteurizing process. The refrigerant chiller circuit operated during warmer months and during the autumn and winter a dry air cooler used outside air to chill the water to 11OC. 800kW was delivered by the dry cooler when the outside air temperature reached about 6OC. Operating the dry cooler instead of the chiller saved 80% of the energy otherwise required by the compressor circuit. Hence the colder the autumn and winter weather the better the energy saving!

An estimated 33% of energy saving was anticipated, delivering a 2-year pay back on the capital cost of the dry cooler – however, the winter of 2009/10 was particularly cold and I was informed the refrigerant chiller had barely operated between November 2009 and March 2010! The project manager (now retired) was very pleased.

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