Page 38 - Climate Control News Oct-Nov 2020

Data Centres
Low cost evaporative
cooling strategies
Indirect exhaust air evaporative cooling can reduce the load on mechanical chillers.
CONDAIR PTY LTD MANAGING DIRECTOR, IAN EITZEN, LOOKS AT THE DIFFERENT WAYS HUMIDIFIERS CAN BE USED IN DATA CENTRES TO PROVIDE LOW COST EVAPORATIVE COOLING.
ADIABATIC EVAPORATION IS a process whereby water changes from a liquid to the vapour phase. The heat required to evaporate the water is taken from the air stream. The air stream is cooled, whilst simulta- neously increasing the humidity as well.
Adiabatic evaporation can be considered air humidification, as the moisture content of the air stream increases in the process. This pro- cess, often referred to as evaporative cooling, can be designed specifically to provide low en- ergy cooling of the air stream.
The use of evaporative cooling in data centre environmental control strategies is now relative- ly commonplace. The nature of evaporative cool- ing perfectly suits the requirements of a data centre’s climatic operating window.
Unlike a regular office temperature of around 23°C, a data centre’s upper tempera- ture condition can be as high as 28°C. When the outdoor climate conditions are suitable, data centre cooling systems may use the out- door air rather than mechanical cooling in their data halls.
During the warmer months, when the outdoor air conditions are too warm to successfully low- er the indoor temperature to the desired set- point, evaporative cooling can be used to provide additional low energy cooling capacity.
A litre of cold water, when evaporated into the air, provides 0.68kW of adiabatic cooling. A single cold water evaporative cooler can supply around 1,000 litres of moisture while operating on less than 1kW of electricity, so they offer great potential for low energy, high capacity cooling. Depending on the condition of the air stream, evaporative cooling can offer a temper- ature reduction of up to 12°C. More and more air handling units are being developed with an evaporative cooling element to take advantage of this low cost, low energy form of tempera- ture control.
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Direct evaporative cooling is ideal for use in dry climates.
Indirect evaporative cooling uses a heat exchanger.
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