DATA CENTRES
The outdoor air is drawn into the AHU, run through the heat recovery (HR) device before being exhausted. Warm air is extracted from the data halls, run through the HR and its temperature reduced by the cooler outdoor airstream, without mixing directly with it. This cooled air is then recirculated back into the data halls to reduce the internal temperature. The effectiveness of this strategy obviously
depends on the temperature of the outdoor air being below the data hall’s target condition. To maximise the potential cooling from this system, and expand its use into times when the outdoor temperature is too high, a cold water humidifier can be applied to the external airstream prior to the HR system. This reduces its temperature and increases the cooling capacity of the system. As global humidification and evaporative
cooling specialists, Condair frequently become involves with a third type of evaporative cooling strategy, indirect exhaust air evaporative cooling. This method sees a cold water humidifier cooling the warm air that is extracted from the indoor atmosphere. This cooled exhaust air is then fed through an HR unit before being ejected outside. A fresh air supply brings air in from outside and runs it through the HR unit, where it is cooled by a few degrees by the cooler exhaust airstream. This incoming fresh air can then be introduced to the data halls or cooled further mechanically, if required, before being supplied to the room. This strategy can reduce the load on
mechanical chillers, thus lowering a building’s overall cooling costs. It is also interesting, as it can be useful irrespective of the outdoor climate. Both the direct and indirect cooling strategies previously outlined rely somewhat on certain outdoor conditions being available, with regards humidity and temperature. An exhaust air indirect evaporative cooling strategy uses the air being returned from the indoor environment, which is mostly consistent regardless of the ambient outdoor climate. We often see this type of cooling strategy used in hot and humid regions across Asia, as well as parts of Europe, particularly Germany, where the drive to reduce a building’s energy consumption is paramount. Wherever the data centre or whatever AHU
cooling strategy is being employed, there is nearly always an evaporative cooling method that can enhance performance or reduce energy consumption. The data centre industry’s insatiable need for low cost, high capacity cooling has driven effective collaboration between data centre designers, AHU design teams and humidifier manufacturers, such as Condair, to produce more and more innovative solutions. Long may it continue!
www.acr-news.com November 2020 33
Exhaust air evaporative cooling
Direct evaporative cooling
Indirect evaporative cooling.
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