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The flow
of cold air used in high density racks requires the room
to be laid out with the racks positioned in a hot aisle
/ cold aisle arrangement.
The “cold aisles” have perforated floor tiles so that
the cold air generated by the perimeter units rises from
the plenum under the raised floor. The units are
arranged face to face so that the cold air, which has a
temperature of between 20°C and 22°C (depending on the
supplier), flows through the racks where it picks up
heat before being discharged at the rear of the racks
into the “hot aisles”, at a temperature anywhere up to
35°C, depending on the actual server heat load.
The natural upward lift of warm air towards the ceiling
and from there to the suction side of the perimeter
units can be optimised by using a duct system in the
upper part of the room which may be a false ceiling or
plenum placed on top of the perimeter units. This
ensures that the air flow to the blade server is
maintained at a constant temperature, meaning that the
server is always operating at ideal ambient conditions.
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