Emerson Liebert Xtreme Density Specifications download pdf (Page 15)

Starting a New Equipment Cooling Project

2.2 Implementing a Hot-Aisle/Cold Aisle Design

A best practice is to use rows of equipment racks in an alternating arrangement of “cold aisles” and

“hot aisles.” This is best accomplished when the layout of the file-server farm area is first being

planned. and it is exceedingly more difficult to accomplish when the computer room is already popu-

lated with operating hardware.

A cold aisle is defined as having perforated floor tiles that allow cooling air to come up from the ple-

num under the raised floor, and a hot aisle has no perforated tiles. In the cold aisle, the equipment

racks are arranged face to face so the cooling air discharged up through the perforated floor tiles is

sucked into the face of the computer hardware and exhausted out the back of the equipment rack onto

the adjacent hot aisles.

Hot aisles are literally hot because the objective of the alternating cold and hot aisle design is to sepa-

rate the source of cooling air from hot air discharge which returns to the computer-room cooling unit.

Therefore, no perforated tiles should be placed in the hot aisles. as this would mix hot and cold air and

thereby lower the temperature of the air returning to the cooling units, which reduces their usable

capacity.

Figure 10 Hot aisle-cold aisle arrangement with under-floor source

Cold air supplied

through perforated

floor tiles is drawn

into racks

Heated air expelled from

racks is drawn into

cooling unit and returned

to floor supply

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Emerson Liebert Xtreme Density Specifications Page 15