Emerson Liebert Xtreme Density - Manual (Page 18)

Starting a New Equipment Cooling Project
12
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 populated with
operating hardware.
In the cold aisle, the equipment racks are arranged face to face so the cooling air discharged up
through the perforated floor tiles is drawn 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 13 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