Emerson Xtreme Density manual Implementing a Hot-Aisle/Cold Aisle Design

Starting a New Equipment Cooling Project

2.2Implementing 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

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