Hot Aisle/Cold Aisle remains a common consideration for data center architects, engineers, and end users. Conceived by Robert Sullivan of the Uptime Institute, hot aisle/cold aisle is an accepted best practice for cabinet layout within a data center. The design uses air conditioners, fans, and raised floors as a cooling infrastructure and focuses on separation of the inlet cold air and the exhaust hot air.
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In this scheme, the cabinets are adjoined into a series of rows, resting on a raised floor. The fronts of the racks face each other and become cold aisles, due to the front-to-back heat dissipation of most IT equipment. Computer Room Air Conditioners (CRACs) or Computer Room Air Handlers (CRAHs), positioned around the perimeter of the room or at the end of hot-aisles, push cold air under the raised floor and through the cold aisle, Perforated raised floor tiles are placed only in the cold aisles concentrating cool air to the front of racks to get sufficient air to the server intake. (naturally all the servers should be mounted so that their intake is facing the front of the rack, and their exhaust is facing the rear). As the air moves through the servers, it's heated and eventually dissipated into the hot aisle. The exhaust air is then routed back to the air handlers.
The heat removal capacity of the design is influenced by raised floor height, tile placement and perforation, air handler locations, and room architecture. Sound, integrated designs are necessary, as all of these parts must work in tandem to maintain the data center's environmental settings.