A computer room air conditioning (CRAC) unit is a device that monitors and maintains the temperature, air distribution and humidity in a network room or data center. CRAC units are replacing air-conditioning units that were used in the past to cool data centers. According to Industrial Market Trends, mainframes and racks of servers can get as hot as a seven-foot tower of powered toaster ovens, so climate control is an important part of the data center's infrastructure.
There are a variety of ways that the CRAC units can be situated. One CRAC setup that has been successful is the process of cooling air and having it dispensed through an elevated floor. The air rises through the perforated sections, forming cold aisles. The cold air flows through the racks where it picks up heat before exiting from the rear of the racks. The warm exit air forms hot aisles behind the racks, and the hot air returns to the CRAC intakes, which are positioned above the floor.