In a FLOODED supply and return air distribution system, the only constraints to the supply and return air flow are the walls, ceiling, and floor of the room. This leads to heavy mixing of the hot and cold air flow.
In a TARGETED supply and return air distribution system, a mechanism (e.g. duct, perforated tile, cooling unit placed within IT rows) directs the supply and return airflow within 3 meters (10 feet) of the IT equipment intake and exhaust In a CONTAINED supply and return air distribution system, the IT equipment supply and return air flow is completely enclosed to eliminate air mixing between the supply and the return air streams.
Each of the three approaches; flooded, targeted, or contained, can be used in either the supply path or the return path. This results in 9 possible combinations, or types of air distribution. All of these types have been used in various circumstances, and occasionally different types are mixed together in the same data center. A critical goal of a data center air distribution system is to separate the IT equipment exhaust air from the IT equipment intake air in order to prevent IT equipment from overheating. This separation also significantly increases the efficiency and capacity of the entire heat rejection
system. Depending on location of cooling unit (i.e. perimeter or row-based, when equipment power density increases, the corresponding increase in exhaust air volume and intake air volume requires an air distribution type that mitigates the propensity for mixing between the supply and exhaust airstreams. For this reason targeting or complete containment (depending
on location of cooling unit) of the supply air to the equipment intake or return air from the equipment exhaust becomes necessary as power density increases.
