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"Once the segregation system is in place, an additional study and a way of describing the efficiency of air separation is required."

09/03/2017

Air Segregation Systems

Segregation of air leads to good air management. Although a containment system can be installed, the reality is different and two fundamental problems arise: first, even with a perfect containment system, the amount of air supplied needs to be controlled to meet the requirements of the IT equipment; second, containment is only part of the solution, since good segregation is required.

Once the segregation system is in place, an additional study and a way of describing the efficiency of air separation is required.

Availability of flow Af (ratio of air volume of the cooling units to the volume of air required by the IT equipment).

Air Segregation Efficiency, Air Segregation Efficiency (ASE). The ideal case of a 100% ASE is achieved when there is zero bypass and zero recirculation i.e. the containment systems by themselves reduce or even eliminate bypass flow and recirculation is false.

Note the bypass grate in the hot aisle and pass wires. If the cold aisle does not receive sufficient air flow there will be recirculation, and if it receives too much air there will be bypass. This is easily to show if one opens slightly the door of the cold aisle and notes with a sheet of paper in which direction the air flows.

Usually an air supply slightly larger than required (with consequent bypass flow) is preferable to a lower air supply (which would cause recirculation). A greater supply of air is an opportunity to save energy from the fans while a smaller supply than necessary would lead to the existence of hot spots.

Flow availability Af indicates whether the air supply is above or below the needs of the IT equipment. A value of Af greater than 1 represents a higher than necessary air supply, while a value less than 1 indicates a lower supply. An Af equal to 1 would represent a perfect air flow, but as already mentioned, in practice it is preferable that the air flow is greater to avoid recirculation.

Sources:

Tozer, Robert, and Covadonga Pardo. "Mitos Sobre Los Sistemas De Contención De Aire." Mitos Sobre Los Sistemas De Contención De Aire. Datacenter Dinamics, 12 Sept. 2016. Web. 15 Nov. 2016.