![]() ![]() Servers and other IT hardware cooled by immersion cooling do not require fans to circulate the dielectric liquid, thus they are removed from the system prior to immersion. This discrepancy in the definition of PUE for the different cooling methods results in the PUE of air-cooled data centers generally being overstated when compared against the PUE of a liquid immersion cooled facility of the same power usage. The PUE for liquid immersion cooling excludes these values from the IT Equipment Energy component because these system elements (in particular on board fans) are generally removed from the IT equipment as they are not necessary to circulate the dielectric coolants. The PUE for air-cooled data centers includes the power used by the fans and other active cooling components found in the servers. The definitions of PUE for air-cooled devices and liquid immersion cooled devices are different which makes such direct comparisons inaccurate. Power use at data centers is often measured in terms of Power Usage Effectiveness (PUE). These systems are replaced with liquid circulation pumps and heat exchanger and/or dry cooler systems. Immersion cooling reduces energy consumption through the elimination of the air cooling infrastructure including on-board server fans, CRACs, A/C compressors, air-circulation fans, necessary duct work, air handlers, and other active ancillary systems such as dehumidifiers. Depending on which aspect is relevant, these strategies may be positioned as any overlapping definition. These may not always fit in any designated definition. There are numerous solutions in the industry already with unique and diverse approaches. ![]() "Hybrid" refers to combinations of the forementioned shapes and forms. For a facility interface, CDU's are usually designed for 100 kW or more, whereas an integrated heat exchanging device is usually designed for 10-100 kW cooling capacity. The water circuit for open bath immersion systems is either connected to a CDU which circulates the dielectric liquid, or to an integrated heat exchanging device which is part of the tank. Regardless of the term, open bath systems can be fully sealed, but are always opened from the top to service IT equipment. This liquid can be based on single- or two-phase technology. Multiple electronic assemblies are sharing the same liquid. Open bath systems are usually tanks which contain a larger body of dielectric liquid where electronics are immersed into the bath. “Open bath” refers to the “open” liquid-air interface and thus surface tension between the liquid and the air being a distinctive element. The closed circuit is facilitated by a CDU or Coolant Distribution Unit, which usually can facilitate multiple racks at once. The dripless connectors usually require a small closed circuit cooling loop with a coolant to protect the flow integrity through relatively small pipes and connectors. These chassis are usually based on traditional rack style implementations. "Enclosed chassis" require dripless connectors to interface to the individual chassis. The gas is cooled again by a heat exchanging method to allow return flow into the larger liquid volume.
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