The merits of open bath immersion cooling of datacom equipment

This paper discusses the economic and environmental merits of passive 2-phase immersion in semi-open baths of dielectric fluid for cooling datacom equipment such as servers. The technique eliminates the need for hermetic connectors, pressure vessels, seals and clamshells typically associated with immersion cooling and the connectors, plumping, pumps and cold plates associated with more traditional liquid cooling techniques. A board level power density of 11.7W/cm² can be sustained with 100 cm³ of fluid per kW. The modular 80 kW baths modeled can eject 130 kW per m² of floor space via water-cooled condensers. It is estimated that 28°C water at 15 gpm could maintain average CPU junction temperatures, T_j<;60°C and 62°C water at 30 gpm could maintain T_j<;85°C, maximizing the availability of the heat for other purposes. Alternatively, the heat can be transferred directly to ambient air without water as an intermediate. The costs and greenhouse gas emissions associated with conservative annual fluid emission estimates are found to be less than those associated with the electrical power required for traditional chassis fans and liquid pumps. Since these fugitive losses occur at one point, more efficient capture techniques can be easily applied.