By Josh Perry, Editor
[email protected]

The most recent article from Advanced Thermal Solutions, Inc. (ATS), a leading-edge thermal engineering company based in Norwood, Mass., explores two techniques for immersion cooling of servers in data centers.

This article explores immersion cooling technologies for servers. (Wikimedia Commons)

It reviews a single-phase immersion cooling technology from Green Revolution Cooling (GRC) and a passive, two-phase immersion cooling technology from 3M.

“When compared with traditional liquid cooling techniques, the liquid immersion cooling uses dielectric fluid as a working agent and open bath design,” the article explained. “This eliminates the need for hermetic connectors, pressure vessels, seals and clamshells. There are several different liquid immersion cooling methods.”

The Green Revolution Cooling technology included a liquid-filled rack for traditional servers with a dielectric mineral oil as coolant. The racks are filled with 250 gallons of dielectric fluid and are installed vertically into slots before being submerged.

“Pumps are used to circulate the cold coolant from the chiller to the rack,” the article continued. The coolant returns to the chiller, after removing heat from the servers. Because of its high heat capacity and thermal conductivity, the GreenDEF™ (dielectric fluid) can cool the servers more efficiently than air.”

3M has also studied immersion cooling with its range of Novec engineered fluids. As in the GRC design, the servers are aligned vertically in the rack and then submerged. The elevated temperatures cause the Novec fluid to boil and the evaporation dissipates large amounts of heat.

“The evaporated fluid travels to the upper portion of the server rack, where it condenses to liquid on the surface of the heat exchanger cooled by the cold water,” the article explained. “The condensed liquid flows back to the rack bath, driven by the force of gravity. In 3M’s server rack, the liquid bath is also semi-open to the outside environment.”

Because of the passive nature of this cooling method, no pump is required.

“In both immersion cooling technologies, the servers have to be vertically installed inside the server rack, which will reduce the date center footprint usage efficiency,” the article noted. “Because the liquid baths used in immersion cooling are open to the environment, coolant is gradually and inevitably lost to the ambient during long term service.”

Read the full description of both technologies at https://www.qats.com/cms/2019/03/26/immersion-liquid-cooling-of-servers-in-data-centers.