Immersion cooling and power

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Patrick Le Fèvre – 2019-12-06 – Rev 1.0.0

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POWERBOXHow does immersion cooling work?

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→ Immersion cooling involves putting electronics directly in a non-conductive fluid, allowing heat to be transferred directly from components into the heat transfer fluid

→ In traditional cooling systems, heat must transfer through several levels of thermal interface materials, air, heat exchangers and working fluids

→ Immersion cooling simplifies thermal design and increases heat transfer efficiency

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POWERBOXTwo-phases immersion cooling

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→ Two-phases passive immersion cooling exponentially increases heat transfer efficiency from boiling and condensation of the engineered fluids. This simple approach features almost no moving parts.

→ Electronic components are submerged in a non-conductive liquid bath in an accessible, sealed enclosure

→ The generated heat boils fluid into a gaseous state and it rises to the top of the enclosure

→ The gas condenses on the lid or a condensation coil and rains back into the bath to repeat the cycle

→ Heat transfer efficiencies can exceed boiling water in a material that can safely come in direct contact with electronics

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POWERBOXSingle-phase immersion cooling

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→ In single-phase immersion cooling the fluid has a higher boiling point and remains in its liquid phase throughout the process.

→ Electronic components are submerged in a non-conductive liquid bath in an accessible, sealed enclosure

→ The heat from the chip is transferred to the fluid

→ Pumps are often used to flow the heated fluid to a heat exchanger, where it is cooled and cycled back into the bath

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POWERBOXAdvantages over conventional air cooling

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→ Higher efficiency and energy savings (>90% electricity savings)

→ Reduced capital and operational expenses→ Improved performance→ Higher density→ Improved hardware reliability→ Faster time to market→ Fits any form, size or shape of electronics

components and boards→ Non-flammable, inherent fire protection→ Works in confined spaces and extreme

environments (hot & humid etc.).→ Reduced environmental impact

Source 3M and Allied Control

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POWERBOXAdvantages over conventional air cooling

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→ Silent OperationNo fans anymore required to cool servers and rooms reducing noise and maintenance cost

→ Electro Chemical MigrationImmersing servers into dielectric fluid dissipates any risk with ECM

→ Tin & Zinc WhiskersIn case of whisker formation they will be rapidly removed, limiting growth and filtered in the circulation system

→ Stable and constant thermal environment:As the cooling fluid is constantly pumped and heat is quickly extracted from any hot components, IT hardware components are exposed to less stress and less temperature fluctuations.Source Submer

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POWERBOXPower to immersed applications

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→ Main datacentersDatacenters and high capacity routers are usually powered by a 48V DC bus and voltage stepdown to local payload. Main power supplies and usually not immersed, only POL on the board are in contact with the liquid

→ Sub-serversSub-servers are using highly integrated architecture and power supply immersed. In many case the power supply is molded and a copper plate use to conduct the heat to liquid

→ Industrial embedded serversThis third category is the one using open frame power supply immersed and requiring specific attention during the design

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POWERBOXWhat to consider?

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→ The type of cooling solution will influence the design rules for the power supply and the type of components to use

→ Cooling fluids have higher dielectrics than air though creepage distance should be considered with attention

→ All immersed boards must be cleaned with high attention to avoid contamination

→ Labels and other glued parts must be qualified for the specific fluid to sustain on place during operation

→ Board layout optimized to facilitate liquid circulation

Source 3M and Sahithi Reddy Nagilla thesis

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POWERBOXDesign process

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→ Cooling agent evaluation in regards to metal compatibility (e.g. certain cooling agent increasing electro migration between copper and aluminum)

→ Location of the power supply within the system, defining layout and shape

→ Creepage distances evaluation→ Components selection to privilege efficient

cooling and immersed technology compatibility (e.g. electrolytic capacitors reaction to permanent immersion)

→ Cleaning process compliant with the cooling agent

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POWERBOXOur capabilities

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→ Designing power solutions for demanding applications since 1974

→ More than 3500 custom design power solutions delivered to market

→ Deep knowledge in powering Marine and sub-sea applications and dealing with similar requirements as for immersed computer

→ Part of Nordic research network, including university involved in energy efficiency and new technologies

→ International presence and video-conferencing system connecting our experts with customers all around the world

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