Immersion cooling

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Immersion cooling technology encompasses systems in which electronic components are directly exposed to and interact with dielectric fluids for cooling purposes. This includes systems using single-phase or two-phase dielectric fluids, leveraging their thermal capabilities to manage and dissipate heat generated by electronic components. [1]

Contents

Heat is removed from the system by putting the coolant in direct contact with hot components, and circulating the heated liquid through heat exchangers. This practice is highly effective as liquid coolants can absorb more heat from the system than air. Immersion cooling has many benefits, including but not limited to: sustainability, performance, reliability, and cost.

The fluids used in immersion cooling are dielectric liquids to ensure that they can safely come into contact with energized electronic components. Commonly used dielectric liquids in immersion cooling are synthetic hydrocarbons, esters (natural and synthetic) and fluorochemicals. [2]

Dielectric liquids

In general, the dielectric liquids used for immersion cooling fall into the following categories: synthetic hydrocarbons (synthetic oils), esters (natural and synthetic) and fluorochemicals. [2] (fully engineered liquids). Dielectric liquids are divided into single- and two-phase applications, which differ in whether or not the cooling fluid turns into a gas during the cooling cycle.

Forms

An enclosed chassis is an Immersion solution type with which dielectric liquid is circulated through a sealed server chassis [3] . This requires (dripless) connectors to interface to the individual chassis. These chassis are typically aimed at traditional rack style placement of systems. The connectors usually require a small closed-circuit cooling loop with a coolant to protect the flow integrity through pipes and connectors. The closed circuit is facilitated by a Coolant Distribution Unit (CDU), which may facilitate multiple racks at once.

An open bath refers to the "open" liquid–air interface [3] and thus surface tension between the liquid and the air is a distinctive element. Open bath systems are usually tanks which contain a larger body of dielectric liquid where electronics are immersed into the bath. Multiple electronic assemblies share the same liquid. Regardless of the term, open-bath systems can be fully sealed (especially with 2-phase immersion), but are always opened from the top to service IT equipment. [2] The tank for open bath immersion systems is either connected to a CDU which circulates the dielectric liquid, or contains an integrated heat exchanging device which is part of the tank, to facilitate heat rejection to (typically) the Facility Water System (FWS). For a facility interface, CDUs are usually designed for 100 kW or more, whereas an integrated heat exchanging device is usually designed for 10-100 kW cooling capacity.

Hybrid cooling refers to combinations of enclosed and open bath apparatus and the use of cold plate technology in immersion. [2]

Servicing and maintenance

Due to the vertical positioning of IT equipment, an essential element for datacentre thermal management tooling and maintenance is a hoisting device for the servers. A hoisting system typically involves mechanical lifting of the servers for placement and removal.

Evolution

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. These systems are replaced with liquid circulation pumps and heat exchanger and/or dry cooler systems.

Power use at data centers is often measured in terms of power usage effectiveness (PUE). The definitions of PUE for air-cooled devices and liquid immersion cooled devices are different which makes such direct comparisons inaccurate. The PUE for air-cooled data centers includes the power used by the fans and other active cooling components found in the servers. 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. 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. [4]

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. Thermal pastes which are typically used on heat spreaders for CPUs and other chips may require replacement with a different compound in order to avoid the thermal degradation within the dielectric liquid. [5] Depending on the type of application, solder, Indium foil, and thermally conductive epoxies may be used as a replacement materials.

The temperatures used in immersion cooling are determined by the highest temperature at which the devices being immersed can reliably operate. For servers this temperature range is typically between 15 and 65 °C (59 and 149 °F); [6] however, in ASIC-based crypto mining devices, this range is often extended up to 75 °C. [7] This increase in the high end of the temperature range allows data center operators to use entirely passive dry coolers, or much more efficient evaporative or adiabatic cooling towers instead of chiller-based air cooling or water chillers. This increase in the temperature range also allows operators using single-phase immersion coolants to more effectively use the change in outdoor temperatures to get more efficient cooling from their systems because the single-phase systems are not limited in their effectiveness by the boiling point of the coolant as is the case with two-phase coolants. [8]

Multiple relevant brands like Intel and Meta have already validated the advantages of submerging servers. [9] [10]

Current commercial applications for immersion cooling range from datacenter-oriented solutions for commodity server cooling, [11] [12] server clusters, HPCC applications [13] and cryptocurrency mining. [14] and mainstream cloud-based and web hosting architectures. Electric vehicle and battery manufacturers also employ liquid immersion cooling in batteries, drive-train, kinetic energy recovery systems, electric motors, electric motor controllers, and other on-board electronic subsystems.[ citation needed ] Liquid immersion cooling is also used in the thermal management of LEDs, lasers, X-Ray machines, and magnetic resonance imaging devices.[ citation needed ]

Immersion cooling is applied to electronic components in deep-sea research where remotely operated underwater vehicles with electronic equipment are filled with single-phase liquid dielectrics to both protect them from corrosion in seawater and as a pressure-compensating fluid to prevent the housing from being crushed by the extreme pressure exerted on the ROV while working in the deep sea.[ citation needed ] This application also includes the cooling of the electric motors used for under sea propulsion.

Until about 2014, the technology was typically only utilized in special very intensive supercomputing projects, like the Cray Computer Applications. [15] Even though the expected increase in global energy consumption by data centers has remained steady, [16] there is an increased focus on energy efficiency which has driven the utilizing of liquid immersion cooling in both data centers and crypto mining operations to reevaluate its application. The advent of new very high density CPUs and GPUs for use in real-time processing, artificial intelligence, machine learning, and data mining operations is leading users and data center operators to evaluate liquid immersion cooling for ability to cool high density racks as well as reduce the total mechanical footprint of data centers.

The growing adoption of higher TDP CPU and GPU chipsets in the data center in recent years has seen immersion cooling scale as a data center solution for addressing the technical limitations of air-cooled platforms. With platforms like NVIDIA's Grace-Blackwell GB200 NVL72 requiring up to 140kW of cooling per rack, [17] large-scale liquid cooling is emerging as an important technology to deliver hosting capability for these new platforms. This large-scale need is driving new form factors, industry adoption and methods of deployment.

History

19th and 20th century immersion milestones:

21st century immersion milestones:

Other uses

Domestic or process heating

Since 2016, immersion cooling in particular for bitcoin mining has become a popular method to generate usable heat. Immersion cooling offered a means to silently convert the waste heat from the mining operation to heat water, melt snow, power in-floor heating, and heat hot tubs, pools, shops, outbuildings, sheds, and greenhouses. There is a compelling case to combine bitcoin mining operations with indoor vertical farms and traditional greenhouses to offset or eliminate the heating cost of the facilities. Indoor and outdoor recreation facilities both public and private can also benefit from the "free" waste heat. Some companies provide computing-based heating for residential and commercial operations. [25]

Immersion Cooling of Li-Ion Battery

Overheating of Li-ion cells and battery packs is an ongoing technological challenge for electrochemical energy conversion and storage, including in electric vehicles. Immersion cooling is a promising thermal management technique to address these challenges. [26] Immersion cooling of batteries is specifically beneficial in abuse conditions, where the thermal propagation is needed to be avoided across the battery module or pack. Immersion cooling is gaining prominence as an emerging application within the automotive industry. With a heat transfer capability 50 to 100 times greater than indirect cooling methods, immersion cooling stands out as an efficient and powerful solution. [27] Presently, immersion cooling is predominantly utilized in motorsport and high-end vehicle models, showcasing its effectiveness in cutting-edge automotive technologies. [28]

See also

Related Research Articles

<span class="mw-page-title-main">Radiator</span> Type of heat exchanger; radiant body through water or other liquids

A radiator is a heat exchanger used to transfer thermal energy from one medium to another for the purpose of cooling and heating. The majority of radiators are constructed to function in cars, buildings, and electronics.

<span class="mw-page-title-main">Cutting fluid</span> Coolants and lubricants used in metalworking

Cutting fluid is a type of coolant and lubricant designed specifically for metalworking processes, such as machining and stamping. There are various kinds of cutting fluids, which include oils, oil-water emulsions, pastes, gels, aerosols (mists), and air or other gases. Cutting fluids are made from petroleum distillates, animal fats, plant oils, water and air, or other raw ingredients. Depending on context and on which type of cutting fluid is being considered, it may be referred to as cutting fluid, cutting oil, cutting compound, coolant, or lubricant.

<span class="mw-page-title-main">Heat sink</span> Passive heat exchanger that transfers heat

A heat sink is a passive heat exchanger that transfers the heat generated by an electronic or a mechanical device to a fluid medium, often air or a liquid coolant, where it is dissipated away from the device, thereby allowing regulation of the device's temperature. In computers, heat sinks are used to cool CPUs, GPUs, and some chipsets and RAM modules. Heat sinks are used with other high-power semiconductor devices such as power transistors and optoelectronics such as lasers and light-emitting diodes (LEDs), where the heat dissipation ability of the component itself is insufficient to moderate its temperature.

<span class="mw-page-title-main">Heat pipe</span> Heat-transfer device that employs phase transition

A heat pipe is a heat-transfer device that employs phase transition to transfer heat between two solid interfaces.

<span class="mw-page-title-main">Water cooling</span> Method of heat removal from components and industrial equipment

Water cooling is a method of heat removal from components and industrial equipment. Evaporative cooling using water is often more efficient than air cooling. Water is inexpensive and non-toxic; however, it can contain impurities and cause corrosion.

<span class="mw-page-title-main">Data center</span> Building or room used to house computer servers and related equipment

A data center is a building, a dedicated space within a building, or a group of buildings used to house computer systems and associated components, such as telecommunications and storage systems.

Liquid cooling refers to cooling by means of the convection or circulation of a liquid.

Internal combustion engine cooling uses either air or liquid to remove the waste heat from an internal combustion engine. For small or special purpose engines, cooling using air from the atmosphere makes for a lightweight and relatively simple system. Watercraft can use water directly from the surrounding environment to cool their engines. For water-cooled engines on aircraft and surface vehicles, waste heat is transferred from a closed loop of water pumped through the engine to the surrounding atmosphere by a radiator.

For fluid power, a working fluid is a gas or liquid that primarily transfers force, motion, or mechanical energy. In hydraulics, water or hydraulic fluid transfers force between hydraulic components such as hydraulic pumps, hydraulic cylinders, and hydraulic motors that are assembled into hydraulic machinery, hydraulic drive systems, etc. In pneumatics, the working fluid is air or another gas which transfers force between pneumatic components such as compressors, vacuum pumps, pneumatic cylinders, and pneumatic motors. In pneumatic systems, the working gas also stores energy because it is compressible.

<span class="mw-page-title-main">Chiller</span> Machine that removes heat from a liquid coolant via vapor compression

A chiller is a machine that removes heat from a liquid coolant via a vapor-compression, adsorption refrigeration, or absorption refrigeration cycles. This liquid can then be circulated through a heat exchanger to cool equipment, or another process stream. As a necessary by-product, refrigeration creates waste heat that must be exhausted to ambience, or for greater efficiency, recovered for heating purposes. Vapor compression chillers may use any of a number of different types of compressors. Most common today are the hermetic scroll, semi-hermetic screw, or centrifugal compressors. The condensing side of the chiller can be either air or water cooled. Even when liquid cooled, the chiller is often cooled by an induced or forced draft cooling tower. Absorption and adsorption chillers require a heat source to function.

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Fluorinert is the trademarked brand name for the line of electronics coolant liquids sold commercially by 3M. As perfluorinated compounds (PFCs), all Fluorinert variants have an extremely high global warming potential (GWP), so should be used with caution (see below). It is an electrically insulating, stable fluorocarbon-based fluid, which is used in various cooling applications. It is mainly used for cooling electronics. Different molecular formulations are available with a variety of boiling points, allowing it to be used in "single-phase" applications, where it remains a liquid, or for "two-phase" applications, where the liquid boils to remove additional heat by evaporative cooling. An example of one of the compounds 3M uses is FC-72 (perfluorohexane, C6F14). Perfluorohexane is used for low-temperature heat-transfer applications due to its 56 °C (133 °F) boiling point. Another example is FC-75, perfluoro(2-butyl-tetrahydrofurane). There are 3M fluids that can handle up to 215 °C (419 °F), such as FC-70 (perfluorotripentylamine).

Perfluoro(2-methyl-3-pentanone) is a fluorinated ketone with the structural formula CF3CF2C(=O)CF(CF3)2, a fully-fluorinated analog of ethyl isopropyl ketone. It is used as an electronics coolant liquid and fire protection fluid sold commercially by 3M under brand names such as Novec 1230, Novec 649, and FK-5-1-12. It is also known as “waterless water” or “dry water”.

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<span class="mw-page-title-main">Thermal management (electronics)</span> Regulation of the temperature of electronic circuitry to prevent inefficiency or failure

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<span class="mw-page-title-main">Waste heat</span> Heat that is produced by a machine that uses energy, as a byproduct of doing work

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<span class="mw-page-title-main">Aquasar</span> Supercomputer system from IBM Research

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References

  1. ↑ "OCP Immersion Project Charter v1.00.pdf". Google Docs. Retrieved 2025-01-15.
  2. 1 2 3 4 "Open Compute Project - Immersion Requirements". Open Compute Project. Retrieved 2025-01-15.
  3. 1 2 3 "OCP_CE_Glossary_Harmonized". Google Docs. Retrieved 2025-01-15.
  4. ↑ Habibi Khalaj, Ali; Halgamuge, Saman K. (2017). "A Review on efficient thermal management of air- and liquid-cooled data centers: From chip to the cooling system". Applied Energy. 205: 1165. Bibcode:2017ApEn..205.1165H. doi:10.1016/j.apenergy.2017.08.037.
  5. ↑ Pambudi, Nugroho Agung; Sarifudin, Alfan; Firdaus, Ridho Alfan; Ulfa, Desita Kamila; Gandidi, Indra Mamad; Romadhon, Rahmat (2022-12-01). "The immersion cooling technology: Current and future development in energy saving". Alexandria Engineering Journal. 61 (12): 9509–9527. doi: 10.1016/j.aej.2022.02.059 . ISSN   1110-0168. S2CID   247823719.
  6. ↑ Pambudi, Nugroho Agung; Sarifudin, Alfan; Firdaus, Ridho Alfan; Ulfa, Desita Kamila; Gandidi, Indra Mamad; Romadhon, Rahmat (2022-12-01). "The immersion cooling technology: Current and future development in energy saving". Alexandria Engineering Journal. 61 (12): 9509–9527. doi: 10.1016/j.aej.2022.02.059 . ISSN   1110-0168. S2CID   247823719.
  7. ↑ "Application-Specific Integrated Circuit (ASIC) Miner". Investopedia. Retrieved 2022-06-21.
  8. ↑ "The immersion cooling technology: Current and future development in energy saving". Alexandria Engineering Journal.
  9. ↑ "Ice X: Intel and SGI test full-immersion cooling for servers". Computerworld, Inc. April 8, 2014.
  10. ↑ "Facebook throws servers on their back in HOT TUBS of OIL". The Register. October 14, 2013.
  11. ↑ "Liquid immersion cooling relief for ultra-dense data centers". TechTarget. October 5, 2014.
  12. ↑ "What is liquid immersion cooling? - Definition from WhatIs.com". WhatIs.com. Retrieved 2017-07-25.
  13. ↑ "Immersion Cooling Steps Up for HPC Clusters". insideHPC. May 7, 2014.
  14. ↑ "BitFury to Launch Energy Efficient Immersion Cooling Data Center". Business Wire. December 11, 2015.
  15. ↑ "Cray-2 Machines". 7 August 2021.
  16. ↑ "Energy demand data centers globally by type 2021".
  17. ↑ TrendForce. "Press Center - NVIDIA Blackwell's High Power Consumption Drives Cooling Demands; Liquid Cooling Penetration Expected to Reach 10% by Late 2024, Says TrendForce | TrendForce - Market research, price trend of DRAM, NAND Flash, LEDs, TFT-LCD and green energy, PV". TrendForce. Retrieved 2024-08-29.
  18. ↑ "Transformer's History and its Insulating Oil" (PDF). Archived from the original (PDF) on 2018-08-26. Retrieved 2018-08-25.
  19. ↑ "Constant Current Transformer" (PDF).
  20. ↑ 5519 to 5523, 6908, 7658, 8495, 8548
  21. ↑ "Multi-liquid heat transfer".
  22. ↑ "Immersion cooling system for modularly packaged components".
  23. ↑ "Immersion cooled high density electronic assembly".
  24. ↑ "Fluid Selection and Property Effects in Single and Two-Phase Immersion Cooling" (PDF). John R. Saylor, Avram Bar-Cohen, Senior Member, IEEE, Tien-Yu Lee, Terry W. Simon, Wei Tong, and Pey-Shey Wu. November 4, 1988.
  25. ↑ "Open Compute Project - Heat Reuse". Open Compute Project. Retrieved 2025-01-15.
  26. ↑ Salvi, Swapnil; Surampudi, Bapiraju; Swarts, Andre; Sarlashkar, Jayant; Smith, Ian; Alger, Terry; Jain, Ankur (2023-10-27). "Experimental and Theoretical Analysis of Immersion Cooling of a Li-Ion Battery Module". Journal of Electrochemical Energy Conversion and Storage. 21 (4): 1–31. doi:10.1115/1.4063914. ISSN   2381-6872.
  27. ↑ "Mercedes-AMG reveals performance hybrid and battery-electric AMG derivative strategy". Green Car Congress. 2021-03-31. Retrieved 2023-11-30.
  28. ↑ "Mercedes-AMG E Performance Plug-In Hybrids Will Have 800+ Horsepower". Car and Driver. 2021-03-30. Retrieved 2023-12-01.
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