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Immersion liquid cooling for ultra-dense data centers

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Direct immersion cooling helps maintain the right temperature for servers and paving the way for the next generation of ultra-dense systems. Not air or water, but oil is the future of data centers. Server placement in data centers becomes denser and leads to higher rack temperatures. I would also recommend visiting automobileremedy.com/blog/oil-in-coolant/ for more guides about oil in coolant.

Immersion in liquid refrigerant can replace traditional air cooling methods for data centers and large, high-density servers.

Modern servers require multiple fans to direct large airflows towards hot components through carefully sculpted corridors in each chassis. But ventilation increases the system's energy consumption and significantly increases noise as well as risks.

On-site fan failures can cause problems. Modern processor designs are working to reduce power consumption and heat generation, but it is clear that traditional air cooling systems limit the potential density of processors and systems.

Designers hope to overcome the limitations of air cooling by immersing server hardware or other systems directly in liquid.

Direct immersion cooling is a new technology that could revolutionize the data center industry, but it requires trade-offs. The pros and cons, the possible benefits and the requirements needed to support it, need to be considered more closely.

One large radiator

Liquid is an excellent cooling medium because it is much denser than air, and dense media generally facilitate changes in thermal energy. Chiller water circulating in data centers has been one of the main refrigerants in heat exchangers for a long time.

But water and electricity cannot be mixed. Water conducts electricity and is corrosive.

Disturbances in the water circuit can have devastating consequences for systems and structures. These arguments are holding back the development of water cooling in most data center providers.

“We've had a number of water-cooled episodes that have implications for the service,” said Tim Noble, CIO and Advisory Board member for ReachIPS Inc., a cloud and IT services provider based in Cupertino, California. "Removing fluid from the workspace prevents risks of flooding or leaks."

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The new method is to select different fluids for the cooling system. Plain water is replaced by another substance that is non-conductive and non-corrosive to coatings, such as mineral oil or various mixtures (such as 3M from Novec or GreenDEF from Green Revolution Cooling).

The selected composition allows hot components (or the entire system) to be directly immersed for more efficient cooling without damaging components or altering the electromagnetic characteristics of sensitive electronic circuits.

Two approaches

There are two main approaches to immersion liquid cooling: simple and two-phase cooling.
Simple cooling is based on the principle of completely immersing the servers in a bath of cooling liquid. Heat from the processor, memory elements, hard drives and other devices is absorbed by the liquid, which circulates through a conventional chiller or other heat exchanger and maintains the temperature at the desired level.

Immersion systems (such as Green Revolution Cooling's CarnotJet) are a simple and efficient process.

Some systems rely on circulating coolant through individual shielded blades rather than submerging an entire rack. One of the manufacturers of such systems, LiquidCool Solutions, routes the system through an array of server modules and creates a common circulation loop.

A two-stage approach to liquid cooling is used in systems such as the Immersion-2 from Allied Control. Servers and other equipment are in the filled tub. The liquid of choice by this manufacturer, which is non-corrosive and non-conductive, has a much lower temperature threshold for boiling - usually close to 49'C Celsius (about 120 'Fahrenheit).

Heat from the server processor and other components causes the liquid to boil. The temperature is reduced when the generated steam condenses around a cooled coil or other condenser to collect and reuse the liquid.

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