Two-phase immersion cooling: Microsoft cools servers with liquid boiling at 50 ° C

Microsoft reports successes with two-phase immersion cooling for Azure servers, which could be widely used in the future. The so-called “Two-Phase Immersion Cooling” uses a liquid boiling from 50 degrees Celsius; the boiling point of water is 100 degrees Celsius under normal pressure at sea level.

Boiling liquids keep servers at their temperature

As the company explains in a report in its Innovation Stories series entitled To cool datacenter servers, Microsoft turns to boiling liquid, the great advantage of two-phase immersion cooling is the quick dissipation of heat directly from the components. As with water, most of the energy is absorbed when the unspecified liquid evaporates. In addition to the short-circuit aspect, relying on the non-suffering liquid instead of water has another advantage: Most of the waste heat can be efficiently “boiled” at 50 ° C, which does not yet result in a critical temperature on the components. On the contrary: In Microsoft’s test, the failure rate of the hardware would have been lower than with classic air cooling.

Inside the tank, the steam that rises from the boiling liquid meets an actively cooled condenser in the tank lid, which converts the steam back into liquid and lets it rain back on the submerged servers, creating a closed cooling circuit. A second cooling circuit for the condenser is still required.

For the first time in a production environment

” We are the first cloud provider to use two-phase immersion cooling in a production environment, ” said Husam Alissa, one of the two senior engineers in Microsoft’s Datacenter Advanced Development department at the data centers in Redmond, Washington.

The use of two-phase immersion cooling in the production environment is the next step in a long-term plan for Microsoft to keep pace with the rapidly increasing demand for ever faster and more powerful computers and servers in data centers, while the progress with conventional air-cooled hardware is steady slowed down. In this context, the company already speaks of ” Moore’s Law for the data center “.

More efficient cooling for more and more performance

Two-phase immersion cooling system
Two engineers check a two-phase immersion cooling tank in the data center (Image: Microsoft)

Since the transistor widths have shrunk so immensely and physical limits have been reached, the trend of Moore’s Law, named after Intel co-founder Gordon Moore, has slowed significantly. At the same time, global demand for faster computers for high-performance applications such as computing artificial intelligence has accelerated.

To meet the increased demand for power, the computer industry has turned to chip architectures that can handle more electrical power. The power consumption of processors (CPUs), for example, has risen from 150 watts to more than 300 watts per chip and graphics processors (GPUs) and accelerators (GGPUs) for high-performance computing and machine learning have reached more than 700 watts, says Husam Alissa.

Air cooling is not enough

“ Air cooling is not enough. This drives Microsoft to a two-phase immersion cooling, in which the surfaces of the chip can be boiled directly, ”adds Christian Belady, Vice President of the Microsoft development group for data centers.

The engineer removes a server blade from a two-phase immersion cooling tank (Image: Microsoft)
The engineer removes a server blade from a two-phase immersion cooling tank (Image: Microsoft)

The heat transfer in liquids is orders of magnitude more efficient than in air and, according to Chrstian Belady, also brings Moore’s Law a little way back into the data center.

The move to liquid cooling brings a way of thinking similar to Moore’s law for the entire data center and enables us to continue the trend of Moore’s law at the data center level.

Chrstian Belady, Microsoft

Project Natick has a model for the future

Two-phase immersion cooling is similar to Project Natick, which is exploring the potential of underwater data centers that can be up and running quickly and operated for years sealed on the ocean floor in submarine-like tubes without any on-site maintenance, according to Microsoft. Should it be confirmed that hardware cooled in this way lasts longer, the new two-phase immersion cooling system would be predestined for use in remote or difficult-to-access servers.

The first servers with two-phase immersion cooling are already running in a hyperscale data center and performing complex calculations. In the future, such a tank will also be used under a 5G cell phone mast in the middle of a city for high-tech applications such as self-driving cars.

Years ago, Roman “der8auer” Hartung worked on an all-in-one water cooling system with a two-phase cooler for end customers. But the development never got beyond a trade fair exhibitor. After a big announcement, the project was discontinued without comment.

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