Immersion Cooling Facts

Basics

What is Immersion Cooling?

Immersion cooling is an IT cooling practice by which IT components and other electronics, including complete servers, are submerged in a dielectric (electrically non-conductive) fluid that has significantly higher thermal conductivity than air (typically >1,000x the heat capacity by volume). Heat is removed from the system by circulating liquid into direct contact with hot components, then through water cooled heat exchangers.

Basics

Is Immersion Cooling a new technology?

Immersion Cooling is not new. The first reference to the specific use of dielectric fluids being used to cool “computers” is in 1966 by IBM and in 1982, Cray computing registered a patent for high density immersion cooled technology. 

GRC was founded in 2009 and has had commercial deployments of its rack based Immersion Cooling systems for over 10 years. The company deployed the world’s first turnkey immersion cooled (modular) datacenter, the ICEtank, in 2013.  

Asperitas was founded in 2014 and launched their first Immersed Computing® solution in 2017, after an extensive R&D phase with an ecosystem of cutting edge partners. Asperitas is leading the Open Compute sub project on Immersion Cooling for standardisation development.

 

Basics

What is single-phase Immersion Cooling?

Single-phase Immersion Cooling, as the name suggests, is where the coolant stays in a single (liquid) phase, and does not evaporate. The coolant captures the heat from the immersed components and is circulated through a heat exchanger that transfers the heat to a water loop, which in turn can be cooled with an evaporative/adiabatic cooling tower, dry-cooler (radiator), or an existing chiller plant (not required, but compatible).

Basics

How is single-phase different from two-phase Immersion Cooling?

Two-phase Immersion Cooling is where the coolant is designed to evaporate (change phase from liquid to gas) at lower temperatures, boiling off when it comes in contact with hot components. The evaporated coolant vapor is then condensed back to the liquid state through the use of condenser coils, typically located at the top of a sealed rack.

There are primarily two kinds of coolants used for Immersion Cooling: Fluorocarbon-based coolants which are typically used for two-phase applications, and Hydrocarbon-based fluids which are solely used for single-phase Immersion Cooling.

Basics

What are the pros and cons of two-phase (Fluorocarbon-based) vs. single-phase (Hydrocarbon-based) Immersion Cooling?

  • Upfront costs: Single-phase Immersion Cooling offers dramatically lower upfront costs due to its simpler overall design, and lower coolant costs.
  • Energy efficiency: Both forms of Immersion Cooling offer exceptional energy efficiency (pPUE 1.01 – 1.03).
  • Cooling capacity: Two-phase Immersion Cooling can typically support extreme rack densities, with some providers claiming to support up to 250kW in a single rack. Some single-phase solutions also claim to support up to 200kW per rack. However, given the power density of commercially available hardware, most mainstream applications for Immersion Cooling range from 15 – 50kW per rack.   
  • Complexity/usability: Single phase offers an inherently simpler architecture. The lack of evaporation allows for an open bath design, thereby eliminating any inhalation risks or the loss of fluid due to evaporation. The absence of a sealed rack also allows for easier access to servers and hence simpler maintenance SOPs. However, two-phase coolants (fluorocarbon) have the advantage of self-drying hardware that can make material handling easier. 

Basics

How is the fluid being circulated in Immersion Cooling systems?

Single-phase immersion requires circulation of the dielectric liquids by pumps or by natural convection flow through integrated or external heat exchangers.

Fluid

Are Hydrocarbon-based coolants the same as mineral oil?

Hydrocarbon fluids used for single-phase Immersion Cooling are typically synthetic fluids, which should not be confused with mineral oil.  Mineral oils can often have imperfections, impurities, and limit material compatibility. Synthetic fluids, on the other hand, are manufactured at a molecular level which results in an inherently stable product that offers superior performance and material compatibility.

They are clear, odorless, non-toxic fluids that are readily used in domestic products such as cosmetics and other household products, which have well-established material handling practices, minimal regulations, and no direct GWP (Global Warming Potential). The latter can be a challenge with Fluorocarbons.

Both GRC and Asperitas exclusively work with superior synthetic immersion fluids which are well developed by reputable partners and fully tested and optimized for Immersion Cooling.

Fluid

What is the difference between single-phase and two-phase coolants?

There are primarily two kinds of coolants used for Immersion Cooling: Fluorocarbon-based coolants which are typically used for two-phase applications, and Hydrocarbon-based fluids which are solely used for single-phase Immersion Cooling. 

Fluorocarbon-based coolants may be used in single-phase applications, but typically offer little benefit at a significantly higher cost and added complexity.

Fluid

Is the fluid expensive?

One of the advantages of using single-phase Immersion Cooling technology is that the fluids being used are not influencing the business case strongly, while, at the same time, offering the most reliable environment for electronic components.

Fluid

Do you need to replace the fluid?

Unlike fluorocarbon fluids, the hydrocarbon fluids used by GRC and Asperitas do not evaporate under normal operating conditions and do not need to be replaced through the life of the datacenter (15+ years). Regular lab tests are performed on the coolants to test for any variance in critical properties over time. Commercial deployments dating back to as early as 2010 have been running efficiently and reliably, with no degradation in the coolant’s performance.

 

Fluid

Are there additional risks, like fire hazard?

The fluids used by Asperitas and GRC have a very low flammability rate and do not readily ignite. The US National Fire Prevention Association (NFPA) 704 diamond rates such coolants as 0-1-0 substances. This means that it poses no health hazard, has a high flash point, and is stable even under fire exposure conditions.

IT

Can I use standard hardware?

From a user perspective you are making a tremendous investment in IT hardware, which should be taken seriously and treated with care. Standard hardware that was originally designed for air cooling can be optimized for immersion. This consists of removing components such as fans that have no use in immersion, and replacing materials such as thermal paste with materials that have better performance and longevity in fluids. Both GRC and Asperitas are working closely with leading OEMs to provide immersion ready servers that may be optimized for immersion or specifically designed to exploit the higher thermal capacity and improved reliability offered by immersion.

IT

Does it mean all the components are different?

No. Standard components – from motherboards, PSUs, memory, storage and CPUs to GPUs can be used. Saying this, GRC and Asperitas use various optimized components to increase lifespan and performance.

IT

Can I use optics?

While optical networking is possible with immersion, it does require some specialized components to work reliably. Some immersion enthusiasts and newer providers claim that you can use any standard fiber optic cable/connector in an immersion environment. However, we have found that to not be factual and/or a reliable way to deal with fiber optics in immersion.

Optical networking is based on the refraction of light through mediums of varying refractive indices (air, fiber cables, connectors, etc.) when a liquid fills a space that was designed to be an air gap, it changes the refractive index and can cause signal loss. In a static environment this could be resolved by optimizing the refractive index of the liquid. In a dynamic environment, however, such as an Immersion Cooling rack, the flow of the liquid, the variation in its density (due to temperature variation) that causes a change in the refractive index of the coolant, and the possibility of bubbles getting trapped in the miniscule gaps can all cause issues with signal reliability.

In addition, materials used in the optical transceivers may not be suitable for operation in immersion fluids. This may result in discoloration, which in turn has an effect on the light signal which travels through these materials.

Hence, both GRC and Asperitas recommend using specialized optical cables and connectors that deliver a much more reliable connection and signal stability.

IT

Can I use Immersion Cooling for storage, networking and compute?

Yes, you can. Both GRC and Asperitas have a track record in delivery a range of systems including all components.

IT

How about warranty on hardware and components, will it remain?

Several OEMs offer standard warranty and both GRC and Asperitas are working closely with system integrators and OEMs to offer you warranty models meeting your expectations.

IT

Can I service IT hardware which has been immersed?

Yes, you can. Components can be replaced, and GRC and Asperitas are offering different approaches to do so. The horizontal, open rack design allows easy access to each immersed server individually.

Facility

Can I run Immersion Cooling systems in any datacenter?

Yes, you can. Generally though, Immersion Cooling requires a water circuit running to the systems, which may be more than what you are used to.

Facility

Can I take Immersion Cooling to my colocation provider?

Usually, colocation providers will be happy to facilitate Immersion Cooling, it will allow them to facilitate high density environments without having to make large investments. Both GRC and Asperitas are working with several colocation providers as partners.

Facility

What about the floor loading?

Liquid-Immersion-Cooling systems such as those offered by GRC and Asperitas are designed to be installed on raised floors and concrete slabs alike. And while it may seem obvious, it is important to point out that when talking about floor loading, pressure on the floor is a more important consideration than gross weight alone. Because our racks are horizontal, they help evenly spread weight across their footprint, yielding a floor loading that is often less than that of an air-cooled rack. Actually, liquid-Immersion Cooling eliminates the need for raised floors entirely, but if you already have a raised-floor infrastructure there is no need to remove it, and likely no need to reinforce or modify it in any way.

Facility

What about floor space utilization?

While it is true that an individual horizontal rack has a slightly larger footprint than a vertical rack, when you look at the fully burdened datacenter footprint, Immersion Cooling produces significant space savings: no hot/cold aisles or high ceilings are required, neither is room for air circulation. Immersion Cooling does not need the height you will see in traditional datacenters, in fact in most cases the same data hall can be designed to have two levels with Immersion Cooling instead of just one traditional level. With immersion you will achieve a higher performance and more IT power per unit area.

Organisation

I need to comply with several standards and certifications, is Immersion Cooling compliant?

GRC and Asperitas systems are compliant to the most common system certifications, check your specific provider for details or for tailored certifications for your application. We have track records in serving customers and delivering to datacenters with the highest requirements possible.

Organisation

Do I need to train my staff for working with Immersion Cooling?

For new users of Immersion Cooling, servicing and maintaining Immersion Cooling is simply different to air-cooled systems. It is not more complicated. Our perspective is that the right approach is to train staff and we offer this service.

Organisation

What’s driving the popularity of Immersion Cooling now?

Compute is hot, literally, datacenter densities are going up on all levels: servers, rack and facility. Cooling is becoming a serious issue, combined with the need to integrate sustainability this is a challenge which is complex and expensive with air cooled systems. Immersion Cooling is able to facilitate the next generation hardware and in an energy efficient way, while also being climate independent.

Organisation

Is Immersion Cooling not primarily used for cryptocurrency miners?

Immersion Cooling is used by all kinds of users, including high performance computing, enterprise, telecom and emerging technologies. Customers of GRC and Asperitas include financial institutions, universities, oil & gas companies, government & defence organizations, cloud providers, telecom providers and more.

Organisation

How can I learn more about Immersion Cooling?

Asperitas and GRC are actively involved in several industry associations and communities, like ASHRAE and OCP, where research is being shared, standards are developed and best practices are presented. Following those activities is a great way to gain more in-depth vendor agnostic information on Immersion Cooling.