It is well recognised and understood that data centers emit a large amount of heat as the IT hardware processes so much data and works so hard to do so. This performance makes data centers particularly energy-hungry, but also at risk of error – as if the assets overheat, they malfunction and experience performance disruption and sometimes even a full cease of operations.

A variety of measures are implemented worldwide to help reduce the energy consumption of data centers and improve their sustainability credentials as a result. One of the newest innovations gaining traction in this space is immersion cooling for data centers; and here the Procurri team explain what that is, how it works, and the benefits of it.

What is Immersion Cooling… and is it anything like Immersion Heating?

Many of us are familiar with the principle of immersion heating, where a heating element is submerged directly into a liquid or material to use its contact with it to directly heat it. Immersion cooling is the opposite principle. Immersion cooling submerges data center hardware into a cooling fluid in order to dissipate the heat they emit through standard operation.

While immersion heating is fairly common and mainstream, it’s considered fairly expensive to use. Immersion cooling is only really used in large data center environments and does not have a mainstream application as such.

How does Immersion Cooling work without disrupting electronics?

Of course, electronic equipment can not simply be put in any cool liquid as it will rust and usually cease to operate. Instead, Immersion Cooling uses dielectric fluid. Dielectric liquids are thermally conductive (so they conduct temperature) but not electrically conductive (so they do not conduct electrical flow). This means that while such fluids can be used to dissipate heat, they don’t disrupt the function of any electrical components within.

Dielectric fluids include synthetic fluorocarbons, silicone fluids and mineral oil hydrocarbons. These fluids come in a variety of states and can either remain as a liquid or cycle through a liquid and gas state. Both have their uses, and dependent on the hardware being cooled, a single-phase or two-phase system may be most appropriate.

Are Immersion Cooling and Liquid Cooling the same thing?

While they sound very similar and are often mistaken for one another, immersion cooling and liquid cooling are not the same process.

Liquid cooling in a data center context refers to a variety of cooling techniques including evaporative cooling, waterborne data center cooling, DTC (direct-to-chip) cooling and rear-door server rack cooling. Immersion cooling is simply another type of cooling using liquids.

Generally speaking, liquid cooling method uses a coolant in a circulative motion to cool; usually through tubes and blocks next to hardware, offering only direct contact between the tubes and the assets. To see a server rack cooling system (the most commonly used liquid cooling process type), you may notice waterblocks and tubes networked throughout it, but no fluid will actually touch the system. Immersion cooling, however, submerges the entire servers in a non-conductive liquid into a specifically designed tank.

The difference between Single-Phase Immersion Cooling and Two-Phase Immersion Cooling

It is a common misconception that the ‘phases’ in immersion cooling refer to steps in the process, with two-phase immersion cooling taking a doubled-up approach compared to single-phase. In truth, the phases reference states of matter of the fluid being used for cooling. The cycles and the types of fluid being used differ.

Single-Phase Immersion Cooling

In single-phase immersion cooling, the dielectric fluid used remains in a liquid state throughout. Heat from the server components that are immersed in the fluid is transferred into it. As the fluid conducts the heat and rises in temperature itself, it is cycled out of the immersion tank to run through a heat exchanger. In this exchanger, the fluid is re-cooled before being returned to the immersion tank at the now lowered temperature, and the cycle continues.

Two-Phase Immersion Cooling

In two-phase immersion cooling, the dielectric fluid cycles from a liquid state to a gas. Heat from the immersed server components is allowed to raise the temperature of the fluid enough so that it boils. The steam gas created from the boiling fluid rises and heats a condenser coil in the top of the immersion chamber (which remains sealed). The condenser coil cycles the fluid out of the chamber to a separate cooling system. This is most commonly a cooling tower but can be a variety of solutions. From here, the coolant is returned to the sealed chamber at the now lowered temperature, and the cycle continues.

It should be noted that there are two key differences between the two phase types of immersion:

• The boiling point of the immersion fluids used is considerably lower in two-phase immersion cooling systems than those of single-phase immersion cooling systems
• The nature of the liquid changing to gas in two-phase immersion cooling systems requires an immersion chamber to be wholly sealed throughout the cooling process; whereas that in a single-phase immersion cooling system need not be. This is often considered to be the most critical difference, as any maintenance or fixes on the hardware entail a cooling and unsealing process, which is typically extremely costly (with businesses sharing anecdotal examples of over $5,000 a minute!).

The Benefits of using Immersion Cooling in Data Centers

There are a wide variety of methods on offer for the cooling of data centers; but immersion cooling has benefits above many others. Such advantages include:

Low energy usage

PUE (Power Usage Effectiveness) is usually measured by dividing the total energy consumed by the entire data center by the energy consumed by the computing equipment within it alone. Energy efficiency can be considered to be more effective the closer it gets to 1. PUE averages vary worldwide and by size of data center, but in 2022 the average was believed to be somewhere around 1.58. Single-phase immersion cooling can decrease a PUE from this down as far as 1.05.

Physical space saving

While exact configurations depend on hardware requirements, immersion cooled data center systems take up considerably less floor and physical space than those of air-cooled data center systems. Power rack density is vastly improved as no additional air flow is required between servers or other hardware – meaning that immersion cooled systems can take up a third of the space compared to air-cooled. The optimum space saving can be achieved by introducing submerged server cooling tanks throughout a data center rather than using any combination of other cooling methods.

Increased rack density

As above, immersion cooling allows for increased rack density. On average, a fully populated data center can hold between 5-7 kW worth of server compute in a 42U cabinet. Immersion cooled racks, however, can hold 380 kW of server compute in a 42U cabinet.

No requirement for A/C

The most traditional cooling method for data centers was the infrastructure including raised floors for air flow and air conditioning units placed strategically throughout. Immersion cooling removes any requirement for air conditioning. Depending on the data center configuration, air conditioning units can account for up to 40% of all energy used – which is negated immediately with the use of immersion cooling in its place.

Reduced noise output

The air conditioning units usually used to cool data centers utilise fan power to do so, and are traditionally fairly loud in doing so. Removing the air conditioning requirement from a data center takes with it the noise output, greatly reducing it.

Future-proofing hardware

The demand for computing power in data centers is growing all the time, and with it comes demand for more space, more energy, and better investment. With immersion cooling offering cost savings, less physical impact and quieter, more sustainable output, it’s clear that this method allows for efficient working while providing space for expansion and growth.

Want to investigate Immersion Cooling for your data center?

There are a whole host of factors that businesses must work through when considering introducing immersion cooling into their data center/s. These include:

• The preparation of existing hardware for immersion
• The training of maintenance staff, or the hiring of qualified third party maintenance staff
• Agreeing maintenance and repair processes for immersed hardware
• Finding and managing vendors for immersion tanks and dielectric fluid/s.

Procurri works with data centers of all configurations, types and cooling systems including those utilising immersion cooling. Our third party maintenance teams work with immersion cooled data centers around the world to best extend the value of IT assets. Get in touch today to discuss your options with our expert technicians!