Single Phase vs. Two-Phase Immersion Cooling for Data Centres


Data centres are becoming central to the conveniences of modern life. From artificial intelligence to cryptocurrency, the demand for computing power is growing at a breakneck pace. In fact, the data centre market is projected to expand by $615.96 billion USD from 2021 to 2026, which is a rate of 21.98%. Alongside this growth comes the huge consumption of energy: Hyperscale data centres used 86.58 terawatt hours globally in 2021, compared to 31.11 terawatt hours in 2015 (a 178.3% increase).

As a result, businesses are seeking systems that boost their efficiency and sustainability. Immersion cooling has emerged as one such powerful I.T. solution. However, two types have arisen: Single-phase immersion cooling and two-phase immersion cooling. To determine which one is right for your business, it’s important to learn what each system is, along with each of its advantages and disadvantages.

What is single-phase immersion cooling?

When you compare single-phase vs. two-phase immersion cooling, single-phase immersion cooling remains as a liquid throughout the entire process. In contrast, two-phase immersion cooling transforms the liquid into a gas.

With the single-phase method, computer parts are immersed in a non-conductive dielectric fluid. The liquid is then pumped into a heat exchanger, where it’s cooled and circulated back to the hardware.

Single-phase immersion cooling is especially crucial in high-density computing environments. Many servers are packed into tight spaces, causing large amounts of heat to emit. Single-phase liquid immersion keeps temperatures down, allowing data centres to keep operating at high efficiency.

Common applications for single-phase immersion cooling include:

  • Cryptocurrency & blockchain: As computers process complex mathematical calculations, they demand more power and emit more heat. Single-phase immersion cooling keeps your data operations sustainable and reduces your costs.
  • Artificial intelligence (AI): AI runs on algorithms that mimic human intelligence, consuming massive amounts of energy. Single-phase immersion cooling allows you to run in top form while minimizing power consumption.
  • Hyperscale data centres: From cloud computing to 5G, our communities need large-scale data centres to keep operating at their best. With many computers crammed into compact spaces, single-phase immersion cooling keeps temperatures down and minimizes costs.

How do I choose between single-phase and two-phase cooling?

Choosing between single-phase vs. two-phase depends on a variety of factors, such as your operational environment and budget. Let’s weigh the pros and cons of each immersion cooling solution.

Single-phase immersion cooling pros

  • Simpler design: Compared to two-phase cooling, single-phase requires less complex equipment, such as tanks, heat exchangers, pumps, and pipes. 
  • Long shelf-life for liquid: Since the dielectric fluid in single-phase cooling doesn’t boil away, it doesn’t need to be replaced often and can last for over 10 years.
  • Lower operating costs: Single-phase immersion cooling liquids are much less expensive than two-phase liquids. This, coupled with their long-lasting benefits, make them the most cost-effective option.
  • Reliability: Due to their liquid form, single-phase systems are much less susceptible to corrosion and breakdowns compared to gas exposure from two-phase systems. The coolant also protects computing parts from dust and debris.

Single-phase immersion cooling cons

  • Slightly less efficient: Both single-phase and two-phase immersion cooling systems are much more powerful than air cooling systems. However, single-phase doesn’t quite achieve the same energy savings as two-phase does.

Two-phase immersion cooling pros

  • Most efficient option: Two-phase immersion cooling can bring your system’s power usage effectiveness (PUE) down from 1.01 to 1.02. This narrowly beats single-phase systems, which achieve a PUE of 1.02 to 1.03. 
  • Higher-density operations: Two-phase systems can support up to 250 killowatts (kW) of power per rack, while single-phase systems can handle 200kW per rack. Both are strong methods for cooling any data centre, but two-phase beats single-phase in this area.

Two-phase immersion cooling cons

  • Safety concerns: In two-phase cooling, the fluorinated fluids become an aerosol, which you can inhale if exposed to it. This can linger in your lungs and cause health problems.
  • Metal erosion: Over time, the gas in two-phase immersion cooling can corrode the metal in your computing parts. This can cause massive system breakdowns and failures.
  • High cost of coolant: Since the fluorocarbon coolants in two-phase cooling become gas, they need to be regularly replaced. They are also much more expensive the single-phase coolants.
  • Global warming potential: The fluorinated fluids in the two-phase method can cause global warming if released into the atmosphere, while single-phase coolants don’t present this safety risk.

FAQs on single-phase immersion cooling

Is a single-phase immersion cooling system expensive?

Both single-phase and two-phase immersion cooling systems require significant upfront and operating costs. However, single-phase systems have simpler designs and longer-lasting liquids, making them the less expensive option. This allows you to achieve more cost savings in the end.

Which is the most efficient cooling system for high-density servers?

Two-phase immersion cooling systems are the most efficient solution. They reduce your power usage the most out of the two options, and they are capable of higher-density operations. However, this must be compared with their complexity, higher costs, and safety concerns. For many business owners, these challenges can outweigh the slight gains in efficiency. 

What are the challenges of implementing single-phase cooling?

Similar to two-phase cooling, single-phase cooling demands extensive design, engineering, and manufacturing expertise to be successful. It’s not meant for home server racks or even smaller data centres. Only large data centres will have the need and funds for immersion cooling, but the cost and energy savings are well worth it over time. It’s very important to hire an expert who can guide you through the planning and installation process.

Why go with the Intelliflex immersion cooling solution?

Intelliflex offers a start-to-finish solution for all your immersion cooling needs. Our technology reduces your power consumption and boosts your sustainability in high-density data centres. As a single-phase system, it allows you to reach significant energy efficiency while still being cost-effective, simpler to set up, and reliable to maintain. Be sure to reach out to our experts to start planning how to amp up your data performance.