What are the Key Differences Between Single-phase and 2-phase Full Immersion Cooling?

Full Immersion Cooling delivers tremendous benefits, both from a capital and expense perspective…

If you choose the right systems approach and the right liquid dielectric coolant.

Photo of a single-phase liquid cooled server immersed in Engineered Fluids' dielectric coolant.

Full Immersion Cooling

Total Cost of Ownership Comparison


Single-phase Coolant®


2-phase Coolant®

Coolant Cost per Liter$$$$$$
Tank & System Cost$$$$
Ease of Use++– –
Coolant Heat Capacity+++++
Operating Temperature Range++
Dielectric Strength++++
Micro-cavitation ExposureNoYes
Material Compatibility+++
Supports Off the Shelf Hardware++– –
Shipping Weight / Floor Loading+++– – –
Legally Available for Use GloballyYesNo
Environmental Impact (GWP)09000
User Health and Safety+++– –
Aquatic Safety+++– – –

What is a Single-phase, Liquid Immersion Cooling?


A single-phase coolant does not boil or undergo a phase change at anytime during the cooling process. This completely eliminates all pressure, fumes, vapors, and corrosion due to micro-cavitation created by a coolant’s state transition from liquid to gas.


The coolants used in SLIC solutions are Newtonian fluids that are circulated within the system at very low pressure and low flow rates using inexpensive, off-the-shelf hoses, pipes, pumps, and cooled with standard radiators, dry coolers, or heat exchangers.


Direct immersion of electronics in a non-electrically conductive (dielectric) engineered coolant such that no protective cover, enclosure, coatings, or other means of insulation is required to be applied to the electrical circuits, chips, or device.


The removal of thermal energy from a device through absorption into a high capacity dielectric coolant for transmission to a heat rejection device or heat reuse appliance through the circulation of the coolant without the use of compressors or phase change.

SLIC Immersed Server

SLIC is a simple, efficient, and inexpensive method of cooling electrical components, devices, and sub-systems by fully immersing the device directly into a single-phase dielectric heat transfer fluid that is either passively circulated by the natural convection of the heated coolant or actively circulated by pumping the dielectric coolant in, through and around the electrical device being cooled, and then transferring the heat absorbed by the coolant to a heat rejection device such as a radiator, dry cooler, liquid-to-liquid heat exchanger, or cooling tower.

Single-phase vs Two-phase Dielectric Coolants

The terms “single-phase” and “two-phase” refer to the behavior of the dielectric coolant as it is heated by the electronic devices.

A single-phase fluid remains in its liquid form during the entire cooling process, while a two-phase fluid undergoes a phase change and becomes a gas.  This difference is critical to understanding the design, operation, and potential hazards of your cooling solution.

At Engineered Fluids we specialize in single-phase, dielectric coolants for a number of reasons:

  • Single-phase coolants do not require a complex cooling infrastructure.  You can safely use them in open or closed systems, using common off-shelf pumps, piping, and heat rejection devices like heat exchangers, cooling towers, chillers, or dry coolers.

  • Single-phase coolants do not boil away and need to be replaced regularly.  In fact, our ElectroCool, AmpCool, and VoltCool Dielectric Coolants have a 25 year expected useful life, and are offered with an industry unique 5 and 10 year warranty!

  • Our single-phase coolants have no vapor pressure, and therefore do not produce any smell during operation or storage.  In addition, since they cannot enter a gaseous or aerosol state, they cannot contaminate the air or the environment.  From a health and safety perspective this is critical, as it means you cannot inhale our coolants and they can never re-condense and remain in your lungs, or form “a toxic dew” throughout your workplace.

We believe that single-phase, liquid immersion cooling is simply most effective and safest approach to managing electronics heat rejection.

SLIC Cooling for Electronics

The Dangers of Two-phase Immersion Cooling…

For a two-phase fluid to operate effectively as a heat transfer fluid they must have a boiling point below the operating temperature of the device you are cooling because they remove heat through the phase process of transitioning from a liquid to gas.

The most common two-phase dielectrics belong to a group of chemicals called “fluorinated fluids.”  Fluorinated fluids have relatively low boiling points, are extremely dense (often 2-3x that of water), and are very expensive.

Because of the process by which they cool and fluorinated fluids own chemical properties, there are a number of potential risks and dangers involved in two-phase Immersion Cooling:

  • Two-phase coolants can produce very high pressures in systems because they must transition to a gas and then be recondensed to remove heat from a system.  This requires a complex system with significant safety systems in place to ensure there is no build up of pressure, or that the coolant is simply boiled off into the workplace or environment.

  • The boiling action of two-phase systems creates micro-cavitation which erodes the metals on the electronics devices you are cooling as well as the metal components of the cooling system.  This erosion can cause your electronic device to malfunction or fail due to broken trace and connectors.  In addition, your devices risk catastrophic failure, especially in power supplies, due to the build up of these eroded metallic particles in the coolant.  Eventually this metallic particle contamination destroys the dielectric strength of coolant causing shorting between systems.

  • Most two-phase cooling systems require water be brought directly into the data room to chill the condenser and remove the collected heat.  Anytime you have high pressure water in a data room you have a significant risk of failure.

  • Unlike single-phase coolants, two phase coolants will simply evaporate or boil away unless they are fully contained.  fluorinated fluids are very expensive and so is their replacement due to loss.

  • The other dangerous side effective of two-phase fluorinated coolants becoming an aerosol is that you can breath in these fumes and then they recondense in your lungs.  Because fluorinated fluids are heavier than water and are inert they can remain in your lungs long after you have been exposed.   In addition, these two-phase coolants will recondense on everything throughout the data room, leaving a “toxic dew” throughout your facility.

  • Again, unlike our single-phase coolants which have a Global Warming Potential of 0 (Yes, Zero!) fluorinated fluids have a GWP of over 9,000!   Just for comparison, carbon dioxide has a GWP of 1, and methane has a GWP of 56.

Learn More About Engineered Fluids vs Other Dielectrics

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