By Priya Raman · Updated September 13, 2026 · 6 min read
Short answer
Immersion cooling submerges servers in a dielectric fluid that absorbs heat directly. Single-phase systems pump the fluid through a heat exchanger; two-phase systems let it boil and condense. It removes most fans and handles very dense racks, but it changes hardware, service and fluid handling, and the heat still has to be rejected by chillers or dry coolers.
Immersion cooling places servers in a bath of non-conductive (dielectric) fluid. The fluid touches the components directly, absorbs their heat and carries it to a heat exchanger, so fans can be removed or greatly reduced. There are two main forms: single-phase, where the fluid stays liquid, and two-phase, where it boils at the hot surfaces and condenses again. Either way, the heat must still leave the building through a facility loop, usually served by chillers or dry coolers.
What is the difference between single-phase and two-phase immersion?
Single-phase. The fluid, often a synthetic oil or engineered hydrocarbon, stays liquid. Pumps move it through the tank and a heat exchanger. The design is mechanically simple and fluid loss is low.
Two-phase. The fluid has a low boiling point and boils on hot chips. The vapor rises, condenses on a coil at the top of the tank and drips back. Boiling moves heat very effectively, but the fluids are specialized, sealed tanks are required, and some fluid families are under regulatory and environmental scrutiny.
| Factor | Single-phase | Two-phase |
|---|---|---|
| Fluid state | stays liquid | boils and condenses |
| Tank | open or lightly sealed | sealed, pressure managed |
| Fluid loss | low | must be controlled |
| Heat removal per chip | high | very high |
| Complexity | lower | higher |
| Fluid cost and supply | moderate | typically higher |
What does an immersion system consist of?
- Tank. A sealed or semi-sealed enclosure holding servers vertically or horizontally.
- Dielectric fluid. Chosen for heat capacity, viscosity, material compatibility and safety data.
- Heat exchanger or condenser. Moves heat from the tank fluid to a water or water-glycol loop.
- Pumps and controls. Maintain flow, monitor fluid temperature and level.
- Facility loop. Carries heat to the plant outside.
Servers are usually modified or purpose-built: fans are removed, and materials such as certain cable jackets and thermal pastes must be compatible with the fluid.
How does the heat leave the building?
Immersion does not remove heat, it relocates it. The tank heat exchanger feeds a facility water loop, which then rejects heat through chillers, dry coolers or cooling towers. Immersion fluids tolerate warm coolant, so facility water can often run warmer than in air-cooled halls. In a mild climate that can mean dry coolers and little compressor work. In Central Texas summers, trim cooling from chillers is usually still needed. For a plant-level view see data center cooling explained and liquid cooling for AI data centers.
What are the pros and cons?
Advantages
- Handles very high rack density.
- Cuts or removes server fan energy and noise.
- Even temperatures across components.
- Allows warmer facility water and more free cooling hours.
Drawbacks
- Different hardware, warranty and maintenance model.
- Hands-on service is messier: servers come out of the fluid.
- Fluid cost, supply, disposal and fire and safety documentation.
- Floor loading: tanks full of fluid are heavy.
- Few technicians have experience with it, and standards are still evolving.
When does immersion make sense?
It tends to fit new, high-density builds, such as AI training clusters or crypto-style compute, where the operator controls hardware choices and wants to design the thermal plant around warm water. It is harder to justify in a mixed legacy hall where most equipment is standard air-cooled. Direct-to-chip cooling is currently the more common choice for mainstream servers, so compare both before committing. A useful metric when comparing is PUE, though it does not capture water use or fluid impacts.
What should you check before piloting immersion?
A pilot is the safest way to learn, but only if it is set up to answer real questions.
- Fluid compatibility. Confirm that plastics, cables, seals and labels are compatible with the dielectric fluid. Not every component tolerates it.
- Floor loading and layout. Tanks full of fluid are heavy and require different access than racks.
- Heat rejection path. Immersion moves heat into a fluid loop, but the heat still has to leave the building. Check what temperature the loop can run at and whether the existing plant can serve it; see how a chiller works and data center chillers and cooling towers in Texas.
- Maintenance workflow. Pulling hardware from a tank is slower and messier than sliding out a server. Decide how parts will be handled and cleaned.
- Measurement. Track power, fluid temperature and flow so the pilot can be compared with air or direct-to-chip options in liquid cooling for AI data centers.
Define what success looks like before the first server goes in. A pilot without a measurement plan produces opinions instead of data.
Frequently asked questions
Is immersion cooling safe for electronics?
The fluids are dielectric, meaning they do not conduct electricity, and are designed to be compatible with components. Compatibility testing with the specific server hardware is still essential, and vendors define approved fluids.
Does immersion cooling eliminate the need for chillers?
Not necessarily. It lowers the cooling load on air systems, but the heat must still be rejected. In hot climates a chiller or trim cooling is often needed during summer peaks.
Is two-phase better than single-phase?
It moves more heat per unit of surface, but it is more complex and the fluid choice involves regulatory questions. Single-phase is simpler and widely used. The right answer depends on density, budget and fluid availability.
SpecServis engineers in Ukraine have worked on refrigeration and chiller plants, and we are planning to enter the Central Texas market. If you work on data center cooling, see our open positions or partnership options.
