Technology guide, established

Heat rejection

Heat rejection is the plant that finally dumps data centre heat to outdoor air or water: dry coolers, adiabatic coolers, cooling towers, evaporative systems and chillers. Liquid cooling with warm water lets more hours run on dry or adiabatic coolers without compressors, trading footprint and water use against energy.

Also called: dry coolers, adiabatic coolers, cooling towers, evaporative cooling, free cooling, chillers

What it is

Dry coolers pass facility water through finned coils with fans. Adiabatic units pre-cool air with water sprays or pads on hot days. Evaporative towers use water evaporation and need water treatment. Chillers add compressors when outdoor conditions or required temperatures demand it.

How to compare

Ask for the ambient rating point, fluid in and out temperatures, fan power, sound basis and distance, footprint, and annual water use at the site climate. Kelvion's V-shape dry cooler range, for example, is stated at 25 °C ambient with 40 °C in and 35 °C out. Figures at other rating points are not comparable.

Sourcing considerations

Water availability and permits, noise limits, plume and legionella control, refrigerant choice for chillers, and controls integration with CDUs. Recent consolidation matters: Vertiv bought ThermoKey (dry coolers) in June 2026.

Prototype vs shipping

Mature and shipping. Newer hybrid plant packages (for example Nortek StatePoint) are also marketed. Check reference sites at similar climate.

Questions to ask suppliers

Rating ambient and fluid temperatures
Fan power at design and part load
Water use per year at the site, and water quality needs
Sound power and sound pressure at a stated distance
Footprint and weight
Free cooling hours assumed and climate data source

Start a requirement brief

Suppliers with public evidence

Listed alphabetically. Inclusion means a public source shows the company offers products or services for this technology. It is not a ranking or endorsement. Compare these suppliers.

Projects using or planning it

Microsoft Mount Pleasant campus (Fairwater, Wisconsin)