AI data centre cooling

TOPIC HUB · AI DATA CENTRE COOLING

AI data centre cooling

The reference for practitioners on AI-density cooling: direct-to-chip liquid cooling (DLC), single-phase and two-phase immersion, cooling distribution unit (CDU) architecture, fluid supply chain, vendor landscape, and hyperscaler procurement patterns.

01Direct answer

AI data centre cooling is the thermal management architecture required for AI compute racks operating at 100-500+ kW per rack, well beyond the 15-30 kW/rack that traditional air cooling economically supports. The dominant new architectures are direct-to-chip liquid cooling (DLC) and immersion cooling (single-phase in dielectric oil; two-phase in fluorinated fluids). CDUs (cooling distribution units) at rack-scale or row-scale provide the secondary-loop pumping + heat exchange between the facility loop and rack loop. Vendor landscape is concentrating around a small set of specialists (CoolIT (Ecolab), Asetek, Motivair, Boyd, Submer, LiquidStack, GRC) with hyperscaler design wins driving consolidation. The specific supply-chain constraint is fluorinated fluid manufacturing capacity for two-phase immersion, plus qualified fluid-safe pump + valve components. Insurance + safety standards (NFPA 70E, ASHRAE TC 9.9) apply but liquid-cooling-specific standards are still evolving.

02Key concepts

Direct-to-chip (DLC)

Liquid cold plates mounted directly on GPU/CPU packages; primary + secondary loop architecture.

Single-phase immersion

Server hardware submerged in dielectric oil; simpler than two-phase but larger footprint per kW.

Two-phase immersion

Servers submerged in fluorinated fluid that boils at controlled temperature; higher density but supply-constrained fluid.

CDU

Cooling distribution unit; interface between facility loop and rack/row liquid loop.

PUE

Power usage effectiveness; ratio of total facility power to IT power. Liquid cooling targets sub-1.1 PUE.

Rear-door heat exchanger

Rack-mounted air-to-liquid heat exchanger; bridge architecture for retrofit.

Facility loop

Chilled water or hot water loop from central plant to rack/row.

Rack loop

Secondary loop from CDU to cold plates or immersion tank.

03Structural decomposition

The AI cooling architecture stack

Facility plant. Chillers, dry coolers, cooling towers; central plant sized to AI density
Facility loop. Distribution piping (chilled water or elevated hot water) to racks
CDU. Cooling distribution unit; heat exchange + secondary loop pumping
Rack loop. Manifolds + hoses + connectors distributing to compute blades
Cold plates or immersion tank. Point-of-thermal-load: direct contact with GPU/CPU packages
Return + heat rejection. Return path to facility loop and eventual ambient rejection

04Deep-dive research

The Thermal StackHow heat became the binding constraint on AI compute.
The Thermal Stack technical companionFluid chemistry, thermal transport, and leak sensitivity.
CoolIT direct-to-chipDLC vendor dynamics and the CoolIT (Ecolab) integration.
Submer immersion coolingImmersion cooling vendor landscape and fluid supply.
Cooling + 800V DC co-emergenceHow liquid cooling and 800V DC power architectures reinforce each other.

05Standards + regulation

ASHRAE TC 9.9 Mission Critical FacilitiesData centre thermal operating envelopes; W3-W5 water temperature classes for liquid cooling.
OCP Advanced Cooling SolutionsWorking group on rack-scale liquid + immersion cooling standards.
NFPA 70EElectrical safety in workplace; applicable when liquid cooling intersects live electrical.

06Commercial + investment implications

Commercial + investment angles

Cooling is a high-M&A-activity segment. CoolIT (Ecolab) set the vertical-integration precedent; expect more consolidation. Fluid supply concentration (two-phase immersion) is a specific supply-chain thesis. See Case Study 04: Eaton/Boyd one year on for a recent strategic acquirer entry into cooling.

07Frequently asked

When does an AI facility need liquid cooling?

Above roughly 30-40 kW/rack sustained. Air cooling economics break down as density rises, and the incremental facility infrastructure to support high-density air cooling (larger CRACs, cold aisle containment, more airflow) eventually costs more than the incremental liquid-cooling infrastructure. Hyperscaler AI-density (100+ kW/rack) is unambiguously liquid.

DLC vs immersion: which wins?

Both persist. DLC is easier to retrofit into existing rack forms and is dominant for GPU-centric AI training clusters. Immersion offers higher density per square metre and simpler thermal management for edge cases (extreme density, high-ambient siting). Neither is universally superior.

Why is two-phase fluorinated fluid supply a concern?

Manufacturing capacity for the specific fluorinated fluids used in two-phase immersion (3M Novec, Solvay Galden, etc.) is concentrated among a small number of chemical suppliers, some of whom face regulatory pressure on PFAS/fluorochemistry. Growth in immersion demand could outpace fluid supply expansion.

How do cooling and 800V DC power architectures interact?

They co-emerge because both are driven by AI-density economics. High-density racks need both. Sidecar power racks (Mt. Diablo) can share thermal envelopes with liquid-cooled compute racks. See DC-DC VIII: Cooling co-emergence.

What is the biggest vendor concentration risk in cooling?

CDU + high-current disconnect connectors, specifically for hyperscaler-scale deployments. CoolIT (Ecolab) + Motivair + Boyd + Asetek dominate DLC; concentration in specific hyperscaler design wins matters more than aggregate share.

08Further reading

See also: AI Power Semiconductors (thermal envelope of GPUs), 800V DC (power/cooling co-architecture). Full series: The DC-DC Transition.

Definition AI data centre cooling refers to the thermal management architectures used for accelerator-dense server racks above 100 kW/rack. Air cooling is inadequate at these densities; the industry has shifted to liquid cooling, either through direct-to-chip (DLC) via cold plates or through full-rack immersion in dielectric fluid.

AI data centre cooling architectures by rack power density
Rack power	Dominant cooling architecture	Vendor concentration	Typical deployment
Under 30 kW/rack	Air cooling with hot/cold aisle containment	Diverse (Vertiv, Schneider, Stulz, Rittal)	Traditional enterprise + legacy colocation
30-60 kW/rack	Rear-door heat exchanger (liquid-assisted air)	Motivair (Schneider), CoolIT (Ecolab), Vertiv	Colocation + inference workloads
60-150 kW/rack	Direct-to-chip liquid cooling (single-phase)	CoolIT, Motivair, Boyd (Eaton), Vertiv	H100/H200 hyperscale + training clusters
150-500 kW/rack	DLC + facility loop chilled water	Same, with CDU manufacturers layered	GB200 NVL72 + Rubin generation training
500+ kW/rack (emerging)	Two-phase immersion or two-phase cold plates	LiquidStack, ZutaCore, Iceotope	First-of-a-kind Rubin Ultra + custom silicon