Direct liquid cooling (direct-to-chip)

What it is

Cold plates sit on the hottest chips and a closed technology cooling loop carries the heat to a CDU. Remaining components still need some air cooling, so most halls are hybrid. Single-phase systems use treated water or water-glycol (often PG25). Two-phase systems (for example Accelsius NeuCool, ZutaCore HyperCool) boil a dielectric refrigerant at the cold plate and avoid water in the white space.

Where it fits

New AI halls and retrofits where rack density outgrows air. Vendors such as LiquidStack note that air cooling struggles beyond roughly 30 to 50 kW per rack. Treat such thresholds as vendor guidance, not a standard.

Sourcing considerations

The system crosses supplier boundaries: server OEM cold plates, rack manifolds, quick disconnects (for example UQD and MQD/MQDB couplings), CDU, and facility water. Agree who owns fluid quality, flushing, leak detection and warranty at each interface. Ask for wetted materials lists and coolant qualification. Negative pressure systems (Chilldyne) trade pump design for reduced leak risk.

Prototype vs shipping

Single-phase DLC with CDUs is commercially shipping from many vendors. Two-phase systems are shipping from some specialists (Accelsius MR250 is listed as a product) but have a smaller installed base. Treat new cold plate and connector standards (OCP MQD/MQDB specification approved Oct 2026) as emerging.

Questions to ask suppliers

• Which party supplies and warrants cold plates, manifolds, quick disconnects and CDU
• Approved coolant and fluid maintenance plan
• Leak detection method and response
• Facility water temperature class needed (ASHRAE W class)
• Share of heat captured by liquid vs residual air
• For two-phase: refrigerant type, GWP, regulatory status and refill logistics

Start a requirement brief