Warm Water Cooling

Warm water cooling raises the supply temperature of the secondary liquid circuit — the water entering CDUs and cold plates — from the conventional 7–12°C of chilled water systems to 30–50°C. Modern server processors and GPUs can operate with inlet coolant temperatures up to 45°C, allowing the facility to reject heat via a dry cooler or cooling tower without running a chiller for a much larger proportion of the year.

The benefit is a significant reduction in chiller energy and improved PUE, particularly in temperate climates. At 45°C supply, a UK facility can potentially operate in free-cooling mode for 8,000+ hours per year. Intel and NVIDIA both publish inlet temperature specifications for warm water operation. The trade-off is reduced thermal headroom for overclocking and tighter control requirements on the facility side.