Direct-to-chip cooling has become the default liquid architecture for many rack-scale AI systems because it targets GPUs and CPUs while preserving standard rack service patterns. The hard work is at the interfaces.
The four design boundaries
Treat the server loop, rack distribution, CDU, and facility loop as explicit scopes. Each boundary needs an owner, an acceptance test, and a compatible materials list.
- Server cold plates, hoses, and quick disconnects
- Rack manifolds and branch isolation
- CDU pumps, heat exchangers, filters, and controls
- Facility water, chillers or economizers, and heat rejection
Capacity follows temperature
A CDU's delivered capacity depends on supply temperatures and approach. Warmer technology coolant can improve economizer hours and heat-reuse potential, but the server vendor defines the allowable inlet range.
Plan for mixed air and liquid loads
Cold plates rarely capture every watt. Quantify the air-side remainder for memory, networking, storage, power supplies, and rack leakage before downsizing room cooling.