# Coolant Distribution Unit **Domain:** Thermal Engineering / Data Centers **Doc Type:** Technical Interface Node **Maturity:** Developed ## Definition A **coolant distribution unit** is the hydraulic and control interface that transfers heat between a facility cooling loop and a technology cooling loop while regulating flow, pressure, temperature, isolation and monitoring. ## Governing Variable The CDU governs the thermal-fluid boundary between building infrastructure and liquid-cooled information technology. ## Material and Computational Manifestation Heat exchangers, pumps, valves, filters, sensors, controls, alarms and leak-management functions make the interface operational. The CDU may serve one rack, several racks or a larger cooling domain depending on design. ## Relation to Governance The unit dissolves the old assumption that a server is thermally self-contained. It makes facility state a direct precondition of rack-scale computation and creates a clear target for [[wiki/Telemetry|telemetry]], maintenance and standardization. ## Constitutional Question and Failure Modes Who can change setpoints, how local equipment fails safely and whether operators can service the unit without proprietary dependency are operational-governance questions. Failure modes include pump loss, cross-contamination, control oscillation and a shared CDU becoming a common-mode failure domain. ## Related Ontology [[wiki/Direct-to-Chip Liquid Cooling|Direct-to-Chip Liquid Cooling]] · [[wiki/Thermal Architecture|Thermal Architecture]] · [[wiki/Rack-Scale Computing|Rack-Scale Computing]] · [[wiki/Facility Digital Twin|Facility Digital Twin]]