What is CDU?
CDU (Coolant Distribution Unit) na equipment wey dey exchange heat, circulate and control between facility cooling system and IT equipment liquid cooling loop.Inside common liquid-liquid architecture, e separate Facility Water System (FWS) and server side Technology Cooling System (TCS) via heat exchanger, and control secondary side coolant temperature, pressure and flow rate.
This layer of isolation na key: facility water quality, pressure and temperature conditions, normally no suppose directly affect cold plate, quick connector and server internal pipes. CDU na heat boundary, also hydraulic boundary and operation responsibility boundary.
This paper dey discuss liquid-liquid CDU wey common for single-phase cold plate liquid cooling. Selection method for liquid-gas CDU, immersion cooling and two-phase system different, no fit apply directly.
CDU core role no just "provide flow"
Heat exchange and loop isolation
Decouple facility-side heat transport conditions from IT-side coolant requirements, reducing the risk of conflicting material, water quality, and pressure requirements.
Temperature control
Regulate valve, pump speed, or heat exchange capacity based on supply liquid setpoints, facility water conditions, and load changes.
Pressure and flow control
Provide flow rates that meet the design window for cold plates, manifolds, and hoses, while avoiding overpressure, cavitation, or insufficient local flow.
Monitoring and alarming
Collect signal like temperature, pressure, differential pressure, flow, liquid level and leak, and connect to BMS/DCIM based on project need.
Filtration and liquid maintenance
Support loop cleanliness and liquid status management through filtration, fluid replenishment, venting, and sampling.
Fault isolation and maintenance
Combine pump redundancy, bypass, isolation valve and maintainable parts, control scope of single point of failure.
What conditions should be checked simultaneously when selecting CDU?
Only comparing the 'max kW' on the nameplate is easy to misjudge. Rated heat exchange capacity is only meaningful under specified facility supply water temperature, secondary side supply and return temperature difference, fluid type, flow rate, and pressure drop conditions. Inquiries or technical clarifications should at least include:
- Target IT heat load, recent peak, projected expansion path, and allowable capacity margin
- Facility side supply and return water temperature, available flow rate, allowable pressure drop, water quality, and the most unfavorable operating conditions throughout the year
- Secondary coolant type, concentration, material compatibility, design supply temperature, and temperature difference
- Pressure drop for cold plate, manifold, quick connector, hose, and filter under design flow rate
- Redundancy targets for pumps, controllers, heat exchangers, and power supplies, as well as whether downtime is allowed during maintenance
- Leak detection, liquid level, filtration, venting, make-up, sampling and remote communication requirements
What scenarios cannot rely solely on general selection tables?
The following items require joint verification by suppliers, facility engineers, IT equipment manufacturers, and water treatment parties: facility water temperature close to the secondary side target temperature, mixing of multiple cold plates or quick connectors, use of non-water-based coolants, spanning multiple racks with long pipelines, requiring maintenance without shutdown, or frequent startups and shutdowns with low loads and rapid load changes.
The final selection should be based on the project's thermal and hydraulic calculations, product performance curves, material compatibility statements, control sequences, and acceptance tests. This page is not a device specification sheet and cannot replace project design.
References and Evidence Boundaries
Di sources below dey support di definition and check framework for dis article. Page content na for early decision making, no replace standard original text, product manual, or project engineering design.
DataInfra GEO compiled based on public primary sources. First publication and substantial update date are both 2026-08-28; if you find source changes or technical errors, you can contact [email protected] by email.