Definition
A Coolant Distribution Unit (CDU) is the bridge between a facility's cooling plant and the liquid-cooled hardware it serves. It sits between two loops: a primary loop carrying facility water that ultimately rejects heat outdoors, and a secondary loop of clean, controlled coolant that circulates through the equipment. Inside the CDU, a heat exchanger transfers heat from the secondary loop into the primary loop without ever mixing the two fluids, while a pump, sensors, and controls regulate the secondary loop's flow, temperature, and pressure.
Why the two-loop split matters
Keeping the equipment loop separate lets operators run a purpose-chosen coolant (often deionized water or a water-glycol blend, or a dielectric fluid in immersion setups) that is filtered and chemically stable, protected from whatever quality and pressure the building water happens to have. The CDU holds the coolant at a precise set-point and flow rate, which is what makes cold plates and immersion tanks behave predictably under heavy, variable load.
Role in mining
As ASIC power densities climb, direct liquid and immersion cooling increasingly rely on a CDU to interface the tank or cold-plate loop with a dry cooler or cooling tower outside. A well-sized CDU lets a site run warmer primary-water set-points, which improves overall efficiency, and its redundant pumps guard against a single point of failure taking down a whole row of hardware.
The CDU's exchanger is a specialized Heat Exchanger, and it is the workhorse that makes Single-Phase Immersion Cooling scale cleanly.
In Simple Terms
A Coolant Distribution Unit (CDU) is the bridge between a facility’s cooling plant and the liquid-cooled hardware it serves. It sits between two loops: a…