CDU (coolant distribution unit)
Beginner
A box with pumps that sends cool, clean liquid to the computers and passes their heat on to the building’s water pipes.
Novice
The unit that separates the clean liquid flowing through servers from the building’s water. It pumps that liquid, controls its temperature, pressure and cleanliness, and moves the heat across a heat exchanger.
Expert
Five functions: temperature control, flow control, pressure control (including negative-pressure designs to limit leaks), fluid treatment, and heat exchange with isolation. Liquid-to-air CDUs reject heat into the room; liquid-to-liquid CDUs into facility water. Rack-mounted units cover tens of kW; floor-mounted units hundreds of kW to over 1 MW.
Explained in Power and cooling (Systems).
See also: Direct-to-chip liquid cooling (cold plates).