RDHx · Rear-Door Heat Exchanger
A rack door with a water coil that cools server exhaust before it reaches the room, without piping liquid to the chips. Typically 30–40 kW per rack, over 50 kW with active fans; named active doors are rated about 75–78 kW at stated water and air temperatures.
A radiator-style door on the back of a rack that cools exhaust air with liquid before it enters the room.
Also written as: Rear-Door Heat Exchanger
Current numbers
up to 75 kW — Motivair ChilledDooractive RDHx capacity per rack: Motivair ChilledDoor, rated to ~75 kW at 100% heat capture
30–40 kW typical RDHx; >50 kW with active fansRear-door heat exchanger capacity SemiAnalysis reports (Feb 2025): 30–40 kW typical, >50 kW with active door fans
100% sensibledesign target for a CDU- or warm-water-fed RDHx: coil supply held above the white-space dew point, so nothing condenses