The Definitive Guide toAI Data Centers
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GuideGlossaryRear-door heat exchanger

Rear-door heat exchanger · RDHx

A radiator-style door on the back of a rack that cools exhaust air with liquid before it enters the room.

Current numbers

~10–30 kW typical; to ~50 kW on current productpassive RDHx capacity per rack (server fans only, zero added fan power)as of 2026-04 · register ↗
~50–100 kWactive RDHx capacity per rack — newest high-capacity doors reach ~100 kW; Motivair ChilledDoor rated to ~75 kW at 100% heat captureas of 2026-04 · register ↗
10–100 kWRDHx capacity per rack (passive ~15–30 kW; active ~50–100 kW); ~$8–15k/rackas of 2026-04 · register ↗

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