What Are Rear Door Heat Exchangers (RDHx)?

A Rear Door Heat Exchanger (RDHx) is a passive, liquid-based cooling device that attaches to the back of a standard server rack, replacing the conventional perforated rear door. Its purpose is to capture and remove the hot exhaust air directly from the servers before it can mix with the room's ambient air.

Think of it as a high-efficiency radiator for your server rack. It uses chilled water (or another coolant) circulating through a coil to absorb heat from the air being expelled by the servers.

Key Components

Chilled Water Coil: A serpentine tube with densely packed aluminum or copper fins to maximize surface area for heat transfer.

Fans (Usually): While often called "passive," most modern RDHx units include redundant, hot-swappable fans. These fans ensure airflow isn't restricted by the dense coil and can ramp up if server fans slow down.

Quick-Connect Hoses: Allow the door to be swung open for server access without draining the entire cooling system.

Control Unit: Monitors temperature sensors and controls water flow valves and fan speeds automatically.