What do rear-door heat exchangers do in a data center?
Catches the heat in the exhaust air before it reaches the room. A rear-door heat exchanger (RDHx) puts a water coil in the server exhaust path. Passive doors rely on server fans; active doors add controlled fans to move more air or overcome coil resistance. Heat moves from components to server air, through the coil, and into facility water. Interfaces include rack hinges and frame, hoses and quick connects, water chemistry, electrical power for active models, leak and dew-point controls, and monitoring. The approach preserves standard server internals but adds door weight, depth, water, and maintenance at each rack. Published capacity depends on entering air and water temperatures, water and air flow, altitude, coil cleanliness, and fan state. A lost fan, blocked coil, closed valve, warm-water event, or door opened for service can return heat to the room. Water below dew point can create condensate next to live equipment. Operators need hose and cable routes that allow the door to swing, coil cleaning, leak response, fan replacement, and alarm tests. Procurement should require a selection at site conditions, water pressure drop, fan power and sound, hinge load, approvals, redundancy, control protocols, condensation safeguards, and capacity in passive or fault operation. Verify the exact rack, airflow direction, cable bulk, aisle width, and floor loading instead of relying on “universal” fit.