A rear door heat exchanger places a large coil, fluid connections and service hardware on the back of a server rack. The sheet metal frame has to carry that mass, preserve the air seal and swing without interfering with cables or adjacent cabinets. It also has to protect the coil during manufacturing, shipping and maintenance.
The heat-transfer design belongs to the cooling-system owner. A sheet metal supplier needs released coil interfaces, door loads, hinge geometry, gasket requirements and verification points.
Scope boundary - A fabricated RDHx door or coil carrier does not have a thermal rating by itself. Capacity depends on the coil, coolant conditions, airflow, rack heat load and controls in the tested system.
Map the Interfaces Before Designing the Door
Start with:
- rack rear-opening envelope
- coil outline, thickness, mass and mounting points
- wet and dry operating mass
- center of gravity in open and closed positions
- hinge axis and maximum swing
- latch and gasket compression line
- manifold, hose and quick-disconnect envelope
- cable and service clearance behind the rack
- shipping and lifting arrangement
ASHRAE describes rear-door or in-rack heat exchangers as rack-level liquid-assisted cooling approaches that transfer a large portion of equipment waste heat from air to liquid. That system context is important: the door frame has to preserve both the air route and the liquid-component service envelope.
Hinge Load and Door Sag
An RDHx door is often deeper and heavier than a perforated rack door. Hinge loads change as the door opens, and hose routing can add forces not visible in the closed assembly.
The OEM should provide load cases for:
- closed operating position
- fully open service position
- opening and closing cycles
- shipping restraints
- accidental handling loads
- hoses connected and disconnected
The drawing should control hinge-axis straightness, bracket position and frame twist. Use an inspection setup that represents the rack interface and coil mass rather than measuring the empty outer frame on a bench.
Gasket Lands and Air Bypass
Air that bypasses the coil does not contribute to the intended heat exchange. Define a continuous gasket land with:
- controlled width and flatness
- corner transitions
- compression stops where needed
- latch positions that distribute pressure
- replaceable gasket and service method
Do not place weld buildup, fastener heads or coating runs in the sealing path. If the gasket is periodically opened, select and validate it for that use through the system specification.
Condensate and Leak Management
Coolant conditions should be controlled to avoid condensation, but the mechanical design still needs a response to leaks and wet service. Coordinate:
- drip tray or containment geometry
- drain and sensor locations
- slopes and low points
- protected electrical zones
- hose abrasion and bend clearance
- access for leak inspection
The fabricator can build trays and sensor brackets to released drawings. Leak detection logic, coolant control and facility integration remain outside the sheet metal scope unless assigned.
Coil Protection Without Blocking Air
The door may need removable guards, service panels or shipping protection. These features should protect fins and tubing while maintaining the validated airflow path.
Define:
- minimum clearance to coil faces and headers
- perforation or grille geometry
- tool access for coil mounting
- removable panel retention
- shipping braces and removal instructions
- no-step and handling labels
Material, Finish and Bonding
Coated steel and aluminum are common structural choices. Material selection should consider mass, hinge loads, galvanic interfaces, condensation and the rack finish system.
Specify:
- substrate and coating system
- masked bonding locations
- compatibility with coil and coolant hardware
- corrosion requirements
- cosmetic zones
- thread and gasket protection during coating
If doors or removable panels require bonding, identify dedicated straps or contact points. Do not assume painted hinges provide a reliable electrical path.
First-Article Verification
Check the RDHx mechanical assembly for:
- fit to a controlled rack interface
- hinge alignment and full swing
- loaded door sag and latch engagement
- gasket contact around the perimeter
- coil and manifold bracket location
- hose and cable clearance through travel
- drip-tray slope and sensor position
- guard and service-panel removal
- bonding points and finish masking
- packaging restraints
RDHx RFQ Package
Send the rack model, coil drawing, wet and dry mass, hinge and latch requirements, gasket section, manifold envelope, containment design, material and finish, inspection plan, packaging and forecast volume. State whether the supplier assembles customer-supplied coils or delivers only the frame and door structure.
See our rear door heat exchanger fabrication page and custom data center racks, or send the released mechanical package.
Technical Reference
- ASHRAE Handbook: Data Centers and Telecommunication Facilities - overview of datacom airflow and liquid-assisted rack cooling
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