Chassis Thermal issues:
An equipment chassis normally draws air in through the bottom front of the chassis just below the card cage. The exhaust air is pushed out the rear of the chassis. Fans may be placed under the card cage pulling in the air, or at the rear of the chassis pushing the air out of the chassis. The number and placement of the fans has a determination as to the size of the chassis. Fan Manufacturers produce a number of different sizes and capabilities. So the number of required fans is determined by the fan size, and the amount of tolerated heat rise within the electronic chassis.
In addition to the use of chassis fans, Rack fan trays may also be used to reduce the inlet air temperature to the chassis. Fan trays move air within the rack reducing its temperature; how ever fan trays may also be placed directly under a chassis to support air flow. Vendors that produce them are listed on the Fan Tray Manufacturers page.
Slot By-pass cards may be used to force air next to circuit cards when one or more chassis slots are empty. Of course Front Panels and Filler Panels are always required to control the flow of air within the chassis
Determine the heat generated by the equipment within the chassis. Determine the amount of air flow required to keep the card temperature at the required level. Design in the number of required fans which deliver the amount of air flow needed. Factor in the chassis inlet air temperature in the rack, and add an additional fan tray if required. Temperature Sensor Manufacturers
How To Specify a Equipment Chassis
Equipment Chassis Thermal Specifications:
MIL_PRF_85726B; Enclosure, Standard Avionics, Forced Air-Cooled
