Totally enclosed naturally cooled electronic enclosures

This paper describes an easy-to-use methodology for thermally evaluating non-vented electronic equipment enclosures that are sealed to limit electromagnetic interference and to preclude entry of surrounding environmental contaminants. A closed form equation is presented that facilitates system thermal characterization and is derived from the combined effects of internal buoyancy induced air flow and enclosure surface heat exchange. Algorithms are described that permit enclosure thermal design evaluations based on spatially variant heat loads, buoyancy-induced pressure rise, and enclosure geometry. Graphical and step-wise computational procedures are developed that enable rapid system characterization for establishing electronic equipment enclosure thermal profiles including the effects of heat dissipation, internal vent open area, flow impedance, surface area, chimney height, and altitude. Analytical and test verification methods are described that permit enclosure induced flow impedance (K/sub sys/) and effective chimney height (H~) characterizations required for determining system thermal signatures. Simplified evaluation methods are presented for assessing enclosure design trade-offs and for establishing thermal design feasibility before performing detailed computer simulations.