MODELING OF NATURAL CONVECTION IN ELECTRONIC ENCLOSURES

An analytical model is developed for natural convection from a single circuit board in a sealed electronic equipment enclosure. The circuit card is modelled as a vertical isothermal plate lo-cated at the center of an isothermal, cuboid shaped enclosure. A composite model is developed based on asymptotic solutions for three limiting cases: pure conduction, laminar boundary layer convection and transition flow convection. The conduc-tion shape factor and natural convection models are validated using data from CFD simulations for a wide range of enclosure geometries and flow conditions. The model is shown to be in good agreement, within 10 % RMS, with the numerical data for all test configurations. NOMENCLATURE A area, m2 b plate to enclosure spacing, m cp specific heat, J/kgK deff effective diameter, m F(Pr) Prandtl number function g gravitational acceleration, m/s2 GL body gravity function k thermal conductivity,W/mK L length, m L general scale length, m n,m combination parameter