Paper Title
A Numerical Study of Natural Convective Heat Transfer from the Uniform Heat Flux of a Vertical and Horizontal Slender Cuboid with an Exposed Upper Surface Mounted on a Flat Adiabatic Base

Abstract
A numerical study was undertaken of laminar natural convective heat transfer from slender cuboid with a relatively narrow square cross-section and an exposed top surface. The cuboid was perpendicularly mounted on a flat adiabatic base plate and uniform heat flux boundary conditions were assumed. Three positions were considered for the slender cuboid: horizontal; pointing vertically upward; and pointing vertically downward. This situation is relevant to cooling applications in electrical and electronic components. The flow was considered symmetrical along the vertical center-plane through the slender cuboid. The governing equations were solved in terms of dimensionless variables using the FLUENT commercial CFD solver. From the solution the values of the mean Nusselt number for the slender cuboid, Nu, were calculated using the following parameters: the heat flux Rayleigh number, Ra*; the dimensionless slender cuboid width, i.e., the ratio of the width to the height of the heated slender cuboid, W = w/h; the Prandtl number, Pr; and the position of the slender cuboid relative to the vertical, φ. Results were obtained only for Pr = 0.7. Values of φ of 0o, 90o and 180o, and values of Ra* in the range 103 to 109 and of W in the range 0.25 to 0.05 were considered. The effects of W, Ra*, and φ on the mean Nusselt number for the combined and for the individual surfaces of the slender cuboid are presented. Keywords - Edge effects, Constant heat flux, Natural Convective Heat Transfer, Numerical Simulations, Slender Cuboid.