Shape Effect of a Vertical Hollow Louvered Frustum on Natural Convection Flow

Using numerical simulations, the shape effect of a vertical hollow frustum with surface holes was examined by maintaining the Rayleigh number ([Formula: see text]) within a laminar regime while all the frustum shapes have the same surface area. The frustum was kept either in the air or on the ground. Here, the Nusselt number (for both inner and outer surfaces) as a function of the surface orientation ([Formula: see text]) gives a notion to the shape effect on natural convection heat transfer. A comparison of [Formula: see text] between the inner and outer surfaces and also for the straight and inverted frustums is made. For a straight frustum in the air, the outer surface has always much higher [Formula: see text] than the inner surface. At all [Formula: see text] and [Formula: see text], this behavior of [Formula: see text] remains consistent for an inverted frustum that is kept on the ground. Similarly, a straight frustum on the ground exhibits the same behavior within a broad [Formula: see text] range. Furthermore, the inner surface always takes the larger [Formula: see text] value for a straight frustum than for an inverted one when both the frustums are resting on the ground. With the exception of [Formula: see text] and [Formula: see text], the reverse is true when both of them are in the air.