Laminar Natural Convection in a Horizontal Rhombic Annulus

Abstract

This paper presents the simulation of heat transfer and flow patterns in an enclosure between two isothermal concentric cylinders of rhombic cross sections. Four different values of the enclosure gap (E_g = 0.875, 0.75, 0.5, and 0.25) and three different rhombic angles (Ω = 10^°, 20^°, and 30^°) are considered. At low Rayleigh numbers (10³-10⁵) the flow is weak and conduction is the dominant mode of heat transfer. Convection plays a key role starting at higher Rayleigh numbers (10⁶-10⁷). For all cases studied, there is no tendency for flow separation at the horizontal corners. The flow strength is found to increase with increasing rhomsic angel, increasing enclosure gap, and increasing Rayleigh number. The critical Rayleigh number at which the heat transper is influenced by convention decreases with ihcreasing gap values and increasing rhombic angle; it is as high as 10⁶-10⁷ for E_g = 0.25 and decreases to about 10⁴ for E_g = 0.875.