Numerical analysis of heat transfer in annulus composite material at different operation conditions

Abstract

In this article natural air convection in an inclined annular cage in three dimensions is investigated numerically. This study will examine the impact of the radius ratio of an annulus on heat transfer employing two distinct methods to optimizing effective thermal conductivity: minimizing and maximizing. The annulus is built of graphite/epoxy laminated composite material. There are 12 fins attached to the inner cylinder of the two concentric cylinders that make up the annulus enclosure, which is filled with porous medium. Regarding the annulus's inclination angle “δ”, two scenarios—a horizontal annulus and a vertical annulus—are considered. Constant walls temperature boundary condition and steady state conditions apply to the system with 0.2, 0.3, 0.4 and 0.5 different radius ratio, inclination angle (0^o and 90^o), and modified Rayleigh number “Ra*”   ranged from 10 to 500, The Nusselt number decreased for all parameters as the radius ratio Rr decreased, indicating a wider cold outer cylinder gap. For large values of modified Rayleigh number, the average Nu number ”Nu_avg.” decreases with an increase in δ, and increases with a rise in the modified Rayleigh number; for low values of Ra*, δ has no effect. For horizontal, and vertical states “δ=0 o, and 90^o respectively, at higher and lower thermal conductivity, the divergence of the average Nusselt is 5.1% and 10%, respectively. In horizontal cylinder adding fins on the inner cylinder is more substantial for due to its impeding effect, and Nu_L increases with cylinder length. For the outer cold cylinder, a link between Ra* and δ and the average Nusselt number has been established.