Heat Transfer in Inclined Enclosure of Silica Aerogel/Glass Fiber Composite Material

Abstract

is performed for natural convection of air in a three dimensional inclined annulus enclosure. The annulus material is made of silica aerogel/glass fiber composite materials. The annulus enclosure is filled with silica sand between two inclined concentric cylinders with fins attached to the inner cylinder. Constant walls temperature boundary conditions are considered under steady state condition. The parameters affected on the system are modified Rayleigh number (10 ≤Ra * ≤ 500) and the annulus inclination angle δ (0 o , 30 o , 45 o , 60 o and 90 o ). The effect of fibres filler in composite material is investigated and two values of effective thermal conductivity are performed: the minimum and the maximum values considering the fiber alignment effect. The results showed insignificant effect of the inclination angle on the average Nusselt number for the low values of Ra * . The average Nu number increases with an increase in modified Rayleigh number and decrease with the increase of δ for high values of Ra * . The deviation between the average Nu for the maximization and minimization of the thermal conductivity is equal to 2.26% for δ=90 o (horizontal annulus) and 0.46% for δ=0 o (vertical annulus). A correlation for the average Nusselt number in terms of Ra * and δ, has been developed for the outer cold cylinder and for the two cases of maximization and minimization of thermal conductivity.