Effect of Porosity on the Natural Convection Heat Transfer in an Inclined Annular Porous Medium.

Document Type : Research Studies

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Mechanical Power Engineering Department., Faculty of Engineering., El-Mansoura University., Mansoura., Egypt.

Abstract

Experimental study was carried out for the steady laminar natural convection of air in an inclined annulus porous medium, with constant heat flux heated inner cylinder and an isothermally cooled outer  cylinder. The primary objective of the study is to show the effect of porosity of the annulus on the local and maximum temperatures of the heated inner cylinder and the local and mean Nusselt number. The geometrical parameters of the annulus are: diameters of 21/45mm, gap width=12mm, length of 492mm, and an aspect ratio (length/gap width) = 41. The operating parameters are: heat flux 4 ≤Q≤324W, Rayleigh number 10≤Ra≤550 and inclination angle θ=0,30,60 and 90o. The spherical bead diameter are varied from d = 3.11 to 3.97 to 6.35 mm with porosity of 0.42. 0.43 and 0.45 respectively. The results show great influence of the porosity on the local and maximum surface temperatures as well as the local and mean Nusselt number.
The average Nusselt number is correlated with the inclination angle and the Rayleigh and Darcy numbers.

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