Natural Convection Within an Arbitrarily Oriented Eccentric Annulus

Abstract

In this paper, the natural convection within an annulus formed between two eccentric circular cylinders has been numerically investigated. The annulus is placed horizontally and heated isothermally from its inner wall while its outer wall is isothermally cooled. The resulting laminar natural convection flow within the annulus is predicted at different orientations of the annulus symmetry line, ASL. The full governing equations are solved numerically using Fourier Spectral method. The process of heat convection within the annulus is dependent on Rayliegh number, Prandtl numbers, outer to inner cylinder radius ratio, eccentricity and angle of inclination of ASL to the horizontal, λ. The Prandtl number and radius ratio are fixed at 0.7 and 2.6, respectively. The Rayleigh number is taken within the range up to 10 5 , while λ is varied from horizontal position(λ =0) to vertical position (λ = 90). The results for mean Nussult number are obtained and discussed together with the details of both flow and thermal fields. The study has shown that for a given value of Rayleigh number as λ increases the steady mean Nusselt number increases for negative eccentricities while it deceases for same but positive eccentricities. The study has also shown that for same RaL and λ≠0, the rate of heat transfer in the annulus is higher in case of negative eccentricities than that for same positive eccentricities.