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, l . 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
105, while l is varied from horizontal position(l =0) to vertical position (l = 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 l 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 l≠0, the rate of heat transfer in the
annulus is higher in case of negative eccentricities than that for same positive
eccentricities.