Numerical investigation of the three-dimensional natural convection inside concentric and eccentric annuli with specified wall heat flux

A numerical investigation for three-dimensional natural convection in concentric and eccentric annuli with open ends is made by a zonal grid approach, which extends the outlet boundary from the open end of the annuli to a far enough outside position that can be reasonably specified with the ambient flow properties. It is found that the eccentric annulus has a poorer natural convection heat dissipation rate, as compared to the concentric annulus. The inner cylinder surface temperatures decrease toward the outlet plane. It is also found that higher temperatures around the inner cylinder occur in the region near its bottom (the contacting point of the inner and outer cylinders) for the eccentric annulus, whereas in the region near its top for the concentric annulus. The variation of the inner cylinder surface temperatures is smaller for the case of concentric annulus, as compared to the eccentric annulus. The maximum inner cylinder surface temperatures occur right at the bottom of the inner cylinder for the eccentric annulus, whereas right at the top of the inner cylinder for the concentric annulus.