Natural convection heat transfer between eccentric horizontal cylinders

A numerical study is presented of the laminar natural convection flow between vertically eccentric horizontal cylinders. The inner and outer cylinders are heated and cooled, respectively, in order to maintain constant surface temperatures, and a physical model is developed to account for the effects of the fluid buoyancy and the eccentricity of the outer cylinder. Results show that both eccentricity and buoyancy have a significant influence on the heat transfer and flow field of a fluid between horizontal cylinders. It is found that the effect of buoyancy, which enhances the average heat transfer, increases with the Grashof number. By decreasing the distance between the two annuli at one point, eccentricity increases the heat transfer due to conduction. Moderate positive values of eccentricity, representing a more favorable geometry between the cylinders, enhance the convective heat transfer, while negative values, representing less favorable geometry for convection, reduce the contribution by convection. Estimations of the temperature and flow fields, as well as the local heat transfer rates, are presented for several cases, and the variation of the average heat transfer rate and average shear stress with Grashof number and eccentricity is examined.