Numerical Investigation of Laminar Natural Convection in a Circular Enclosure with a Rectangle Cylinder

Laminar natural convection arising from horizontal rectangle cylinder to its concentric cylindrical enclosure is numerically studied. The Rayleigh number is varied in the range of 10³≤Ra≤10⁶. According to the form of isotherms and the streamline patterns, the basic features of flow and heat transfer for four rectangle cylinders with different aspect ratios are reported. And the local and average Nusselt numbers along the outer and inner walls have been present. It is found that the flow pattern and thermal stratification are modified, if the aspect ratio varies. And the vortexes occurring on the top of the rectangle cylinder have considerable effects on the average Nusselt numbers, when the aspect ratio exceeds to 1.2.