Natural convection suppression in horizontal annuli by azimuthal baffles

Numerical computations based on the control volume approach using orthogonal coordinates are carried out for conjugate natural convection within a horizontal cylindrical annulus. The purpose is to study the possible suppression of convections by azimuthal baffles. The baffles are placed at the top, central and bottom regions of the annular gap. The Rayleigh number based on the annular gap width is varied from 1.0 x 102 to 106 for radius ratios of 4.0 and 1.4. The fluid is air, and the transport properties depend on temperature. The most efficient way of reducing heat transfer is the case where the baffle prevents direct flow onto the inner and outer cylinders. When the baffle is at the position where the crescent-shaped streamlines are stretched, an increase of heat transfer occurs. Only a small reduction in heat transfer is obtained when the baffle is placed in the stagnant region of the annulus. (author)