NATURAL-CONVECTION HEAT-TRANSFER IN A 3-DIMENSIONAL DUCT

A computational analysis is conducted to investigate the three-dimensi onal heat transfer and flow characteristics of laminar natural convect ion in a vertical duct, open to the ambient at the top and bottom and enclosed on all four sides. Detailed data are presented for air (Pr = 0.7) in a square duct heated/cooled isothermally or uniformly on one s ide with the remaining three walls assumed adiabatic. Numerical data a re also obtained and presented for comparisons by way of a two-dimensi onal channel now approximation. The channel flow model that neglects t he slowing down of the streamwise velocities due to the friction of th e lateral walls predicts considerably higher local and average Nusselt numbers than the three-dimensional analysis for a square duct. Presen t numerical results are compared to published experimental data. The n umerical data are in good agreement with the experimental data of Elen baas,5 Wirtz and Stutzman,7 and Sobel et al.,8 but significantly under predict the experimental data of Sparrow and Bahrami.9