variavel0=<b>Tito Dias Jr</b> - tito@fem.unicamp.br DE-FEM-UNICAMP
<b>Luiz Fernando Milanez</b> - milanez@fem.unicamp.br DE-FEM-UNICAMP
<b>Abstract.</b> In this work, the laminar natural convection in high aspect ratio three-dimensional enclosures has been numerically studied. The enclosures studied here were heated with uniform heat flux on a vertical wall and cooled at constant temperature on the opposite wall. The remaining walls were considered adiabatic. Fluid properties were assumed constant except for the density change with temperature on the buoyancy term. The governing equations were solved using the finite volumes method and the dimensionless form of these equations has the Prandtl number and the modified Rayleigh number as parameters. The influence of the Rayleigh number and the cavity aspect ratio on the Nusselt number with Prandtl number of 0.7 were analyzed. Results were obtained for values of the modified Rayleigh number up 10^6 and for aspect ratios ranging from 1 to 20. The results were compared with two-dimensional results available in the literature and the variation of the average Nusselt number with the parameters studied were discussed;
<b>Keywords.</b> natural convection, tridimensional enclosures, uniform heat flux.