Natural convection in trapezoidal cavities with baffles mounted on the upper inclined surfaces

A numerical investigation has been undertaken to study the effects of mount ing baffles to the upper inclined planes of trapezoidal cavities (represent ing a building or attic space). Two thermal boundary conditions are conside red: (a) the vertical and upper surfaces are heated while the lower surface is cooled (summerlike conditions); (b) the lower surface is heated while t he other surfaces are cooled (winterlike conditions). For each boundary con dition, computations are performed for two baffle heights and two baffle lo cations. Rayleigh number (Ra) values range from 10(3) to 5 x 10(7) for summ erlike conditions and from 10(3) to 10(6) fur winterlike conditions. For bo th boundary conditions, results obtained with air as the working fluid reve al a decrease ill hear transfer in the presence of baffles. In winterlike c onditions, convection starts to dominate at all Ra much lower than that in summerlike conditions. The decrease in heat transfer becomes increasingly m ore significant as the baffle gets closer to the heated vertical wall for t he bottom-cooled situation and as the baffle gets closer to the symmetry li ne for the bottom-heated case. In general, this decrease in heat transfer i s higher with taller baffles. Average Nusselt number (Nu) correlations for both boundary conditions are presented.