Effect of the subdivision of an obstacle on the natural convection heat transfer in a square cavity

In this paper, a numerical study is carried out on thermal natural convection in a square cavity with adiabatic horizontal walls, thermally active vertical walls (maintained at constant but different temperatures) and containing blocks. The governing parameters are the Rayleigh number (103 ⩽ Ra ⩽ 108), the relative thermal conductivity of the solid blocks (10−3 ⩽ kr ⩽ 103) and their number (N = 1, 4, 16 and 64). The effect of these parameters on the fluid flow (air) and heat transfer through the active walls of the cavity is analyzed in the case where the volume occupied by the fluid is maintained constant. In comparison with an enclosure equipped with one block located in its centre, the results obtained in the case of the block’s fragmentation show that the heat transfer and the flow intensity could be significantly reduced by increasing the number of the blocks and their relative conductivity, kr. It is also demonstrated that, the results of the saturated porous medium are recovered when the number of blocks is large enough (1600 < N < 8100).

► We examine the effect of the subdivision of a block on natural convection.
► The onset of convection is delayed with the increase of the number of the blocks.
► The blocks with low conductivity are favorable to convection heat transfer.
► Results of the blocks-filled cavity can be recovered by the porous medium model.