Natural Convection Heat Transfer in a Square Enclosure with an Inside hot Block

A two-dimensional natural convection heat transfer in a square cavity having a hot square obstacle located centrally is investigated numerically by the lattice Boltzmann method. In this paper, the variables of interest like flow velocity and the temperature are treated using the MRT-D2Q9 model and the MRT-D2Q5 model, respectively. The left and right vertical walls are kept at the same cold temperature while the horizontal walls are assumed to be adiabatic. Concerning the bottom square block, a hot temperature is imposed. In the present research the Prandtl number is taken to be 0.71 corresponding to the air. The effects of Rayleigh number (10(3) <= Ra <= 10(6)), dimension (0.2 <= W <= 0.8) and location (0.1 <= D <= 0.4) of the active block upon dynamic and thermal fields of fluid are examined. Detailed analysis of results reported in form of the distributions of streamlines, isotherms and local Nusselt are discussed. In general way, the modification of geometrical dimensions of the square block and its horizontal position disrupt the fluid flow and heat transfer structures. The increased block dimensions has enhanced the heat transfer due to increasing the surface area of the bottom block.