Blockage effects in natural convection in differentially heated enclosures

Natural convection in a differentially heated enclosure filled with discret e solid objects is analyzed numerically. The effect of six square shaped so lid objects on the natural convection in a rectangular enclosure of aspect ratio 2 is addressed for different solid geometrical arrangements and therm al conductivities. The investigation is performed for Ra = 1 x 10(5) and 1 x 10(7) for thermal conductivity ratio between the solid bodies and the flu id (k(r)) of 0.1, 1.0, 10 and 100. The problem aims to clarify the boundary effects associated with the location. size and the thermal conductivities of the solid objects. It is known that natural convection in porous media i s highly affected by the boundary phenomena when high permeability is consi dered. Also, the problem has importance in understanding the thermal equili brium between the solid and the fluid in permeable media, as well as other applications in which obstacles are unavoidable. It is found that placing t he solid bodies near to the walls reduce the rate of heat transfer due to t he blockage effects. But, placing low conductor bodies far from the boundar y layer region may enhance the rate of heat transfer compared with enclosur es: without obstacles. Also, compared with low conductivity bodies; it is f ound that placing high conductor bodies within the boundary layer enhances the rate of heat transfer. As expected, it is shown that Prandtl number has a weak influence on the predictions for Pr greater than or equal to 0.71.