Radiation-natural coupled heat transfer in a circular enclosure embedded with a rectangle cylinder

Laminar natural convection coupled with radiation arising from horizontal rectangle cylinder to its concentric cylindrical enclosure has widely applications over the electronic equipment and aviation industry. In this paper, this model is numerically studied with the Rayleigh number varied in the range of 10³≤Ra≤10⁷. According to the local and average Nusselt numbers along the outer and inner walls, the radiation effect on the heat transfer of the different aspect ratios cavity has been presented. It is found that as the Rayleigh numbers increase, the ratio declines due to the convection part augment more than the radiation for HR=0.6 and 1.0. On the contrary, the ratio increases for HR=1.4.