Numerical Investigation of Natural Convection in Heterogeneous Rectangular Enclosures

The aim of this study is to investigate numerically the steady natural convection resulting from horizontally heating a rectangular enclosure filled with a fluid and containing uniformly distributed, conducting, fixed and disconnected solid blocks (i.e., not touching each other). In particular, the effects of solid volume fraction, solid-fluid thermal conductivity ratio, and total number of blocks on the heat transfer process are determined by solving the mass, momentum, and energy conservation equations using the finite-volume method. The enclosure aspect ratio is varied from 0.25 to 4, the Rayleigh number from 10(5) to 10(8), and the Prandtl number is set as unity. Results of the numerical simulations are presented in terms of the surface-averaged Nusselt number, streamfunction, and streamline and isotherm distributions. The interference phenomenon caused by the solid blocks on the natural convection process is considered in detail and used to explain and predict the surprising and complex behavior of surface-averaged Nusselt number.