NATURAL CONVECTION IN A POROUS LAYER LOCALLY HEATED FROM BELOW - A REGIONAL LABORATORY MODEL FOR A NUCLEAR WASTE REPOSITORY.

This paper reports a numerical and experimental study of free convective flow and heat transfer in a rectangular two-dimensional domain approximating the region around a nuclear waste repository. The domain is locally heated from below, the top surface is cooled, and the remaining bounding surfaces are adiabatic. Average heat transfer rates along the heated surface, streamline, and isotherm patterns are presented. Very good agreement is found between the experimental and numerical results. The slope of the Nusselt versus Rayleigh number curve varies with the Rayleigh number, and this variation is found to be critically dependent on the aspect ratio and heated length fraction. A physical mechanism to account for this trend is proposed. Finally, implications of the study for the design and location of a nuclear waste repository are discussed.