Natural convection melting of a frozen porous medium

Abstract

Melting of an ice-porous media (glass beads) system contained in a rectangular test cell has been studied both experimentally and numerically in order to examine the effects of natural convection and density inversion of water in the melt region. When the superheat across the liquid region is small the flow in the porous media is weak and the interface is almost planar. For larger superheats, the strength of natural convection flow, the interface velocity and shape are all found to depend on the imposed temperature difference and the permeability of the porous medium. The measured temperature distributions are compared with predictions of a numerical model that considers both conduction in the solid and natural convection in the liquid regions. The model is based on volumetric averaging of the macroscopic transport equations, with phase change assumed to occur volumetrically over a small temperature range. Both Brinkman and Forchheimer extensions are added to the Darcy equations. The effect of density inversion of water on the fluid flow and heat transfer is modeled. Reasonably good agreement is found between the experimental data and numerical predictions. The numerical and experimental results establish conclusively that natural convection in the melt region causes the front shape to become nonplanar and increases the melting rate.