Direct Contact Melting of a Packed Bed

Direct contact melting of a packed bed is studied experimentally. The effect of several parameters, including material properties, particle size, bed loading (applied external force), and thermal boundary conditions, is examined. Two types of melting are observed. If the load on the bed is small and the top of the bed is maintained at a temperature below the melting temperature, then crusting can occur. During this type of melting liquid flows away from the heated surface due to capillary action, and resolidifies forming a crust. The crust prevents downward movement of the packed bed, and melting of the solids below the crust results from convection and conduction. Eventually the crust is melted and the process repeats itself, resulting in a highly unsteady melting rate. If the bed load and the temperature at the top of the bed are sufficiently high, then direct contact melting persists. In this case the melting rate is steady and the parametric behavior can be predicted using a modification of an available theory for direct contact melting of monolithic solids. Although this theory accurately predicts the parametric behavior, the prediction of the actual melting rate is more than an order of magnitude higher than the experimental results.