Heat transfer problems involving phase change occur in a large number of practical situations: solidification in casting processes, purification of silicon wafers using laser-induced melting, and in latent-heat storage devices. Latent heat storage device posses the advantages of a high density of energy storage and the ability to supply heat at a constant temperature. This allows the design of compact storage systems. For such a design the authors must know the duration of a complete melting cycle and the variation of the Nusselt number over time, given the storage configuration, the phase change material (PCM) used, and the heat transfer conditions at the boundary. The problem of melting inside a horizontal cylinder has been studied by several investigators. The earlier studies assumed that conduction was the only mode of heat transfer, while others assumed that the solid core was supported at the center, which prevented the unmelted solid from sinking to the bottom. Nicholas and Bayazitoglu performed experiments which confirmed that the solid core does move downward; they also solved the problem numerically, but without the presence of natural convection. Elmasry and Sengupta solved the problem numerically, taking all its features into account; however, their solution was handicapped by themore » presence of a singularity at the origin. Finally, Beer and Bareiss performed an analytical solution which was confirmed by experiments. In this study, the authors have considered all the features of the problem; they have also made use of Beer's results to model the melting in the contact zone.« less