Nusselt Number and Melt Time Correlations for Melting Inside a Horizontal Cylinder Subjected to an Isothermal Wall Temperature Condition

The design of latent-heat storage devices requires the knowledge of the cycle time (the total melt-down time of the Phase Change Material (PCM)), and the variation of the Nusselt number along the wall over time, given the properties of the PCM and the wall temperature. In order to answer these questions, we have extended a previous work by the same authors, which studied numerically the process of melting of a PCM within a horizontal tube subjected to a constant wall temperature. This numerical model accounts for the irregular, time-dependent shape of the solid-liquid interface, the downward motion of the solid core due to density differences and the natural convection in the liquid phase. In the present work, we study the effect of a variation in the Rayleigh, Stefan, and Prandtl numbers, and obtain useful correlations for the melt time and the Nusselt number.