Experiments were performed in which melting of a phase-change medium occurred in a closed vertical tube which was rotated about a vertical axis colinear with that of the tube. The melting was initiated and maintained by a step-change increase in the wall temperature of the containment tube. During the course of the experiments, parametric variations were made in the rotational speed, in the temperature difference which drives the melting, and in the duration of the melting period. The phase-change medium was 99% pure n-eicosane paraffin with a melting temperature of 36.3°C. It was found that rotation gave rise to considerably more rapid melting than that for no rotation, with the time required to achieve a given amount of melting being halved due to rotation. The rate at which energy could be stored was also significantly increased by rotation. Furthermore, at any duration of the melting period, the shape of the unmelted solid differed markedly in the presence or absence of rotation, being either straight-sided or sloped-sided. The melted mass results for all of the investigated conditions were very tightly correlated in terms of the Froude, Stefan, Grashof, and Fourier numbers.