Phase change of paraffin in a hemicylindrical storage unit is investigated numerically and experimentally. The predicted findings are confirmed by comparison with the experimental results of the present work. Good agreements are achieved between the two approaches. The influence of the hot wall temperatures of 80, 85, and 90 °C is examined. The conduction mechanism is dominant only during the initial periods of the charging process, while buoyancy-driven convection is prevalent at later stages. The charging rate and stored energy both increased, whereas the melting time is reduced as the wall temperature increases. The Nusselt number increases sharply at the initial period of the fusion process, followed by a decaying trend with time until it stabilizes when the charging process is terminated. Increasing the cell diameter from 20 to 40 cm will raise the melting time by 300% for the wall temperature of 90 °C. In addition, under the same operating conditions, the melting of the phase change material (PCM) inside the hemicylindrical cell is faster than that observed in a rectangular one with equivalent volume. Savings in melting time due to using hemicylindrical container instead of a rectangular one of equivalent PCM volume are about 7.1%, 8.3%, and 11.7% for hot wall temperatures of 65, 75, and 85 °C, respectively.