Thermal energy storage systems inherently store heat at different heating positions. In other words, the heat storage performance changes depending on the heating positions. In this study, the effects of the heating surface position and reinforcement of the open-cell metal foam on the phase change material melting fraction were experimentally investigated. For this purpose, a small-scale rectangular cube was made of plexiglass having a volume of 274cm(3). One of the surfaces of the cube was heated with a constant heat flux, whereas other surfaces were isolated from the room temperature in the environment. Three different constant heat fluxes were applied on the bottom, top, and side surfaces of the cube in the experiments. Paraffin (n-heptacosane), with a phase change point at 59 degrees C-61 degrees C and as phase change material with a rapid heat charge/discharge, was used in the thermal energy storage system. Depending on the heating position and surface heat flux, it was observed that the effect of natural convection significantly increased within the liquid phase change material. Additionally, the results indicate that the presence of metal foams can enhance the heat transfer rate of phase change materials. According to the sensitivity analysis, the effect of independent parameters on the melting ratio of the phase change material was listed in order of importance as time, surface heat flux, heating position, and metallic foam.