The present study explores numerically the process of melting of the phase-change material (PCM) for cooling electronic components or heat storage applications. The system studied is a rectangular enclosure filled with PCM. Three protruding generating heat sources are attached on one of the vertical walls of the enclosure, and generating heat at a pulsed form and uniform volumetric rate. The power generated in heat sources is dissipated in PCM. The advantage of using PCM is that it is able to absorb high amount of heat generated by heat sources due to its relatively high energy density. To investigate the thermal behavior and thermal performance of the proposed system, a mathematical model based on the mass, momentum and energy conservation equations was developed. After validating the proposed mathematical model against experimental data, numerical investigations were next conducted to examine the impact of the frequency of the pulsed power generated and the aspect ratio of the enclosure on the cooling capacity and energy storage of the PCM-based heat sink.