The present study deals with the investigation of melting behaviour of phase change materials (PCMs) during the cyclic heating. For this work, a computational fluid dynamic (CFD) study of heat and mass transfer during melting and solidification of PCM is carried out for the constant and variable (sinusoidal) heat supply. For the constant heat flux a step function ranging from 500 W/m2 to −500W/m2 and for variable heat flux, a sine function having a similar area as step function was considered at one wall of the container to provide heating and cooling of the PCMs. The results are reported in terms of melting interface, melt fraction during melting and solidification, temperature variation, the variation of melted PCM velocity, and rate of energy storage and release. From the results, it is observed that the melting time is reduced with variable heat flux as compared to constant heat flux and it is also pointed out that the melting time of PCM is lower as compared to solidification time