Phase Change Materials (PCMs) are known to be capable of storing a substantial amount of energy in relatively low volume. Also, since the phase change process occurs in a nearly constant temperature, PCMs are suitable to be used as storage units. The present study focuses on the effect of Heat Transfer Fluid (HTF) flow parameters on heat transfer and melting process of PCM. The numerical results are validated against available experimental data. Then, the numerical study is extended to investigate the impacts of HTF flow parameters such as inlet temperature and mass flow rate. According to the obtained numerical results, the overall performance of the system is enhanced by increasing the inlet parameters of the HTF flow. In addition, the exergy analysis indicated that the stored exergy increases with increasing flow rate and inlet temperature of HTF. On the other hand, the exergy efficiency does not increase monotonically, but it reaches its maximum value in intermediate values of inlet flow rate and temperature.