Thermal energy storage plays an important role in a wide variety of industrial, commercial, and other applications when there is a serious mismatch between the supply and demand of energy. Latent heat storage with phase change materials is very attractive, because of its high-energy storage density and its isothermal behavior during the phase change process. Here, the heat transfer enhancement in a two-dimensional enclosure containing nanofluids is solved using Fluent 6.2 software. Starting with steady natural convention, the phase change behavior is simulated considering different volume fractions of the SiC-H2O nanofluids. The simulation results show that the freezing rate of nanofluids is enhanced due to the addition of nanoparticles. The higher the volume fraction is, the shorter the total freezing time. Adding 5% SiC nanoparticles into water, the total freezing time can be saved by 17.4%. The computation results show that adding nanoparticles is an efficient way to enhance the heat transfer in a latent heat thermal energy storage system.