Study of melting behavior of phase change material in a square enclosure with constant and variable heat flux at different wall heating conditions: A numerical approach

Latent heat thermal energy storage system offers the most promising cost-effective solution in thermal energy storage applications like solar water heaters to building air conditioning, textile industries, pharmaceutical industries, etc. In this article, the melting process of phase change material (PCM) in a square enclosure with constant, linearly increasing, linearly decreasing and sinusoidal heat flux on different sides of the wall is studied. The result shows that double-wall heating has the highest melting rate followed by side-wall heating and bottom-wall heating. This happens because double-wall heating increases the heat transfer area. Between side-wall heating and bottom-wall heating with uniform heat flux, side-wall heating gives a higher melting rate due to the higher length of solid-liquid interface promoting the heat transfer to solid PCM, thus increasing the melting rate. Again, for different heat distributions of side-wall heating the linearly decreasing heat flux provides the highest melting rate. This type of heat distribution actually transfers more heat to the lower part of the container, which counters the effect of convection, resulting in an enhanced melting process. On the other hand, in the case of distributions at bottom-wall heating, linearly increasing heat flux shows the highest melting rate. In addition, for linearly increasing heat flux, the shape of the liquid cavity is triangular, which gives more space and thereby intense natural convective circulation. This enhanced convection heat transfer leads to a higher melting rate.