Numerical and experimental investigation of supercooling and natural convection in octadecane phase change material

With the increasing global interest in energy savings, latent heat thermal energy storage (LTES) systems are used for energy harvesting and preservation, thus reducing the demand for traditional energy sources. The main concept of solid–liquid LTES systems is to absorb and release the latent heat of a material through consecutive melting/solidification cycles. Supercooling is a phenomenon that prevents the solidification of a liquid having a temperature lower than its melting temperature. Considering this phenomenon in designing the numerical models gives a better prediction of the system’s energy performance. This work is the first attempt to include supercooling in a two-dimensional COMSOL model. The model accommodates natural convection during the melting process and supercooling during the cooling process of the phase change material (PCM). A set of experiments using octadecane PCM are performed. The effect of supercooling and natural convection on the temperature curve and the energy behavior of the PCM are shown. The effect of cooling rate, volume of PCM and container structure on the degree of supercooling are also discussed. A small degree of supercooling in octadecane is recorded when having small volume, low cooling rate and a smooth surface. The obtained experimental results validate the proposed numerical model.