A numerical study on the combined effect of dispersed nanoparticles and embedded heat pipes on melting and solidification of a shell and tube latent heat thermal energy storage system

The thermal analysis of melting and solidification processes of Rubitherm 55 in a vertical shell and tube based latent heat thermal storage unit is presented in this study. To resolve the low heat transfer rate issue within the phase change material due to its low thermal conductivity, hybrid enhancement methods are considered. Heat pipes are placed horizontally to act as a bridge between the heat transfer fluid and the phase changed material stored in the shell. In addition, nanoparticles with high thermal conductivity are added to the phase change material. Aluminum oxide, silver, copper and copper oxide are the nanoparticles used for this study. The effects of various parameters, such as the heat pipes quantity, nanoparticles type, and concentration are studied on the overall performance of the system. It was concluded that embedding heat pipes significantly decreases the melting and solidification times. It was also shown that increasing the nanoparticles concentration decreases the melting or solidification time as well as the stored or released energy per unit of mass. However, the significance of the effect of type of nanoparticles was dependent upon the quantity of the heat pipes in the storage unit.