Numerical study of heat transfer and melting process in a NEPCM filled 3D cuboid cavity: Application non-uniform temperature

In this numerical study, a cubic box filled with a Nanoparticle Enhanced Phase Change Material (NEPCM) (mixture “N-Octadecane/alumina (Al2O3)"), is considered. Using Comsol-Multiphysics program, the configuration is treated as a 3D symmetric numerical simulation problem under fixed boundary conditions. Besides, heat transfer fluid (HTF) generates a non-uniform temperature that varies linearly along an internal tube installed in the lowest area of the enclosure to ensure the melting of the NEPCM. Therefore, the purpose of the study is to highlight the effect of the nanoparticles volume fraction (varying from 0 to 6%) on thermal distribution and melting performances. The obtained findings figure out that the PCM melts irregularly and is affected by the non-uniform temperature of the HTF tube. Hence, the third dimension should be considered, particularly in PCM ring tank simulations, in order to obtain reliable predictions compared to practical and experimental studies. Additionally, the Al2O3 nanoparticles have a valuable effect on improving the thermal conductivity of NEPCM, where thermal resistance and melting time are reduced with the increase of the nanoparticles volume fraction. Compared to the case of pure PCM, the heat transfer enhancement yields to an augmentation in the melting rate by about 11% and 9.5% for the volume fractions of 6% and 3%, respectively. Moreover, there is a significant increase in the amount of stored thermal energy when nanoparticles are dispersed in the PCM.