Numerical simulation of the melting process of nanostructured based colloidal suspensions phase change materials including the effect of the transport of the particles

Nanostructured phase change materials (NEPCM) colloidal suspensions, got the attention from the scientific community due to their promising thermal properties that allow for faster solidification, and melting times. However, most of the experimental investigation shows the opposite, that the melting and freezing times are increased as the volume of the particles is increased. This investigation will be the first in the literature to include the mass transport of the particles, for the case of melting of NEPCM that will help understanding better the melting process of the NEPCM. In this paper, the development of the solid-liquid interface, the distribution of the nanoparticle profiles, as well as the development of the thermal convection, will be investigated for the case of melting of nanostructured phase change materials (NEPCM) colloidal suspensions, inside a rectangular cavity. The numerical model is based on the one-fluid-mixture approach combined with the single-domain enthalpy-porosity model for phase change. The linear dependence of the liquids, and solidus temperatures with the concentration of the nanoparticles was assumed. The NEPCM consists of water and copper nanoparticles, the nanoparticle size was selected to be 5 nm and 2 nm. The suspension was melted inside a rectangular cavity, heated from the left side. It was observed that for the case of dp = 2 nm, as the mass fraction of the particles increases the solid-liquid interface changes from a planar to unstable morphology during melting. Furthermore, as the mass fraction of the particles increases the temperature of the suspension decreased similarly to experimental observations. Also, I found that the rate of the rejection of the particles and the particles size plays an essential role in the development of the liquid fraction, concentration field, and the resulted thermal convection.