Solidification of a PCM with nanoparticles in triplex-tube thermal energy storage system

Effects of incorporating alumina nanoparticles on solidification of a phase-change material (PCM) in triplex-tube thermal energy storage (TES) system were numerically investigated in this study. A time-dependent, two-dimensional simulation of the entire solidification process was carried out for different nanoparticle loadings under constant charging temperatures of the heat transfer fluid (HTF). Results from this study were compared to previous related work and good agreement was obtained. Impacts of incorporating nanoparticles on flow structure and heat transfer characteristics over different stages of the PCM solidification process were also analyzed and discussed. Total solidification times were predicted for all nanoparticle volume fractions and inlet HTF temperatures considered. The results show that dispersing alumina nanoparticles of volumetric concentrations of 3-8% results in total time saving between 8% and 20%. The results also show that the presence of nanoparticles does not show much difference at the early stages of the solidification process, but as time elapses and/or volume fraction increases, the rate of solidification increases.