Solidification enhancement in a triplex-tube latent heat energy storage system using nanoparticles-metal foam combination

Thermal storage systems utilizing Phase Change Materials (PCMs) are known to exhibit slow thermal response. This is mainly due to the relatively low thermal conductivity of most PCMs used in the systems. Thus packing the PCMs in better performing containment vessels and/or employing heat transfer enhancement additives is required for improved performance of these systems. Nanoparticle-metal foam combination as a compound enhancement approach along with triplex-tube heat exchanger as a modified exchanger design were used in this study to improve the PCM solidification rate. A mathematical model based on the thermal equilibrium assumption which takes into account the non-Darcy effects of porous foam and the Brownian motion of nanoparticles was formulated and validated with previous related experimental studies. The influence of nanoparticle volume fraction and metal foam porosity on the evolution of the solid-liquid interfaces, distribution of isotherms, and liquid-fraction profile over the whole solidification process was studied. Results show that dispersing nanoparticles in the presence of metal foams results in total time saving up to 96% depending on foam structure and volumetric nanoparticle concentration.