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

- Combines nanoparticles with metal foam in a triplex-tube PCM energy storage system.
- Melting time of the PCM is modeled, validated with experiments and studied.
- The combination was found to greatly reduce the melting time of the PCM.
- Allied parameters responsible for improved performance of the system were revealed.

Phase change material (PCM) energy storage systems have relatively low thermal conductivity values which greatly reduces the systems' performance. In this study, a compound porous-foam/nanoparticles enhancement technique was used to significantly improve melting of a phase change material (PCM) in a triplex-tube heat exchanger applicable to liquid desiccant air-conditioning systems. A mathematical model that takes into account the non-Darcy effects of porous foam and 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 instantaneous evolution of the solid-liquid interfaces, distribution of isotherms, and liquid-fraction profile under different temperatures of the heat transfer fluid (HTF) were investigated. Results show that dispersing nanoparticles in the presence of metal foams results in melting time savings of up to 90% depending on the foam structure and volumetric nanoparticle concentration. Although the melting time decreases as the porosity decreases and/or volume fraction increases, high-porosity metal foam with low volume-fraction nanoparticles is recommended. This ensures minimal PCM volume reduction and promotes positive contribution of natural convection during the melting process.