Branching of fins and addition of Al2O3 nanoparticles for rapid charging and discharging of latent heat storage unit

Low thermal conductivity of phase change material (PCM) limits the thermal performance of latent heat storage (LHS) units. This study numerically investigates the performance enhancement offered by fin structures alone and the fin-nanoparticles hybrid strategy during a complete melting-solidification cycle for a concentric tube LHS unit. Extended surfaces are incorporated as fins of straight, single- and double-branched designs with pure PCM, which reports time savings of 4.7%, 11%, and 14.2%, respectively, compared to the Y-shaped three-fin base case. A maximum heat transfer enhancement of 15.1% is achieved for the double-branched fin design proving it to be the best option. Al2O3 nanoparticles are further added into the best design in volumetric concentrations of 1%, 5%, and 10% which results in an additional time savings of 14.1%, 23.3%, and 33.1%, respectively, as compared to the pure PCM case. The corresponding increase in the heat transfer rates is 11.6%, 9.8%, and 8.8%. The total energy storage capacity is reduced by 4.1%, 15.5%, and 26.9% for the nanoparticles' concentrations of 1%, 5%, and 10%, respectively. Therefore, the optimum concentration of the nanoparticles comes out to be 1% based on the trade-off between time saving and energy storage features.

Automated summary

This study numerically investigates the performance enhancement of a concentric tube LHS unit using a fin structure and a fin-nanoparticles hybrid strategy. The results show that the double-branched fin design achieves the highest heat transfer enhancement, while adding 1% Al2O3 nanoparticles achieves the best balance between time saving and energy storage features.