Numerical study of a thermal energy storage unit using a star snowflake fractal cross-section loaded and nano-enhanced phase change materials

Purpose. Storing thermal energy has emerged as a solution for improving energy efficiency by recovering waste heat. Improving heat transmission rates in thermal energy storage (TES) systems is crucial to the TES thermal efficiency. This research examines the thermal efficiency of the TES unit of a star snowflake fractal cross-section loaded with nano-enhanced phase change materials (NEPCM). Design/methodology/approach. The porous enthalpy approach is used to represent the phase transition development. The impacts of nanoparticle concentrations ( φ = 0 - 8 % ), the location of the inner tube (down, center, low), and the wavy number of the external shell (N = 4, 6, 8) are presented and analyzed. Findings. The obtained numerical findings indicated that increasing φ and N, besides placing the inner tube at the lower part of the TES system, enhanced the heat transmission rates and reduced the discharging time of the NEPCM. It was noted that positing the inner tube in the bottom section of the TES system and using an undulation number of 8 improved the heat transmission rate by 66% and 7.6%, respectively. On the other hand, the NEPCM melting time was decreased by 25% when φ = 8 8% .