Numerical investigation and optimization of thermal characteristics in multi-tube phase change heat storage systems

This study focuses on multi-tube thermal energy storage technology, aiming to address the low thermal energy storage efficiency of conventional multi-tube latent heat systems. Through structural design and performance analysis of the multi-tube system, Computational Fluid Dynamics simulations were employed to investigate the internal heat and mass transfer mechanisms. The results demonstrate that the multi-tube configuration significantly enhances energy storage density. Under the same volumetric constraints, the optimal fractal-based simplified structure achieves peak performance with approximately 12 tubes. Compared to traditional non-fractal storage structures, the thermal storage capacity and charging rate increase by 127.32%, while the melting time decreases by 85.47%. A single-factor comprehensive analysis reveals that an eccentric angle of 28.5° yields higher thermal storage capacity and heat transfer rates. Additionally, larger eccentric distance leads to optimal overall heat transfer performance. Finally, multi-objective optimization (NSGA-II) was applied to the system, yielding optimal values for heat storage (1439.39 J) and melting time (364.44 s), with the corresponding distance and angle optimized at 41.59 mm and 29.95°, respectively.