Effect of fin length and angle on the melting process of phase change materials in vertical latent heat storage unit

The installation of fins offers an effective solution for addressing the poor thermal conductivity of phase change materials (PCMs) in latent heat thermal energy storage (LHTES) systems. This paper aims to investigate the combined effects of unequal fin length arrangements and the inclination angle of fins on the performance of an LHTES system during the charging process. The LHTES system consists of a cylindrical container filled with paraffin (RT55) serving as the PCM. Numerical models are established and validated, followed by simulating various fin structures to analyze the complete melting time of the PCM. The characteristics of the melting process are further examined in four representative cases, including the full melting time, evolution of the melt fraction, average maximum velocity, streamline contours, temperature uniformity, and average Nusselt number. The results reveal that the optimal case, featuring unequal length and downward annular fins, achieves a significant 49.8% reduction in the complete melting time of the PCM compared to the benchmark case with ordinary annular fins. Moreover, the optimal configuration increases the largest average maximum velocity of the PCM by 35.36%, resulting in a more uniform temperature distribution and a higher Nusselt number.