Comparative analysis on melting performance of PCM using rectangular and branching fin configurations in a shell and tube type thermal energy storing unit

Phase change materials (PCMs) are widely used in various applications, however, their low conductivity and long phase transition time hinder thermal energy supply. Thus, numerous researchers have studied various fin designs to solve this problem. In this study, with the unique combinations of two, three and four rectangular fins and straight, curved and angled branching fins, nine novel cases have been proposed to examine the melting enhancement of PCM in shell and tube-type heat exchangers. A numerical two-dimensional analysis has been conducted in a transient state using N-eicosane PCM, considering the natural convection effect. The CFD of this numerical model has been validated with pertinent literature work. The evolution of the solid-liquid interface and natural convection has been visualized by liquid fraction, isotherm expansion and velocity streamlines. At first, three proposed branching designs are compared for different numbers (two, three and four) of rectangular fins. Following the methodology, evaluating the impact of branching fins for two and four rectangular fins, the best branching design was the angled fins with 8.25 % and 28.58 % melting time improvement, respectively, compared to the curved fins, which performed the worst. For three rectangular fins, straight branching fins were identified as the best with a 21.2 % melting time improvement compared to the angled branching fins as the worst performer. Lastly, among all the nine cases, two rectangular fins with angled branching perform the best, with 84.6 % melting time savings. The worst performer is four rectangular fins with curved branching, saving 40 % melting time compared to no fin case. In addition to that, the cases with two rectangular fins significantly outperform other cases in terms of energy storage rate.