Influence of fin geometry on convection-driven melting of a phase change material

This work investigates the melting of a Phase Change Material (PCM) layer in a rectangular cavity heated from below, where metallic fins are used to enhance heat transfer. The study examines how fin geometry controls melting and natural convection, focusing on sinusoidal wavy fins placed in different orientations and comparing them with straight fins under identical conditions (same fin number, height, base positions, and total fin area). The influence of fin shape is assessed through the time evolution of liquid fraction, melting dynamics, natural convection intensity, and overall heat-transfer performance. Results show that fin geometry strongly affects both convection structures in the liquid PCM and the overall melting rate. Wavy fins promote faster and more uniform melting during convection-driven stages, yielding transient liquid fractions up to 16.6% higher than with straight fins. They also induce distinct flow features, including small convection cells along upward-oriented fin sections and transient plume instabilities between adjacent fins. Straight fins, when adequately spaced, favor the development of large recirculation cells and can trigger the detachment of solid PCM drops that melt rapidly once they settle into warmer liquid regions, thereby enhancing late-stage melting. Among the different wavy-fin configurations, alternating fin orientations lead to the most stable convection regime and the shortest total melting time. Overall, the results show that effective fin design must consider how convection develops between fins and the role of convection in enhancing melting in regions near the walls where heat transfer is weakest. • Fin shape controls PCM melting behavior and natural convection patterns. • Straight fins can trigger solid PCM drops that sink and melt rapidly. • Wavy fins promote more uniform and faster melting at early times. • Alternating oriented wavy fins provide the faster overall melting.