Enhanced thermal response of phase change materials using optimized fin geometries in a dual-enclosure heat storage unit

The inherently low thermal conductivity of phase change materials (PCMs) poses a significant limitation to the performance of latent heat thermal energy storage (LHTES) systems. This study presents a comprehensive numerical investigation into the melting behavior of RT-27 PCM within a two-dimensional chamfered dual-enclosure, equipped with internal and external aluminum fins of four distinct geometries: rectangular, triangular, U-shaped, and wavy. The system is subjected to constant heat fluxes of 500, 1000, 1500, and 2000 W/m². The enthalpy–porosity method is employed in ANSYS Fluent 2021 to solve the governing equations, and model validation is performed against experimental data to ensure reliability. Results demonstrate that fin geometry substantially influences melting rate, thermal uniformity, and energy storage efficiency. At a heat flux of 1000 W/m², the U-shaped fin achieved complete melting in 2000 s, with an average temperature of 365 K and stored energy of ∼160 kJ/kg. In contrast, the triangular fin exhibited the slowest response, completing melting in 2700 s with a lower average temperature of 315 K and energy storage of ∼75 kJ/kg. Increasing heat flux to 2000 W/m² reduced melting time to 1400 s in the U-shaped configuration, confirming its superior thermal performance. The wavy and rectangular fins also showed favorable results, balancing thermal response and uniformity. The findings confirm that the integration of U-shaped and rectangular fins enhances heat propagation, reduces phase-change duration, and improves energy storage capacity. These insights provide a strategic framework for designing compact, high-efficiency LHTES systems for applications in energy, electronics, and thermal management technologies.