Numerical investigation of melting characteristics of fin-assisted single and dual PCM latent heat storage system under time-dependent solar heat flux

This study investigates the thermal performance of a finned rectangular chamber filled with phase change material (PCM) under realistic, solar-like time-dependent heat flux conditions. The key novelty lies in coupling a dual-PCM system (paraffin wax and lauric acid) with variable flux conditions, which together reveal new physical trends beyond what has been reported in prior studies of fins, blended PCMs, or constant boundary conditions. The effects of inclination angle (15°, 30° and 45°), number of fins (single and three-fin configurations), fin length (1 and 2 cm), and chamber thickness (2.5 and 5 cm) on the melting and solidification processes are studied as well. The results show that the melting time decreases with the reduction of inclination angle, with the shortest melting duration occurring at a 15° tilt. Furthermore, adding fins to the chamber accelerates the melting process, for instance at 15°, the melting time with three fins decreases by 8.78% compared to the finless configuration. Increasing fin length also reduces the melting time, with a 3.51% decrease when using 2 cm-long fins instead of 1 cm. The melting duration is increased by 106.05% when the chamber thickness increases from 2.5 to 5 cm. Moreover, a dual PCM configuration reduces the melting time by 29.64% compared to paraffin wax alone. The study also finds that decreasing the number of fins increases latent heat storage but reduces sensible heat. Additionally, the average Nusselt number is higher in the three-fin configuration, and both sensible and total heat storage values increase with the tilt angle. These findings provide insights into optimizing the thermal response of PCM-based systems for solar thermal applications.