The three-dimensional (3D) MHD mixed convection mode confined 3D wavy trapezoidal enclosure is examined. The bottom plane of the trapezoidal system is irregular, particularly a wavy plane with various undulation numbers \(\:N\). The forced convection phenomenon arises due to the displacement of the top region plane, whereas the porosity-enthalpy methodology characterizes the progression of charging. The heat transfer is enhanced using the nanoencapsulation phase change material (NePCM), consisting of Polyurethane as a shell and Nonadecane as a core, with water as the primary liquid base. The (GFEM) is used to treat the governing system, and a comparison between the HT (heat transmission) irreversibility and FF (fluid friction) irreversibility is performed using the function of the Be_Avg. The significant findings revealed that parabolic behaviors for the melting ribbon curve are given at lower values of Re and higher values of Ha. Also, reducing the undulation number is better for obtaining a higher heat transmission rate. The average Nusselt number was lowered by 60% and 19%, respectively, at the highest Reynolds number when the Hartmann number increased from 0 to 100 and N from 2 to 8. Also, the values of \(\:Re\) between 1 and 100 improve the heat transfer rates up to 51%.

Latent Heat Transfer Thermal Energy Storage (LHTES) units are crucial in managing the variability of solar energy in solar thermal storage systems. This study explores the effectiveness of strategically placing layers of anisotropic and uniform metal foam (MF) within an LHTES to optimize the melting times of phase-change materials (PCMs) in three different setups. Using the enthalpy–porosity approach and finite element method simulations for fluid dynamics in MF, this research evaluates the impact of the metal foam’s anisotropy parameter (Kn) and orientation angle (ω) on thermal performance. The results indicate that the configuration placing the anisotropic MF layer to channel heat towards the lower right corner shortens the phase transition time by 2.72% compared to other setups. Conversely, the middle setup experiences extended melting periods, particularly when ω is at 90°—an increase in Kn from 0.1 to 0.2 cuts the melting time by 4.14%, although it remains the least efficient option. The findings highlight the critical influence of MF anisotropy and the pivotal role of ω = 45°. Angles greater than this significantly increase the liquefaction time, especially at higher Kn values, due to altered thermal conductivity directions. Furthermore, the tactical placement of the anisotropic MF layer significantly boosts thermal efficiency, as evidenced by a 13.12% reduction in the PCM liquefaction time, most notably in configurations with a lower angle orientation.

Latent heat thermal energy storage (LHTES) represents a promising renewable energy technology that can help alleviate the global energy shortage. This work numerically investigates the thermal charging process in a n-octadecane PCM-based double-pipe LHTES using a 2D COMSOL Multiphysics model. The study evaluates and analyzes the performance enhancement of the LHTES with various metallic fins, different distributions, inner tube placement, and Cu nano-additive concentrations. The study examines five fin arrangements, C 1 to C 5, three positions of the inner tube, P 1 to P 3, and three concentrations of Cu nanoparticles, 0%, 2%, and 4%. Results showed that among the five arrangements examined, C5 had the lowest melting time, up to 18.5% lower than the worst-performing configuration (C4). The inner tube position P2 outperforms P1 and P3, obtaining 99% melting in 24 min. Moreover, the 4% Cu concentration was superior, resulting in complete melting in 21 min, which is an improvement of 12.5% compared to the pure PCM.