A comprehensive numerical analysis of heat transfer enhancement in NEPCM-water mixtures using oscillating fin and oriented magnetic fields

This study investigates heat transfer in a square cavity filled with nano-encapsulated phase change material (NEPCM) and water, featuring a flexible oscillating fin and subjected to an inclined magnetic field. Arbitrary Lagrangian-Eulerian (ALE) was used to solve the governing equations. The study includes verifying the effect of the following parameters: Rayleigh number from 10 3 to 10 5 , Hartmann number from 0 to 30, Stefan number from 0.1 to 0.9, NEPCM concentration from 0.01 to 0.04, fusion temperature from 0.1 to 0.9, oscillation amplitude from 0.05 to 0.15, magnetic field angle from 0 o to 90 o . The results showed that heat transfer enhanced by increasing Rayleigh number and NEPCM concentration, with Nusselt number increasing by 82.8 % as Rayleigh number rises from 10 4 to 10 5 . Conversely, increasing Hartmann number suppresses convection, reducing Nusselt by 17 % as Hartmann increases from 5 to 30. An optimal fusion temperature of θ f ≈ 0.5 maximizes heat transfer efficiency. The flexible fin's oscillation amplitude modestly improves heat transfer, while the magnetic field's inclination angle exhibits a non-linear effect with an optimal angle around 45°. These results offer guidance on how to best optimise NEPCM-based thermal management systems for a range of applications.