Conduction-Dominated Thermal Regulation of Graphene-Doped Paraffin Phase Change Material for Battery Systems: Influence of Fin Geometry and Heating Orientation

This study presents a numerical investigation of melting performance in a square enclosure (50 mm × 50 mm) filled with paraffin RT42 enhanced with 10% graphene nanoplatelets (GnP), under two heating orientations: lateral (Case I) and vertical (Case II). Three internal geometries—no fins, straight fins, and undulated fins—were analyzed to assess the combined effects of enhanced thermal conductivity and fin-induced conduction on phase change behavior. The finite volume method with enthalpy–porosity formulation was used under conduction-dominated conditions. Grid independence was ensured with a 0.2-mm mesh (y+ ≈ 0.5–0.9), and the model was validated against benchmark results with deviations under ±3%. Results confirmed negligible natural convection, with maximum velocity magnitudes around 3.41 × 10−30 m/s, indicating conduction-dominated melting. At 90 min, the melted mass fraction reached 85% (lateral) and 88% (vertical) without fins. Straight fins improved melting to 95–97%, while undulated fins led to 98% melting under lateral and 100% under vertical heating. Temperature uniformity was highest with undulated fins and vertical heating, maintaining 311–315 K. The findings highlight the superior thermal performance of vertical heating combined with undulated fins, offering valuable guidance for compact, conduction-based thermal energy storage systems in low-convection or microgravity environments.