Control of melting behavior of phase change materials in an annulus enclosure through fin orientation and nanoparticles

This study investigates the enhancement of latent heat thermal energy storage systems through the synergistic integration of fin orientation and copper nanoparticle (NP) additives in paraffin wax phase change material (PCM). The study employed the enthalpy-porosity approach to analyze the effect of fin orientation and nanoparticles (NPs) on the melting behavior of paraffin wax in annular enclosures. The NP-enhanced-PCM was placed in an annular space alongside a finned tube at different angles and temperatures for the heat transfer fluid circulating through the inner tube. Because of the dominance of convective heat transfer (HT), it was observed that the melting rates on the top side of the investigated annulus are markedly higher than those on the lower side. The numerical results revealed three key findings: (1) Vertical fin orientation (α = −90°) achieves the most significant improvement, reducing total melting time to 181 min (70.8% faster than horizontal fins at 620 min, and 45% faster than inclined fins at 328 min); (2) NP incorporation enhances thermal conductivity, with 4 vol% concentration reducing the melting time by 11% compared to pure PCM; and (3) HT fluid temperature elevation from 60°C to 70°C accelerates melting by 73.4%, enabling complete phase change in just 46 min. The analysis reveals a distinct thermal performance dichotomy: while natural convection in the upper regions enables rapid melting, the lower section remains constrained by conduction-dominated HT.