Effect of copper rod length on the melting behavior of paraffin wax in hemispherical latent heat storage units

Abstract The inherently low thermal conductivity of phase change materials (PCMs) stills a major limitation for their use in latent heat thermal energy storage (LHTES) units, as it significantly reduces the charging procedure and decreases system responsiveness. This study presents a novel numerical examination of the isolated effect of a single vertical copper rod of varying lengths on the melting performance of RT42 paraffin wax within a hemispherical cell. Unlike previous studies that focused on fins or composite structures in other geometries, this work uniquely quantifies the impact of systematically increasing rod length (0, 10, 20, and 30 mm) on melting enhancement in hemispherical configurations. Four cases had been simulated using ANSYS Fluent 16 with enthalpy-porosity technique to obtain transient heat transfer, fluid flow, and evolution of melting front. It was shown that the copper rod boosted thermal exchange and shortened the total time of melting, and it took 300 min (no rod) to 150, 120, and 90 min when using 10, 20, and 30 mm copper rod, respectively. The highest reduction in melting time was 70 percent and the corresponding increment in the melting rate was 233 percent in the longest rod compared to the finless. Besides, the existence of the rod resulted in the existence of more homogeneous temperature distributions and stronger convective currents, which increased the overall thermal efficiency. The findings provide valuable design guidance, demonstrating that the thermal conductivity limitation of organic PCMs can be effectively overcome through simple geometric modifications using high-conductivity inserts.