Comprehensive thermal analysis of a nano-enhanced PCM in a finned latent heat storage system

This study investigates the melting performance of a novel shell-and-tube latent heat thermal energy storage (LHTES) system using copper nanoparticle (Cu-NP)-enhanced paraffin wax based phase change material (PCM) within a finned triangular tube configuration. Addressing the critical challenge of low heat transfer rates in LHTES systems, the research combines geometric optimization (tube eccentricity and inclination) with material enhancement (Cu-NPs) to improve thermal efficiency. A numerical model employing the enthalpy-porosity method systematically evaluates the effects of Cu-NP concentration (0–8 %), tube eccentricity (top/center/bottom), and inclination angle (0°/60°/90°) on melting dynamics, using melt fraction, Nusselt number (Nu), and Bejan number (Be) as performance metrics. Results demonstrate that geometric adjustments dominate thermal performance: a 60° inclination reduces melting time by 42 %, while bottom eccentricity achieves a 58 % reduction by enhancing natural convection. While higher concentrations of Cu-NPs improve thermal conductivity and lower entropy generation, their influence on melt fraction and temperature increase is relatively limited. Heat transfer analysis indicates that natural convection is found to dominate heat transfer above the tube, while conduction prevails in the lower region. Evaluation of Nusselt and Bejan numbers reveals the critical balance between convective heat transfer enhancement and thermodynamic irreversibility. The optimal configuration (60° inclination, bottom eccentricity, and 4 % Cu-NPs) balances melting efficiency and thermodynamic irreversibility. This study highlights geometric optimization as a more effective strategy than nanoparticle addition for LHTES design, offering practical insights for energy storage applications.