Thermal Performance Optimization of PCM Systems Using Graphene Nanoparticles and Advanced Fin Geometries Under Variable Heat Input Conditions

Abstract

Phase change material (PCM)-based thermal energy storage systems offer high energy density but are often limited by low thermal conductivity, leading to inefficient heat transfer and extended melting times. This study presents a hybrid thermal enhancement strategy combining 10% graphene nanoparticle (GNP)-doped PCM with advanced fin geometries in a fixed 5000 mm² rectangular enclosure, subjected to both lateral and vertical heat flux inputs. Using a validated enthalpy-porosity numerical model, four fin configurations plain— wall, square, curved, and tree-shaped were— investigated to evaluate melting time, thermal uniformity, and enthalpy gain. The inclusion of 10% GNPs increased the effective thermal conductivity from 0.15 to 0.45 W/m·K, which accelerated the melting process and improved energy storage capacity. Among all configurations, the square fin combined with GNP-PCM demonstrated the highest thermal efficiency, reducing the melting time to 4900 s (a 34.7% decrease compared to the baseline) and achieving an enthalpy gain of 7.2 × 10⁵ J, representing a 36% increase. The square fins facilitated strong convective loops and uniform thermal gradients, while GNPs enhanced conductive heat transfer throughout the domain. Furthermore, simulations revealed that vertical heat input, while often neglected, significantly impacts system performance causing—up to a 32% delay in melting and a 28% reduction in energy storage. These findings underscore the importance of directional heating and hybrid enhancement techniques. The results provide critical insights for designing high-performance thermal management systems in renewable energy, electronic cooling, and electric vehicle battery applications.