Energy-efficient thermal management of electronics and heat exchangers using nano-encapsulates phase change materials in polygonal geometries

Efficient thermal management is a critical challenge in compact energy systems, high-power electronics, and renewable energy devices, where excessive heat can degrade performance, reduce reliability, and limit operational lifetime. Thermal energy storage using phase change materials (PCMs) offers a promising strategy to mitigate these issues, yet conventional PCMs often suffer from slow phase-change dynamics and limited heat transfer. This study investigates the performance of nano-encapsulated phase change materials (NEPCMs) dispersed in a base fluid within a polygonal annular enclosure subjected to a horizontal magnetic field. The influence of inner cylinder geometry, outer cylinder rotation, buoyancy ratio, and Richardson number on thermal and solutal transport, flow structures, and NEPCM activation is systematically analyzed. Key findings reveal that square inner cylinders enhance convective mixing, leading to up to 3.3% improvement in heat transfer and 15.8% increase in mass transfer compared to circular geometries. Buoyancy-dominated regimes with cooperative thermal-solutal effects can boost thermal performance by over 137%, while clockwise rotation of the outer cylinder aligns with natural convection, further improving heat and mass transfer. NEPCM phase change is concentrated at regions of high thermal load, enabling targeted latent heat absorption and effective energy storage. These results provide practical insights for designing compact thermal management systems and energy storage devices. The combined effect of geometry, rotation, and NEPCM behavior under magnetic fields demonstrates potential for mitigating hot spots, enhancing heat removal, and improving overall system reliability in high-density electronics, compact heat exchangers, and renewable energy applications.