Phase change and thermal performance optimization in NEPCM-filled enclosures with multiple cylinders

Purpose Optimizing thermal management in systems with multiple heat sources, such as in electronics cooling, requires innovative coolants. Nano-encapsulated phase change materials (NEPCMs) offer superior thermal energy storage via latent heat, but their interaction with complex flow fields from multi-cylinder arrays is not well understood. This study aims to analyze natural convection and melting of NEPCM nanofluid within a square enclosure containing multiple hot cylinders. Design/methodology/approach The non-dimensional governing equations are solved using a finite element method. A parametric study evaluates the effects of cylinder number (N), spacing (S), NEPCM concentration (ϕ), fusion temperature (Θf) and Rayleigh number (Ra). Findings The results show that the optimal system configuration is regime-dependent. At low Ra, four cylinders with larger spacing perform best. At high Ra, flow congestion and thermal wake effects cause this configuration to become the worst, with a two-cylinder system proving most efficient. NEPCM concentration is the most significant performance driver, increasing the average Nusselt number by 137%–190% as ϕ rises from 0.01 to 0.05, depending on spacing. A higher fusion temperature further enhances performance at high Ra. Research limitations/implications This study is limited to the 2D configuration and stationary flow condition. Practical implications This work demonstrates that synergistic design of the enclosure geometry and NEPCM properties is crucial. The findings provide essential guidelines for developing high-performance thermal management systems. Originality/value While existing literature has extensively studied natural convection with multiple cylinders or with NEPCMs separately, the interplay between complex multi-cylinder geometries and the dynamic phase change behavior of NEPCM suspensions remains unexplored. This study bridges this gap by systematically investigating the coupled effects of parameter on the flow structure, melting dynamics, thermal performance and entropy generation. The primary novelty lies in understanding how the latent heat of NEPCMs modulates and is modulated by the complex flow fields generated by interacting multiple heat sources.