Computational analysis of natural convection in a nano-encapsulated phase change material-water-filled porous cavity with a tilted elliptical heater and corrugated cold wall using finite element method

Abstract

Purpose This study aims to numerically explore natural convection and latent heat transfer in a square porous cavity filled with a H2O/nano-encapsulated phase change material (NEPCM) mixture. Particular attention is paid to the influence of cavity geometry, block inclination and wall undulations on heat transfer and melting behavior. Design/methodology/approach This setup includes a central, inclined, heated elliptical block and features a corrugated cold wall. The dimensionless governing equations under the local thermal equilibrium (LTE) assumption are solved using the Galerkin-based finite element method. An exhaustive parametric analysis is conducted to evaluate the influence of main parameters, including Rayleigh number (103–106), Darcy number (10−5–10−1), Stefan number (Ste) (0.2–1), porosity (0.1–0.9), nanoparticle volume fraction (0%–5%), fusion temperature (0.05–0.95), block tilt angle (0° – 180°) and wall undulation shape (sinusoidal, triangular and rectangular). Selected validations were adopted to ascertain simulation accuracy and consistency. Findings It turned out that increasing specific settings is the keynote to improving or mitigating the average Nusselt number (Nuavg). The findings highlighted that higher Rayleigh and Darcy numbers, as well as porosity and nanoparticles’ volume fraction, improve the Nuavg, while a greater Ste mitigates thermal performance due to slower melting. An optimal fusion temperature is identified where latent heat absorption is maximized. Tilt angles close to 90° improve vortex formation and heat transfer efficiency. In terms of thermal performance, sinusoidal and triangular wall geometries outperform rectangular geometries, especially for low undulations. Furthermore, this numerical study seems germane to latent thermal energy storage systems. Research limitations/implications Future research could further explore thermal systems involving phase change and porous structures under additional factors, either by adding nanomaterials, encapsulating phase change materials, other boundary conditions or redesigning heat transfer surfaces to further improve their thermal performance. Practical implications The geometric configuration considered herein has practical applications in different engineering sectors, such as solar energy, waste heat recovery from building materials, advanced electronics, cooling technologies, fuel cells, mixing processes and even nuclear energy and many more. Originality/value To the best of the authors’ knowledge, this work is the first to provide new insights into the coupled effects of porous structures, latent heat storage and cavity geometry on the natural convection of H2O–NEPCM mixture in a cavity characterized by the Darcy–Brinkman model and the LTE assumption. The study of such a mixture in such a little-explored configuration revealed strong thermal interactions between conduction, convection and phase change. The obtained findings deal useful guidelines for the design of advanced passive cooling and high-efficiency latent heat energy storage systems.