Heat transfer and entropy generation in a non-isothermally heated chamber filled by NEPCM water nanofluid

Abstract

Effective thermal management under non-isothermal heating is critical for systems such as battery modules, electronics cooling, and solar energy devices. Motivated by this need, the present study investigates natural convection and entropy generation in a square chamber filled with a nano-encapsulated phase change material (NEPCM)-water nanofluid. The chamber features isothermal vertical walls, an adiabatic top wall, and a bottom wall subjected to both isothermal and sinusoidal heating. A finite element method is employed to examine the effects of Rayleigh number, fusion temperature, Stefan number, and NEPCM volume fraction. Results show that the average Nusselt number increases with rising Rayleigh number (Ra) and nanoparticle volume fraction, while entropy generation varies depending on operating parameters. The NEPCM-water enhances thermal performance with up to similar to 15 % higher heat transfer at Ra = 10(3) and reduces entropy generation by approximately 28.6 % under non-isothermal heating at Ra = 10(5). The study bridges a key gap by analysing the coupled influence of latent heat storage and spatially varying heating, providing insights for optimising energy-efficient thermal management systems.