Entropy generation analysis of conjugate natural convection in a vertically partitioned hexagonal chamber filled with different combinations of nanofluids

This research presents a comprehensive numerical investigation of entropy generation in a vertically divided, differentially heated, regular hexagonal chamber with conjugate free-convection flow, filled with either similar or dissimilar combinations of nanofluids. The governing dimensionless equations for mass, momentum, and energy are solved using a finite element approach over a wide range of Rayleigh numbers (10 3 ≤ Ra ≤ 10 6 ), covering conduction-dominated to convection-dominated regimes. Combinations of two different nanofluids (Al 2 O 3 -water and Cu-water), three different dimensionless partition thicknesses ( T p = 0.10, 0.15, 0.20), and partition materials (stainless steel: AISI 302, zinc, and silver) are considered to evaluate their effects on the temperature distribution, streamline patterns, heat transport rate, entropy generation, and ecological coefficient of performance. Results indicate that increasing the Rayleigh number significantly strengthens convective circulation, enhances heat transport, and shifts the dominant irreversibility mechanism from thermal to fluid-frictional. Furthermore, the use of a specific combination of nanofluids slightly improves thermal transport while reducing total entropy generation. The study finally identifies optimal operating conditions that minimize thermodynamic irreversibility and maximize heat transfer efficiency, contributing valuable perceptions for the design of advanced hydrothermal systems and energy-efficient heat transfer devices.