Impacts of nanoparticle shape and periodic heating on entropy generation inside a tilted nanofluid filled rectangular cavity

Abstract

This paper deals with the utilization of TiO₂-water nanofluid to investigate the MHD free convection (FC) flow and entropy generation inside a tilted rectangular cavity in the presence of uniform magnetic field. The bottom and the left vertical walls of the cavity are heated periodically, but the right vertical one is kept cool with a comparatively low temperature. The upper wall is a superb insulator. The walls are in no slip boundary condition. The novelty of this work lies in the fact that, to date, no study has been addressed entropy generation optimization in cavities considering the both effects of inclination and periodic heating, as far as the author know. An analysis is conducted on the optimization of local entropy (LE) that results from the combination of HT and fluid movement throughout FC. The study of temperature distributions in terms of isothermal contours (IC), fluid flow patterns in terms of stream functions (SF) and HT rate in terms of Nu are presented in this investigation. The simulation is carried out for 10³ ≤ Ra ≤ 10⁶, 0 ≤ φ ≤ 0.04,  30⁰ ≤ ω ≤ 90⁰, 0 ≤ Ha ≤ 80 and 0.2 ≤ AR ≤ 0.8. The continuity, momentum and energy equations are solved with the help of finite element Galerkin method after transforming them into non-dimensional form using some non-dimensional variables. The findings reveal that heat transfer and entropy generation in nanofluid-filled tilted cavities are strongly influenced by thermal, magnetic, particulate, and geometric parameters. High Ra and lamina-shaped nanoparticles enhance convection and heat transport, though at the expense of increased irreversibility, while moderate Ha and low-to-moderate particle concentrations (φ ≈ 0.02) provide an optimal balance of efficiency. Geometric optimization, particularly an inclination angle of ω ≈ 60° and aspect ratio AR ≈ 0.4, minimizes entropy generation while maintaining effective circulation. These findings are significant as they establish optimal parameter ranges that enhance heat transfer while maintaining energy efficiency, providing practical design strategies for thermal management. Such insights are highly relevant to applications like electronic cooling, solar collectors, energy storage, and magneto-hydrodynamic systems, where balancing performance with reduced entropy generation is essential for reliable operation.