Irreversibility analysis and thermal performance of quadratic radiation and Darcy-Forchheimer flow over non-isothermal needle with velocity slip: Effects of aggregation and non-aggregation dynamics

Abstract

The importance of nanofluid flow across thin geometries in thermal engineering, biological applications, and energy systems has led to much research into this topic. Classical boundary layer theories first guided studies on heat transport across needles; subsequently, magnetohydrodynamic (MHD), porous media, radiation effects, and convective heat transfer processes were included. Although recent developments have brought nanoparticles to improve thermal conductivity, their behavior especially under aggregation and non-aggregation conditions remains a subject of much investigation. This study quantitatively analyses the flow, heat transfer, and entropy generation properties of nanofluid flow over a slender needle, accounting for the influences of an inclined magnetic field, quadratic thermal radiation, Darcy-Forchheimer porous media, heat generation/absorption, viscous dissipation, Joule heating, velocity slip, convective heating, and nanoparticle aggregation. By using the bvp4c solver inside MATLAB, the controlling nonlinear boundary layer equations may be resolved. Findings show that the velocity profile grows with velocity slip but shrinks with increasing magnetic field strength, porous medium resistance, Darcy-Forchheimer drag, and inclined angle owing to increased resistive forces. Thermal energy dissipation causes the temperature profile to rise with increasing Biot number (Bi) and Eckert (Ec) numbers. Stronger convective effects in non-aggregation scenarios provide greater entropy creation. Skin friction diminishes with rising magnetic field intensity, slip, porous resistance, and needle thickness; however, it escalates with elevated nanoparticle volume fractions. The Nusselt number increases with the radiation, and temperature ratio, whereas it decreases with the Eckert number and nanoparticle volume percentage. Heat absorption exceeds heat production by 16.51%–28.61% in the non-aggregation model and by 17.30%–29.03% in the aggregation model when Bi grows from 0.2 to 0.8. Heat absorption situations often provide greater heat transfer rates than heat production. The research shows that nanofluid properties, resistance of porous media, and MHD forces all interact intricately to determine thermal and flow parameters. The results provide the groundwork for future technical optimizations of cooling and thermal management systems based on nanofluids.