Effects of Activation Energy and Joule Heating on Reactive MHD Micropolar Nanofluid Flow Over a Permeable Stretching Sheet

In this work, the effect of combined Joule heating and activation energy on steady magnetohydrodynamic micropolar nanofluid flow along a permeable stretching surface is investigated. The novelty of this model is the coupling of micropolar microrotational physics with thermal radiation, viscous dissipation, Dufour diffusion, and temperature-dependent chemical kinetics. The governing nonlinear partial differential equations are converted to a set of coupled ordinary differential equations by similarity transformations and then numerically solved by the fourth-order Adams-Moulton method with a shooting technique. The results indicate that there was significant improvement in the thermal field by the Joule heating effect, which caused the surface heat transfer rate to decrease by 4.17% due to the Joule heating. On the other hand, for a higher activation energy, chemical reaction kinetics decreases, and thus, the number of nanoparticles increases as the rate of mass transfer decreases by 15.02%. Moreover, the effect of viscous dissipation and thermal radiation increases the thermal boundary layer thickness while the cross-diffusion transport of the species is dominated by Brownian motion and thermophoresis. These insights provide practical design mechanisms for optimizing advanced nanofluid thermal management systems in high-temperature engineering applications.