Zeta-potential electroosmotic transport of magnetized yield-stress hybrid nanofluids for thermodynamic enhancement of convectively cooled microchannel

Electroosmotic transport has emerged as an attractive strategy for improving coolant circulation and thermal regulation in compact microchannel cooling systems, where efficient heat removal is essential for maintaining stable thermal performance. Nevertheless, the coupled influence of zeta-potential electroosmosis, yield-stress rheology, magnetic actuation, and thermodynamic irreversibility on hybrid nanofluid transport within convectively cooled microchannels remains largely unexplored. This study develops a thermodynamic model for zeta-potential electroosmotic transport of a magnetized Bingham-Papanastasiou hybrid nanofluid (HNF) flowing through a convectively cooled microchannel. The main novelty lies in integrating the combined effects of electric and magnetic fields, electroosmotic transport, non-Newtonian rheology, and thermal transport within a unified thermodynamic framework. The formulation incorporates electroosmotic forcing, pressure-driven flow, transverse magnetic field, Joule heating, viscous dissipation, thermal radiation, internal heat generation, variable thermophysical properties, and wall convection. The coupled nonlinear governing equations are transformed into dimensionless form and solved using the weighted residual Galerkin method. The effects of the governing parameters on velocity, temperature, entropy generation, Bejan number, skin-friction coefficient, and local Nusselt number are systematically examined. The analysis demonstrates that increasing the zeta potential substantially strengthens electroosmotic transport, producing a more uniform coolant distribution and enhanced thermal performance. For the investigated internal heat-generation condition, the local Nusselt number of the HNF was approximately 83.98% higher than that of the base fluid, demonstrating the strong influence of hybrid nanoparticles on the thermal response under this particular operating condition. Although magnetic forces increase hydrodynamic resistance, they also provide an effective mechanism for regulating coolant transport and thermodynamic irreversibility. The combined action of electroosmotic driving and hybrid nanoparticles offers a promising pathway for reducing thermal losses and improving cooling efficiency in compact microchannel cooling systems. These findings provide useful design guidance for electroosmotic microchannel thermal-management systems operating under high heat-transfer demands.