Irreversibility assessment of nonlinear mixed convection in TiO2–H2O nanofluid with slip and non-uniform thermal source/sink effects

The present study investigates entropy generation analysis for nonlinear mixed convection TiO2-H2O nanofluid flow over a moving vertical plate with spatially varying heat sources/sinks, slip effects, and viscous dissipation. The obtained set of nonlinear ordinary differential equations from governing equations is solved by applying the MATLAB bvp4c technique, and the accuracy of the computational scheme is validated against benchmark results available in the literature. The findings reveal that TiO2 nanoparticle loading enhances thermal conductivity and heat transport rate, leading to higher fluid temperatures and thicker thermal boundary layers, while simultaneously intensifying entropy generation away from the wall due to viscous effects. Mixed convection exhibits distinct behaviours in assisting and opposing flow regimes; assisting flow reduces entropy generation near the wall due to enhanced convective transport, whereas opposing flow amplifies irreversibility. Nonlinear buoyancy produces crossover effects in entropy distributions and Bejan number profiles, indicating a shift in dominant irreversibility mechanisms across the boundary layer. Velocity slip reduces only entropy generation by weakening near-wall shear stress and viscous dissipation, whereas thermal jump simultaneously decreases both entropy generation and Bejan number by limiting wall-to-fluid heat transfer. The velocity slip and thermal jump can act as key parameters that redistribute and modulate the dominant sources of irreversibility within the flow domain. Spatially varying and thermally varying heat sources elevate temperature and entropy in the far field while reducing near-wall irreversibility, whereas heat sinks produce the opposite effect. Furthermore, an increase in the Brinkman number enhances entropy generation and shifts the dominance toward heat transfer irreversibility, as reflected by a reduction in the Bejan number. Surface drag and heat transfer rate are found to be strongly affected by mixed convection nanoparticle loading, slip conditions, Eckert number, and non-uniform heating. The nanoparticle addition enhances heat transfer at the expense of increased drag, velocity slip reduces skin friction with a moderate impact on thermal performance. Overall, the findings highlight the critical interplay between nonlinear buoyancy, interfacial slip, viscous heating, and non-uniform thermal conditions in controlling entropy generation and provides useful insights for optimizing advanced thermal systems.