Activation energy effects on heat and mass transfer in MHD flow of tri-hybrid nanofluids over orthogonal porous disks with variable geometry

This work presents a detailed numerical investigation of the transport phenomena of a tri-hybrid nanofluid composed of F e 3 O 4 , A l 2 O 3 and T i O 2 nanoparticles dispersed in water, flowing between orthogonally moving, permeable porous disks subjected to an external magnetic field. Unlike previous works, the present model incorporates both nanolayer thermal conductivity and activation energy effects, enabling a more realistic representation of interfacial transport and reactive diffusion processes. By applying similarity variables, the governing equations of flow, heat, and mass transport are reduced to a system of nonlinear ODEs, which are then solved numerically using a Runge-Kutta-based shooting algorithm. The results reveal that increasing nanolayer thickness significantly enhances the heat transfer rate due to interfacial conductivity effects, while higher activation energy suppresses mass diffusion by imposing a stronger energetic barrier. The magnetic parameter further intensifies shear stress and modifies velocity distributions, highlighting controllability in MHD systems. The reliability of the model is confirmed through grid independence testing and comparison with existing literature. These findings provide important insights into optimizing the performance of thermal systems utilizing advanced nanofluid configurations in porous media, with potential applications in magnetic cooling devices, membrane reactors, and biomedical flow systems where enhanced heat and mass transfer are critical.