Chemical reaction for thermodynamic irreversibility in MHD tetrahybrid nanofluid flow with thermal radiation, heat source and multi-dissipation

Abstract This study explores entropy generation in the magnetohydrodynamic flow of a tetra hybrid nanofluid. ( $${\text{Al}}_{2} {\text{O}}_{3} - {\text{Cu}} - {\text{SiO}}_{2} - {\text{TiO}}_{2} /{\text{H}}_{2} {\text{O}}$$ ) over a permeable surface embedded in a Darcy–Forchheimer porous medium, motivated by the need to enhance thermal system efficiency and minimise energy losses. The model incorporates key physical effects, including multiple dissipation mechanisms (Ohmic, viscous, Darcy, and Forchheimer), thermal radiation, internal heat generation, activation energy, and chemical reaction. The transformed nonlinear equations are solved numerically using the bvp4c technique. Results reveal that thermal radiation and heat source significantly elevate temperature and entropy generation, indicating increased irreversibility, while magnetic field and porous resistance strongly suppress fluid motion. Activation energy enhances species concentration, whereas a higher Schmidt number reduces mass diffusion. The Bejan number decreases under stronger magnetic and porous effects but increases with radiation and inertial resistance. The combined influence of these parameters provides deeper insight into controlling heat and mass transfer in advanced nanofluid systems. The findings are particularly relevant for applications in energy systems, cooling technologies, and thermal management, where minimising entropy generation is crucial for improving performance and efficiency.