Thermal runaway and distribution effects on a three-step exothermic reaction of magneto-Casson fluid with chemical kinetics and convective channel wall

The essential contributions of exothermic combustion processes in thermal system designs cannot be overemphasized. A system involving a three-step reaction–diffusion of magneto-Casson fluids has implications for safety management, energy systems, and chemical engineering. Thus, this study examines the thermal runaway phenomenon and its propagation influences on a three-step exothermic reaction of a gravity-driven magneto-Casson fluid, considering convective heat distribution and chemical kinetics along a channel. The study is characterized by an overwhelming temperature rise due to the exothermic heat accumulation, which poses substantial challenges in natural and industrial processes. The interaction between Casson fluid rheological properties, chemical reaction rates, activation energy, and thermal energy with the magnetic field influence is explored. The theoretical model integrating the Casson fluid model is coupled with nonlinear chemical kinetics for a three-step exothermic combustion. Following Newton’s cooling law, the thermal convective exchange at the channel wall is modeled. The dimensionless terms such as the magnetic field intensity, Brinkman number, Grashof number, and Frank-Kamenetskii parameter are utilized to analyze the reaction stability, dissipation, and heat distribution. The study employs a Galerkin weighted residual technique to solve the coupled equations for appropriate parametric sensitivities analysis of the flow characteristics and chemical kinetics on the thermal runaway onset. The main findings revealed that a three-step reaction leads to system complexity, where the reaction intermediate stabilizes and amplifies thermal effects depending on the activation energy. The distribution of temperature in the channel wall provides mitigating runaway risks in industrial applications and gives insights into reaction conditions optimization.