<p>It presents a novel study of thermal radiation, heat source/sink and an Arrhenius-exothermic reaction in a microchannel with a constant free convection flow over an imposed transverse magnetic field. Appropriate transformation is applied to flow nonlinear equations, resulting in a dimensionless frame. The equations of temperature and velocity are solved in non-dimensional form under the appropriate boundary conditions using in built-in MATLAB solver bvp4c method. The basic flow characteristics of temperature, velocity and volumetric flow rate are explored in response to a range of control parameters. The results are eloquently analysed and diagrammatically depicted in the form of various illustrations and plots. An increment in the Hartman number causes a retardation of flow, which is observable. It is used in a variety of scientific and infrastructure applications, including solar communication systems exposed to airflow, electronic devices cooled at room temperature by airflow, nuclear units maintained during unscheduled shutdowns, and cooling systems that occur when conditions are low. An exothermic fluid’s constant flow was suggested for numerical analysis in this research. An important benchmark for verifying the correctness of certain numerical or empirical approaches may be defined with the use of this study’s findings. According to the comparison with the previously published findings, the limiting cases are very consistent.</p>