Impact of Temperature‐Dependent Variable Viscosity on Arrhenius‐Controlled Heat Transfer Flow in a Microchannel

Recent analytical studies assume that fluids have a constant viscosity. However, to make correct predictions about heat transmission and flow creation, physical parameters, particularly viscosity, must be considered as they change with temperature. Therefore, this paper investigates fully developed natural convection of an exothermic fluid over an upward‐facing plate with variable viscosity and asymmetric/symmetric wall heating. Using the homotopy perturbation method (HPM), the highly nonlinear governing equations are semi‐analytically solved. The temperature‐dependent viscosity is represented by the Reynold model as an exponential function. The principal focus of the research is to observe and report the impacts of varying viscosity while accounting for the chemically reactive parameter. The obtained solutions are graphically represented and thoroughly discussed. From the computational analysis, it is confirmed that a higher viscosity variation parameter enhances both fluid velocity and shear stress at the lower plate. Additionally, it is observed that the viscous heating parameter raises both fluid temperature and velocity. Understanding these effects is critical for many engineering and biological applications, including microreactor design, biomedical systems, and thermal management systems. Specifically, variable viscosity formulations better anticipate or represent the behavior of lubricants, polymer processing fluids, and biological fluids (e.g., nanofluids) under high‐speed flow and high‐temperature flux.