The role of electromagnetic control and radiative heat transfer in micropolar nanofluid thin-film flow with influence of nanoparticle aggregation

Efficient heat transfer and minimization of entropy in micropolar nanofluids are essential for applications such as lubrication systems and energy storage devices. Dispersion of nanoparticles helps improve fluid properties like viscosity and thermal conductivity, which enhances system performance. In contrast, aggregation of nanoparticles can reduce these benefits and negatively affect performance. This study investigates the entropy optimization and heat transfer characteristics of an unsteady, laminar thin-film flow of an electromagnetic micropolar nanofluid. The fluid dynamics are modeled using the Maxwell–Bruggeman and Krieger–Dougherty effective medium theories to capture both nanoparticle aggregation and nonaggregation effects. The Krieger–Dougherty model describes the variation in viscosity due to nanoparticle concentration and clustering, while the Maxwell–Bruggeman model characterizes the thermal conductivity as influenced by nanoparticle distribution. Through the application of similarity transformations, the governing partial differential equations are reduced to a set of nonlinear ordinary differential equations, which are then solved numerically using the Chebyshev collocation method. The results indicate that an increase in spin gradient viscosity and electric field leads to a rise in the velocity profile. Moreover, the fluid temperature decreases as the Eringen parameter increases. For nanoparticles without aggregation, the friction coefficient decreases slightly by approximately 0.35%, whereas the Nusselt number increases by about 3.13%.