Control and Optimization of Thermal Transport in Unsteady Thin Film Flow of Aggregating Micropolar Nanofluids

The increasing demand for industrial development, efficient energy utilization, and cost reduction has motivated extensive research into nanomaterials and radiative heat transfer. This study investigates the thermal transport characteristics of an aggregating micropolar nanofluid in unsteady thin film flow, considering the effects of variable viscosity and thermal conductivity. The working fluid consists of molybdenum disulfide (MoS₂) nanoparticles dispersed in ethylene glycol, with the nanoparticle volume fraction varied over the range of 0–5%. The influences of radiative heat transfer, electromagnetic effects, spin gradient viscosity, electric field, and microinertia are examined for both aggregating (Agg) and non-aggregating (W-Agg) nanofluids. The Krieger–Dougherty and Maxwell–Bruggeman models are employed to characterize the effective viscosity and thermal conductivity, respectively, particularly at higher nanoparticle concentrations. The governing equations are transformed into a dimensionless system of coupled nonlinear differential equations and solved using the Chebyshev collocation method. The effects of the governing thermofluidic parameters on velocity, entropy generation, skin friction coefficient, and heat transfer rate are systematically analyzed. The results show that fluid velocity increases with increasing spin gradient viscosity and electric field strength for both Agg and W-Agg nanofluids. In the absence of nanoparticle aggregation, the shear stress decreases by approximately 0.35%, whereas the heat transfer gradient increases by about 3.13%. Furthermore, nanoparticle aggregation produces measurable changes in velocity and entropy generation, highlighting its important role in momentum and thermal transport. These findings demonstrate the potential of electromagnetic and micropolar effects for controlling thermal transport and improving the performance of nanofluid-based thin film systems.