Influence of advanced Xue and Yamada–Ota thermal conductivity models on Williamson hybrid nanofluid stagnation-point flow over a rotating surface

Purpose This study aims to examine the heat transfer enhancement using multi-walled carbon nanotubes (MWCNTs) and aluminum oxide (Al2O3) in engine oil (EO). The experimental literature is used to validate the results. Design/methodology/approach The Williamson fluid model has been used, which includes EO as one of its subclasses. The investigation of stagnation-point unsteady flow is carried out using the Xue and Yamada–Ota thermal conductivity models in combination with a transverse magnetic field. A more realistic approach to real flow phenomena is achieved by simulating governing equations using the control volume finite element method to find out the results in three-dimensional (3D) and 2D forms. The homotopy analysis method has also been applied to solve the transformed form of the governing equations. Findings The parameter study and its impact on the thermal conductivity models have been observed. The dynamic viscosity results are derived from experimental literature, and the simulated results are compared with the experimental data. The heat transfer rate has seen a rise of 9%–20.71% in the case of the Yamada–Ota model using Al2O3/EO Al2O3/EO hybrid nanofluid. Originality/value The combination of the Williamson fluid model and the stagnation-point flow over a sphere represents the main contribution. The incorporation of the enhanced Xue and Yamada–Ota models for thermal management constitutes the second significant contribution for this particular model. This unified treatment of advanced nanofluid modeling, porous–magnetic coupling, MWCNT-Al2O3/EO hybrid nanofluid, experimental validation and dual-solver methodology for a rotating sphere configuration has not been reported previously.