Thermal performance of hybrid nanofluid mixed convective flow in a horizontal channel equipped with dimpled surfaces and rotating solid cylinder subjected to magnetic field: Sensitivity analysis

Efficient heat transfer mechanism in channel flows is essential for thermal management in applications heat exchangers, compact thermal systems, electronic cooling, automotive cooling, aerospace designing and chemical processing, etc. In order to improve the thermal performance relative to the conventional methods, this study presents a novel numerical investigation of mixed convective hybrid nanofluid flow in a horizontal channel equipped with heated dimpled surfaces and a centrally located rotating solid cylinder under magnetic field effects, integrating geometrical enhancement, active flow modulation, entropy generation, and sensitivity analysis within a unified framework. In addition, 3D numerical analysis is incorporated to provide deeper physical insight of the fluid flow and heat transfer characteristics. The problem is formulated incorporating conservation equations of mass, momentum and energy for hybrid nanofluid transport, which is numerically solved using finite element method. Statistical evaluation is performed using response surface method. The findings reveal that fluid motion is accelerated effectively by the rotating cylinder, which increases further with the decrease in magnetic field strength and hybrid nanoparticle concentration in base fluid. Moreover, cylinder rotation speed significantly intensifies three-dimensional flow mixing, leading to enhanced convective heat transfer, while axial and spanwise fluid motion are suppressed with magnetic damping. A maximum heat-transfer enhancement of 35.83% is recorded at high rotation speed of the cylinder compared to the stationary case without magnetic field influence, whereas an increase in magnetic field strength suppresses thermal transport, reducing heat transfer enhancement by 13.39%. The inclusion of hybrid nanofliud significantly improves thermal performance, resulting in up to 46.37% heat transfer enhancement. Response surface analysis identifies that the optimal thermal enhancement occurs simultaneously at high rotational speed and hybrid nanoparticle volume fraction. Sensitivity results indicate a strong positive dependence of heat transfer rate of hybrid nanoparticle loading and cylinder rotation, with magnetic field strength exerting a negative influence. In addition, the analysis of entropy generation and Bejan number provide the information on the most significant sources of irreversibility, which could be utilized to optimize the thermal processes. The 3D results confirm and extend 2D findings by providing in-depth physical insight and improving the applicability of the model to the realistic engineering systems. This study offers a new understanding of the interaction of dimpled geometry, hybrid nanofluid, and rotating flow modulation under uniform magnetic field, which provides a new configuration to the design of improved thermal systems.