Abstract
<title>Abstract</title> <p> This study investigates the MHD flow and heat transfer performance of ethylene glycol (C <sub>2</sub> H <sub>6</sub> O <sub>2</sub> ) – Silver (Ag) nanofluids between two concentric cylinders, by incorporating the effects of thermal radiation, internal heat sink, viscous dissipation, and porous media. A comparative analysis is performed using the Maxwell-Garnett and Patel models to evaluate nanofluid thermal conductivity enhancements. The interplay of external magnetic fields and nanoparticle dispersion introduces complex thermal-fluid dynamics, influencing energy transport significantly. A set of highly nonlinear ordinary differential equations governing the momentum and energy balance is derived and solved using the BVP4C numerical method in MATLAB. The study analyses the influence of key dimensionless parameters such as Hartmann number, radiation parameter, Eckert number, and nanoparticle volume fraction on flow velocity and temperature profiles. Results show that the Bruggemann model predicts higher heat transfer rates compared to the Maxwell - Garnett model, especially at elevated nanoparticle concentrations. The presence of MHD and radiation effects enhances thermal boundary layer development, offering better control of heat transfer. This comparative investigation offers critical insights for optimizing thermal systems in nuclear cooling, biomedical applications, and energy-efficient industrial processes, providing a foundation for the design of advanced thermal management technologies in cylindrical geometries under MHD influences. </p>