Thermal Performance and Irreversibility in an MHD Baffles Annulus With a Rotating Cylinder: For Advanced Cooling in Nuclear and Electronic Applications

Advanced thermal management systems used in nuclear reactor cooling, high‐power electronic devices, and magnetically controlled energy systems increasingly rely on optimized mixed convection and entropy minimization under complex physical effects. In this context, the present computational study investigates the conjugate pure mixed convection, entropy generation, and thermal performance of a CuO–water nanofluid within a radial‐baffles annular enclosure containing a rotating, heat‐generating cylinder under an inclined magnetic field. A thorough investigation examines the effects of nanoparticle volume fraction ( ϕ = 1%, 3%, and 5%) and the geometric radius ratio ( R r = 2 and 3) throughout a broad spectrum of Grashof, Reynolds, and Hartmann numbers. The findings indicate a significant trade‐off: although elevated nanoparticle concentrations improve thermal conductivity, the resultant rise in viscosity predominantly inhibits convection, leading to a decrease in the mean Nusselt number by as much as 90.6% and an increase in the mean fluid temperature by up to 1164%. Contrarily, this suppression reduces overall entropy generation by more than 91% and improves the thermal performance criteria by as much as 1292%. Geometrically, the confined enclosure ( R r = 2) enhances the Nusselt number by 55.7% while elevating the operating temperature by 87.7%. In contrast, the larger enclosure ( R r = 3) attains a 55.7% improvement in thermal performance coefficient by optimally balancing heat transport and irreversibility. The inclined magnetic field creates a unique diagonal symmetry in the flow and temperature fields, hence stabilizing the transport phenomena. This study illustrates that the ideal design is exclusively application‐specific, offering crucial directives for sophisticated thermal management systems and cooling applications.