Enhanced Heat Transfer in Magnetohydrodynamic Annular Flow of Liquid Potassium Using Electrically Conducting Walls

ABSTRACT Liquid potassium is a prime candidate for fusion reactor cooling due to its excellent thermal properties and high electrical conductivity. However, its magnetohydrodynamic behavior under strong magnetic fields is significantly influenced by wall electrical conductivity, a factor often oversimplified in previous studies. This work presents a three‐dimensional numerical analysis using the finite volume method to systematically quantify the impact of three electrical boundary configurations on heat transfer and fluid dynamics in a potassium‐filled vertical annulus subjected to a radial magnetic field: fully insulated walls (EI), conductive inner/outer walls (EC‐Inner/Outer), and conductive top/bottom walls (EC‐Top/Bottom). Results demonstrate a non‐monotonic dependence of heat transfer on geometry. Increasing the annular gap ratio ( R ) consistently enhances the Nusselt number, while an optimal aspect ratio ( A ) near unity is observed, beyond which thermal stratification degrades performance. A regime‐dependent optimal configuration is identified: for intermediate gaps (0.5 ≤ R ≤ 0.85) under strong magnetic fields (Ha = 80), the EC‐Top/Bottom configuration mitigates Lorentz damping, enhancing heat transfer by 5%–10%. For wider gaps ( R > 0.85), fully insulated walls become optimal. This performance inversion arises from current path reconfiguration by conductive walls, which weakens the bulk induced electric field by up to 32% and fundamentally restructures the Hartmann and Roberts boundary layers.