Electromagnetic coupling phenomena in co-axial rectangular channels

In the Water-Cooled Lithium Lead (WCLL) blanket, the eutectic alloy lithium-lead (PbLi) is used as tritium breeder and carrier, neutron multiplier and heat transfer medium. The liquid metal is distributed to and collected from the breeding zone through a compact poloidal manifold composed of two co-axial rectangular channels. The external channel, tasked with distribution, and the internal one, assigned to the collection, are co-flowing and share an electrically conductive wall (cw=0.1). The liquid metal, interacting with the reactor magnetic field, leads to the arising of MagnetoHydroDynamic (MHD) effects that are expected to significantly modify the flow feature and electrically couple the external and internal channels. In this work, the general-purpose CFD code Ansys CFX 18.2 is used to study the coupling phenomena in a wide range of magnetic fields (up to Ha=2000) for a prototypical square co-axial channel. Characteristic flow features and their evolution with increasing magnetic field and varying mass flow rate between the channels are discussed and compared with the uncoupled case, which is in turn composed by a rectangular electro-conductive annulus (external) and a square electro-conductive duct (internal). A correlation is found linking the pressure loss in the studied configuration and an equivalent square channel through a corrective factor ε, which exhibits an asymptotic behavior for Ha > 1000.