Numerical Analyses on Liquid-Metal Magnetohydrodynamic Flow in 180°-Turn Channel

Numerical calculations have been performed on liquid-metal magnetohydrodynamic (MHD) flow in a 180°-turn (i.e. hairpin-shaped) channel, in order to contribute to design of a fusion reactor blanket. A magnetic field is applied in a direction perpendicular to an inlet channel, a turning channel (turning section) and an outlet channel. The continuity equation, the momentum equation and the induction equation have been solved numerically. In this study, attention is focused on pressure drops along the channels and pressure distribution in the turning channel. The Hartmann number (indicating magnetic field strength), the Reynolds number and the channel aspect ratio, in the present calculations, cover 100 to 500, 1000 to 5000 and 1 to 1/4, respectively. The following things have become clear from calculation results. The total MHD pressure drop from a channel inlet to a channel outlet agrees approximately with that for the total channel length, meaning that the loss coefficient for the turning channel is nearly zero or small. For large Reynolds numbers, the pressure in the peripheral region of the turning channel becomes larger than that at the channel inlet, due to the centrifugal force acting in the turning channel. It is considered that this pressure increase should be taken into account in designing a fusion reactor blanket.