MHD pressure drop of lithium single-phase flow and helium–lithium two-phase flow in a circular channel

In order to confirm the effectiveness of a helium–lithium annular two-phase flow for the reduction of magnetohydrodynamic (MHD) pressure drop in a liquid metal single-phase flow in the cooling of the first wall and blanket of magnetic-confinement fusion reactors, the characteristics of MHD pressure drop were investigated experimentally for a lithium single-phase flow and a helium–lithium two-phase flow in a horizontal electrically thin conducting circular channel in the presence of a uniform transverse magnetic field. It was found that the skin friction coefficients of the lithium single-phase flow were approximately one half of the values estimated from Miyazaki et al.ʹs analytical expression, Cf=kpM2/2Re, where kp=c/(1+c). In general, the MHD pressure drops of the helium–lithium two-phase flow increased with an increase in applied magnetic flux density. However, the ratio of the pressure drop of the helium–lithium two-phase flow to that of the lithium single-phase flow at the same lithium mass flux decreased remarkably with an increase in the magnetic flux density. This result means that the helium–lithium two-phase flow cooling is effective for the reduction of the high MHD pressure drop of the lithium single-phase flow cooling.