Magnetic Influence on Natural and Marangoni Convections in a Zone of Metal Melted by High Heat Flux

抄録

In readiness for utilization as material for the first wall of fusion reactors that will simul-taneously generate high heat flux and a high magnetic field, the heat transfer and melting behavior of stainless steel has been numerically analyzed applying the finite difference method. Envisaging the application of a heat flux of 2.34 kW/cm² axially on an 8 mm thick, 60 mm diameter stainless steel disk under an axial magnetic field of intensity varied parametrically, the analysis clarifies the effect of differences in applied magnetic field intensity on the configu-ration of the melted metal zone boundary, on the flow pattern of convective circulation generated within the same zone, and on the radial temperature distribution across the zone. The analysis is performed both for the cases of natural convection alone taken into account and of combina-tion with Marangoni convection. As a result, it is shown that, assuming steady state, the surface flow velocity at the point of interest varies with the applied magnetic field intensity approximately in inverse proportion to the square of Hartmann number in the case of natural convection alone, and that the same applies to the case of combination with Marangoni con-vection, though with greater deviation from the foregoing analytical result toward higher magnetic field intensities. It is also shown that the assumption of steady state (adopted in deriving the above relation between surface flow velocity and Hartmann number) becomes valid after the lapse of a short time after the start of heat flux application.