Magnetohydrodynamic flow in the dual coolant blanket

The magnetohydrodynamic flow in the improved Dual Coolant Blanket is analyzed with focus on velocity distribution and pressure drop for a fully developed flow in the long poloidal rectangular channels. The fluid in the channels is insulated from the electrically conducting walls by means of ceramic flow channel inserts for pressure drop reduction. It is found that the pressure drop for the poloidal flow is low even if the insulation provided by the insert is not perfect. The distribution of velocity in a laminar regime is not optimal for heat transfer if the electric conductivity of the insert is too high. Then most of the fluid is carried along the side walls in jets with high velocity. Such flows tend to develop instabilities associated with intense mixing. Three-dimensional effects near expansions and contractions cause a major fraction of the total pressure drop. Results for flows in these geometric elements have been obtained by using empirical correlations which had been derived for different geometries. More detailed analysis would require 3D inertial computations which are foreseen in future. For validation experiments are recommended. (orig.)