THE EFFECTS OF IMPERFECT INSULATOR COATINGS ON MHD AND HEAT-TRANSFER IN RECTANGULAR DUCTS

The integrity of the electrically insulating coating at the coolant ch annel walls represents a feasibility issue for a self-cooled liquid me tal blanket. The effects of cracks in the insulating layer on MHD pres sure drop are investigated, for various crack locations, sizes and res istivities. It is shown that, once the crack resistance exceeds the Ha rtmann layer resistance, the MHD pressure drop increases significantly . Using the 2-D fully-developed MHD flow code, it has been found that the crack location has a large impact on the MHD pressure drop: for th e same crack sizes and resistivities, the pressure gradient increases as the cracks move towards the central plane. The effect of the insula tion on heat transfer is discussed. The heat transfer capability is re duced in the presence of the insulator coating.