Design and Fabrication of a Flat-Plate Multichannel He-Cooled Refractory HX for Divertor Applications

A flat-plate He-cooled divertor would provide a flat surface facing the plasma, would minimize the number of otherwise complex sub-modules needed to cool large areas, and could greatly reduce the complexity of the coolant manifold systems. We recently designed and manufactured a unique flat-plate multichannel refractory metal heat exchanger (HX) that employs open-cell refractory foam to enhance heat transfer from the heated plate to the helium coolant. The structural material of the flat-plate HX box (102 mm wide and 165 mm long) is powder metallurgy molybdenum. Three flat-plate HX boxes were fabricated, two with a heated surface plate made of 4-mm thick Mo, TZM, and one 3-mm thick W. Four supplyand five return ducts, each 4.8 mm wide by 61 mm long run parallel underneath the heated plate. A thin sheet of Mo-foam (~2 mm × 70 mm ×80 mm; H/W/L) is sandwiched between the ducts and the heated plate. Advantages of using foam are detailed in a separate paper in these proceedings. The supply ducts push helium up towards the heated plate and then circumferentially through the foam into the neighboring return ducts. Key to optimizing the design was achieving uniform helium flow upwards to the heated plate along the entire length of the supply ducts, while simultaneously minimizing end-effects due to the short active duct length (~80 mm). A series of geometric features were designed to obtain relatively uniform flow distributions throughout the HX box. Here we report on the final design based on CFD analysis and thermostructural finite element.