Development Status of the Helium-Cooled Porous Tungsten Heat Exchanger Concept

The development status of a helium cooled refractory metal heat exchanger (HX) concept using tungsten foam for enhanced heat transfer is presented. The HX design is based on azimuthal flow of helium through the foam sandwiched between two concentric tungsten tubes. This concept holds the promise for an efficient and low pressure-drop HX concept for plasma facing components, such as divertors. A prototypical flat-top HX-tube is being manufactured for testing at the high heat flux testing facility at SNL. Concept design optimization requires knowledge of the enhanced heat transfer coefficients due to the foam structure. Solid models of representative metal foams were developed for use in CFD analysis. Initial CFD results show improved heat transfer between the heated wall to the coolant. For a 1-mm thick foam with a specific density of 12% and a pore density of 65 PPI an average heat transfer coefficients of 40 000 W/m²-K was estimated, along with a pressure drop of ~60 kPa. For a 10 MW/m² surface heat load and an inlet helium temperature of 600degC at a pressure of 4 MPa, maximum structural temperatures were estimated to be 1060degC. This preliminary design has a maximum combined primary plus secondary von Mises stress of less than 600 MPa.