Thermal performance and flow instabilities in a multi-channel, helium-cooled, porous metal divertor module

Pressurized helium is under consideration for cooling Langmuir probes and plasma facing components of next generation fusion experiments. Helium is non-corrosive, does not activate, separated easily from tritium, vacuum compatible, and undergoes no phase transformations. Recently, the thermal performance of a bare-copper, dual-channel, helium-cooled, porous metal divertor mock-up, designed and fabricated by Thermacore Inc., was evaluated on Sandiaʹs 30 kW Electron Beam Test System equipped with a closed helium flow loop. The module uses short circumferential flow paths to minimize pressure drops and pumping requirements while achieving optimal thermal performance by providing a very large effective surface area. The module was tested under both uniform and non-uniform heat loads to assess the effects of mass flow instabilities. It survived a maximum absorbed heat flux of 29.5 MW/m2 on a 2-cm2 area. Results on the power sharing between the two channels is presented and compared with that of a previous design. These experimental results coupled with appropriate modeling provide insight on flow instabilities in multi-channel, helium-cooled heat exchangers.