Abstract
Cooling of the fusion blanket first wall remains a significant challenge, given the adverse conditions of heat and particle flux encountered near the plasma. Helium emerges as an attractive cooling candidate, due to its chemical and neutronic inertness and separability from hydrogenic species (e.g. tritium). Due to the low thermal mass of helium, optimization of these coolant channels is warranted to provide high heat transfer performance at low pumping costs. Increasingly, computational fluid dynamics (CFD) simulations are employed to model and optimize these flow channels, and accompanying experimental data are needed to validate the predictions of these models. To provide experimental data, a high-pressure helium flow visualization upgrade has been designed for the Helium Flow Loop Experiment (HFLE) facility. This apparatus was built to ASME boiler and pressure vessel standards to withstand operating pressures of 4 MPa and mated to high-pressure glass windows. Seedless flow visualization is performed via high-speed background oriented schlieren (BOS), with image correlation used for time-resolved 2D velocimetry at frequencies in excess of 60 kHz. Rectangular flow channel test articles are additively manufactured via laser powder bed fusion and installed into this visualization apparatus, with one-sided heating supplied by resistive heaters. The chosen test geometries were informed by preliminary CFD simulations, and the helium flow structures observed via BOS (detachment, recirculation, etc.) will be used for the validation of these accompanying models. Details of the design of this apparatus are discussed herein.
