SUMMARY

In magnetic fusion energy (MFE) reactors, the target plates of the divertor, as one of the few solid surfaces directly exposed to the plasma, play a critical role of removing helium ash and other impurities and maintaining the high temperatures in the core plasma required to sustain fusion. In long-pulse MFE reactors, the divertors are expected to withstand steady-state heat fluxes in excess of 10 MW/m^2. The helium (He)-cooled modular divertor with multiple jets (HEMJ), one of the concepts originally proposed for the European Union demonstration power plant (DEMO), has been extensively studied over the past 15 years. This doctoral thesis proposes to study the thermal-fluids characteristics of the HEMJ divertor using a “reversed heat flux” approach, where the He heats (instead of cools) the divertor. To date, reversed heat flux experiments have been conducted on a single HEMJ “finger” module cooled by an impinging jet of water. The dimensionless heat transfer coefficient (HTC) or Nusselt number and dimensionless pressure drop, or pressure loss coefficient, are in good agreement with previous correlations for a similar HEMJ module cooled by He and heated by an RF induction heater, as well as with numerical predictions. These results for a single HEMJ module demonstrate that these thermal-fluid characteristics are independent of the direction of the heat flux. Based on these results, the proposed doctoral research will use for the first time the reversed heat flux approach to evaluate the thermal-fluids performance of a nine-finger HEMJ unit, and provide experimental and numerical evaluation of this configuration.