SUMMARY

A modular helium-cooled divertor design for the "post-ITER" demonstration reactor based on the multi-jet impingement concept (HEMJ) has been developed at Forschungszentrum Karlsruhe. The design goal is to accommodate a surface heat flux of at least 10 MW/m^2 at an acceptable pumping power. The purpose of this research is to perform thermal-hydraulic analyses and validation experiments in support of the HEMJ divertor design. The design optimization process showed that the HEMJ design can remove a heat load of up to 12 MW/m^2 at an acceptable pumping power. The thermal-hydraulic analyses were performed using the FLUENT CFD software package; extremely high heat transfer coefficients were predicted (~30 kW/m^2-K). This investigation has been undertaken to validate the results of the numerical simulations. A one-to-one scale test module that closely matches the geometry of the HEMJ design was constructed and tested. Experiments were performed using air as the coolant at different Reynolds numbers spanning the value for the actual helium-cooled HEMJ design. The experiments were performed at heat fluxes of up to 1.0 MW/m^2. The temperature distributions and local heat transfer coefficients were measured over a wide range of operational conditions. The experimental data was compared with the results of a-priori analyses performed using the FLUENT CFD package with the same model options used in the original HEMJ divertor design calculations. The results of this investigation assess the adequacy of the numerical model and its applicability to the design of the HEMJ divertor, as well as other gas-cooled high heat flux components at fusion reactor operating conditions.