Computational fluid dynamic studies on plasma facing heat sink concept for fusion tokamak application

Highlights: • A modular divertor heat sink concept is proposed for fusion tokamak application. • Effects of important parameters on the heat transfer characteristics are critically discussed. • The use of multiple nozzles of various shapes is investigated by 3-dimensional CFD studies. • Thermo-mechanical analysis is performed toward ensuring acceptability of the design from structural integrity consideration. - Abstract: Development of an efficient divertor heat sink concept capable of extracting intense heat flux while maintaining temperatures and thermo-mechanical stress levels within allowable limits is a challenging task to meet in the scenario of the future fusion power plant known as DEMO. Typically, divertor is expected to extract a steady state heat flux up to 10 MW/m². In the present study, an efficient divertor concept based on helium gas cooling has been proposed for the fusion grade tokamak. The effects of critical thermal hydraulic parameters and geometrical parameters on the heat transfer characteristics of the divertor module are studied as a function of Reynolds number (Re). This includes critical parameters, viz., thimble diameter (D_T), nozzle diameter (D_N), the ratio of nozzle-to-wall space and nozzle diameter (H/D_N) and nozzle shape. Elliptical nozzles at specific orientation are found to give the best performance, whereas triangular nozzles are found to give the worst performance for identical Reynolds numbers. Similarly, a minimum thimble temperature and pressure drop in the circuit is achieved at H/D_N ~1.66. The proposed design is found to have a margin of 10%, i.e., capable of handling 11 MW/m² against target heat flux values of 10 MW/m². The stress values arising out of temperature gradient and pressures are found to be within acceptable limits, demonstrating the reliability of the proposed concept.