On the thermal-hydraulic optimization of DEMO divertor plasma facing components cooling circuit

Highlights: • The thermal-hydraulic performances of the DEMO divertor Plasma Facing Components (PFCs) cooling circuit have been optimized. • The effects of increasing inlet/outlet manifolds diameters and placing a diffuser at the inlet of each Vertical Target have been assessed. • A numerical approach based on the Finite Volume Method has been followed, adopting the ANSYS-CFX code. • The "optimized" configuration foresees a total pressure drop of 1.098 MPa and a minimum margin against CHF occurrence of 1.462. - Abstract: Within the framework of the Work Package Divertor, Subproject: Cassette Design and Integration (WPDIV-Cassette) of the EUROfusion action, a research campaign has been jointly carried out by ENEA and University of Palermo to investigate the thermal-hydraulic performances of the DEMO divertor cassette cooling system. Attention has been focussed on the divertor Plasma Facing Components (PFCs) cooling circuit and a parametric analysis has been carried out in order to assess the potential impact of proper layout changes on its thermal-hydraulic performances, mainly in terms of coolant total pressure drop, flow velocity distribution and margin against critical heat flux occurrence. The research activity has been carried out following a theoretical-computational approach based on the finite volume method and adopting a qualified Computational Fluid-Dynamic (CFD) code. Results obtained have allowed to select a revised PFCs cooling circuit configuration, suitable to comply with the prescribed thermal-hydraulic limits assumed for the DEMO divertor design. They are reported and critically discussed.