CFD modeling of ITER cable-in-conduit superconductors: Part II. Effects of spiral geometry on the central channel pressure drop

In the first paper of this series, we proposed a novel approach to help understand some of the complex processes occurring in dual-channel cable-in-conduit conductors (CICC) as used in the superconducting coils of the international thermonuclear experimental reactor (ITER): the constitutive relations including transport coefficients needed in input by standard global 1D tools for the analysis of thermal-hydraulic transients in ITER coils, e.g., the Mithrandir/M&M code, are derived from local 3D analysis. A first validation of the model was performed showing very good agreement with available experimental data from different applications. The same advanced computational fluid dynamics (CFD) tool, the FLUENT code, including sophisticated turbulence models, is used here to compute the pressure drop corresponding to an imposed mass flow rate in several geometries relevant for the central channel of the ITER CICC. The validation is extended to include more ITER-relevant conditions showing good accuracy with error bars on the friction factor ∼±15%. We then apply the validated model to the study of the expected dependencies of the pressure drop in the central channel of an ITER CICC on the size of the gap and on the diameter of the delimiting spiral.