MHD effects and heat transfer analysis in magneto-thermo-fluid-structure coupled field in DCLL blanket

Abstract

The study on DCLL blanket in ITER is related to magneto-thermo-fluid-structure coupled field issue. A key element in the DCLL concept is the flow channel insert (FCI) which serves as an electrical insulator to reduce the magnetohydrodynamic (MHD) pressure drop, and as a thermal insulator to decouple the high temperature PbLi from the reduced activation ferritic steel (RAFS) structure. In the present work, 16 geometrical models of flow ducts are introduced to study the MHD flow and heat transfer in DCLL blanket in magneto-thermo-fluid-structure coupled physical field. The PISO method on unstructured collocated meshes is applied to simulate the metal liquid flow and heat transfer in the blanket. The consistent and conservative scheme is employed to solve the incompressible Navier-Stokes equations with the Lorentz force included based on the electrical potential formula. The finite element method is used to study thermal mechanical behaviors of FCI. The velocity distribution, MHD pressure drop, electric current stream lines and temperature distribution in liquid blanket, thermal deformations of FCI in various geometrical models under external strong magnetic field are investigated. The pressure drop reduction factor is defined to analyze the influence of FCI structure on the MHD effects in the liquid metal blanket. The nonlinear coupling effects among magnetic field, heat transfer and FCI structure are revealed. The results show that thicker FCI and wider gap would increase the MHD pressure drops in bulk flow; the thicker FCI has smaller displacement but its strain and stress change non-monotonously; the wider gap can enhance the heat transfer performance but lead to larger stress in FCI. The optimal design is essential for the structural safety and high heat efficiency of the system.