3D numerical study of pressure equalization in MHD flow in a rectangular duct with insulating flow channel insert

A flow channel insert (FCI) made of a Silicon Carbide (SiC) composite or foam is the key element of the dual-coolant lead-lithium (DCLL) blanket concept. Pressure equalization openings in the FCI wall are designed to equalize possible pressure differences in the flowing liquid metal (LM) between the bulk flow inside the FCI box and that in the thin gap between the FCI and the outer ferritic steel duct, thus reducing the mechanical stress in the FCI. In the present study, the MHD flow and associated pressure equalization effects are simulated with a numerical code in 3D. Two pressure equalization mechanisms have been identified and studied: one is due to LM flow through the flow equalization slot, and the other is due to induced electric currents flowing across the non-ideally insulating FCI wall. The second effect appears to both dominate and provide a more effective way of pressure equalization compared to the purely hydrodynamic mechanism. Parametric studies have been performed to address the impact of the FCI electrical conductivity, slot size, and the duct length. Finally, recommendations on the FCI design are proposed to result in more effective pressure equalization.