2-D moving mesh modeling of lithium dryout in open surface liquid metal flow applications

• Published in: Fusion engineering and design 2020-05, Vol.154, p.111512, Article 111512
• Main Authors: Szott, M., Ruzic, D.N.
• Format: Article
• Language: English
• Subjects: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Acceleration; Computational fluid dynamics; COMSOL Multiphysics; Dryout; Finite element method; Free surfaces; Heat flux; Heat transfer; Liquid levels; Liquid lithium; Liquid metals; Lithium; Magnetohydrodynamics; Moving mesh; Plasma facing component; Thermoelectric magnetohydrodynamics; Two dimensional models
• ISSN: 0920-3796; 1873-7196
• DOI: 10.1016/j.fusengdes.2020.111512

•Open surface liquid metal flows can exhibit dryout under high heat flux.•Dryout phenomenon is modeled in 2-D using COMSOL Multiphysics.•Coupled moving mesh and laminar flow modules capture behavior of the liquid lithium free surface.•Shaping the trench bottom can mitigate the effect to keep solid PFC materials protected. Liquid lithium displays increasing promise as a replacement for solid plasma facing components (PFCs) in fusion device applications. The Liquid Metal Infused Trench (LiMIT) system, developed at the University of Illinois (UIUC), has demonstrated how thermoelectric magnetohydrodynamics (TEMHD) can be harnessed to drive liquid lithium flow in an open surface PFC. However, in the highest heat flux applications, large local acceleration is created via TEMHD, and the sudden increase in velocity can cause the liquid level to expose the underlying solid, eliminating the protective benefits of the lithium. In order to study potential mitigation strategies, a 2-D COMSOL Multiphysics model was developed using the moving mesh module to capture free surface flow. The model depicts the development of the dryout phenomenon for 2 test cases – slow (1 cm/s) and medium (10 cm/s) flow in 5 mm deep trenches – including the liquid level reduction under the high heat flux and the pileup of slower flow both upstream and downstream of the heat stripe. The effectiveness of trench shaping dryout mitigation strategies is examined. For the slow flow case, it is shown that a 1.8 mm ledge placed under the heat stripe will stop dryout, and for the medium flow case, a 2.7 mm ledge is required to mitigate the effect. This model can be used to identify strategies for increasing the viable heat load for open surface liquid lithium PFCs.