Liquid magnetohydrodynamics — recent progress and future directions for fusion

Abstract

This paper reports on recent research into magnetohydrodynamic (MHD) phenomena applicable to fusion technology. In Europe, experiments on the relative enhancement of heat transfer in liquid metal (LM) flows in ducts with electrically thin or insulated walls show a factor of two increase due to strong shear flow boundary layers when compared to slug flow solutions. This increase has no associated increase in pressure drop. Stronger enhancement is possible with mechanical promoters, but pressure drop increased concomitantly. Electrical turbulence promoters have been shown in theory to aid in heat transfer as well, although preliminary experiments in Europe show no enhancement and a 20% increase in pressure drop. Experiments in Japan show that the maximum enhancement for liquid Lithium occurs for values of the interaction parameter in the N =10 -20 range. Other recent experimental efforts in Europe, Japan and Russia on natural convection in the presence of magnetic field, formation of insulator coatings and modeling of insulator imperfections are also described. In the USA, design and analysis of liquid systems utilizing all-liquid walls have lead to interest in turbulence simulations for heat transfer at free surfaces of both LMs and Flibe. Free surface flows are particularly sensitive to changes in MHD drag since no applied pressure can be used to drive the free surface flow. For this reason, Flibe is considered a prime candidate for liquid walls and is also considered in Japan as the top candidate for Large Helical Device (LHD) breeder blanket. Experimental work with Flibe simulants is currently underway in Japan, and under development in the USA. Analysis of LM flows under liquid wall conditions is being performed in the USA as well. In Russia some further experiments were made for divertor/first wall LM free surface flow, LM heat pipes and porous structures with Li evaporation.

Study of Conjugate Heat Transfer in Electromagnetic Liquid Metal Dream Pipe

“…For further details on the current status and future scope of Liquid Metal Magneto Hydrodynamic Heat Transfer Systems, one may refer to the survey article by Morley et al [29].…”

Physical Model Development and Benchmarking for MHD Flows in Blanket Design

“…Recent reviews of the present status of modeling and experiments in liquid metal MHD pertaining to fusion and metallurgy were made by Morley et al 31 , Kirillov et al 25 , and Davidson…”

“…A comprehensive code development activity at the scale investigated here has not been carried out hitherto, and there is to date, a lack of a well accepted set of benchmark problems in this area. The design of unit problems in multi-physical MHD flows is of contemporary interest, as expressed in various survey articles in the literature (Morley et al 31 , Kirilov et al 25 , Brooks et al 8 , and Molokov et al 28 ).…”

“…While lamenting upon the lack of reliable computational or analytical techniques for flow prediction for realistic problems 11 , the need for modeling complex geometry and imperfect wall insulations 25 , and, for a substantial benchmarking process in experiments and computations 31 has been identified by these authors. We believe that this Phase-II project addressed this need substantially.…”

Study of Magnetohydrodynamic Surface Waves on Liquid Gallium

“…electrically conducting liquids, such as liquid lithium or liquid salt (Flibe), are proposed as the material facing the burning plasma in fusion reactors, directly handling the heat flux and breeding tritium from neutrons [2][3][4][5] . The liquid is typically under extreme mechanical and thermal stresses due to the required fast flows and the high heat flux on the free surface 2 .…”