A comprehensive review of experimental and numerical studies on liquid metal-gas two-phase flows and associated measurement challenges

Liquid-gas two-phase flows are commonly encountered and studied phenomena in various low temperature ordinary liquids. In contrast, a two-phase flow occurring in a Liquid Metal (LM) system is rarely encountered and therefore seldom studied. Advantages and criticalities of such a phenomenon primarily depend on the system under consideration. A LM-gas two-phase flow presents advantages toward process efficiency enhancements in certain metallurgical processes including homogenization, refining and degassing. However, such a phenomenon could equally indicate the onset of a postulated accidental event in the context of LM-cooled advanced nuclear reactors, affecting the design, safety and efficiency, thereof. Even with such critical importance and growing popularity of LMs in various roles, relevant two-phase studies remain at large a scarcity. Significant parametric differences for these advanced fluids preclude direct adoption of well-established correlations applicable to ordinary aqueous systems. A need, therefore, arises for a detailed consolidation of database on LM-gas two-phase flows. This review aims to provide interested researchers with a chronologically collated critical account of relevant studies with a primary emphasis on specific methods utilized and measurement tools developed. The review also throws light on state-of-the-art Molecular Dynamics simulation studies of LM-gas two-phase flows. It is expected that the findings, analysis and outlook presented would be equally beneficial to investigators in the field of LM process optimizations, to designers of LM-cooled advanced nuclear reactors, and to researchers in the concentrated solar power and nuclear fusion applications.