Study on thermal mixing of liquid–metal free-surface flow by obstacles installed at the bottom of a channel

Highlights: • Experiments of thermal mixing in liquid metal film-flow by obstacles were performed. • Delta-wing obstacle showed good thermal mixing performance. - Abstract: One of the key challenges of the liquid divertor concepts in fusion reactors is the heat removal from the surface of liquid metal film-flow to the bottom wall, because thermal radiation and particle fluxes from the fusion core are deposited on the free-surface. This study investigates the possibility of the enhancement of heat removal by using various obstacles installed at the bottom of the liquid metal free-surface flow. Cubic and delta-wing obstacles are examined in this study. The obstacles installed at the center of the flow channel, upstream of the free-surface heat source. The experiments were conducted in the range of Re from 2000 to 18,000 under constant heating. The temperature on the bottom wall increased with increase of flow rate. The delta-wing obstacle showed the better thermal performance compared to the cubic obstacle and without obstacle case. Since the delta-wing obstacle generated the strong vortex with increasing Re, thermal mixing of liquid-film enhanced, and eventually led to highly localized heat fluxes at the bottom wall. Therefore, it is possible to remove the high heat flux locally from the wall.