Experimental detailed analysis of flow and temperature fields of free surface flows with turbulence promoters for investigation of surface heat removal mechanism

As for a liquid molten salt divertor proposed for a fusion DEMO reactor divertor that maintains the plasma-facing surface in a healthy condition through free-surface flow, one of the key challenges is how to suppress the surface temperature despite the low heat transfer performance of molten salt. Introducing turbulence promoters is a well-known method for enhancing heat transport. In this study, a pebble-sunk structure (PSS) was used as a turbulence promoter in an open channel with flowing water as a simulant fluid, and the temperature and flow fields were measured experimentally. The experimental results showed that the change in surface temperature caused by the introduction of a turbulence promoter was 75%–107% of that in a smooth channel, and the temperature fluctuation intensity near the free surface and kinetic energy were enhanced largely when the PSS was introduced. Reynolds stress was also enhanced, consistent with the improved heat transport performance of the turbulence promoter.