<p>In a steam generator (SG) of sodium-cooled fast reactors (SFR), heat exchange takes place between liquid sodium in a shell side and water or steam inside heat transfer tubes. When steam leaks from a raptured heat transfer tube, a high-velocity and high-temperature jet with sodium-water chemical reaction is formed in the shell side. It is known that the reacting jet may cause wastage on the wall of the adjacent tubes. At this time, it is thought that fine sodium droplets are torn off from the sodium surface and entrained into the steam jet. The high-velocity sodium entrained droplets attack the wall of a neighboring tube and cause a wastage on the tube wall, which may lead to a failure propagation. Prevention of failure propagation is important issue in designing the SG. In Japan Atomic Energy Agency, an analysis code for the sodium-water reaction phenomenon, called SERAPHIM, has already been developed. In order to validate evaluation of the droplet entrainment model introduced in this analysis code, experimental data is required. In the past, some experiments have been carried out to visualize the gas-liquid interface of the air injected into the water to capture the droplet entrainment behavior; however, since the air jet velocity reaches sonic speed, it was very difficult to visualize the gas-liquid interface. Due to the above-mentioned difficulties, experimental data on droplet entrainment behavior is still lacking. The objective of this research is to visualize the behavior of droplets entrained from the gas-liquid interface of the air jet into the stagnant water pool in detail for validation of the SERAPHIM, and the droplet diameter and the droplet velocity are measured. To make visualization inside the jet possible, the test section with a narrow depth was used. The frame straddling method was used to visualize the droplets inside the jet. The frame straddling method, which acquire a set of image with a shoot time interval was applied to measure the velocity vector of droplets. Visualization experiment was conducted with variation of the air jet velocity. Then, clarify the effect and behavior of the difference in nozzle outline is varied with on the entrainment phenomenon. The nozzle outline used the rounded fan-shaped nozzle and the square nozzle. Due to the difference in nozzle outline, there is a difference in jet behavior when the jet interface expands. And the effects of entrainment behavior on the droplet diameter and velocity were discussed.</p>

Droplet Entrainment Phenomena Affected by Interfacial Behavior of a High-Speed Gas Jet Into a Liquid Pool

Paper Proceedings: https://asmedigitalcollection.asme.org/ICONE/ICONE28/volume/85246

2021 28th International Conference on Nuclear Engineering (ICONE28)

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