Observations of Initiation Stage of Spontaneous Vapor Explosions for Droplet Scale

Takashima, T.

doi:10.1299/kikaib.73.1092

Cited by 2 publications

(6 citation statements)

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“…2 and frames (4) to (6) in Fig. 4 show clearly that the phenomenon of splashing of the melt does not cause vapor explosion with rapid fragmentation.…”

Section: Mechanism For the Initiation Of Spontaneous Vapor Explosionmentioning

confidence: 85%

“…The average expansion speed of the vapor bubble diameter from frame (6) to frame (9) is approximately 2.1 m/s, which is about 1.1 times the vertical expansion speed. Figure 4 shows a typical sequence of the vapor film and droplet figure images taken of conditions that include a water temperature of 24 °C with 4 g molten tin of 650 °C droplet at 8000 fps and shutter speed of 1/21,000 s [6]. The tin was dropped from a 10-mm-diameter nozzle to observe details.…”

Section: Entire Vapor Explosion Processmentioning

confidence: 99%

“…The splash phenomenon occurs when a water droplet is dropped onto a hot molten metal surface if the interface temperature region between both liquids is higher than the spontaneous nucleation temperature of water. Tin particles remain in water by splashing, as indicated by the circle in frame (6) in Fig. 4.…”

Section: Details Of the Droplet And Vapor Film On Film Boilingmentioning

confidence: 99%

“…The splashing occurs at the bottom of the droplet; it was observed three times at t = 19.5 ms, 19.875 ms, and 30.375 ms. Figures 2 and 4 show that the local collapse of the vapor film does not propagate to the entire droplet. Frame (6) in Fig. 2 shows that almost the entire droplet surface was covered by the vapor film up to t = 61.0 ms, at which time the vapor explosion with fragmentation begins.…”

Section: Details Of the Droplet And Vapor Film On Film Boilingmentioning

confidence: 99%

“…The droplet shape changes and transforms the disk-shaped part and tail part [frames (4) to (6)]. The vapor film collapse then begins at the local area of the bottom of the droplet [frame (7)].…”

Section: Details Of the Vapor Film Collapsementioning

confidence: 99%

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Observations of initiation stage of spontaneous vapor explosions for droplet scale

Takashima

2007

Heat Trans. Asian Res.

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In this study, the initiation stage of spontaneous vapor explosions generated by single droplets of molten tin submerged in water was investigated using a highspeed video camera operated with a reflected light system. Photographs of the formation process of vapor film, the process of vapor film disturbance, and the initiation process of the vapor explosions for different masses of molten tin and different nozzle diameters were obtained. The results demonstrate that partial thermal interaction between tin and water does not cause a vapor explosion with fragmentation. The vapor film disappears locally during the formation of the vapor film around the hot liquid droplet. Direct contact between the hot molten tin surface and water is thereby generated. However, the local disappearance of the vapor film does not progress and the vapor film is reconstructed. A vapor explosion occurs when the vapor film collapses at the local area of the bottom or edge of the disk-shaped droplet.

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“…2 and frames (4) to (6) in Fig. 4 show clearly that the phenomenon of splashing of the melt does not cause vapor explosion with rapid fragmentation.…”

Section: Mechanism For the Initiation Of Spontaneous Vapor Explosionmentioning

confidence: 85%

Section: Entire Vapor Explosion Processmentioning

confidence: 99%

Section: Details Of the Droplet And Vapor Film On Film Boilingmentioning

confidence: 99%

Section: Details Of the Droplet And Vapor Film On Film Boilingmentioning

confidence: 99%

Section: Details Of the Vapor Film Collapsementioning

confidence: 99%

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Observations of initiation stage of spontaneous vapor explosions for droplet scale

Takashima

2007

Heat Trans. Asian Res.

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A Numerical Analysis Research on Earlier Behavior of Molten Droplet Covered with Vapor Film at the Stage of Triggering and Propagation in Steam Explosion

Zhong

Meng

et al. 2014

Science and Technology of Nuclear Installations

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When the molten fuel with high temperature falls into the cavity water, it will be dispersed into droplets which are covered with vapor films due to the rapid heat transfer with phase transition. This situation cannot be simply described by liquid-liquid or gas-liquid systems. And there are no sufficient experimental studies on the behavior of droplet covered with vapor film because of the rapid reaction and the difficulty in capture of the film configuration. In this paper, a multiphase code with the volume of fluid (VOF) method is used to simulate the earlier behavior of droplet when vapor film exits. The earlier behavior is defined as behavior of the droplet before its disintegration. Thermal effect and pure hydrodynamic effect are, respectively, considered. The simulation results indicate that the film thickness and material density have significant effect on the earlier behavior of droplet. The situation assumed in Ciccarelli and Frost’s model (1994) is observed in current simulation of earlier thermal droplet behavior. The effect of triggering pressure pulse on earlier hydrodynamic behavior is also discussed and it indicates that vapor film has little effect on the hydrodynamic droplet deformation when the intensity of the pressure pulse is very high.

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Observations of Initiation Stage of Spontaneous Vapor Explosions for Droplet Scale

Cited by 2 publications

References 0 publications

Observations of initiation stage of spontaneous vapor explosions for droplet scale

Observations of initiation stage of spontaneous vapor explosions for droplet scale

A Numerical Analysis Research on Earlier Behavior of Molten Droplet Covered with Vapor Film at the Stage of Triggering and Propagation in Steam Explosion

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