A Study on the Mechanism of Spontaneous Vapor Explosions with Single Molten Tin Drops and Water.

Observations of initiation stage of spontaneous vapor explosions for droplet scale

“…Differences of the experimental apparatus from those used in previous works [3,4] and this experiment are using insulation materials for the furnace and the use of the slide board instead of stainless steel, with the addition of 4-mm-and 10-mm-diameter nozzles to the previously used 6-mm nozzle.…”

“…The rapid heat transfer attributable to such boiling rapidly expands the vapor bubble and generates low pressure within the vapor bubble through the cyclic movement of expansion and collapse of the vapor bubble. This movement also causes fine fragmentation of the hot liquid and enhances the heat transfer areas with the increase of the heat transfer rate [3][4][5]. Details of the mechanism at each stage in a vapor explosion, however, have limited experimental observations and have not yet been sufficiently clarified.…”

“…Figure 1 shows a schematic diagram of the experimental apparatus. The principle and the structure of the experimental apparatus are almost identical to those used in previous studies [3,4]. Two 6.5-mm diameter and 100-mm-long cartridge-type 200 W heaters are installed in a furnace.…”

Destabilization of film boiling and pressure change in vapor film when an external pressure wave is supplied

“…The pressure change in the R-113 was also measured by another pressure transducer (3) which had been set in liquid and at the same level as the other transducer. The pressure transducer signals were amplified by each amplifier (4) and were recorded in a digital storage oscilloscope (5). To observe the vapor film destabilization phenomenon, still photographs were taken with a 35-mm camera (11) and a strobe lamp (12) with exposure times of about 4 µs.…”

“…In previous papers, the authors observed the vapor film collapse during a spontaneous vapor explosion in a tin drop/water system [5] and that of the triggered vapor explosions by a pressure wave in a lithium nitrate/ethanol system [6]. The spontaneous collapse of the vapor film around a tin drop was initiated from one end of the disk-shaped drop.…”