Interfacial instability of a condensing vapor bubble in a subcooled liquid
Interfacial instability of a condensing vapor bubble in a subcooled liquid
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DOI：
10.1140/epjst/e2015-02370-6
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发表时间：
2015-04
期刊：
影响因子：
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通讯作者：
I. Ueno;J. Ando;Y. Koiwa;T. Saiki;T. Kaneko
中科院分区：
文献类型：
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作者：
I. Ueno;J. Ando;Y. Koiwa;T. Saiki;T. Kaneko
重点研究了注入过冷池的汽泡的凝结和坍塌过程。我们尝试采用蒸汽发生器通过孔口向过冷池提供蒸汽来提取汽液相互作用，而不是使用浸没的加热面通过沸腾现象来实现蒸汽气泡。该系统使人们能够探测暴露在过冷液体中的单个过热蒸汽气泡的时空行为。在本研究中，在大气压下，以指定的过冷度将水蒸气以恒定的流量通过孔板注入过冷水池。水池的过冷度从0 K到70 K，水蒸气温度保持在10 1∘C不变。高速摄像机以高达30万帧/秒(Fps)的帧速率捕捉到注入的水蒸气的行为，以跟踪气泡形状的时间变化。结果表明，暴露在过冷池中的汽泡在过冷度大于30 K左右时发生突然崩塌，并且伴随着自由面上出现的精细扰动或不稳定而发生突然崩塌。然后，我们在气泡的轴对称形状的假设下，评估了气泡V的表观‘体积’的时间变化。研究还发现，汽泡体积达到最大值后，汽泡的不稳定性略有出现。当汽泡表面出现不稳定性时，汽泡相应‘半径’R的二阶导数为负值，即=3√3V/4π，并说明了汽液界面不稳定性的波数随过冷度的增加而增大。
A special attention is paid to the condensing and collapsing processes of vapor bubble injected into a subcooled pool. We try to extract the vapor-liquid interaction by employing a vapor generator that supplies vapor to the subcooled pool through an orifice instead of using a immersed heating surface to realize vapor bubbles by boiling phenomenon. This system enables ones to detect a spatio-temporal behavior of a single bubble of superheated vapor exposed to a subcooled liquid. In the present study, vapor of water is injected through an orifice at constant flow rate to the subcooled pool of water at the designated degree of subcooling under the atmospheric pressure. The degree of subcooling of the pool is ranged from 0 K to 70 K, and the vapor temperature is kept constant at 101∘C. The behaviors of the injected vapor are captured by high-speed camera at frame rate up to 0.3 million frame per second (fps) to track the temporal variation of the vapor bubble shape. It is found that the abrupt collapse of the vapor bubble exposed to the subcooled pool takes place under the condition that the degree of subcooling is greater than around 30 K, and that the abrupt collapse always takes place accompanying the fine disturbances or instability emerged on the free surface. We then evaluate a temporal variation of the apparent ‘volume’ of the bubbleVunder the assumption of the axisymmetric shape of the vapor bubble. It is also found that the instability emerges slightly after the volume of the vapor bubble reaches the maximum value. It is evaluated that the second derivative of the corresponding ‘radius’Rof the vapor bubble is negative when the instability appears on the bubble surface, whereR=3√ 3V/4π.We also illustrate that the wave number of the instability on the liquid-vapor interface increases as the degree of subcooling.