1I-1 超音波霧化によるミスト発生制御とエタノール濃縮分離 : 可視化解析とプロセス開発(招待講演1)
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概要
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Ultrasonic atomization (USA) can be induced by applying ultrasound of high frequency, i.e., on the order of MHz, to a gas-liquid interface from the liquid underneath. It will preferentially occur, due partly to its high directivity, in comparison to acoustic cavitation induced favorably under lower-frequency (<MHz, thus technically-easier-to-attain larger-amplitude) conditions. When the liquid is subjected to high-frequency (≥1MHz) ultrasound, the atomization starts almost instantaneously in association with liquid jet formation and breakup. The atomization sequence, including the dynamics of interfacial oscillations, is visually analyzed via high-speed imaging. Selective ethanol separation from its aqueous solution is attempted through USA coupled with mist recovery by two-stage cooling. It is found that the USA process could be more closely triggered by sudden increase in the surface roughness of microscale, which would be viewed as localized surface patches of two-dimensional capillary waves, often associated with contraction-expansion sequence of the surface topology. Such surface patches can then lead themselves to further instability to generate a swarm of liquid droplets of microscale around the expanded phase of liquid column. Two separate recoveries, in the 1st and 2nd stages, with lower and higher ethanol contents, respectively, can be realized by optimizing-from an energy-saving perspective-cooling temperatures and carrier-gas flowrate; regarding the latter operating parameter, ethanol-rich mist consisting of small-size droplets tends to be carried selectively in favor of lower gas flowrate. The two-stage cooling process has thus an advantage of obtaining desired product by virtue of collectivity and transportability, respectively.
- 超音波エレクトロニクスの基礎と応用に関するシンポジウム運営委員会の論文
- 2009-11-18