Yamamoto Takuya, Okino Shinya
Department of Chemical Engineering, Graduate School of Engineering, Osaka Metropolitan University, 1-1, Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan.
Department of Mechanical Engineering and Science, Graduate School of Engineering, Kyoto University, Kyoto daigaku-Katsura 4, Nishikyo-ku, Kyoto 615-8540, Japan; Department of Mechanical Engineering, Tokyo Denki University, 5 Senju Asahi-cho, Adachi-ku, Tokyo 120-8551, Japan.
Ultrason Sonochem. 2025 Jun;117:107361. doi: 10.1016/j.ultsonch.2025.107361. Epub 2025 Apr 17.
In the present study, a planar laser induced fluorescence (P-LIF) measurement, reaction rate measurement, the sonochemical luminescence (SCL) observation, and the particle image velocimetry (PIV) measurement were conducted to clarify the effect of macroscopic mass transfer on sonochemical reaction rate in an ultrasonic bath. The concentration distribution was measured by the fluorescence intensity of Rhodamine 6G (Rh6G), which was illuminated by a CW-YAG laser sheet. The concentration of Rh6G decreases first in the high reaction zone measured by the SCL observation, and the resulting low-concentration zone expands to the low reaction zone through macroscopic convective mass transfer, which can be observed as solute plumes. Therefore, it is concluded that the mass transfer rate can slightly affect the chemical reaction rate due to the nonuniform concentration distribution in the early stage of sonochemical reaction. The reaction rate is slightly underestimated due to the spatial variation of the concentration in the early stage of ultrasonic degradation. The effect of macroscopic mass transfer on the sonochemical reaction rate was evaluated by first Damköhler number, which was calculated based on the flow velocity obtained by the PIV measurement and the reaction rate constant obtained by the decomposition experiment. Finally, it could be concluded that the first Damköhler number evaluates the effect of macroscopic mass transfer on the sonochemical reaction rate quantitatively and this dimensionless number can be applied to other ultrasonic bath with different condition.
在本研究中，进行了平面激光诱导荧光（P-LIF）测量、反应速率测量、声致化学发光（SCL）观测以及粒子图像测速（PIV）测量，以阐明宏观传质对超声浴中声化学反应速率的影响。通过连续波YAG激光片照射的罗丹明6G（Rh6G）荧光强度来测量浓度分布。通过SCL观测发现，在高反应区Rh6G浓度首先降低，随后形成的低浓度区通过宏观对流传质扩展到低反应区，这可观察为溶质羽流。因此，可以得出结论，由于声化学反应初期浓度分布不均匀，传质速率会对化学反应速率产生轻微影响。由于超声降解初期浓度的空间变化，反应速率会被略微低估。通过基于PIV测量获得的流速和分解实验获得的反应速率常数计算得到的第一达姆科勒数来评估宏观传质对声化学反应速率的影响。最后，可以得出结论，第一达姆科勒数能够定量评估宏观传质对声化学反应速率的影响，并且这个无量纲数可应用于其他不同条件的超声浴。
