Study the effect of channel oscillation on the mass transfer rate of bubbles in small channels


Study the effect of channel oscillation on the mass transfer rate of bubbles in small channels

Haghnegahdar, M.; Boden, S.; Hampel, U.

In many industrial processes involving disperse gas and liquid, the mass transfer rate between the contacting phases is an essential parameter for the efficient design, optimization and control of the processes.
In the present study, we investigate the influence of channel oscillation on the shape, rise velocity and dissolution rate of single elongated Taylor bubbles in millimetre-sized channels. Using videoscopic observation, the position of the rising air bubble’s front tip in stagnant liquid (deionized water) in a vertical channel with circular cross section was subsequently tracked which gives the instantaneous bubble front tip rise velocity. The glass channel is vibrated using a calibrated vibration generator in horizontal direction. The amplitude (0-1.4 mm) and frequency (0-44 Hz) of vibration are adjusted by a wave generator and measured using the high precision Laser confocal displacement meter. The mass transfer rate was calculated by measuring the changes in the size of the CO2 rising bubbles. The method which was used to measure the variation of the bubble volume is X-ray radiography technique. This technique was qualified to disclose the volume of Taylor bubbles in capillaries and enabled the acquisition of a series of bubble size images of Taylor bubbles. The processed images which give volume of the bubble with high accuracy as a function of time, are used to evaluate the liquid-side mass transfer coefficient between bubble and liquid using the mass conservation equation.
The videoscopic observation of air bubbles shows that horizontal channel oscillation induces surface waves on the left and right-hand side of the Taylor bubble, which travels downward on the bubble interface. In addition, it was shown that the free rise velocity of bubbles increases as the amplitude and frequency of horizontal channel motion enlarge. Furthermore, the results for the short term dissolution of single CO2 bubbles reveal the intensification effect of channel oscillation on the mass transfer rate of Taylor bubbles.

Keywords: Vibration; Mass transfer; Small channels; CO2

  • Poster
    10th World Congress of Chemical Engineering, 01.-05.10.2017, Barcelona, Spain

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Publ.-Id: 26235