DOI QR코드

DOI QR Code

Flow visualizations and analysis on characteristics of bubbly flows exhausted from a venturi-type bubble generator with an air vent

공기유입구를 가진 벤츄리 형상의 기포발생기에서 토출되는 기포 유동 특성의 가시화 측정 분석

  • Bae, Hyunwoo (Graduate School, Department of Mechanical Engineering, Seoul National University of Science and Technology) ;
  • Lee, Seungmin (Graduate School, Department of Mechanical Engineering, Seoul National University of Science and Technology) ;
  • Song, Moonsoo (Department of Mechanical and Automotive Engineering, Seoul National University of Science and Technology) ;
  • Sung, Jaeyong (Department of Mechanical and Automotive Engineering, Seoul National University of Science and Technology)
  • Received : 2019.04.15
  • Accepted : 2019.04.25
  • Published : 2019.04.30

Abstract

Flow visualizations have been carried out to analyze the characteristics of bubby flows exhausted from a venturi-type bubble generator with an air vent. For various design parameters and operating conditions of the bubble generator, the images of bubbly flows was recorded using a high-speed camera and a microscope. Then the amount and size distribution of bubble was evaluated by an image processing technique. The results show that for increasing the amount of bubble, it is more effective to reduce the venturi throat than to enlarge the air vent diameter. If the water flow rate increases, the bubble generation rate increases but reaches a status of saturation, whose condition depends on Reynolds number at a given air vent diameter. The bubble size increases as the diameter of venturi throat decreases and Reynolds number increases. However, the air vent diameter is not a significant factor on bubble size.

GSSGB0_2019_v17n1_60_f0001.png 이미지

Fig. 1. Geometry of a bubble generator

GSSGB0_2019_v17n1_60_f0002.png 이미지

Fig. 2. Experimental setup for visualizing micro bubbly flows

GSSGB0_2019_v17n1_60_f0003.png 이미지

Fig. 3. Images of bubbly flows according to the type of the bubble generator and water flow rate; Qwater = (a) 400 ml/min, (b) 500 ml/min, (c) 600 ml/min

GSSGB0_2019_v17n1_60_f0004.png 이미지

Fig. 4. Area fraction of bubble with respect to liquid phase

GSSGB0_2019_v17n1_60_f0005.png 이미지

Fig. 5. Variations of bubble area fraction according to Reynolds number at the venturi throat

GSSGB0_2019_v17n1_60_f0006.png 이미지

Fig. 6. Bubble size distributions for each type of bubble generator; (a) type 1, (b) type 2,(c) type 3, (d) type 4

GSSGB0_2019_v17n1_60_f0007.png 이미지

Fig. 7. Bubble diameter according to the evaluation methods for each type of bubble generator; (a) type 1, (b) type 2, (c) type 3, (d) type 4

GSSGB0_2019_v17n1_60_f0008.png 이미지

Fig. 8. Variations of bubble diameter according to Reynolds number at venturi throat

Table 1. Design parameters and operation conditions

GSSGB0_2019_v17n1_60_t0001.png 이미지

Acknowledgement

Supported by : 중소벤처기업부

References

  1. Agarwal, A., Ng, W. J., Liu, Yu., 2011, "Principle and Applications of Microbubble and Nanobubble Technology for Water Treatment," Chemoshpere, Vol. 84, pp. 1175-1180. https://doi.org/10.1016/j.chemosphere.2011.05.054
  2. Sadatomi, M., Kawahara, A., Matsuura, H., Shikatani S., 2012, "Micro-Bubble Generation Rate and Bubble Dissolution Rate Into Water by a Simple Multi-Fluid Mixer with Orifice and Porous Tube," Exp. Thermal Fluid Sci., Vol. 41, pp. 23-30. https://doi.org/10.1016/j.expthermflusci.2012.03.002
  3. Sadatomi, M., Kawahara, A., Kano, K., Ohtomo, A., 2005, "Performance of a New Micro-Bubble Generator with a Spherical Body in a Flowing Water Tube," Exp. Thermal Fluid Sci. Vol. 29, pp. 615-623. https://doi.org/10.1016/j.expthermflusci.2004.08.006
  4. Gabbard, C., 1972, "Development of a Venturi Type Bubble Generator for Use in the Molten-Salt Reactor Xenon Removal System," ORNL-TM-4122, pp. 1-30.
  5. Sung, G., Sung, J., Lee, M. H., 2016, "Development and Performance Test of a Micro Bubble Irrigation System for Root Canal Cleaning of Tooth," J. Korean Society of Visualization, Vol. 14, No. 1, pp. 40-45. https://doi.org/10.5407/JKSV.2016.14.1.040
  6. Baylar, A., Aydin, M. C., Unsal, F., and Ozkan, F., 2009, "Numerical Modeling of Venturi Flows for Determining Air Injection Rates Using FLUENT V6. 2," Math. Comput. Appl., Vol. 14, pp. 97-108.
  7. Guerra, V. G., Bettega, R., Goncalves, J. A. S., Coury, J. R., 2012, "Pressure Drop and Liquid Distribution in a Venturi Scrubber: Experimental Data and CFD Simulation," Industrial & Eng. Chem. Res. Vol. 51, pp. 8049-8060. https://doi.org/10.1021/ie202871q
  8. Sung, J., Park, S. M. and Yoo, J. Y., 2004, "Time-Resolved Two-Phase PIV Measurements of Freely Rising Bubble Flows with an Image Separation Method," J. Korean Society of Visualization, Vol. 2, No. 1, pp. 39-45.
  9. Lau, Y. M., Sujatha, K. T., Gaeini, M., Deen, N. G., Kuipers, J. A. M., 2013, "Experimental Study of the Bubble Size Distribution in a Pseudo-2D Bubble Column," Chem. Eng. Sci., Vol. 98, pp. 203-211. https://doi.org/10.1016/j.ces.2013.05.024