Journal of the Korean Society of Visualization (한국가시화정보학회지)

The Korean Society of Visualization (한국가시화정보학회)
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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
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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.

Keywords

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Fig. 1. Geometry of a bubble generator

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Fig. 2. Experimental setup for visualizing micro bubbly flows

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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

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

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

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

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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

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

Table 1. Design parameters and operation conditions

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