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Experimental Study of Different Regimes of Bubble Growth and Formation

Hamidi, Amir Hossein | 2017

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 49852 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Afshin, Hossein; Firoozabadi, Bahar
  7. Abstract:
  8. Bubble growth and formation is used in many of the two-component processes including gas and liquid such as extracting pure metal from ore, separation of water from oil, distillation and absorption. The regime of bubble formation determines the main characteristics of the mentioned process like bubble shape and volume, its formation time and the interaction of the successive bubbles such as collision or coalescence. So predicting the regime of bubble formation and its characteristics helps the engineers to control the process. In this presented research, through doing experiments, different regimes of air bubble formation in water and Aqueous glycerol i.e. single, double, multiplex and chaining are observed, analyzed and separated from each other using non-dimensional Froud and Bond numbers. The Bond number in the experiments was less than 0.05, a supplamantary to previous researches which mostly considered Bond number to be larger thean 0.1. A high speed camera has been used to record the bubble formation process and the resulted images have been analyzed through a Matlab code. In the following, using experimental results and governing theoretical relations, a new relation predicting the volume of the first bubble at the time of detachment in double regimes with coalescence is achieved. To obtain the mentioned relation, the rate of the forming bubble momentum change relative to the rising bubble is considered to be larger than the surface tension force of the rising bubble. The results of this research show that increasing Bond number results in the decrease of critical Froud number separating two successive regimes from each other. Moreover, increasing liquid viscosity causes the regime transition to occur in smaller flow rate of injected air into the forming bubble. The presented new model to predict the volume of the first bubble in double regimes with coalescence shows the continuous increase of the first bubble volume with the increase of the air flow rate. Meanwhile, the proposed model and experimental results show almost no change in the averaged bubble formation time when the air flow rate increases in double and multiplex regimes
  9. Keywords:
  10. Bubble Formation ; Bubble Size ; Regime-Switching Model ; Bubble Growth ; Bubble Formation Regimes ; Dynamic Regime ; Bubble Volume

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