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Investigation on the Effect of air Inlet on the Behavior of Air-Water two Phase Flow in a Large Diameter Vertical Tube

Kebriaee, Mohammad Hassan | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 40214 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Saidi, Hassan
  7. Abstract:
  8. Knowledge of Air-water two phase flows is significant to different engineering systems such as chemical reactors and power plant and petrochemical and petroleum industry. One of the most industrial cases of two phase flow is two phase flow in vertical large pipes. Because of gravity, two phase flow in Vertical pipes is different from horizontal pipes. Considering these flows can play a significant role in long-term reliability and safety of industrial systems. There are many parameters that effect on flow characteristics such as length and diameter of pipe and shape and condition of air inlet. Effect of air inlet is on the shape of bubbles and this can effects on flow pattern and another characteristics of flow such as void fraction profile and bubble diameter. in this project in order to find two phase flow behavior along vertical large diameter pipes we simulate air inlets with different number of holes and different hole diameters in the same flow rate of air. Also in experimental part an especial test section have been designed and constructed in laboratory and we test two phase flow characteristic in a round tube with 5cm diameter and 5 height. In computational part, flow characteristics such as cross-sectional void fraction and velocity and pressure were considered. To achieve this aim, main equations of flow have been developed for investigation of flow behavior in air-water two phase flows. 3-d numerical analyses were performed by a designed and written CFD package which is based on VOF model. Geometries, which have been studied in this article, are: round tubes with diameter of 5 cm and length of 1 and 5 m. The results showed that at the entrance of the pipe the effect of air inlet geometry is significant while at the whole pipe this effect suppressed. Furthermore increasing the velocity at the inlet can increase average void fraction and decrease pressure loses along the pipe axis. Numerical results were compared with available empirical correlations and this comparison shows good agreement between this work and empirical correlations. Also experimental results show that if gas velocity and flow rate increase, discharge velocity and flow rate increase as well. In a same gas flow rate, if slip ratio increase, outlet liquid increase. Also the length of slugs in this study was 5, 3 and 9 cm.
  9. Keywords:
  10. Water and Air Two Phase Flow ; Air Inlet ; Large Diameter Vertical Tube ; Flow Behavior

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