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Investigation of Flooding Phenomena in Gas-liquid Flow

Safi Samghabadi, Mohsen | 2017

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 49974 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Nouri-Broujerdi, Ali
  7. Abstract:
  8. In a counter current two phase flow systems that liquid flows downward due to gravity on the pipe wall and gas flows upward due to pressure gradient in the pipe core, Flooding and reversal Flooding are important phenomena. Flooding is beginning of velocity direction change of liquid from downward to upward that with zero axial velocity of liquid in interface, liquid is on verge of moving upward. When mass flow rate of liquid or gas increase, some part of liquid film are separated and enter the gas stream. With further increase in mass flow rate of liquid or gas in flooding point, reversal flooding occurs that cause to all liquid film flows upward. Flooding and reversal flooding phenomena are an important criteria in the design of equipment such as evaporators, heat pipes, thermosyphons, and nuclear reactors. In this thesis, governing equations of continuity and momentums of laminar flow are solved analytical with assumptions of developed flow and our results were compared with experimental results. For example, according to results, in a pipe with 8 mm diameter when 6.7 gr/s water is flow downward, we need 0.36 gr/s air for occurring flooding. In addition, using the Kelvin-Helmholtz method, the flow stability was investigated. In this method, the response of the flow parameters considered as the sum of the base and perturbation responses and then, they are introduced into the momentum and continuity equations and the governing equations linearized respect to the perturbation parameters. The obtained equations construct an eigenvalue problem that for solving this problem perturbation method was employed. In this method, the parameters of the equations are expanded in terms of a small parameter and then they put into equations. By doing this, solving the main complex equations leads to solving several simpler equations. To determine the stability of flow, perturbation is considered exponential. If power of exponential perturbation is negative, perturbations are damped and if it is positive, disturbances grow over time. The results of the stability study show the counter current flow is always unstable for the practical mass flow rates of the liquid and by increasing the pressure gradient, the instability zone decreases
  9. Keywords:
  10. Flooding ; Linear Stability ; Perturbation Method ; Kelvin-Helmholtz Instability ; Reversal Flooding ; Counter Current Two Phase Flow

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