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Modeling Gas- Liquid Flow in the Cyclone by Computational Fluid Dynamics

Parviz Sedghi, Roghayyeh | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 41158 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Farhadi, Fathollah
  7. Abstract:
  8. Cyclones are efficient devices in order to separate suspended particles and droplets from gas media and this effieciency is mainely because of spiral flow nature affecting the particles and droplets and taking them towards the wall. Therefore, particles and droplets move downwards toward down outlet by the gravity force. In consequence, they are being separated of the gas flow and relatively pure gas flow exits the cyclone. In this project, GAMBIT software has been used to produce three dimensional meshes including coarse, medium and fine sizes for two different geometries of cyclone. After simulation, little differences between the obtained results were revealed, showing that modeling is not dependant on the grid size. Having produced the grids, turbulent and spiral flow of single phase (air) was simulated by using FLUENT software. Turbulence has been modeled by RSM and RNG k-ε models and predicted velocity profiles have been compared with the experimental data of Boysan’s work. Two turbulence models data compared and, it was concluded that RSM model is much closer to the experimental data than RNG k- ε for the prediction of cyclonic flow. In this modeling, velocity inlet and outflow were used as boundary conditions. To investigate the performance of the cyclone and its separation efficiency, lagrangian method has been used. Firstly, the air flow was modeled in the FLUENT and hydrodynamic of the flow was validated through a comparison between calculated and measured pressure drops from modeling and experimental data of Iozia’s work. Flow field was extracted from FLUENT and the equations of particle motion were solved by a FORTRAN code. In each run, one single drop entered the cyclone in the gas flow. Changing the primary position of the drops, 1000 drops were tracked and the fractional efficiency of cyclone was defined by counting the number of separated droplets from the gas flow. Droplets with diameter of range 1 to 10 μm and density of 876 kg/m3 were selected and subsequently, fractional efficiency estimated by modeling has been compared with experimental data of Iozia’s work with acceptable consistency (approximately 80% accuracy)
  9. Keywords:
  10. Gas Cyclone ; Computational Fluid Dynamics (CFD) ; Two Phase Flow ; Separation Efficiency ; Turbulent Swirling Flow

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