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Hydrodynamic Investigation of Tapered Fluidized Beds in the Presence of Jet

Ebrahimi, Behzad | 2016

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 49406 (06)
  4. University: Sharif University of Technology
  5. Department: Energy Engineering
  6. Advisor(s): Molaei Dehkordi, Asghar
  7. Abstract:
  8. Numerous experimental and modeling efforts have been paid done to investigate the behavior of gas-solid fluidized beds. Existence of a velocity gradient in the axial direction in tapered fluidized beds causes unique dynamic characteristics of this type of beds relative to cylindrical fluidized beds. Because of these characteristics, fluidized beds with inclined walls have found wide applications in industrial processes. Gas bubbles play an important role in the hydrodynamics of bubbling gas-solid fluidized beds; so, fundamental understanding of the bubbling behavior of fluidized beds is required to describe bubble-related phenomena such as solids mixing, segregation, reaction conversion, heat and mass transfer, erosion of heat-transfer tubes and particle entrainment. In this study, hydrodynamic behavior of solid particles was simulated in tapered fluidized beds with a gas jet at the entrance. Simulations were performed using TFM approach. MFIX (Multiphase Flow with Interphase Exchanges) software developed in the department of National Energy Technology Laboratory (NETL) was used to model the gas-solid system. Validation of the obtained results was conducted using experimental data reported in the literature. The simulation results showed good agreement with the experimental data. Hydrodynamic behavior of the solids particles in 2D tapered fluidized beds was studied by examining the solids circulation pattern, bubble characteristics, and jet penetration length. Effects of various parameters including the geometry and the angle of the bed, initial static bed height, and operating conditions of the jet nozzle such as jet nozzle location were investigated. Investigation of the solids circulation pattern shows that tapered fluidized beds, like cylindrical beds, have rising flow at the center of bed and falling flow near the wall. By decreasing jet velocity, increasing initial static bed height ratio, increasing jet nozzle distance from the center and increasing the angle of the bed, the dependent parameters such as jet penetration length, solids velocity and equivalent bubble diameter decrease
  9. Keywords:
  10. Gas Bubbles ; Tapered Fluidized Bed ; Jet Nozzle ; Hydrodynamics ; Eulerian-Eulerian Approach ; Solid-Gas Fluidized Bed

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