Loading...

Modeling and Numerical Simulation of Compressible Gas-liquid Two-phase Flow in Ducts of Spatially Varying Cross-section

Shafiei Ghazani, Ardalan | 2019

532 Viewed
  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 52021 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Nouri-Borujerdi, Ali
  7. Abstract:
  8. In this thesis, gas-liquid two phase flow through channels of spatially varying cross-sections are investigated numerically. These flows have several industrial applications such as nozzles, diffusers, pipeline blowdown, valves and channels with sudden expansions or contractions. Finite volume method in conjunction with a second order Advection Upstream Splitting Method (AUSM+_up) is employed to discretize the governing equations. At low Mach numbers, a pressure-based algorithm with a pressure correction equation is derived. Using the pressure-based algorithm accelerates the convergence rate of the numerical solution of the flows through sudden expansions. The pressure adjacent to the expansion section drops drastically due to the compressibility of the vapor generated by flash evaporation. As the flow passed the expansion section, a conical free jet of liquid develops which is surrounded by the two phase liquid-vapor mixture. Subsequently, the two phase flow reaches thermodynamic equilibrium downstream. The numerical results indicate that the behavior of the two phase flows through a converging-diverging nozzle depends on the inlet vapor quality. At low inlet qualities, the vapor quality decreases along the nozzle before the location of the shock wave and it increases after that. While, the condensing behavior of the nozzle changes to the evaporating behavior when the flow passes over the shock wave with high inlet vapor quality. As the subcooled liquid expands through the nozzle, vapor generates at the throat and the location of the onset of vapor generation does not change by a further increase in the inlet subcooling degree. In the case of short pipe depressurization, equilibrium model totally overestimates pressure and void fraction, the relative error of equilibrium model in the prediction of pressure variation with time exceeds 50%, however, this error for the nonequilibrium model is less than 20%
  9. Keywords:
  10. Gas-Liquid Two Phase Flow ; Varying Cross Section ; Computational Fluid Dynamics (CFD) ; Phase Transition ; Compressibility ; Pressure Correction

 Digital Object List

 Bookmark

  • تصویب
  • PRINTWOCODE
    • نسخه نهايي-نهایی-کتابخونه
    • Papers