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Class 1 0

Class 1 0. 2012-04-10. Horizontal gas-liquid flow patterns. Dispersed Bubble Flow Stratified Flow Stratified–Wavy Flow Plug Flow Slug Flow Annular–Dispersed Flow. Benjamin bubble. B P/S C A WA. Bubble Flow Plug or Slug Flow Churn Flow Annular Flow Wispy Annular Flow.

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Class 1 0

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  1. Class 10 2012-04-10

  2. Horizontal gas-liquid flow patterns • Dispersed Bubble Flow • Stratified Flow • Stratified–Wavy Flow • Plug Flow • Slug Flow • Annular–Dispersed Flow Benjamin bubble

  3. B P/S C A WA Bubble Flow Plug or Slug Flow Churn Flow Annular Flow Wispy Annular Flow Links point to http://www.thermopedia.com/ Vertical gas-liquid flow patterns Taylor bubble

  4. The effect of pipe inclination Θ = +10°

  5. The effect of pipe inclination Θ = +2°

  6. The effect of pipe inclination Θ = +0.25°

  7. The effect of pipe inclination Θ = 0°

  8. The effect of pipe inclination Θ = −1°

  9. The effect of pipe inclination Θ = − 5°

  10. The effect of pipe inclination Θ = − 10°

  11. Relative flow directions • Co-current flow (as shown above) • Counter-current flows (one of the mass flow rates is negative): some of the flow patterns exist with opposite flow directions too • Somewhat analogous flow patterns can be identified in liquid-liquid, liquid-solid and gas-solid systems

  12. Even more complex flow patterns in three phase pipe flows • Flow classification is • somewhat arbitrary and subjective in pipes • hardly possible in 3D containers • Further points to observe: • Heat transfer phenomena • Phase transition phenomena

  13. Flow patterns • Flow regimes • Flow pattern maps • Tasks: • Model flow region boundaries • Model flow behaviour within each flow region Alternatively: • Create one fluid model that can correctly reflect fluid behaviour in all flow regimes and thus automatically describes flow pattern transitions

  14. Control (input) parameters: Pipe geometry shape size inclination wall roughness Mass flow rates Fluid properties External heat source Measured (output) parameters: Pressure drop Volume (void) fraction Interfacial area density Transported heat Parameters of two-phase pipe flow

  15. Control (input) parameters: Pipe geometry shape size inclination wall roughness Mass flow rate Fluid properties External heat source Measured (output) parameters: Pressure drop Transported heat Parameters of one-phase pipe flow

  16. Definitions and measurementsof void fraction • Local (time averaged) • Chordal • Cross sectional averaged • Volume averaged

  17. Class 11 2012-04-17

  18. Model variablesin single-phase pipe systems • Cross sectional integral quantities • linear densities • flow rates • Cross sectional average (‘mean`) quantities • ‘mean` densities • ‘mean` fluxes Purpose: reduction of independent variables: (t,x,y,z)  (t,x)

  19. Control (input) parameters: Pipe geometry shape size inclination wall roughness Mass flow rate Fluid properties External heat source Measured (output) parameters: Pressure drop Transported heat Parameters of one-phase pipe flow

  20. Control (input) parameters: Pipe geometry shape size inclination wall roughness Mass flow rates Fluid properties External heat source Measured (output) parameters: Pressure drop Volume (void) fraction Interfacial area density Transported heat Parameters of two-phase pipe flow

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