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Experimental Study of Transient Two-Phase Slug Flow (Air-Water)

Eyhavand Koohzadi, Amin | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 41653 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Borghei, Mahmoud
  7. Abstract:
  8. Fluid transient in a conduit is an unsteady flow, which is followed by the change in the flow rate condition. Pressure transients in pipeline systems are caused by fluid flow interruption from operational changes such as starting/stopping of pumps, sudden changes to valve setting, etc. Fluid transient analysis is commonly based on the assumption of no air in the liquid. However, air entrainment, trapped air pockets, free gas, and dissolved gases frequently are present in the pipeline. In fact, Air changes flow properties and transient pressure peaks in comparison with single-phase flow. Experimental study has been carried out to verify characteristics of transient pressure inside a rectangular, horizontal pipeline (100mm height, 60mm width and 7.20m length) carrying two-phase, air-water slug flow. By closing a gate rapidly, a pressure surge propagates in the pipe and transient pressure changes have been recorded by pressure transducers. At the same time, behavior of the slug inside the pipeline has been recorded using a digital camera. The results show that increasing the air/water discharge ratio has different effects on transient pressure distribution in pipeline length. At the part of slug which air is present, the compressibility of air reduces the maximum transient pressure, while at the neighborhood where no air exists, transient pressure peak is increased up to 22% respect to the single-phase (water) flow with the same discharge. In addition it has been shown that, Kapitsa, Eotvos and Void Fraction numbers have important effect to predict transient pressure changes in a conduit. Finally, relations for forecasting pressure in these situations, together with graphs showing the effect of different parameters, are presented
  9. Keywords:
  10. Slug Flow ; Experimental Studies ; Two-Phase Transient Flow ; Rectangular Section ; Transient Pressure

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