Two Phase Flow in Horizontal Tubes

Two phase gas / liquid flow is important in a variety of chemical engineering applications such as the simultaneous transport of the gas and oil in horizontal pipelines or a vertical wells several flow regimes can occur, depending on many factors, including the orientation of the pipe the individual magnitudes of the liquid and gas flow rates and physical properties such as density, surface tension and viscosity. It hence becomes imperative to study the flow regimes and pressure drop characteristics of two phase flow.

For horizontal pipes, there are seven principal flow regimes shown in the figure above and which occur successively at ever increasing gas flow rates.

1. Bubble flow in which the gas is dispersed as small bubbles throughout the liquid which is the continuous phase.
   
   
2. Plug flow which is an intermediate between bubble flow and slug flow
3. Slug flow in which the individual small bubbles have started to coalesce together in the form of slugs. The liquid phase is still continuous.
   
   
4. Stratified flow in which the gas occupies the top half of the pipe and liquid occupies the bottom half.
5. Wavy flow in which the increasing gas flow rate causes ripples to form on the surface of the liquid.
   
   
6. Annular flow in which the fast moving gas stream is now a continuous phase that encompasses central portion of the tube with the liquid forming a relatively thin film on the tube well.
7. Mist flow in which the velocity of the continuous gas phase is so high that it reaches as far as the tube wall and entrains the liquid in the form of droplets.
   
   

For vertical pipes, there are five principal flow regimes shown in figure below and which occur successively at ever increasing gas flow rates.

1. Bubble flow in which the gas is dispersed as small bubbles throughout the liquid which is the continuous phase.
2. Slug flow in which the individual small bubbles have started to coalesce together in the form of slugs. The liquid phase is still continuous.
3. Churn flow which is an intermediate between slug flow and annular flow
4. Annular flow in which the fast moving gas stream is now a continuous phase that encompasses central portion of the tube with the liquid forming a relatively thin film on the tube well.
5. Wispy annular flow in which the velocity of the continuous gas phase is so high that it reaches as far as the tube wall and entrains the liquid in the form of droplets.