An analytical film drainage model and breakup criterion for Taylor bubbles in slug flow in inclined round pipes

The velocity of Taylor bubbles in inclined pipes is reduced if a lubricating liquid film between the bubble and the pipe wall is not present. An analytical model predicting the gravity-driven drainage of the lubricating film is presented in this article. The model is then used to establish a criterion for film breakup: if t¯bubble=tbubble/τ<0.01 the thin film would not break up, where tbubble is the bubble's passage time, and τ is the characteristic film drainage time based on the fluid properties, pipe geometry, and critical film thickness. The model is validated experimentally with Taylor bubbles in inclined pipes (5° to 90°, the latter being vertical) with stagnant liquids (ethanol, methanol, and mixtures of deionized water and methanol).