Slug flow

About: Slug flow is a research topic. Over the lifetime, 3758 publications have been published within this topic receiving 71157 citations.

Two-Phase Slug Flow

Abstract: Publisher Summary Slug flow is a highly complex type of flow with an unsteady nature The prediction of pressure drop, heat, and mass transfer for such flow is often considered a difficult task The chapter deals with steady slug flow The chapter introduces several options of modeling the hydrodynamic parameters and pressure drop using a unified approach that is applicable for the vertical, horizontal, and inclined cases The chapter also reviews transient phenomena in slug flow by illustrating an example of severe slugging in a pipeline-riser system It is noted that heat transfer in slug flow is of major importance for practical applications The treatment of the two-phase flow is usually considered as a two-phase mixture The severe slugging that consists of one riser and one pipeline is one of the simplest example of slug flow under nonsteady conditions The Boe criterion differentiates between steady and cyclic operations with two exceptions At high liquid flow rates, a steady flow can also exist within the severe slugging region predicted by the Boe criterion There is a region outside the Boe criterion that is in an unsteady state and leads to unsteady oscillations

The generation and collapse of a foam layer at the roof of a basaltic magma chamber

Abstract: Basaltic volcanoes erupt in several different regimes which have not been explained. At Kilauea (Hawaii), eruption can take the form of either fire fountaining, where gas-rich jets propel lava clots to great heights in the atmosphere, or quiet effusive outflow of vesicular lava. Another regime is commonly observed at Stromboli, where large gas slugs burst intermittently at the vent. In an attempt to provide a unifying framework for these regimes, we investigate phenomena induced by degassing in a reservoir which empties into a small conduit. Laboratory experiments are done in a cylindrical tank topped by a thin vertical tube. Working liquids are silicone oils and glycerol solutions to investigate a range of viscosity and surface tension. Gas bubbles are generated at the tank bottom with known bubble diameter and total gas flux. The bubbles rise through the tank and accumulate in a foam layer at the roof. Depending on the behaviour of this foam layer, three different regimes can be distinguished: (i) steady horizontal flow of the foam leading to bubbly flow in the conduit; (ii) alternating regimes of foam build-up and collapse leading to the eruption of a single, large gas pocket; (iii) flow of the foam partially coalesced into larger gas pockets leading to intermittent slug flow in the conduit. These regimes have natural counterparts in basaltic volcanoes.A simple theory is proposed to explain regimes (i) and (ii). The bubbles in contact with the roof deform under the action of buoyancy forces, developing flat contact areas whose size increases as a function of foam thickness. Maximum deformation corresponds to a critical thickness hc = 2σ/eρlgR, where σ is the coefficient of surface tension, ρl the liquid density, g the acceleration due to gravity, R the bubble radius and e the gas volume fraction in the foam. The foam thickness is determined by a balance between the input of bubbles from below and the output into the conduit, and is proportional to (μl Q/e2 ρlg)¼, where μl is the liquid viscosity and Q the gas flux. A necessary and sufficient condition for collapse is that it exceeds the critical value hc. In a liquid of given physical properties, this occurs when the gas flux exceeds a critical value which depends on viscosity, surface tension and bubble size. Experimental determinations of the critical gas flux and of the time between two events of foam collapse are in agreement with this simple theory.

Hydrodynamics of Taylor Flow in Vertical Capillaries: Flow Regimes, Bubble Rise Velocity, Liquid Slug Length, and Pressure Drop

Abstract: Two-phase flow hydrodynamics in vertical capillaries of circular and square cross sections were experimentally studied, using air as the gas phase and water, ethanol, or an oil mixture as the liquid phase. The capillary hydraulic diameters ranged from 0.9 mm to 3 mm, with the superficial gas and liquid velocities covering a span of 0.008−1 m/s, which is typical of that obtained in monolith reactors. Using a high-speed video camera, four distinct flow regimes were observed within the range at which experiments were conducted: bubbly, slug-bubbly, Taylor, and churn flows. Annular flow was observed at excessively high gas and low liquid flow rates, well beyond those of interest to this study. Based on the definition of a two-class flow regime, the combination of two parametersthe slip ratio (S) and the ratio of the superficial gas velocity to two-phase superficial velocity (UG/UTP)was observed to be suitable for determining the transition from homogeneous flow to nonhomogeneous flow. The influence of capill...

Liquid−Liquid Slug Flow in a Capillary: An Alternative to Suspended Drop or Film Contactors

Abstract: The widely used separation process of liquid−liquid extraction is performed in a variety of contactors. The interfacial area in these conventional contactors is often poorly defined, because of the...