Dvora Barnea

A unified model for predicting flow-pattern transitions for the whole range of pipe inclinations

Abstract Models for predicting flow-pattern transitions in steady gas-liquid flow in pipes are summarized and presented. These models incorporate the effect of fluid properties, pipe size and the angle of inclination in a unified way that is not restricted to a specific range of pipe inclinations. Transition mechanisms are presented for each individual boundary and a logical path for systematic determination of the flow patterns is suggested.

Two-Phase Slug Flow

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.

Flow pattern transition for gas-liquid flow in horizontal and inclined pipes. Comparison of experimental data with theory

Abstract Experimental measurements of flow patterns for gas-liquid flow in inclined pipes are reported. The results compare well with a recently published theory for the prediction of flow patterns in horizontal and inclined pipes (Taitel & Dukler 1976).

Holdup of the liquid slug in two phase intermittent flow

Abstract A physical model for the prediction of gas holdup in liquid slugs in horizontal and vertical two phase pipe slug flow is presented. This model can also be used to yield the transition between elonganted bubbles and slug flow within the intermittent flow pattern. In addition a previously published model for predicting the stable slug length in vertical upward slug flow (Taitel et al. 1980) is extended here for the case of horizontal slug flow.

Slurry flow in horizontal pipes—experimental and modeling

Abstract The hydraulic transport of coarse particles in horizontal tubes has been investigated. A physical model for the prediction of the pressure drop and flow patterns is presented. The proposed model is compared with new experimental data and shows good agreement. Comparison with other proposed correlations is also satisfactory.

Flow pattern transition for vertical downward two phase flow

Abstract Experiments of flow pattern for vertical downward gas—liquid flow are reported. In addition theoretically based transition criteria for the flow pattern are presented. The experimental results compare resonably well with the theoretical model for the prediction of flow pattern in vertical downward flow.

The relation between the Taylor bubble motion and the velocity field ahead of it

Abstract The motion of a single elongated (Taylor) bubble propagating in a transparent vertical pipe is studied experimentally in stagnant liquid, as well as in upward and downward liquid flow. Digital image processing of a sequence of video images serves as the main experimental method for the study of the Taylor bubble motion. In addition, the distribution of the velocities in front of the bubble and in the liquid film is measured using Particle Image Velocimetry. The relation between the Taylor bubble motion and the velocity field in front of it is discussed.

Flow pattern transition for downward inclined two phase flow; horizontal to vertical

Abstract Data on the flow pattern transition for gas liquid flow in pipes for downward 0–90° inclination was collected. Mathematical models were developed to predict the flow pattern in the whole range of downward inclination.

A model for slug length distribution in gas-liquid slug flow

Abstract Intermittent, or slug flow, is a very common occurrence in gas—liquid two-phase pipe flow. Usually slug flow is an undesirable flow pattern since the existence of long lumps of liquid slugs that move at high speed is unfavorable to gas—liquid transportation. Considerable efforts have been devoted to the prediction of the slug hydrodynamic characteristics, primarily by considering an average slug length and calculating average parameters. This approach is useful, and in many cases it is adequate for many engineering calculations. There are, however, cases where this information is not sufficient and much more detailed information concerning the slug length distribution, the mean slug length and the maximum possible slug length is essential. This work presents a model that is able to calculate the slug length distribution at any desired position along the pipe. The model assumes a random distribution at the inlet of the pipe and it calculates the increase or decrease in each individual slug length, including the disappearance of the short slugs, as they move downstream. The results of the calculation show that for the fully developed slug flow the mean slug length is about 1.5 times the minimum stable slug length and the maximum length is about 3 times the minimum stable slug length.

A three-layer model for solid-liquid flow in horizontal pipes

Abstract A three-layer model for solid-liquid flow in horizontal pipes is proposed. This model overcomes the limitations of the two-layer model. The model predictions exhibit satisfactory agreement with the experimental data and existing correlations.