Horizontal Annular Two-phase Flow Research Articles

Experimental investigations of the circumferential liquid film distribution of air-water annular two-phase flow in a horizontal pipe

The circumferential film thickness distribution in an air-water horizontal annular two-phase flow was investigated in 26mm pipe diameter by using the conductance probe. The superficial gas and liquid velocities were 10–40m/s and 0.025–0.4m/s, respectively.In general, the film thickness decreases as the liquid velocity decreases and the gas velocity increases. For low superficial gas velocity, high asymmetry of liquid film thickness distribution is generally found. In addition, the liquid film at the upper half of the pipe mostly consists of surge of waves with frequency lower than that of the bottom. At the lowest superficial liquid velocity of the present experimental range, the mean film thickness at the bottom ranges from 0.24mm to 1.3mm. Meanwhile, at the highest superficial liquid velocity, it ranges from 1.0 to 4.29mm, depending on the superficial gas velocity. At the higher superficial gas velocity, a more uniform of liquid film thickness distribution is commonly found. Under this flow condition, the wave at the upper has a similar frequency to that of the lower half and a coherent liquid wave is normally found.To predict the film thickness at any circumferential position, an empirical correlation is proposed on the basis of the physics of the phenomena. In comparison to the available experimental data, the correlation has a good capability to predict the circumferential liquid film thickness distribution.

Effects of Surface Tension on the Liquid Holdup and Wave Characteristics in Horizontal Annular Two-Phase Flow

The wave characteristics of horizontal annular two-phase flow in 16 mm diameter pipe were experimentally investigated using flush-mounted constant electric current method (CECM) sensors and visual observations. To examine the effect of surface tension on the wave velocity and frequency, air and three kinds of liquids with different surface tension were used, i.e., water, 2%-butanol solution, and 5%-butanol solution. The gas and liquid superficial velocities were varied from 12 to 40 m/s and 0.05 to 0.2 m/s, respectively. The liquid holdup was measured directly using CECM, while the wave velocity and frequency were determined using cross correlation and power spectral density functions of liquid holdup signals. Generally, combination of air and liquid with the highest surface tension gives the highest liquid holdup and wave frequency. Simple correlations for wave velocity and wave frequency were also developed.

Liquid film circumferential asymmetry prediction in horizontal annular two-phase flow

This study considers the prediction of the degree of asymmetry in the circumferential distribution of the liquid film in the tube cross section of horizontal annular gas–liquid two-phase flow, endemic of the lower region of this flow regime near the stratified-wavy flow transition boundary. Focusing on disturbance waves as the predominant mechanism for transporting the liquid in the annular film from the bottom to the top of the tube to counterbalance the draining effect of gravity, a new prediction method for the degree of asymmetry in the annular liquid film is proposed that outperforms existing correlations. Flow pattern maps for horizontal gas–liquid two-phase flow of frequent use in the design of evaporators and condensers can thus be explicitly updated to account for both symmetric and asymmetric annular flows. The underlying experimental database contains 184 measured liquid film circumferential profiles, corresponding to 1276 local liquid film thickness measurements collected from 15 different literature studies for tube diameters from 8.15mm to 95.3mm.

Drag reduction in horizontal annular two-phase flow

Experiments of drag reduction in a horizontal, two-phase, annular flow are presented. The experiments were conducted in a high-pressure gas-condensate flow in 19 mm diameter pipe. The drag reducers were high molecular weight poly-alpha-olefin polymers. Motivated by the results of flow visualization, a model was developed which accounted for the drag reduction as a reduction of the height of the short-wavelength waves on the liquid film, and a reduction of the entrainment rate of droplets from the liquid film into the gas core. There was a reasonable quantitative agreement between the model predictions and the present experimental data. The model was also found to be equally effective when applied to drag reduction experiments in air–water annular flow from the literature. It properly account for the variation of drag reduction with superficial liquid velocity, superficial gas velocity, and pipe diameter.

The effects of the number and angle of microgrooves on the liquid film in horizontal annular two-phase flow

Measurements of the liquid film profile and pressure drop were made in tubes with grooves of varying angle (0°, 9° and 18°) as well as tubes with varying numbers of grooves at a common angle (18°). These data indicate that the grooves act to redistribute the liquid film on the inner wall perimeter and that only a relatively small number of grooves (12) is needed to do this. The grooves also affect the stability of the vapor–liquid interface and can generate lower average liquid film thickness. The pressure loss is directly related to the number of grooves for the tubes studied.

The influence of a bend on drop sizes in horizontal annular two-phase flow

The influence of a bend on drop sizes in horizontal annular two-phase flow

Experimental study on the characteristics of liquid layer and disturbance waves in horizontal annular flow

The mechanism for transporting liquid from the bottom of the pipe to the top still to be established in the prediction of the film thickness distribution in horizontal annular two-phase flow. To resolve this issue, using five parallel-wire conductance probes, time records of local liquid film thickness at five circumferential positions were collected. The characteristics of circumferential liquid film thickness profiles and its variation with gas and liquid velocities were obtained. The basic features of probability distribution function, probability density function, auto-correlation, cross-correlation and power spectrum density function of the disturbance waves in annular flow were studied respectively. The characteristics of circumferential profiles of disturbance waves and its variation with gas and liquid velocities were presented.

Observation of Film in a Horizontal Annular Two-Phase Flow by a Photochromic Dye Activation Method

An experimental study has been conducted to investigate the mechanism of liquid film transport in horizontal annular flow by visualizing the motion of the liquid film on the inner tube wall using a photochromic dye activation method. The captured motion clearly reveals spreading of the liquid during the passage of disturbance waves and constant drainage of the liquid film after the passage of the disturbance waves. The present results support the liquid transport mechanism due to the pumping action of the disturbance waves proposed by Fukano and Ousaka rather than the secondary gas flow or surface wave mechanisms proposed by Laurinat et al. and Jayanti et al.

Relationships between Flow Configuration and Statistical Characteristics of Hold-up and Differential Pressure Fluctuations in Horizontal Annular Two-Phase Flow

Relationships between Flow Configuration and Statistical Characteristics of Hold-up and Differential Pressure Fluctuations in Horizontal Annular Two-Phase Flow

Distribution of Entrainment Flow Rate for Air-Water Annular Two-Phase Flow in a Horizontal Tube

An experimental investigation on the distribution of the entrainment flow rate in a horizontal annular two-phase flow was conducted. In this experiment, the isokinetic sampling probe technique was used for the measurement of the entrained droplet flow rate. It was demonstrated that the distribution of the entrained droplet flow rate was sensitive to the flow configuration, the total entrained droplet flow rate in the gas core was smaller than that of the vertical upward flow and the correlation of the entrainment flow rate proposed by Paleev et al. was superior to that by Wicks et al. Furthermore, a new correlation for the critical flow condition of the onset of droplet entrainment was proposed.

Axial and Circumferential Film Flow Rate Prediction in a Horizontal Annular Two-Phase Flow Using the FIDAS-3DT Code

Prediction of developing and transient characteristics of circumferential and axial film velocities in a horizontal annular two-phase flow is carried out with the FIDAS-3DT computer code developed in Japan that can provide three-field representation in subchannel flow using the full conservative equations and simple constitutive relations. The specifications are those from a reported air-water experiment in a 3.9m by 32mm diameter pipe. Steady, fully developed axial flow rates seem to be over-predicted compared to the experimental results. A corrective procedure is suggested which takes into account the radial variation in the axial velocity profile.

Time-dependent behaviour of the liquid film in horizontal annular flow

A crucial point still to be established in the prediction of the film thickness distribution in horizontal annular two-phase flow is the mechanism(s) for transporting liquid from the bottom to the top part of the tube. To resolve this issue, the time-dependent behaviour of the liquid film is studied. Wave characteristics such as velocity and frequency are measured around the circumference. It is inferred from the autospectral density functions of film thickness variation that disturbance waves play an important, but as yet unclear, role in the formation of a liquid film in the top part of the tube. A new mechanism, based on the shape of disturbance waves is proposed.

Film thickness prediction in a horizontal annular two-phase flow

Prediction of developing and transient characteristics of the liquid film in a horizontal annular two-phase flow is carried out using a computer code that provides a three-field representation in subchannel flow. The fully developed steady-state results for film thickness compare satisfactorily with a reported air-water experiment in a pipe 3.9 m long and 32 mm dia. It is concluded that horizontal annular flow modelling may be tractable by the direct application of the conservation equations to mesh cells along the flow.

Prediction of film thickness distribution in horizontal air-water annular flow.

A theoretical model for predicting the circumferential film thickness distribution in a horizontal annular two-phase flow is presented. It is based upon a two-layer film model which consists of a wave layer and a base film. It differs from Laurinat's and Lin's models in that liquid is transferred in the circumferential direction by the disturbance wave spreading which counteracts the drainage due to gravity and that the effects of induced secondary flow in the gas flow and the surface tension force have minor effects on the formation of the liquid film near the top of the tube cross section. The film thickness distribution predicted by the present model agrees with the experimental data much better than that by Laurinat's model.

Developments in the modelling of horizontal annular two-phase flow

Several authors have considered the extension from vertically upward flow to horizontal flow of a model for annular two-phase flow which allows separate descriptions of liquid droplet deposition and entrainment. However, solutions to the equations which result have either not been obtained or have been found to be mathematically and physically unacceptable. In this paper it is shown how to obtain acceptable solutions. In addition, various physical mechanisms which could improve the model are assessed. Of these it is shown that a variable deposition flux could lead to significant improvement between theory and experiment. A model for the variable deposition flux is then developed and is shown to give results at least in qualitative agreement with known experimental results. The inclusion of the variable deposition rate in the governing equations leads to encouraging results for film thickness and film flowrate distributions.

Circumferential Variation of Interchange in Horizontal Annular Two-Phase Flow

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCircumferential Variation of Interchange in Horizontal Annular Two-Phase FlowR. J. Anderson and T. W. F. RussellCite this: Ind. Eng. Chem. Fundamen. 1970, 9, 3, 340–344Publication Date (Print):August 1, 1970Publication History Published online1 May 2002Published inissue 1 August 1970https://doi.org/10.1021/i160035a007RIGHTS & PERMISSIONSArticle Views54Altmetric-Citations21LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (536 KB) Get e-Alerts