An experimental study of stratified–dispersed flow in horizontal pipes (original) (raw)
Related papers
2012
The thesis presents a general one-dimensional mathematical model to simulate two-phase, gas-liquid, annular flow in horizontal as well as vertical pipes, and to mechanistically predict the transition from stratified to annular flow in horizontal pipes. The method is based on the transient one-dimensional two-fluid model whereby the two phases are considered as (i) liquid layer and (ii) a mixture of the gas and liquid droplets in which the droplet concentration in the mixture is considered as a flow variable. The model entails the introduction of a scalar transport equation for the conservation of mass of liquid droplets accounting for liquid transfer to and from the film liquid layer. The interface curvature is modelled by a double circle geometric configuration incorporating a new empirical relation for the specification of wetted angle. The droplet exchange rate between the liquid film and gas core is modelled by employing droplet entrainment and deposition rates derived from modi...
Drop size distributions in dispersed liquid-liquid pipe flow
International journal of multiphase flow, 2001
This paper examines drop size distributions in a 0.063 m pipe for a two-phase mixture of kerosene and aqueous potassium carbonate solution. Measurements have been made for both vertical up¯ow and horizontal geometries, for mixture velocities ranging from 0.8 to 3.1 m/s. Two optical measurement techniques, a backscatter technique using a Par-Tec 300C and a diraction technique using a Malvern 2600, have been used to obtain the drop size distributions of the dispersions created. Both measurement techniques have been found to be limited to dierent concentration ranges. Strati®cation of drop size was observed for low mixture velocities in a horizontal geometry. This did not occur for the vertical geometry.
Oil/water flow in a horizontal pipe—dispersed flow regime
International Journal of Computational Methods and Experimental Measurements, 2020
In multiphase fluid flow, the formation of dispersed patterns, where one of the phases is completely dispersed in the other (continuous medium) is common, for example, in crude oil extraction, during the transport of water/oil mixture. In this work, experimental and numerical studies were carried out for the flow of an oil/water mixture in a horizontal pipe, the dispersed liquid being a paraffin (oil with density 843 kg m −3 and viscosity 0.025 Pa s) and the continuous medium a water solution doped with NaCl (1000 µS. cm −1). The tests were made for oil concentrations of 0.01, 0.13 and 0.22 v/v and velocities between 0.9 and 2.6 ms −1 of the mixture. Experimental work was performed in a pilot rig equipped with an electrical impedance tomography (EIT) system. Information on pressure drop, EIT maps, volumetric concentrations in the vertical diameter of the pipe and flow images were obtained. Simulations were performed in 2-dimensional geometry using the Eulerian-Eulerian approach and the k-ε model for turbulence modelling. The model was implemented in a computational fluid dynamics platform with the programme COMSOL Multiphysics version 5.3. The simulations were carried out using the Schiller-Neumann correlation for the drag coefficient and two equations for the viscosity calculation: Guth and Simba (1936) and Pal (2000). For the validation of the simulations, the pressure drop was the main control parameter. The simulations predicted the fully dispersed flow patterns and the pressure drop calculated when using the Pal (2000) equation for the viscosity calculation showed the best fit. The results of the images of the flows obtained by the photographs and simulations were in good agreement.
Prediction of the liquid film distribution in stratified-dispersed gas–liquid flow
Chemical Engineering Science, 2016
A model for liquid film distribution in gas-liquid stratified dispersed flows has been derived. The model allows the numerical calculation of the local axial liquid film height and velocity profiles. Droplet deposition, gravitational drainage and wave spreading are relevant. The strength of each mechanism depends on the underlying flow conditions. The wave spreading affect is modelled as function of a modified Froude number.
A Model for Wetted-Wall Fraction and Gravity Center of Liquid Film in Gas/Liquid Pipe Flow
SPE Journal, 2011
Summary The model presented in this study unifies the predictions of liquid wetted-wall fraction, film gravity center, and flow-pattern transition between stratified and annular flows. It is based on the instability of the liquid film in an equilibrium stratified flow proposed by Taitel and Dukler (1976) for flow-pattern transition prediction from stratified flow to nonstratified flows. The geometrical relationship between the wetted-wall fraction and the gravity center of the liquid film is established based on the double-circle model proposed by Chen et al. (1997), and is further simplified with explicit approximation. The predictions of the present model are compared and agree well with experimental wetted-wall-fraction measurements and flow-pattern observations from different authors.
Fluid Flow for Chemical Engineers Second
Fluids in motion zyxwv Units and dimensions Description of fluids and fluid flow Types of flow Conservation of mass Energy relationships and the Bernoulli equation Momentum of a flowing fluid Stress in fluids Sign conventions for stress Stress components Volumetric flow rate and average velocity in a pipe Momentum transfer in laminar flow Non-Newtonian behaviour Turbulence and boundary layers Flow of incompressible Newtonian fluids in pipes and channels Reynolds number and flow patterns in pipes and tubes Shear stress in a pipe Friction factor and pressure drop Pressure drop in fittings and curved pipes Equivalent diameter for non-circular pipes Velocity profile for laminar Newtonian flow in a pipe Kinetic energy in laminar flow Velocity distribution for turbulent flow in a pipe ix z xi 1 1 1 4 7 9 17 27 36 43 45 46 48 55 70 70 71 71 80 84 85 86 86 V vi CONTENTS zyxwvutsr 2.9 2.10 zyxwvuts 3
PULSED INJECTION TRACER MIXING IN ANNULAR LIQUID FILMS
The functioning of a Boiling Water Reactor (BWR) relies on the effective heat transfer to a multiphase coolant system through a series of different flow regimes along the height of a subchannel and hence, studying such multiphase flow regimes is important with regards to both safety and efficiency. One such type of flow, namely the dispersed vertical annular flow, is present in the uppermost parts of BWR subchannels and is critical in thermal-hydraulics analysis with regards to predicting dryout. Studying the characteristics of such a highly dynamic flow having varied length and time scales requires information through experiments with advanced instrumentation. This work presents a novel experimental technique to study tracer mixing in liquid films in vertical annular flow in a double subchannel geometry using pulsed tracer injection. A conductive tracer is injected into gas driven, de-ionized water film and traced using a liquid film sensor, a high frequency non-intrusive conductivity based sensor. The pulsing is achieved using an electromagnetic contraption wherein a ferromagnetic ball is periodically attracted and released to impact an elastic membrane sealed, tracer filled chamber. The pressure head in the chamber is maintained using a syringe pump in order to achieve similar pulsed volumes of the tracer. Ensemble averaging of multiple injections has been performed to reveal and quantify average flow parameters including mixing coefficients, bulk and interfacial velocity of liquid films. The experiments are conducted with and without a swirl type spacer to quantify the effect of the spacer on the film flow for different gas and liquid flow rates. The current work provides an important insight into the mixing capabilities of spacers, which is important with regards to numerical modeling of vertical annular flow and the prediction of dryout.
Annular flow entrainment rate experiment in a small vertical pipe
Nuclear Engineering and Design, 1997
Two-fluid model predictions of film dryout in annular flow, leading to nuclear reactor fuel failure, are limited by the uncertainties in the constitutive relations for the entrainment rate of droplets from the liquid film. The main cause of these uncertainties is the lack of separate-effects experimental data in the range of the operating conditions in nuclear power reactors. An air-water experiment has been performed to measure the entrainment rate in a small pipe. The current data extend the available database in the literature to higher gas and liquid flows and also to higher pressures. The measurements were made with the film extraction technique. A mechanistic model was obtained based on Kelvin-Helmholtz' instability theory. The dimensionless model includes the Weber number of the gas and the liquid film Reynolds number. Kataoka and Ishii's correlation (Kataoka, I., Ishii, M., 1982. NUREG/CR-2885, ANL-82-44) is modified based on this model and the new data. The new correlation collapses the present air -water data and Cousins and Hewitt's data (Cousins, L.B., Hewitt, G.F., 1968. UKAEA Report AERE-R5657) The effects of pressure and surface tension were considered in the derivation so it may be applied for boiling water reactor operating conditions. © 1997 Elsevier Science S.A.
International Journal of Heat and Mass Transfer, 2015
The phase distributions and mechanical properties of annular flow can be regarded as random states. Hence the probability analysis is an appropriate method to investigate the possibilities of the relevant events and the statistic results of some characteristic parameters. In the present work, a probability model for fully developed annular flow in vertical pipes is proposed to predict the phase distributions and mechanical characteristics. The probability model works in three mechanisms. First, a vortex generation theory on energy transfer from vortexes to droplets is supposed to describe the atomization process. Second, a random walk theory is applied to track the droplet deposition on the liquid film. Third, the atomization and deposition rates are respectively related to the probabilities of droplet generation and elimination by analyzing the interaction between vortexes and droplets. Based on the knowledge of dynamic equilibrium between atomization and deposition processes, a balance equation is established to close the equation set and the representative parameters of annular flow can be solved. The new model is a statistical method and almost links all the parameters involved in annular flow. By comparing the predicted droplet entrainment with experimental data available in the literature, the present model is well verified and demonstrates advantages both in accuracy and in convenience. Furthermore, the effects on the entrainment of many parameters, including the gas flow rate, liquid flow rate, gas density, liquid density, gas viscosity, surface tension and pipe diameter, are discussed in detail.
Solid-Particles Flow Regimes in Air/Water Stratified Flow in a Horizontal Pipeline
Oil and gas facilities, 2016
(retired) There are a few studies covering solid-particles transport in multiphase pipelines. Solid-particles transport is complicated because it depends on several variables, including flow patterns, fluid properties, phase velocities, and pipe-geometry features such as roughness, diameter, and inclination angle. Each of these variables can have significant effects on the solid-particles-transport process. More attention has been paid recently to the importance of tracking solid-particles-transport management over reservoir life. There are three options available for managing solid-particles transport: applying a cleaning operation, installing solid-particles exclusion facilities, and operating above the critical solid-particles-deposition velocity. Cleaning operations, such as pigging, are only applicable for small amounts of solid particles, and they often result in the pig becoming stuck if the pigging frequency is not high enough. Installing solid-particles exclusion systems (e.g., gravel packs) can reduce production and create excessive pressure drops. The third option, operating above the critical solid-particles-deposition velocity, is preferred for solid-particles-production management as a prevention technique under favorable operating conditions because it has practical applications and can be beneficial commercially. To avoid solid-particles deposition, it is necessary to manage solid-particles transport above solid-particles-deposition velocities. On the other hand, operating under unnecessarily high flow rates is not only cost inefficient, but can also create facility damages; therefore, it is necessary to find the optimum velocity to maintain continuous particle movement. This velocity is called the critical solid-particles-deposition velocity. Solid-Particles Flow Regimes Particle interactions and movement have a significant effect on transport of solid particles. Shamlou (1987) defined the most common classification for solid-particles transport in horizontal pipeline as homogeneous flow, heterogeneous flow, heterogeneous and sliding flow, saltation flow, and stationary bed. Doron and Barnea (1996) and Ibarra et al. (2016) defined three main solid-particles flow regimes as suspension, moving bed, and stationary bed. The suspension solidparticles flow regime was further divided into two subpatterns of pseudohomogeneous suspension and heterogeneous suspension. Well-defined flow regimes will clarify under what conditions the particles are moving more or less independently (i.e., not locked together as in a sliding bed). Flow regimes in this paper are applied to multiphase flow, whereas Doron and Barnea (1996) and other flow-regime publications are applicable for single-phase flow only. According to this study, there are six main solid-particles flow regimes in stratified flow in a multiphase pipeline: fully dispersed solid flow, dilute solids at the wall, concentrated solids at the wall, moving dunes, stationary dunes, and stationary bed. Each one is described in the following subsections and shown in Fig. 1. Fully Dispersed Solids Flow. At high flow rates, there is a suspension of particles in which particles are completely dispersed in the liquid phase, with no particles touching the pipe bottom. Dilute Solids at the Wall. At slightly lower flow rates, some particles drag along the pipe bottom and start rolling on the pipe. In this solid-particles flow regime, no particle interactions are observed at the pipe bottom, hence particle shape is not important.