Experimental Investigation on Flow Regime of Steam-Water Two-Phase Flow in a Pseudo-Pebble-Bed

2011 ◽  
Author(s):  
Xiong Wang ◽  
Zhen Zhang ◽  
Xiao Yan ◽  
Zejun Xiao ◽  
Bingde Chen
Keyword(s):  
Flow Regime ◽  
Slug Flow ◽  
Annular Flow ◽  
Two Phase Flow ◽  
Phase Distribution ◽  
Solid Particles ◽  
Phase Flow ◽  
Pebble Bed ◽  
Two Phase ◽  
System Pressure

In the concept of BWR-PB with a relatively low power level, the core region is filled with a large number of coated particles, which are directly cooled by boiling light water. It’s significant to understand the two-phase flow characteristics in such a complicated pebble-bed structure. A visualization experiment was carried out to investigate the flow phenomena of steam-water two-phase flow in a pseudo-three-dimensional pebble bed using a high-speed video camera. The pebble bed in the experiment was constructed of hundreds of glass beads and a specially designed stainless heating plate, which was used to simulate the heat-generation of solid particles. Based on our observation, five typical flow regimes were identified to distinguish different phase distribution characteristics: bubbly flow, bubbly-slug flow, slug flow, slug-annular flow and pure annular flow. System pressure, mass flow rate and inlet subcooling were considered as the key influence factors for flow regime transition in the experiment. A flow pattern map for low pressure and low inlet subcooling condition was obtained from the experimental data.

On Instabilities in Horizontal Two-Phase Flow

1994 ◽  
Vol 59 (12) ◽  
pp. 2595-2603
Author(s):  
Lothar Ebner ◽  
Marie Fialová
Keyword(s):  
Differential Equation ◽  
Flow Regime ◽  
Slug Flow ◽  
Annular Flow ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Annular Flows ◽  
Flow Regime Maps

Two regions of instabilities in horizontal two-phase flow were detected. The first was found in the transition from slug to annular flow, the second between stratified and slug flow. The existence of oscillations between the slug and annular flows can explain the differences in the limitation of the slug flow in flow regime maps proposed by different authors. Coexistence of these two regimes is similar to bistable behaviour of some differential equation solutions.

Flow Characteristics of Adiabatic Gas-Liquid Two-Phase Flow in a Horizontal Flat Rectangular Microchannel

2011 ◽  
Author(s):  
Hideo Ide ◽  
Kentaro Satonaka ◽  
Tohru Fukano
Keyword(s):  
Void Fraction ◽  
Slug Flow ◽  
Annular Flow ◽  
Two Phase Flow ◽  
Flow Characteristics ◽  
Flow Patterns ◽  
Phase Flow ◽  
Similar Data ◽  
Two Phase ◽  
The Mean

Experiments were performed to obtain, analyze and clarify the mean void fraction, the mean liquid holdup, and the liquid slug velocity and the air-water two-phase flow patterns in horizontal rectangular microchannels, with the dimensions equal to 1.0 mm width × 0.1 mm depth, and 1.0 mm width × 0.2 mm depth, respectively. The flow patterns such as bubble flow, slug flow and annular flow were observed. The microchannel data showed similar data patterns compared to those in minichannels with the width of 1∼10mm and the depth of 1mm which we had previously reported on. However, in a 1.0 × 0.1 mm microchannel, the mean holdup and the base film thickness in annular flow showed larger values because the effects of liquid viscosity and surface tension on the holdup and void fraction dominate. The remarkable flow characteristics of rivulet flow and the flow with a partial dry out of the channel inner wall were observed in slug flow and annular flow patterns in the microchannel of 0.1 mm depth.

An Experimental Study on Air-Water Two-Phase Flow Patterns in Pebble Beds

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Bai Bofeng ◽  
Liu Maolong ◽  
Su Wang ◽  
Zhang Xiaojie
Keyword(s):  
Experimental Study ◽  
Flow Pattern ◽  
Test Section ◽  
Slug Flow ◽  
Annular Flow ◽  
Two Phase Flow ◽  
Flow Patterns ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Pattern Transition

An experimental study was conducted on the air-water two-phase flow patterns in the bed of rectangular cross sections containing spheres of regular distribution. Three kinds of glass spheres with different diameters (3 mm, 6 mm, and 8 mm) were used for the establishment of the test section. By means of visual observations of the two-phase flow through the test section, it was discovered that five different flow patterns occurred within the experimental parameter ranges, namely, bubbly flow, bubbly-slug flow, slug flow, slug-annular flow, and annular flow. A correlation for the bubble and slug diameter in the packed beds was proposed, which was an extended expression of the Tung/Dhir model, Jamialahmadi’s model, and Schmidt’s model. Three correlations were proposed to calculate the void friction of the flow pattern transition in bubble flow, slug flow, and annular flow based on the bubble model in the pore region. The experimental result showed that the modified Tung and Dhir model of the flow pattern transition was in better agreement with the experimental data compared with Tung and Dhir’s model.

Validation of 2D CFD for Two-Phase Transient Flow in a Channel and Comparison With 1D Model

2012 ◽  
Author(s):  
Stamatis Kalogerakos ◽  
Mustapha Gourma ◽  
Chris Thompson
Keyword(s):  
Flow Regime ◽  
Slug Flow ◽  
Two Phase Flow ◽  
Fluid Model ◽  
Volume Of Fluid ◽  
Inviscid Limit ◽  
Phase Flow ◽  
Two Phase ◽  
Vof Model ◽  
Two Fluid

Severe limitations of the use of three-dimensional computational fluid dynamics codes (CFD) arise when trying to simulate multiphase flow in long pipes due to time constraints. 1D codes for two-phase flow, based on two-fluid models, are fast but are known to be accurate only when the velocities are within the Kelvin-Helmholtz inviscid limit [1]. An alternative is to carry out a two-dimensional CFD simulation of a channel based on the Volume of Fluid (VOF) model. 2D CFD has a wider applicability range compared to 1D, it does not have the issue of ill-posedness and it also has better turbulence models built in. Again compared to 1D the 2D VOF model has a better interface description and wall treatment. In this paper a novel method is introduced that allows swift simulations of pipeline two-phase flow in the stratified and slug flow regime, by approximating the pipe as a channel and with a methodology that solves the problem of the interfacial velocity differences, inherent in the volume of fluid model. An initial validation using the wave growth problem has already been carried out [2]. Here a set consisting of 92 experimental cases in the slug flow regime has been simulated with 2D CFD, and the simulation results showed a good agreement with experimental results. Discussions in the paper include also the question of the range of applicability for 2D CFD, and the advantages and disadvantages compared to 3D CFD and also to 1D code based on the two-fluid model. Shear stresses are then extracted from the 2D CFD simulations and used to recalibrate the friction factors [3] used in the 1D code.

Impedance-Based Void Fraction Measurement and Flow Regime Identification in Microchannel Flows

2011 ◽  
Author(s):  
Sidharth Paranjape ◽  
Susan N. Ritchey ◽  
Suresh V. Garimella
Keyword(s):  
Flow Regime ◽  
Void Fraction ◽  
High Speed ◽  
Electrical Impedance ◽  
Two Phase Flow ◽  
Phase Distribution ◽  
Electrical Conductance ◽  
Statistical Characteristics ◽  
Phase Flow ◽  
Two Phase

Electrical impedance of a two-phase mixture is a function of void fraction and phase distribution. The difference in the electrical conductance and permittivity of the two phases can be exploited to measure electrical impedance for obtaining void fraction and flow regime characteristics. An electrical impedance meter is constructed for the measurement of void fraction in microchannel two-phase flow. The experiments are conducted in air-water two-phase flow under adiabatic conditions. A transparent acrylic test section of hydraulic diameter 780 micrometer is used in the experimental investigation. The impedance void meter is calibrated against the void fraction measured using analysis of images obtained with a high-speed camera. Based on these measurements, a methodology utilizing the statistical characteristics of the void fraction signals is employed for identification of microchannel flow regimes.

Effect of Tube Size on Flow Pattern of Air-Water Two-Phase Flow in Horizontal Tubes

2013 ◽  
Vol 746 ◽  
pp. 575-580
Author(s):  
Xue Min Liu ◽  
Zhou Hang Li ◽  
Yu Xin Wu ◽  
Jun Fu Lu
Keyword(s):  
Flow Pattern ◽  
Slug Flow ◽  
Annular Flow ◽  
Two Phase Flow ◽  
Plug Flow ◽  
Tube Diameter ◽  
Superficial Velocity ◽  
Phase Flow ◽  
Transition Line ◽  
Two Phase

Aiming at the diameter range of boiler water wall tubes in practical engineering application, the air-water two phase flow pattern in horizontal tube was experimentally investigated in tubes with different inner diameters of 20mm and 8 mm under atmosphere condition. The stratified flow, wave flow, plug flow, slug flow, annular flow, bubbly flow and mist flow were observed in the tubes. Most of the experimental points agree well with the Baker flow pattern map when they appear in the map. With the experimental results, the range lines between the flow patterns were suggested for the tube of 20mm in inner diameter as well as 8mm. As the water superficial velocity increases, the annular flow transforms into mist flow at a decreasing air superficial velocity. The two phase flow patterns transition line is similar in tendency for different tubes. The slug flow transforms into annular flow at an increasing air superficial velocity as tube diameter decreases. The stratified flow transforms into slug flow at an increasing water superficial velocity as tube diameter decreases. The transition line between plug flow and slug flow is independent of tube diameter.

Research on the Air-Water Flow Regime and Characteristics in Rectangular Channel

2021 ◽  
Author(s):  
Qingche He ◽  
Liangming Pan ◽  
Luteng Zhang ◽  
Meiyue Yan ◽  
Wangtao Xu
Keyword(s):  
Flow Regime ◽  
Void Fraction ◽  
Slug Flow ◽  
Clustering Algorithm ◽  
Two Phase Flow ◽  
Rectangular Channel ◽  
Interfacial Structure ◽  
Phase Flow ◽  
Two Phase ◽  
Rectangular Channels

Abstract Two-phase Flow is widely involved in reactor design and is directly relevant to reactor safety. However, the flow regime in narrow rectangular channels still needs further study because it has a considerable difference from tube and bundle channels. To investigate the two-phase flow regime and interfacial structure characteristics, the air-water experiment with an adiabatic vertical channel of 4 × 66 × 1800, 6 × 66 × 1800 mm have been conducted under atmosphere pressure condition. The impedance void meter was used to measure the global void fraction in narrow rectangular channels. A high-speed camera was used to record the profiles of the flow regime. The flow regime was identified by the random forest clustering algorithm based on a training sample. The profiles of different parameters, including void fraction, pressure loss at Z/D = 150, were analyzed in this paper. Furthermore, based on the parameters’ distribution, the regime transition criteria in narrow rectangular channels were discussed. It is shown that the transition from bubble to slug flow always occurred when the average void fraction is 0.17–0.2. The transition value is 0.57–0.62 when the slug Flow changes to the churn-turbulent Flow and 0.78–0.8 from churn-turbulent to annular Flow. The constant used in the Lockhart-Martinelli correlation is found to calculate the frictional pressure drop in a rectangular channel. Furthermore, the drift-model applied to the rectangular channel is verified.

Void Fraction, Pressure Drop, and Flow Pattern Behavior for Two-Phase Non-Newtonian Slug Flow

2021 ◽  
Author(s):  
Faraj Ben Rajeb ◽  
Syed Imtiaz ◽  
Yan Zhang ◽  
Amer Aborig ◽  
Mohamed M. Awad ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Flow Pattern ◽  
Flow Regime ◽  
Void Fraction ◽  
Slug Flow ◽  
Two Phase Flow ◽  
Flow Patterns ◽  
Intermittent Flow ◽  
Phase Flow ◽  
Two Phase

Abstract Slug flow is one of the most common flow patterns in non-Newtonian two-phase flow in pipes. It is a very common occurrence in gas-liquid two-phase flow in the pipe. Usually, it is an unfavorable flow pattern due to its unsteady nature, intermittency as well as high pressure drop. The differences between slug flow and elongated bubble flow are not clear because usually these two types of flow combined under one flow category. In general, these two-phase flow regimes are commonly defined as intermittent flow. In the present study, pressure gradient, and wave behavior in slug flow have been investigated depending on experimental work. In addition, void fraction has been estimated regarding available superficial liquid and gas velocities. The experimental records of superficial velocities of gas and liquid for slug flow and other flow patterns is used to create flow regime map for the gas non-Newtonian flow system. The effect of investigated flow regime velocities for non-Newtonian/gas flow on pressure drop and void fraction is reported. Pressure drop has been discovered to be reduced in slug flow more than other flow patterns due to high shear thinning behavior.

Sign in / Sign up

Export Citation Format

Share Document