Development of Fiber-Optic Probes to Measure Two-Phase Flow Dynamic Parameters in Support of Flow-Induced Vibration Studies

2014 ◽  
Author(s):  
M. J. Pettigrew ◽  
B. Besner ◽  
N. W. Mureithi ◽  
T. Lafrance ◽  
J. M. Patrick
Keyword(s):  
Liquid Phase ◽  
Flow Velocity ◽  
Gas Phase ◽  
Void Fraction ◽  
Fiber Optic ◽  
Phase Flow ◽  
Flow Induced Vibration ◽  
Two Phase ◽  
Local Flow ◽  
Fiber Optic Probes

Flow-induced vibration in two-phase flows requires the knowledge of flow regime and detailed flow characteristics. This paper outlines the development of fiber-optic probes to measure void fraction, local flow velocity and characteristic size (i.e., bubble diameter) of the two-phase mixture. The principle of operation of such probes is based on the difference in index of refraction between the liquid phase and the gas phase when in contact with a fiber-optic probe supplied with a laser light. The reflected signal levels for the gas phase and the liquid phase are very different thus providing a reliable measure of void fraction. The paper describes the development of fiber-optic probes for measurements of internal two-phase flow in pipes and of external flow across a tube bundle. The use of double probes allows the measurements of local flow velocity and bubble size. Some detail measurements of flow in the gap between tubes in cross flow are presented. The fabrication of the very small and fragile probes required much development effort. The paper describes the difficulties and the solutions to assure good quality probes. Some data processing and data interpretation issues are also discussed.

Experimental Study of Aerosol Behavior During Pool Scrubbing: Part 2 — Decontamination of Aerosol Particle in Two Phase Flow

2018 ◽  
Author(s):  
Wataru Kikuchi ◽  
Kota Fujiwara ◽  
Yuki Nakamura ◽  
Shimpei Saito ◽  
Tomohisa Yuasa ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Gas Phase ◽  
Flow Structure ◽  
Void Fraction ◽  
Nuclear Power ◽  
Power Plants ◽  
Flow Model ◽  
Wire Mesh ◽  
Phase Flow ◽  
Two Phase

In order to decrease the leakage and diffusion of Fission Products (FPs) in a severe accident (SA) of nuclear power plants, BWR have a suppression chamber filled with water to decontaminate the polluted air from the reactor vessel when emergency ventilation is done. It’s called pool scrubbing having a function of decontamination effect that transfer particles from gas to liquid phase by blowing gas containing FP into water. decontamination factor (DF) which is an index of decontamination performance evaluation of pool scrubbing is predicted and calculated by using a flow model in the existing analysis model such as MELCOR code. Evaluation of the DF by pool scrubbing is important in analyzing SA progress of nuclear power plants. For this reason, validation of flow model and decontamination model is important. It is necessary to validate whether the analysis result of each model matches the actual phenomenon. Despite of these needs, generic experimental data on gas-liquid two phase flow including aerosol is insufficient in confirming the validity of existing model. Therefore, the aim of this study is to investigate aerosol behavior in air jet and its relation to bubbly flow structure during pool scrubbing. This is to obtain the flow structure when air - aerosol released to the pool part and are obtained. Transition behavior of particles from the gas phase into the liquid phase was observed by high-speed camera. In addition, the effect of aerosol on void fraction in the pool was measured by wire mesh sensor from the nozzle exit to the water surface ware also observed. Ejecting air-aerosol from the nozzle to the pool part at various flow rates, visualization of bubble diameter, bubble aspect ratio, void fraction and the gas phase velocity were done by using image processing and a wire-mesh sensor. From these results, we compared the parameters by the presence or absence of aerosol. DF is also compared with the model used in the MELCOR code.

Local characteristic of horizontal air–water two-phase flow by wire-mesh sensor

2016 ◽  
Vol 40 (3) ◽  
pp. 746-761 ◽  
Author(s):  
Weiling Liu ◽  
Chao Tan ◽  
Feng Dong
Keyword(s):  
Void Fraction ◽  
Transient Flow ◽  
Two Phase Flow ◽  
Wire Mesh ◽  
Local Characteristic ◽  
Phase Flow ◽  
Flow Conditions ◽  
Two Phase ◽  
Horizontal Pipe ◽  
Local Flow

Two-phase flow widely exists in many industries. Understanding local characteristics of two-phase flow under different flow conditions in piping systems is important to design and optimize the industrial process for higher productivity and lower cost. Air–water two-phase flow experiments were conducted with a 16×16 conductivity wire-mesh sensor (WMS) in a horizontal pipe of a multiphase flow facility. The cross-sectional void fraction time series was analysed by the probability density function (PDF), which described the void fraction fluctuation at different flow conditions. The changes and causes of PDFs during a flow regime transition were analysed. The local structure and flow behaviour were characterized by the local flow spectrum energy analysis and the local void fraction distribution (horizontal, vertical and radial direction) analysis. Finally, three-dimensional transient flow fluctuation energy evolution and characteristic scale distribution based on wavelet analysis of air–water two-phase flow were presented, which revealed the structural features of each phase in two-phase flow.

Axial Development of Vertical Upward Bubbly Flow in a Minipipe

2005 ◽  
Author(s):  
Tatsuya Hazuku ◽  
Naohisa Tamura ◽  
Norihiro Fukamachi ◽  
Tomoji Takamasa ◽  
Takashi Hibiki ◽  
...  
Keyword(s):  
Void Fraction ◽  
Two Phase Flow ◽  
Constitutive Relations ◽  
Interfacial Area ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Measurements ◽  
Local Flow ◽  
Interfacial Area Concentration ◽  
Drift Flux Model

Accurate prediction of the interfacial area concentration is essential to successful development of the interfacial transfer terms in the two-fluid model. Mechanistic modeling of the interfacial area concentration entirely relies on accurate local flow measurements over extensive flow conditions and channel geometries. From this point of view, accurate measurements of flow parameters such as void fraction, interfacial area concentration, gas velocity, bubble Sauter mean diameter, and bubble number density were performed by the image processing method at five axial locations in vertical upward bubbly flows using a 1.02 mm-diameter pipe. The frictional pressure loss was also measured by a differential pressure cell. In the experiment, the superficial liquid velocity and the void fraction ranged from 1.02 m/s to 4.89 m/s and from 0.980% to 24.6%, respectively. The obtained data give near complete information on the time-averaged local hydrodynamic parameters of two-phase flow. These data can be used for the development of reliable constitutive relations which reflect the true transfer mechanisms in two-phase flow. As the first step to understand the flow characteristics in mini-channels, the applicability of the existing drift-flux model, interfacial area correlation, and frictional pressure correlation was examined by the data obtained in the mini-channel.

Towards Understanding Two-Phase Flow Induced Vibration of Piping Structure With a U-Bend

2019 ◽  
Author(s):  
Olufemi E. Bamidele ◽  
Wael H. Ahmed ◽  
Marwan Hassan
Keyword(s):  
Void Fraction ◽  
Vibration Amplitude ◽  
Two Phase Flow ◽  
Bubbly Flow ◽  
Phase Flow ◽  
Flow Conditions ◽  
Flow Induced Vibration ◽  
Two Phase ◽  
Void Fractions ◽  
Flow Induced Vibrations

Abstract The current work investigates two-phase flow induced vibrations in 90° U-bend. The two-phase induced vibration of the structure was investigated in the vertical, horizontal and axial directions for various flow patterns from bubbly flow to wavy and annular-dispersed flow. The void fractions at various locations along the piping including the fully developed void fraction and the void fraction at the entrance of the U-bend were fully investigated and correlated with the vibration amplitude. The results show that the excitation forces of the two-phase flow in a piping structure are highly dependent on the flow pattern and the flow conditions upstream of the bend. The fully developed void fraction and slip between phases are important in modelling of forces in U-bends and elbows.

scholarly journals Energy Demodulation Algorithm for Flow Velocity Measurement of Oil-Gas-Water Three-Phase Flow

2014 ◽  
Vol 2014 ◽  
pp. 1-13 ◽  
Author(s):  
Yingwei Li ◽  
Jing Gao ◽  
Xingbin Liu ◽  
Ronghua Xie
Keyword(s):  
Liquid Phase ◽  
Phase Velocity ◽  
Flow Velocity ◽  
Gas Phase ◽  
Velocity Measurement ◽  
Phase Flow ◽  
Three Phase ◽  
Flow Velocity Measurement ◽  
Three Phase Flow ◽  
Oil Gas

Flow velocity measurement was an important research of oil-gas-water three-phase flow parameter measurements. In order to satisfy the increasing demands for flow detection technology, the paper presented a gas-liquid phase flow velocity measurement method which was based on energy demodulation algorithm combing with time delay estimation technology. First, a gas-liquid phase separation method of oil-gas-water three-phase flow based on energy demodulation algorithm and blind signal separation technology was proposed. The separation of oil-gas-water three-phase signals which were sampled by conductance sensor performed well, so the gas-phase signal and the liquid-phase signal were obtained. Second, we used the time delay estimation technology to get the delay time of gas-phase signals and liquid-phase signals, respectively, and the gas-phase velocity and the liquid-phase velocity were derived. At last, the experiment was performed at oil-gas-water three-phase flow loop, and the results indicated that the measurement errors met the need of velocity measurement. So it provided a feasible method for gas-liquid phase velocity measurement of the oil-gas-water three-phase flow.

Experimental Study on the Fluctuation Characteristics of Pressure Drop and Mass Flux of the Two-Phase Flow in Narrow Channel

2013 ◽  
Author(s):  
Deqi Chen ◽  
Qinghua Wang ◽  
Zhengang Duan ◽  
Liang-ming Pan
Keyword(s):  
Liquid Phase ◽  
Pressure Drop ◽  
Gas Phase ◽  
Flow Rate ◽  
Mass Flux ◽  
Gas Flow ◽  
Working Fluid ◽  
Phase Flow ◽  
Two Phase ◽  
Liquid Mass

In this paper the study focuses on a visual investigation on the gas-water two-phase flow in a vertical circular narrow channel with 2 mm inner diameter under atmospheric pressure. Experiments were carried out with different working conditions, including different gases as gas-phase working fluids such as nitrogen, air, carbon dioxide and argon, and the gas flow rate, Q, varied between 0 ml/s (single liquid phase flow) to 9.0 ml/s, and the liquid mass flux, G, varied between 581.3 kg/m2s to 3201.8 kg/m2s. The influence of liquid mass flux, gas flow rate as well as Eo number and Mo number (using these two non-dimensional parameters to specify the effect of gas-phase properties) on the fluctuation of pressure drop and mass flux were investigated in this study. It is found that the pressure drop increases along with increasing liquid-phase flow rate with identical other working conditions, and the corresponding flow patterns are slug flow even though the liquid-phase flow rates are different. However, the pressure drop decreases at first and then increases along with gas-phase flow rate, with constant liquid flow rate (liquid mass flux), and the corresponding flow patterns include slug flow, slug-annular flow and annular flow. Based on the experimental result, it is also found that the smaller Eo number and Mo number of the gas-phase working fluid, the smaller the fluctuations of the pressure drop and mass flux would be due to the gas-phase working fluid is different.

Numerical Simulation of the Air-Water Two-Phase Flow Across a 90-Degree Vertical-Upward Elbow

2020 ◽  
Author(s):  
Shouxu Qiao ◽  
Wenyi Zhong ◽  
Sijia Hao ◽  
Peiyao Qi ◽  
Sichao Tan
Keyword(s):  
Liquid Phase ◽  
Void Fraction ◽  
Cfd Simulation ◽  
Two Phase Flow ◽  
Fluid Model ◽  
Interfacial Area ◽  
Phase Flow ◽  
Two Phase ◽  
Interfacial Area Concentration ◽  
Flow Models

Abstract The present study investigates the air-water two-phase flow across a 90-degree vertical-upward elbow with the computational fluid dynamics (CFD) simulation. The Eulerian-Eulerian two-fluid model and the Multi Size Group (MUSIG) model are used to predict the development of the detailed interfacial structures between the two phases. The axial development of the void fraction and the interfacial area concentration are investigated and benchmarked with the experimental data measured using the four-sensor conductivity probe. It is concluded that CFD simulation can predict the characteristics distributions of void fraction and interfacial area concentration and their development downstream of the elbow. The double-peaked void fraction distribution is found to be caused by the secondary flow induced by the elbow. The liquid phase on the outer curvature moves to the inner curvature and forms a double counter rotating vortex, entraining the bubbles to form a double-peaked distribution. The elbow effects become dissipated between 33 and 63 hydraulic diameters. The simulation results of liquid-phase and gas-phase parameters can be used to develop the theoretical two-phase flow models for the elbow region.

Two Phase Flow Behavior During Pool Scrubbing

2018 ◽  
Author(s):  
Yuki Nakamura ◽  
Kota Fujiwara ◽  
Wataru Kikuchi ◽  
Shimpei Saito ◽  
Tomohisa Yuasa ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Gas Phase ◽  
Thermal Stratification ◽  
Flow Behavior ◽  
Phase Flow ◽  
Water Tank ◽  
Bubble Behavior ◽  
Two Phase ◽  
Flow Phenomenon ◽  
Severe Accidents

In severe accidents of nuclear power plants, large amounts of gas containing radioactive particles are generated. In the process of gas release into the atmosphere, it is needed to suppress the leakage of radioactive material. The gas is decontaminated by moving radioactive particles from the gas phase to the liquid phase. This effect of capturing particles is called pool scrubbing, and it has been verified great decontamination effect. Therefore, it is extremely important to analyze the effect in evaluating the influence to the environment. But study on its principle is not carried out sufficiently. And also we don’t have enough experimental date to analyze the effect. The purpose of this study is to clarify the gas-liquid two-phase flow behavior which is important in elucidating the mechanism of pool scrubbing. Particularly, this study focused on the behavior of bubble generation and breakup after being injected from the nozzle and the flow structure of rising bubbles in the still water. Furthermore, we evaluate the validity of the model used in the existing severe accidents analysis code such as the MELCOR by comparing the model with experimental data. We measure the gas phase jet injected from the upward nozzle inserted to a test water tank. Nozzle diameter, gas phase flow rate, liquid phase temperature, and water depth were used as parameters. Bubble behavior was observed via a high-speed camera. The bubble rising speed, bubble distribution and void fraction were measured by a wire mesh sensor. In previous studies, experiments using non-condensable gas in normal temperature water have been mainly conducted. In order to conduct the experiment under conditions that simulate actual equipment, steam which is a condensable gas was used in this study. Moreover, it is assumed that thermal stratification is formed in the pressure suppression pool during severe accidents. To reproduce this situation, thermal stratification is formed in the test water tank. For bubble behavior and flow phenomenon, the result of using non-condensable gas was compared with that using steam. We consider the influence of formation of a thermal stratification. As described above, the flow phenomenon in the pool scrubbing was visualized and measured. Finally, we discuss the validity of the analysis code by comparing the calculation formula and model in the analysis code with the experiment data.

Study on Gas-Liquid Two-Phase Flow Distribution Inside a Flute Header

2020 ◽  
Author(s):  
Liping Pang ◽  
Shangmin Li ◽  
Hu Yuan ◽  
Liqiang Duan
Keyword(s):  
Liquid Phase ◽  
Gas Phase ◽  
Liquid Flow ◽  
Two Phase Flow ◽  
Phase Distribution ◽  
Flow Distribution ◽  
Phase Flow ◽  
Two Phase ◽  
Parallel Channels ◽  
Gas Liquid Flow

Abstract When the supercritical boiler is working at low load during flexible operation, the uneven distribution of the gas-liquid flow at the intermediate header may affect the safety of the water-cooled wall at the vertical parallel panels. In order to improve the uniformity of gas-liquid flow distribution in the water-cooled wall of intermediate header and study the internal flow mechanism, a flute inside the header is applied with parallel vertical parallel channels and experiments under different operating conditions are conducted to verify the effectiveness of this geometrical structure. The flow pattern in the experiment belongs to stratified and wavy flow. Computational fluid dynamic (CFD) simulation is conducted in order to investigate two-phase flow distribution behavior inside a flute header. It was found that the radial gas phase distribution in the flute tube shows a symmetrical relationship, and there are two vortexes in opposite directions. With the increasing distance from the inlet, the uniformity of the gas phase distribution becomes even. The gravity is greater than the drag force, which has effect on the two-phase flow distribution. The gas phase velocity has been improved inside flute section and liquid phase flow has more even flow distribution along annular section. It makes liquid phase sent to far end of flute header. That benefits two-phase flow distribution along 10 parallel channels equally.

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