Measurement of Two-Dimensional Void Fraction Distributions of Rising Bubbles in a Simulated Sub-Channel by Wire-Mesh Sensors at Conditions of Forced Convective and Stagnant Flows

2017 ◽  
Author(s):  
Yota Suzuki ◽  
Yusei Tanaka ◽  
Taku Sakka ◽  
Akinori Sato ◽  
Kazuyuki Takase ◽  
...  
Keyword(s):  
Flow Condition ◽  
Two Phase Flow ◽  
Flow Behavior ◽  
Wire Mesh ◽  
Phase Flow ◽  
Two Dimensional ◽  
Two Phase ◽  
Fuel Rods ◽  
Fuel Rod ◽  
Stagnant Flow

Clarifying thermal-hydraulic characteristics in a nuclear reactor core is important in particular to enhance the thermo-fluid safety of nuclear reactors. Spacers installed in subchannels of fuel assemblies have the role of keeping the interval between adjacent fuel rods constantly. Similarly, in case of PWR the spacer has also the role as the turbulence promoter. When the transient event occurs, two-phase flow is generated by boiling of water due to heating of fuel rods. Therefore, it is important to confirm the two-phase flow behavior around the spacer. So, the effect of the spacer affecting the two-phase flow was investigated experimentally at forced convective flow condition. Furthermore, in order to improve the thermal safety of current light water reactors, it is necessary to clarify the two-phase flow behavior in the subchannels at the stagnant flow condition. So, the bubbly flow data around a simulated fuel rod were obtained experimentally at the stagnant flow condition. A wire-mesh sensor was used to obtain a detailed two-dimensional void fraction distribution around the simulated spacer and fuel rod. As a result of this research, the bubbly behavior around the simulated spacer and fuel rod was qualitatively revealed and also bubble dynamics in the sub-channels at the conditions of forced convective and stagnant flows were evaluated. The present experimental data are very useful for verifying the detailed three-dimensional two-phase flow analysis codes.

Behavior of Bubbles Separated by a Cross-Shaped Obstacle Placed in a Circular Flow Channel

2017 ◽  
Author(s):  
Kazuyuki Takase ◽  
Hiep H. Nguyen ◽  
Gaku Takase ◽  
Yoshihisa Hiraki
Keyword(s):  
High Speed ◽  
Nuclear Reactor ◽  
Two Phase Flow ◽  
Flow Direction ◽  
Flow Behavior ◽  
Bubbly Flow ◽  
Wire Mesh ◽  
Phase Flow ◽  
Two Phase ◽  
Validation Data

Clarifying two-phase flow characteristics in a nuclear reactor core is important in particular to enhance the thermo-fluid safety of nuclear reactors. Moreover, bubbly flow data in subchannels with spacers are needed as validation data for current CFD codes like a direct two-phase flow analysis code. In order to investigate the spacer effect on the bubbly flow behavior in a subchannel of the nuclear reactor, bubble dynamics around the simply simulated spacer was visually observed by a high speed camera. Furthermore, the void fraction and interfacial velocity distributions just behind the simulated spacer were measured quantitatively by using a wire-mesh sensor system with three wire-layers in the flow direction. From the present study, bubble separation behavior dependence upon the spacer shape was clarified.

Two-Phase Flow Studies in Boiling Single Channel Flow Using Wire Mesh Tomography (WMT) and Ultrasound Velocity Profile (UVP)

2014 ◽  
Author(s):  
Ari Hamdani ◽  
Thang Tat Nguyen ◽  
Daisuke Ito ◽  
Nobuyoshi Tsuzuki ◽  
Hiroshige Kikura
Keyword(s):  
Velocity Profile ◽  
Void Fraction ◽  
Two Phase Flow ◽  
Single Channel ◽  
Swirling Flow ◽  
Flow Behavior ◽  
Wire Mesh ◽  
Phase Flow ◽  
Two Phase ◽  
Boiling Flow

The objective of this work is to investigate characteristics of co-current boiling flow in a circular pipe with an inner diameter of 52 mm by using wire mesh tomography (WMT) and ultrasonic velocity profile (UVP). The inner wall of pipe is modified by adding fins on the inner pipe’s wall. This modification is intended to change the flow behavior into swirling flow in boiling flow. Firstly, the effect of wall modification on flow behavior is investigated by numerical calculation. Secondly, two-phase flow is investigated experimentally using UVP and WMT. In experiments, local time-average void fraction is measured using WMT and velocity profile is measured using UVP. Furthermore, these measured data, both void fraction and velocity profile, will give information about changing in flow pattern caused by modified inner pipe’s wall.

A Large-Scale Simulation on Two-Phase Flow Characteristics Around Duel Rods in a Tight-Lattice Core

2006 ◽  
Author(s):  
K. Takase ◽  
H. Yoshida ◽  
Y. Ose ◽  
H. Akimoto
Keyword(s):  
Large Scale ◽  
Two Phase Flow ◽  
Water Film ◽  
Axial Position ◽  
Phase Flow ◽  
Two Phase ◽  
Fuel Rods ◽  
Fuel Rod ◽  
Fuel Bundle ◽  
Tight Lattice

Water-vapor two-phase flow structure in a fuel bundle of an advanced light water reactor was analyzed numerically by large-scale direct simulations. A newly developed two-phase flow analysis code was used. It can precisely predict the interface behavior between the liquid and gas phase by using the interface tracking method. The present analytical geometry simulates a tight-lattice fuel bundle with 37 fuel rods and four spacers. The fuel rod outer diameter is 13 mm and gap spacing between each rod is 1.3 mm. Each spacer is installed in an arbitrary axial position in order to keeping the gap width. Water flows upward from the bottom of the fuel bundle. The inlet conditions of water are as follows: temperature 283°C, pressure 7.2 MPa, flow rate 400 kg/m2s, and the Reynolds number 40,000. In the present study three-dimensional computations were carried out under the non-heated isothermal flow condition in order to remove the effect of heat transfer by the fuel rods. The average mesh size in the present numerical study was 0.15 mm. From results of a series of the numerical simulations, the following consideration was derived: 1)The fuel rod surface is encircled with thin water film; 2)The bridge phenomenon by the water film appears in the region where the spacing between fuel rods is narrow; 3)Vapor flows downward the triangular region where the spacing between fuel rods is large; and, 4)A flow configuration of vapor shows the streak structure in the vertical direction.

Upward Vertical Two-Phase Flow Through an Annulus—Part II: Modeling Bubble, Slug, and Annular Flow

1992 ◽  
Vol 114 (1) ◽  
pp. 14-30 ◽  
Author(s):  
E. F. Caetano ◽  
O. Shoham ◽  
J. P. Brill
Keyword(s):  
Flow Pattern ◽  
Annular Flow ◽  
Two Phase Flow ◽  
Flow Behavior ◽  
Bubble Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Through ◽  
Physical Phenomena ◽  
Good Agreement

Mechanistic models have been developed for each of the existing two-phase flow patterns in an annulus, namely bubble flow, dispersed bubble flow, slug flow, and annular flow. These models are based on two-phase flow physical phenomena and incorporate annulus characteristics such as casing and tubing diameters and degree of eccentricity. The models also apply the new predictive means for friction factor and Taylor bubble rise velocity presented in Part I. Given a set of flow conditions, the existing flow pattern in the system can be predicted. The developed models are applied next for predicting the flow behavior, including the average volumetric liquid holdup and the average total pressure gradient for the existing flow pattern. In general, good agreement was observed between the experimental data and model predictions.

Numerical Analysis of Two-Phase Pipe Flow of Liquid Helium Using Multi-Fluid Model

2001 ◽  
Vol 123 (4) ◽  
pp. 811-818 ◽  
Author(s):  
Jun Ishimoto ◽  
Mamoru Oike ◽  
Kenjiro Kamijo
Keyword(s):  
Phase Transition ◽  
Gas Phase ◽  
Liquid Helium ◽  
Two Phase Flow ◽  
Fluid Model ◽  
Numerical Results ◽  
Phase Flow ◽  
Two Dimensional ◽  
Two Phase ◽  
Normal Fluid

The two-dimensional characteristics of the vapor-liquid two-phase flow of liquid helium in a pipe are numerically investigated to realize the further development and high performance of new cryogenic engineering applications. First, the governing equations of the two-phase flow of liquid helium based on the unsteady thermal nonequilibrium multi-fluid model are presented and several flow characteristics are numerically calculated, taking into account the effect of superfluidity. Based on the numerical results, the two-dimensional structure of the two-phase flow of liquid helium is shown in detail, and it is also found that the phase transition of the normal fluid to the superfluid and the generation of superfluid counterflow against normal fluid flow are conspicuous in the large gas phase volume fraction region where the liquid to gas phase change actively occurs. Furthermore, it is clarified that the mechanism of the He I to He II phase transition caused by the temperature decrease is due to the deprivation of latent heat for vaporization from the liquid phase. According to these theoretical results, the fundamental characteristics of the cryogenic two-phase flow are predicted. The numerical results obtained should contribute to the realization of advanced cryogenic industrial applications.

Experiment and Numerical Simulation of Bubble Behaviors in Argon Gas Injection Into Lead-Bismuth Pool

2006 ◽  
Author(s):  
Yumi Yamada ◽  
Toyou Akashi ◽  
Minoru Takahashi
Keyword(s):  
Direct Contact ◽  
Two Phase Flow ◽  
Experimental Result ◽  
Feed Water ◽  
Force Model ◽  
Phase Flow ◽  
Two Dimensional ◽  
Two Phase ◽  
Argon Gas ◽  
Bubble Rising

In a lead-bismuth alloy (45%Pb-55%Bi) cooled direct contact boiling water fast reactor (PBWFR), steam can be produced by direct contact of feed water with primary Pb-Bi coolant in the upper core plenum, and Pb-Bi coolant can be circulated by buoyancy forces of steam bubbles. As a basic study to investigate the two-phase flow characteristics in the chimneys of PBWFR, a two-dimensional two-phase flow was simulated by injecting argon gas into Pb-Bi pool in a rectangular vessel (400mm in length, 1500mm in height, 50mm in width), and bubble behaviors were investigated experimentally. Bubble sizes, bubble rising velocities and void fractions were measured using void probes. Argon gas was injected through five nozzles of 4mm in diameter into Pb-Bi at two locations. The experimental conditions are the pressure of atmospheric pressure, Pb-Bi temperatures of 443K, and the flow rate of injection Ar gas is 10, 20, and 30 NL/min. The measured bubble rising velocities were distributed in the range from 1 to 3 m/s. The average velocity was about 0.6 m/s. The measured bubble chord lengths were distributed from 1mm up to 30mm. The average chord length was about 7mm. An analysis was performed by two-dimensional and two-fluid model. The experimental results were compared with the analytical results to evaluate the validity of the analytical model. Although large diameter bubbles were observed in the experiment, the drag force model for spherical bubbles performed better for simulation of the experimental result because of high surface tension force of Pb-Bi.

Compressibility Effect in Two-Phase Flow and Its Application to Flow Metering With Orifice Plate and Convergent-Divergent Nozzle

1983 ◽  
Vol 105 (4) ◽  
pp. 394-399 ◽  
Author(s):  
H. Pascal
Keyword(s):  
Two Phase Flow ◽  
Flow Behavior ◽  
Orifice Plate ◽  
Phase Flow ◽  
Gas Solubility ◽  
Mass Ratio ◽  
Two Phase ◽  
Compressibility Effect ◽  
Flow Metering ◽  
Solution Gas

The effect of solution gas on the two-phase flow behavior through an orifice plate and a convergent-divergent nozzle has been investigated with regard to the flow metering of compressible two-phase mixtures. A proper thermodynamics approach to consider more accurately the compressibility effect in an accelerated two-phase flow, in particular that through an orifice and Laval’s nozzle in the presence of the solution gas, has been developed. From this approach an equation of state of mixture was derived and used in determining the orifice equation. An analysis of flow behavior has been performed and several illustrative plots were presented in order to evaluate the gas solubility effect in the flow metering with an orifice plate or a convergent-divergent nozzle. A delimitation between critical and noncritical flow has been established in terms of measured parameters and a relationship between the critical pressure and gas-liquid mass ratio was also shown.

scholarly journals Flow Behavior of Single and Two-Phase Flow inside Herringbone Microfin Tubes

2004 ◽  
Vol 2004.57 (0) ◽  
pp. 125-126
Author(s):  
Goki AKIYOSHI ◽  
Mohammad Ariful ISLAM ◽  
Akio MIYARA ◽  
Takahisa KUROKAWA
Keyword(s):  
Two Phase Flow ◽  
Flow Behavior ◽  
Phase Flow ◽  
Two Phase ◽  
Microfin Tubes
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