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.

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.

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.

Void Fraction Measurements for Air-Water Pipe Flows Using Quick-Closing Valves and Wire-Mesh Sensors

2018 ◽  
Author(s):  
Étienne Lessard ◽  
Jun Yang
Keyword(s):  
Void Fraction ◽  
Test Section ◽  
Two Phase Flow ◽  
Measurement Techniques ◽  
Wire Mesh ◽  
Axial Distance ◽  
Phase Flow ◽  
Flow Conditions ◽  
Flow Loop ◽  
Two Phase

In support of a header/feeder phenomena study, an adiabatic, near-atmospheric, air-water flow loop was commissioned simulating a single feeder of a Pressurized Heavy Water Reactor’s primary heat transport system under a postulated Loss of Coolant Accident scenario. An extensive database in representative two-phase flow conditions was collected, 750 tests in total, in order to create a two-phase flow map to be used in the more complex geometries such as header/feeder systems. The flow loop consists of two vertical test sections, for upwards and downwards flow, and one horizontal test section, each with an inner diameter of 32 mm and at least 120 diameters in length. Superficial velocities extended up to 6 m/s for the water and 10 m/s for the air. Void fraction was measured by means of quick-closing valves and a pair of wire-mesh sensors (WMS) in each test section. Two-phase repeatability tests showed that the liquid and gas superficial velocities varied by 1.1% and 0.6% at reference conditions of 2.0 and 2.8 m/s, respectively. The corresponding void fraction measurements varied for the quick-closing valves by at most 6.8%, which indicates a low sensitivity to the closure time of the valves and an appropriate axial distance between them, and 2.3% for the WMS. For both measurement techniques, the largest variations occurred in the vertical downwards test section. For the formal two-phase tests, over 600 distinct flow conditions were performed. The results showed that the two measurement techniques agreed within 5% at high void fractions and low liquid flow rates in vertical flow. For all other cases corresponding to the transitional or dispersed bubbly flow regime, the WMS over-estimated the void fraction by a consistent bias. An empirical correction is proposed, with a root-mean-square error of 6.6% across all tests. The void fraction map resulting from this database provides validation for the WMS measurements, a quantitative assessment of its uncertainty and range of applicability, and will be used as a reference in future tests under similar scale and flow conditions.

Development of Wire Mesh Sensor for Measurement of Void Fraction Distribution in Refrigerant-Air Two Phase Flow

2020 ◽  
Vol 2020 (0) ◽  
pp. S05309
Author(s):  
Masaaki MUTO ◽  
Takuya WAKIYAMA ◽  
Hiroaki TSUBONE ◽  
Hideharu TAKAHASH ◽  
Hiroshige KIKURA
Keyword(s):  
Void Fraction ◽  
Two Phase Flow ◽  
Wire Mesh ◽  
Phase Flow ◽  
Two Phase ◽  
Void Fraction Distribution ◽  
Fraction Distribution

Study of Behavior of Two Phase Flow in Vertical Large Diameter Pipe

2010 ◽  
Author(s):  
Mohammad Hassan Kebriayi ◽  
Hadi Karrabi ◽  
Mohsen Rezasoltani ◽  
M. H. Saidi
Keyword(s):  
Void Fraction ◽  
Two Phase Flow ◽  
Flow Behavior ◽  
Large Diameter ◽  
Petroleum Industry ◽  
Phase Flow ◽  
Empirical Correlations ◽  
Two Phase Flows ◽  
Two Phase ◽  
Cross Sectional

Knowledge of Air-water two phase flows is significant to different engineering systems such as chemical reactors and power plant and petrochemical and petroleum industry. One of the most industrial cases of two phase flow is two phase flow in vertical large pipes. In this paper in order to find two phase flow behavior along vertical large diameter pipes we simulate air inlets with different number of holes and different hole diameters in the same flow rate of air. In addition, flow characteristics such as cross-sectional void fraction and velocity and pressure were considered. To achieve this aim, main equations of flow have been developed for investigation of flow behavior in air-water two phase flows. 3-D numerical analyses were performed by a designed and written CFD package which is based on volume of fluid (VOF) approach. Geometries, which have been studied in this article, are round tubes with diameter of 5 cm and with length of 1 and 5 m. The fluid is assumed to be viscous and incompressible. The pressure-velocity coupling is obtained using the SIMPLEC algorithm. The results showed that at the entrance of the pipe the effect of air inlet geometry is significant while at the whole pipe this effect suppressed. Furthermore increasing the velocity at the inlet can increase average void fraction and decrease pressure loses along the pipe axis. Numerical results were compared with available empirical correlations and this comparison shows good agreement between this work and empirical correlations.

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.

An Experimental Study of Two-Phase Flow in a Tight Lattice Using Wire-Mesh Sensor

2020 ◽  
Author(s):  
Hengwei Zhang ◽  
Yao Xiao ◽  
Hanyang Gu
Keyword(s):  
Void Fraction ◽  
Two Phase Flow ◽  
Wire Mesh ◽  
Phase Flow ◽  
Gas Velocity ◽  
Two Phase ◽  
Fuel Bundle ◽  
Fraction Distribution ◽  
Superficial Gas Velocity ◽  
Tight Lattice

Abstract Tight lattice bundle can improve the conversion ratio and the heat transfer coefficient between the fuel bundle and the coolant, which is widely used in the innovative reactor fuel bundle design. The P/D ratio of a tight lattice bundle is usually less than 1.1, which is smaller than that of a conventional rod bundle. In the small-break loss-of-coolant accident (LOCA), the steam-water two-phase flow will occur in the reactor. The investigation of gas-liquid two-phase flow in the tight lattice is very important to the reactor safety analysis. A dual sub-channels tight lattice was designed in this study. The original reference of the channel is the annular fuel bundle, with the fuel diameter of 15.52mm, pitch of 16.51mm, P/D = 1.06. The original reference of working condition is the stream-water two-phase flow under the pressure of 15.5MPa. The experimental condition is the air-water two-phase flow at the normal temperature and pressure. According to the ratio of a critical bubble diameter in the reactor (steam-water) to that in atmospheric conditions (air-water), the channel is zoomed in 2.7 times. The diameter of the rod in the dual sub-channels tight lattice is 42mm and the pitch is 44.6mm. The total length of the dual sub-channels tight lattice is 3m. A self-developed 16 × 32 Wire-mesh sensor (WMS) was used to measure the void fraction distribution of air-water two-phase flow in the dual sub-channels tight lattice channel. The spatial resolution of the WMS is 2.79mm and the temporal resolution is 5000fps. The WMS was installed at a distance of 2.5m from the channel inlet and 0.5m from the outlet, which can avoid the influence of outlet on bubbles. The experimental range of flow condition is 0.921–1.84m/s for the superficial liquid velocity and 0.0884–1.07m/s for the superficial gas velocity. The instantaneous and time-averaged void fraction distributions in the channel was measured. With the increase of superficial gas velocity, the distribution of void fraction distribution changed from the wall peak to the core peak. The characteristics of bubbles in the sub-channel were also discussed in this study.

Behavior and pressure drop of an upwardly two-phase flow through multi-hole orifices

2017 ◽  
Vol 232 (18) ◽  
pp. 3281-3299 ◽  
Author(s):  
Ammar Zeghloul ◽  
Abdelwahid Azzi ◽  
Abbas Hasan ◽  
Barry James Azzopardi
Keyword(s):  
Standard Deviation ◽  
Pressure Drop ◽  
Void Fraction ◽  
Two Phase Flow ◽  
Flow Behavior ◽  
Orifice Plate ◽  
Critical Threshold ◽  
Phase Flow ◽  
Two Phase ◽  
Phase Pressure

Experimental results on hydrodynamic behavior and pressure drop of two-phase mixture flowing upwardly in a pipe containing single- and/or multi-hole orifice plate are presented. It was found from the measurement of the void fraction upstream and downstream the orifices that the flow behavior is significantly affected by the layout of the orifice plate used and the flow starts to recover after approximately 7 D downstream the orifice. Furthermore, increasing orifice holes number results in decreasing the slip ratio. The standard deviation of the void fraction was used to identify the flow pattern before and after the orifices and found that the critical threshold transition occurred at a standard deviation of 0.2. The flow homogenization necessitates a minimum value of the liquid superficial velocity to occur, and the position where it takes place depends on this velocity and on the orifice holes number. It was also inferred from the two-phase pressure drop data across the orifices that three different flow regimes, where the transition between bubbly-to-slug and slug-to-churn flow, can be identified. An assessment of the predicted two-phase flow multiplier using some previous models dedicated to single-hole orifice was achieved; and found that the model proposed by Simpson et al. is the most reliable one. Single-phase pressure drop was also measured and compared with correlations from literature.

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