Comparison of Local Interfacial Structures Around 90 and 45-Degree Elbows in Horizontal Bubbly Flows

2010 ◽  
Vol 132 (11) ◽  
Author(s):  
Mohan Yadav ◽  
Justin D. Talley ◽  
Seungjin Kim
Keyword(s):  
Test Section ◽  
Two Phase Flow ◽  
Bubbly Flow ◽  
Phase Flow ◽  
Flow Conditions ◽  
Local Data ◽  
Two Phase ◽  
Flow Parameters ◽  
Interfacial Structures ◽  
Spatial Oscillations

This study presents a comparison of the geometric effects of 90 deg and 45 deg elbows in horizontal two-phase air-water bubbly flow. Two separate experiments were performed in the horizontal test section made out of 50.3 mm inner diameter glass tubes. The first set of data was collected with a 90 deg elbow installed, and then a 45 deg elbow was added to the existing facility to acquire the second set of data. A total of 15 different flow conditions, all within the bubbly flow regime, were identified for the 90 deg experiment, and very similar flow conditions were extended to the 45 deg experiment. A double-sensor conductivity probe was employed to acquire the local data at seven different axial positions along the test section, out of which four measurement locations are associated with the 90 deg experiment and three with the 45 deg experiment. The data show that the elbows have a significant effect on the development of interfacial structures as well as the bubble interaction mechanisms. Furthermore, there are characteristic similarities and differences between the effects of the two elbows. While the effect of the 45 deg elbow is evident immediately after the elbow, the 90 deg elbow effect tends to propagate further downstream of the elbow rather than immediately after the elbow. Moreover, it is shown that both elbows induce spatial oscillations in the interfacial structures and two-phase flow parameters, but the degree and the nature of oscillations differ. The effects of the elbows are also compared for the axial transport of the two-phase flow parameters.

Interfacial Structures and Regime Transition in Co-Current Downward Bubbly Flow

2004 ◽  
Vol 126 (4) ◽  
pp. 528-538 ◽  
Author(s):  
S. Kim ◽  
S. S. Paranjape ◽  
M. Ishii ◽  
J. Kelly
Keyword(s):  
Two Phase Flow ◽  
Bubbly Flow ◽  
Superficial Velocity ◽  
Phase Flow ◽  
Two Phase ◽  
Drift Flux Model ◽  
Drift Flux ◽  
Flow Parameters ◽  
Interfacial Structures ◽  
Flux Model

The vertical co-current downward air-water two-phase flow was studied under adiabatic condition in round tube test sections of 25.4-mm and 50.8-mm ID. In flow regime identification, a new approach was employed to minimize the subjective judgment. It was found that the flow regimes in the co-current downward flow strongly depend on the channel size. In addition, various local two-phase flow parameters were acquired by the multi-sensor miniaturized conductivity probe in bubbly flow. Furthermore, the area-averaged data acquired by the impedance void meter were analyzed using the drift flux model. Three different distributions parameters were developed for different ranges of non-dimensional superficial velocity, defined by the ration of total superficial velocity to the drift velocity.

Prediction of Pump Performance Under Air-Water Two-Phase Flow Based on a Bubbly Flow Model

1993 ◽  
Vol 115 (4) ◽  
pp. 781-783 ◽  
Author(s):  
Kiyoshi Minemura ◽  
Tomomi Uchiyama
Keyword(s):  
Two Phase Flow ◽  
Bubbly Flow ◽  
Phase Flow ◽  
Centrifugal Pumps ◽  
Flow Conditions ◽  
Two Phase ◽  
Performance Change ◽  
Void Fractions ◽  
Two Phases

This paper is concerned with the determination of the performance change in centrifugal pumps operating under two-phase flow conditions using the velocities and void fractions calculated under the assumption of an inviscid bubbly flow with slippage between the two phases. The estimated changes in the theoretical head are confirmed with experiments within the range of bubbly flow regime.

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.

Development of Prediction Technology of Two-Phase Flow Dynamics Under Earthquake Acceleration: (12) Bubble Motion Along the Flow in Structure Vibration

2014 ◽  
Author(s):  
Yuki Kato ◽  
Rie Arai ◽  
Akiko Kaneko ◽  
Hideaki Monji ◽  
Yutaka Abe ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Velocity Field ◽  
Test Section ◽  
Two Phase Flow ◽  
Flow Behavior ◽  
Bubbly Flow ◽  
Experimental Results ◽  
Phase Flow ◽  
Bubble Motion ◽  
Two Phase

In a nuclear power plant, one of the important issues is an evaluation of the safety of the reactor core and its pipes when an earthquake occurs. Many researchers have conducted studies on constructions of plants. Consequently, there is some knowledge about earthquake-resisting designs. However the influence of an earthquake vibration on thermal fluid inside a nuclear reactor plant is not fully understood. Especially, there is little knowledge how coolant in a core response when large earthquake acceleration is added. Some studies about the response of fluid to the vibration were carried out. And it is supposed that the void fraction and/or the power of core are fluctuated with the oscillation by the experiments and numerical analysis. However the detailed mechanism about a kinetic response of gas and liquid phases is not enough investigated, therefore the aim of this study is to clarify the influence of vibration of construction on bubbly flow behavior. In order to investigate the influence of vibration of construction on bubbly flow behavior, we visualized bubbly flow in pipeline on which sine wave was applied. In a test section, bubbly flow was produced by injecting gas into liquid flow through a horizontal circular pipe. In order to vibrate the test section, an oscillating table was used. The frequency and acceleration of vibration added from the oscillating table was from 1.0 Hz to 10 Hz and . 0.4 G (1 G=9.8 m/s2) at each frequency. The test section and a high speed video camera were fixed on the oscillating table. Thus the relative velocity between the camera and the test section was ignored. PIV measurement was also conducted to investigate interaction between bubble motion and surround in flow structure. Liquid pressure was also measured at upstream and downstream of the test section. The effects of oscillation on bubbly flow were quantitatively evaluated by these pressure measurements and the velocity field. In the results, it was observed that the difference of bubble motion by changing oscillation frequency. Moreover it was suggested that the bubble deformation is correlated with the fluctuation of liquid velocity field around the bubble and the pressure gradient in the flow area. In addition, these experimental results were compared with numerical simulation by a detailed two-phase flow simulation code with an advanced interface tracking method, TPFIT. Numerical simulation was qualitatively agreed with experimental results.

Local Interfacial Structure in Downward Two-Phase Bubbly Flow

2002 ◽  
Author(s):  
Hiroshi Goda ◽  
Seungjin Kim ◽  
Sidharth S. Paranjape ◽  
Joshua P. Finch ◽  
Mamoru Ishii ◽  
...  
Keyword(s):  
Two Phase Flow ◽  
Bubbly Flow ◽  
Interfacial Area ◽  
Interfacial Structure ◽  
Phase Flow ◽  
Two Phase ◽  
Interfacial Area Concentration ◽  
Flow Parameters ◽  
Local Parameters ◽  
Axial Development

The local interfacial structure for vertical air-water co-current downward two-phase flow was investigated under adiabatic conditions. A multi-sensor conductivity probe was utilized in order to acquire the local two-phase flow parameters. The present experimental loop consisted of 25.4 mm and 50.8 mm ID round tubes as test sections. The measurement was performed at three axial locations: L/D = 13, 68 and 133 for the 25.4 mm ID loop and L/D = 7, 34, 67 for the 50.8 mm ID loop, in order to study the axial development of the flow. A total of 7 and 10 local measurement points along the tube radius were chosen for the 25.4 mm ID loop and the 50.8 mm ID loop, respectively. The experimental flow conditions were determined within bubbly flow regime. The acquired local parameters included the void fraction, interfacial area concentration, bubble interface frequency, bubble Sauter mean diameter, and interfacial velocity.

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.

scholarly journals Investigation on the Handling Ability of Centrifugal Pumps under Air–Water Two-Phase Inflow: Model and Experimental Validation

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 3048 ◽  
Author(s):  
Qiaorui Si ◽  
Gérard Bois ◽  
Qifeng Jiang ◽  
Wenting He ◽  
Asad Ali ◽  
...  
Keyword(s):  
Centrifugal Pump ◽  
Two Phase Flow ◽  
Bubbly Flow ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Phase Flow ◽  
Centrifugal Pumps ◽  
Flow Conditions ◽  
Two Phase ◽  
Local Flow

The paper presents experimental and numerical investigations performed on a single stage, single-suction, horizontal-orientated centrifugal pump in air–water two-phase non-condensable flow conditions. Experimental measurements are performed in a centrifugal pump using pressure sensor devices in order to measure the wall static pressures at the inlet and outlet pump sections for different flow rates and rotational speeds combined with several air void fraction (a) values. Two different approaches are used in order to predict the pump performance degradations and perform comparisons with experiments for two-phase flow conditions: a one-dimensional two-phase bubbly flow model, and a full “Three-Dimensional Unsteady Reynolds Average Navier–Stokes” (3D-URANS) simulation using a modified k-epsilon turbulence model combined with the Euler–Euler inhomogeneous two-phase flow description. The overall and local flow features are presented and analyzed. Limitations concerning both approaches are pointed out according to some flow physical assumptions and measurement accuracies. Some additional suggestions are proposed in order to improve two-phase flow pump suction capabilities.

Local and Area-Averaged Flow Structure of Air-Water Two-Phase Flow in a Vertical Annulus

2008 ◽  
Author(s):  
Basar Ozar ◽  
Jae Jun Jeong ◽  
Abhinav Dixit ◽  
Jose Enrique Julia´ ◽  
Takashi Hibiki ◽  
...  
Keyword(s):  
Flow Structure ◽  
Test Section ◽  
Two Phase Flow ◽  
Interfacial Area ◽  
Phase Flow ◽  
Flow Conditions ◽  
Two Phase ◽  
Interfacial Area Concentration ◽  
Drift Flux Model ◽  
Vertical Annulus

The flow structure of gas-liquid two-phase flow has been investigated in a vertical annulus channel. The annulus consisted of a geometry where the inner diameter was 19.1 mm and the outer diameter was 38.1 mm. The total height of the test section was 4.37 m. Experiments were conducted for nineteen inlet flow conditions. These flow conditions covered bubbly, cap-slug, and churn-turbulent flows. The local flow parameters, such as void fraction, interfacial area concentration, and bubble interface velocity, were measured at nine radial positions within the gap of the annulus at z/Dh = 230 of the test section. Radial distributions of these parameters were interpreted in terms of turbulent velocity profile, lift and wall forces. In addition, the local measurements were used to calculate distribution parameter, C0 in drift-flux model, and area averaged interfacial area concentration. Ishii’s (1977) model was modified and a new correlation of C0 was proposed based on the experimentally obtained C0 values. The area-averaged interfacial area concentration (IAC) values were compared with the most widely used models (Ishii and Mishima, 1980; Spore et al., 1983; Hibiki and Ishii, 2002). The advantages and drawbacks of these models were highlighted.

Vibration Effects on Bubbly Flow Structure in an Annulus

2016 ◽  
Author(s):  
Xiu Xiao ◽  
Qingzi Zhu ◽  
Guanyi Wang ◽  
Shao-Wen Chen ◽  
Mamoru Ishii ◽  
...  
Keyword(s):  
Flow Structure ◽  
Void Fraction ◽  
Test Section ◽  
Two Phase Flow ◽  
Bubbly Flow ◽  
Wall Region ◽  
Phase Flow ◽  
Seismic Vibration ◽  
Two Phase ◽  
Local Parameters

In order to investigate the seismic vibration effect on two-phase flow structure, experiments were performed for upwards bubbly flow in an annulus channel with and without externally-induced vibration. The inner and outer diameters of the annulus are 19.1 mm and 38.1 mm respectively, and the total height of the test section is 2.32 m. To simulate seismic vibrations, the test section is attached to an eccentric cam vibration module with an eccentricity of 9.5 mm. The eccentric cam rotation speed can reach up to 210 rpm. Local two-phase flow parameters were measured along radial direction within the annulus gap using miniaturized four-sensor conductivity probe at axial location of z/Dh = 77. The semi-instantaneous local parameters at different vibration angles were analyzed by tracing the quasi-sinusoidal acceleration signal under vibration conditions. The results showed that the seismic vibration can significantly affect the local parameters in bubbly flow regime. Void fraction can increase by 10% compared with non-vibration condition. During the vibration cycle, the void fraction also changed greatly, especially in the near wall region. The interfacial area concentration (IAC) and Sauter mean diameter displayed the same behavior as the respective void fraction profiles.

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