Experiment of Adiabatic Two-Phase Flow in an Annulus Under Low-Frequency Vibration

2012 ◽  
Author(s):  
Shao-Wen Chen ◽  
Caleb S. Brooks ◽  
Chris Macke ◽  
Takashi Hibiki ◽  
Mamoru Ishii ◽  
...  
Keyword(s):  
Void Fraction ◽  
Two Phase Flow ◽  
Low Frequency ◽  
Flow Regimes ◽  
Operating Conditions ◽  
Phase Flow ◽  
Two Phase ◽  
Specific Flow ◽  
Low Frequency Vibration ◽  
Fft Analysis

In order to investigate the possible effect of seismic vibration on two-phase flow dynamics and thermal-hydraulics of a nuclear reactor, experimental tests of adiabatic air-water two-phase flow under low-frequency vibration were carried out in this study. An eccentric cam vibration module operated at low motor speed (up to 390rpm) was attached to an annulus test section which was scaled down from a prototypic BWR fuel assembly sub-channel. The inner and outer diameters of the annulus are 19.1mm and 38.1mm, respectively. The two-phase flow operating conditions cover the ranges of 0.03≤<jg> ≤1.46m/s and 0.25≤<jf>≤1.00m/s and the vibration displacement ranges from ±0.8mm to ±22.2mm. Steady-state area-averaged instantaneous and time-averaged void fraction was recorded and analyzed in stationary and vibration experiments. A neural network flow regime identification technique and fast Fourier transformation (FFT) analysis were introduced to analyze the flow regimes and void signals under stationary and vibration conditions. Experimental results reveal possible changes in flow regimes under specific flow and vibration conditions. In addition, the instantaneous void fraction signals were affected and shown by FFT analysis. Possible reasons for the changes include the applied high acceleration and/or induced resonance at certain ports under the specific flow and vibration conditions.

Experimental Study of Adiabatic Two-Phase Flow in an Annular Channel Under Low-Frequency Vibration

2013 ◽  
Vol 136 (3) ◽  
Author(s):  
Shao-Wen Chen ◽  
Takashi Hibiki ◽  
Mamoru Ishii ◽  
Michitsugu Mori ◽  
Fumitoshi Watanabe
Keyword(s):  
Void Fraction ◽  
Two Phase Flow ◽  
Low Frequency ◽  
Flow Regimes ◽  
Operating Conditions ◽  
Phase Flow ◽  
Two Phase ◽  
Specific Flow ◽  
Low Frequency Vibration ◽  
Fft Analysis

In order to investigate the possible effect of seismic vibration on two-phase flow dynamics and thermal-hydraulics of a nuclear reactor, experimental tests of adiabatic air-water two-phase flow under low-frequency vibration were carried out in this study. An eccentric cam vibration module operated at low motor speed (up to 390 rpm) was attached to an annulus test section which was scaled down from a prototypic boiling water reactor (BWR) fuel assembly subchannel. The inner and outer diameters of the annulus are 19.1 mm and 38.1 mm, respectively. The two-phase flow operating conditions cover the ranges of 0.03 m/s ≤ 〈jg〉 ≤ 1.46 m/s and 0.25 m/s ≤ 〈jf〉 ≤ 1.00 m/s and the vibration displacement ranges from ±0.8 mm to ±22.2 mm. Steady-state area-averaged instantaneous and time-averaged void fraction were recorded and analyzed in stationary and vibration experiments. A neural network flow regime identification technique and fast Fourier transformation (FFT) analysis were introduced to analyze the flow regimes and void signals under stationary and vibration conditions. Experimental results reveal possible changes in flow regimes under specific flow and vibration conditions. In addition, the instantaneous void fraction signals were affected and shown by FFT analysis. Possible reasons for the changes include the applied high acceleration and induced void/flow structure changes at certain ports under the specific flow and vibration conditions.

Countercurrent Two-Phase Flow Regimes and Void Fraction in Vertical and Inclined Channels

1995 ◽  
Vol 119 (3) ◽  
pp. 182-194 ◽  
Author(s):  
S. M. Ghiaasiaan ◽  
K. E. Taylor ◽  
B. K. Kamboj ◽  
S. I. Abdel-Khalik
Keyword(s):  
Void Fraction ◽  
Two Phase Flow ◽  
Flow Regimes ◽  
Phase Flow ◽  
Two Phase ◽  
Inclined Channels

Ex-Situ Characterization of Two-Phase Flow Regimes in Proton-Exchange Membrane Fuel Cells Under Non-Isothermal Conditions

2010 ◽  
Author(s):  
Arganthae¨l Berson ◽  
Jon G. Pharoah
Keyword(s):  
Proton Exchange Membrane ◽  
Two Phase Flow ◽  
Metal Foam ◽  
Flow Regimes ◽  
Proton Exchange ◽  
Operating Conditions ◽  
Ex Situ ◽  
Phase Flow ◽  
Two Phase ◽  
Exchange Membrane

Efficient water management is crucial for the good performances of proton-exchange membrane fuel cells (PEMFCs). The geometric and physical characteristics of the components of a PEMFC as well as operating conditions have an impact on the transport of water through the porous transport layer (PTL) and the two-phase flow regimes in the microchannels. One parameter of importance is the local temperature, which affects properties such as surface tension and is coupled with phase change. Indeed, a temperature difference of about 5K is expected across the PTL, with spatial variations due to the geometry of the flow field plate. We present preliminary results obtained with a first experimental setup for the ex-situ characterization of two-phase flow regimes in the flow channels. Water is pushed through the PTL, which is sandwiched between a porous metal foam and the flow field plate. The air flow rate, temperature and humidity can be controlled. The cell can be heated up by applying an electrical current through the metal foam. A transparent window is located on top of the flow channel. The two-phase flow within the micro-channels is visualized using a high-speed camera and laser-induced fluorescence. Preliminary results obtained under isothermal conditions at room temperature show that different two-phase flow regimes occur in the channels depending on the operating conditions, in good qualitative agreement with data from the literature. Eventually, a new visualization cell is presented that is expected to correct the flaws of the previous design and will allow a better thermal control. It will be possible to adjust the temperature gradient and the mean temperature in order to observe their impact on two-phase flow regimes for different types of PTL and flow rates. The results will provide a better understanding of water transport in PEMFC and benchmark data for the validation of numerical models.

Two-Phase Flow-Induced Forces on Piping in Vertical Upward Flow: Excitation Mechanisms and Correlation Models

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
M. Giraudeau ◽  
N. W. Mureithi ◽  
M. J. Pettigrew
Keyword(s):  
Void Fraction ◽  
Two Phase Flow ◽  
Low Frequency ◽  
Flow Patterns ◽  
Large Momentum ◽  
Phase Flow ◽  
Upward Flow ◽  
Two Phase ◽  
Correlation Models ◽  
Wide Range

Momentum variation in two-phase flow generates significant low frequency forces, capable of producing unwanted and destructive vibrations in nuclear or petroleum industries. Two-phase flow-induced forces in piping were previously studied over a range of diameters from 6 mm to 70 mm in different piping element geometries, such as elbows, U-bends, and tees. Dimensionless models were then developed to estimate the rms forces and generate vibration excitation force spectra. It was found that slug flow generates the largest forces due to the large momentum variation between Taylor bubbles and slugs. The present study was conducted with a 52 mm diameter U-bend tube carrying a vertical upward flow. Two-phase flow-induced forces were measured. In addition, two-phase flow parameters, such as the local void fraction, bubble size and velocity, and slug frequency were studied to understand the relationship between the force spectra and the two-phase flow patterns. A new two-phase flow pattern map, based on existing transition models and validated using our own local void fraction measurements and force spectra, is proposed. This paper also presents a comparison of the present dimensionless forces with those of previous studies, thus covers a wide range of geometries and Weber numbers. Finally, a dimensionless spectrum is proposed to correlate forces with large momentum variations observed for certain flow patterns.

Vibration Behavior of Rotated Triangular Tube Bundles in Two-Phase Cross Flows

2002 ◽  
Vol 124 (2) ◽  
pp. 144-153 ◽  
Author(s):  
M. J. Pettigrew ◽  
C. E. Taylor ◽  
V. P. Janzen ◽  
T. Whan
Keyword(s):  
Void Fraction ◽  
Two Phase Flow ◽  
Flow Regimes ◽  
Intermittent Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Vibration Behavior ◽  
Void Fractions ◽  
Tube Bundles ◽  
Fluidelastic Instability

The results of a series of tests describing the vibration behavior of several rotated triangular tube bundles subjected to two-phase cross flows are presented. Tube bundles with a pitch-to-diameter ratio of approximately 1.5 were tested over a broad range of void fractions and mass fluxes. Fluidelastic instability, random turbulence excitation, hydrodynamic mass, two-phase damping and local void-fraction were investigated. Well-defined fluidelastic instabilities were observed in continuous two-phase flow regimes. However, intermittent two-phase flow regimes had a dramatic effect on fluidelastic instability leading to lower than expected threshold flow velocities for instability. This effect was more pronounced in Freon two-phase flow than in air-water, and appeared well correlated to the transition between continuous and intermittent flow regimes. Generally, random turbulence excitation forces were much lower in Freon than in air-water. Although very dependent on void fraction, as expected, damping was quite similar in air-water and Freon.

Study of Uneven Distribution in Parallel Petroleum Processing Pipes

2016 ◽  
Author(s):  
Renwei Liu ◽  
Haishan Zhu ◽  
Qingping Li ◽  
Yufei Wan ◽  
Kaifeng Fan
Keyword(s):  
Flow Rate ◽  
Two Phase Flow ◽  
Operating Conditions ◽  
Uneven Distribution ◽  
Petroleum Processing ◽  
Phase Flow ◽  
Operating Pressure ◽  
Two Phase ◽  
Specific Flow ◽  
Central Platform

The aim of this article is to investigate uneven distribution of oil-gas two phase flow in parallel petroleum processing pipelines. On-site analysis on BZ35-2 central platform A and SZ36-1 central platform N/O (two typical platforms in China’s Bohai Bay) shows that uneven distribution is originated mainly by two sources: flow rate difference and dryness difference. A 3-dimensional numerical model of two-phase flow in T-junction before parallel processing units was built. Flow and dryness distribution under different operating conditions were simulated. It is demonstrated that unevenness of flow rate grows worse as the total flow rate increases or operating pressure difference between parallel units becomes larger. Moreover, unevenness of dryness is mainly caused by phase split in a tee. It can be concluded that the phase split will be more obvious when parallel units are located at different heights or gas volume fraction of feed stream and inlet flow rate is small. Besides, flow rate distribution has an effect on dryness distribution. There is a specific flow ratio that will cause the most serious phase split. Finally, according to the conclusions, modification scheme for BZ35-2 central platform A piping layout was proposed. And this work may provide some guidance for process design and practical operation of parallel units.

Measurement of Void Fraction and Pressure Drop of Air-Oil Two-Phase Flow in Horizontal Pipes

2004 ◽  
Vol 126 (1) ◽  
pp. 107-118 ◽  
Author(s):  
J. L. Pawloski ◽  
C. Y. Ching ◽  
M. Shoukri
Keyword(s):  
Pressure Drop ◽  
Flow Regime ◽  
Void Fraction ◽  
High Speed ◽  
Two Phase Flow ◽  
Flow Regimes ◽  
Phase Flow ◽  
Two Phase ◽  
Wide Range ◽  
Flow Regime Maps

The void fractions, flow regimes, and pressure drop of air-oil two-phase flow in a half-inch diameter pipe over a wide range of test conditions have been investigated. The flow regimes were identified with the aid of a 1000 frames per second high-speed camera. A capacitance sensor for instantaneous void fraction measurements was developed. The mean and probability density function of the instantaneous void fraction signal can be used to effectively identify the different flow regimes. The current flow regime data show significant differences in the transitional boundaries of the existing flow regime maps. Property correction factors for the flow regime maps are recommended. The pressure drop measurements were compared to the predictions from four existing two-phase flow pressure drop models. Though some of the models performed better for certain flow regimes, none of the models were found to give accurate results over the entire range of flow regimes.

scholarly journals Identification of two phase flow regimes by void fraction measurements

2005 ◽  
Vol 27 (1) ◽  
pp. 59-65
Author(s):  
Bui Dinh Tri
Keyword(s):  
Void Fraction ◽  
Slug Flow ◽  
Two Phase Flow ◽  
Flow Regimes ◽  
Flow Patterns ◽  
Phase Flow ◽  
Two Phase ◽  
Impedance Probe ◽  
Fraction Measurement

This paper will present a method to identify flow patterns (bubble & slug flow) in vertical air-water two-phase flow by void fraction measurement (using an impedance probe) at Inst. of Mechanics Hanoi.

Flow-Induced Void Fraction Transition Phenomenon in Two-Phase Flow

2010 ◽  
Author(s):  
Xiuzhong Shen ◽  
Kaichiro Mishima ◽  
Hideo Nakamura
Keyword(s):  
Void Fraction ◽  
Two Phase Flow ◽  
Flow Direction ◽  
Flow Regimes ◽  
Phase Flow ◽  
Vertical Pipe ◽  
Two Phase ◽  
Transition Phenomenon ◽  
Drift Flux Model ◽  
Slug Flows

The flow-induced void fraction transition phenomenon was observed in an upward air-water two-phase flow in a vertical pipe with inner diameter D = 200 mm and height z = 25 m. As the two-phase flow develops in a vertical pipe, the void fraction increases firstly in the flow direction in bubbly flow, then decreases in the flow direction, finally increase again. The flow-induced void fraction transition shows an N-shaped changing manner. The present experimental investigation revealed that this phenomenon was attributed to the formation and the growth of local dominant large bubbles in the flow. According to the bubble sizes and behaviors observed in the experiment, the flow regimes were classified into bubbly, churn and slug flows in a vertical large-diameter pipe. The drift velocities in the three flow regimes were measured in this paper. New constitutive equation for drift velocities in bubbly, churn and slug flows was proposed and confirmed in this study. The flow-induced void fraction transition in N-shaped manner can be predicted by using the drift flux model with the newly developed constitutive equations.

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