scholarly journals Countercurrent Flow Limitation at the Junction between the Surge Line and the Pressurizer of a PWR

2012 ◽  
Vol 2012 ◽  
pp. 1-10 ◽  
Author(s):  
Taiga Doi ◽  
Takashi Futatsugi ◽  
Michio Murase ◽  
Kosuke Hayashi ◽  
Shigeo Hosokawa ◽  
...  
Keyword(s):  
Gas Flow ◽  
Low Frequency ◽  
Water Levels ◽  
Countercurrent Flow ◽  
Flow Limitation ◽  
Cylindrical Tank ◽  
Two Phase ◽  
Surge Line ◽  
Cylindrical Tanks ◽  
Tank Geometry

An experimental study on countercurrent flow limitation (CCFL) in vertical pipes is carried out. Effects of upper tank geometry and water levels in the upper and lower tanks on CCFL characteristics are investigated for air-water two-phase flows at room temperature and atmospheric pressure. The following conclusions are obtained: (1) CCFL characteristics for different pipe diameters are well correlated using the Kutateladze number if the tank geometry and the water levels are the same; (2) CCFL occurs at the junction between the pipe and the upper tank both for the rectangular and cylindrical tanks, and CCFL with the cylindrical tank occurs not only at the junction but also inside the pipe at high gas flow rates and small pipe diameters; (3) the flow rate of water entering into the vertical pipe at the junction to the rectangular upper tank is lower than that to the cylindrical tank because of the presence of low frequency first-mode sloshing in the rectangular tank; (4) increases in the water level in the upper tank and in the air volume in the lower tank increase water penetration into the pipe, and therefore, they mitigate the flow limitation.

scholarly journals Effects of Diameters on Countercurrent Flow Limitation at a Square Top End in Vertical Pipes

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Michio Murase ◽  
Koji Nishida ◽  
Toshihide Torige ◽  
Toshiya Takaki ◽  
Raito Goda ◽  
...  
Keyword(s):  
Water Level ◽  
Flow Rate ◽  
Liquid Flow ◽  
Liquid Flow Rate ◽  
Strong Relationship ◽  
Countercurrent Flow ◽  
Flow Limitation ◽  
Vertical Pipe ◽  
Surge Line ◽  
Inclined Pipe

The falling liquid flow rate under flooding conditions is limited at a square top end of a vertical pipe in the pressurizer surge line with the diameter of about 300 mm that consists of a vertical pipe, a vertical elbow, and a slightly inclined pipe with elbows. In this study, therefore, we evaluated effects of diameters on countercurrent flow limitation (CCFL) at the square top end in vertical pipes by using existing air-water data in the diameter range of D = 19-250 mm. As a result, we found that there was a strong relationship between the constant CK and the slope m in the Wallis-type correlation where the Kutateladze parameters were used for the dimensionless gas and liquid velocities. The constant CK and the slope m increased when the water level is increased in the upper tank h. CCFL at the square top end of the vertical pipes could be expressed by the Kutateladze parameters with CK = 1.53±0.11 and m = 0.97 for D ≥ 30 mm. The CK values were smaller for D = 19-25 mm than those for D ≥ 30 mm.

Countercurrent flow limitation at a square top end of vertical pipes and in a pressurizer surge line

2020 ◽  
Vol 363 ◽  
pp. 110624
Author(s):  
Toshiya Takaki ◽  
Michio Murase ◽  
Koji Nishida ◽  
Toshihide Torige ◽  
Akio Tomiyama
Keyword(s):  
Countercurrent Flow ◽  
Flow Limitation ◽  
Surge Line

A Proposed Calculational Model for Two-Phase Countercurrent Flow Limitation in Channels with Abrupt Area Change

1990 ◽  
Vol 89 (2) ◽  
pp. 227-232
Author(s):  
Tanvir Salim ◽  
Woon-Shing Yeung ◽  
R. Thomas Fernandez
Keyword(s):  
Countercurrent Flow ◽  
Flow Limitation ◽  
Two Phase ◽  
Area Change

Countercurrent flow limitation in a pressurizer surge line

2018 ◽  
Vol 326 ◽  
pp. 175-182 ◽  
Author(s):  
Yasunori Yamamoto ◽  
Michio Murase ◽  
Akio Tomiyama
Keyword(s):  
Countercurrent Flow ◽  
Flow Limitation ◽  
Surge Line

Mechanism and Effects of Predominant Parameters Regarding Limitation of Falling Water in Vertical Countercurrent Two-Phase Flow

1996 ◽  
Vol 118 (3) ◽  
pp. 715-724 ◽  
Author(s):  
Y. Sudo
Keyword(s):  
Water Mass ◽  
Two Phase Flow ◽  
Water Injection ◽  
Momentum Equation ◽  
Wall Friction ◽  
Countercurrent Flow ◽  
Phase Flow ◽  
Flow Limitation ◽  
Two Phase ◽  
Channel Configuration

In this study, an investigation was carried out to clarify the mechanism of countercurrent flow limitation (CCFL) or flooding, that is, limitations in the falling water mass flux in countercurrent two-phase flow in vertical channels, and to identify the effects of predominant parameters regarding CCFL, adopting the criterion that the CCFL condition be given by an envelope of momentum equation applied for the entire length of the channel with respect to any void fraction. As a result, it was found that the analytical model proposed could adequately predict all existing experimental results investigated in this study. In the channel configuration, circular, rectangular, and annular or planar channels, channel dimensions of diameter, gap size, width or circumference, and length, interfacial and wall friction, water injection mode, and inlet water subcooling were dominant parameters. Therefore, both the mechanism and the quantitative effects of CCFL have been identified.

Prediction Method of Countercurrent Flow Limitation in a Pressurizer Surge Line and Its Evaluation for a 1/10-Scale Model

2016 ◽  
Vol 2 (3) ◽  
Author(s):  
Michio Murase ◽  
Yoichi Utanohara ◽  
Takayoshi Kusunoki ◽  
Dirk Lucas ◽  
Akio Tomiyama
Keyword(s):  
Numerical Simulations ◽  
Prediction Method ◽  
3D Simulation ◽  
Scale Model ◽  
Countercurrent Flow ◽  
Flow Limitation ◽  
Vertical Pipe ◽  
Pressurized Water ◽  
Surge Line ◽  
Inclined Pipe

The method for predicting countercurrent flow limitation (CCFL) and its uncertainty in an actual pressurizer surge line of a pressurized water reactor (PWR) using 1/10-scale air–water experimental data, one-dimensional (1D) computations, and three-dimensional (3D) numerical simulations was proposed. As one step of the prediction method, 3D numerical simulations were carried out for countercurrent air–water flows in a 1/10-scale model of the pressurizer surge line to evaluate capability of the 3D simulation method and decide uncertainty of CCFL characteristics evaluated for the 1/10-scale model. The model consisted of a vertical pipe, a vertical elbow, and a slightly inclined pipe with elbows. In the actual 1/10-scale experiment, air supplied into the lower tank flowed upward to the upper tank and water supplied into the upper tank gravitationally flowed downward to the lower tank through the pressurizer surge line. In the 3D simulation, however, water was supplied from the wall surface of the vertical pipe to avoid effects of flooding at the upper end (the 3D simulation largely underestimated falling water flow rates at the upper end). Then, the flow pattern in the slightly inclined pipe was successfully reproduced, and the simulated CCFL values for the inclination angle of θ=0.6  deg (slope of 1/100) agreed well with the experimental CCFL data. The uncertainty among air–water experiments, 1D computations, and 3D simulations for the 1/10-scale model was dC=±0.015 for the CCFL constant of C=0.50. The effects of θ (θ=0,1.0 deg) on CCFL characteristics were simulated and discussed.

scholarly journals Experimental Characterisation of the Interfacial Structure during Counter-Current Flow Limitation in a Model of the Hot Leg of a PWR

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Christophe Vallée ◽  
Toshifumi Nariai ◽  
Takashi Futatsugi ◽  
Akio Tomiyama ◽  
Dirk Lucas ◽  
...  
Keyword(s):  
Water Level ◽  
High Speed ◽  
Gas Flow ◽  
Current Flow ◽  
Interfacial Structure ◽  
Flow Limitation ◽  
Two Phase ◽  
Flow Rates ◽  
Counter Current Flow ◽  
Counter Current

In order to investigate the two-phase flow behaviour during counter-current flow limitation in the hot leg of a pressurised water reactor, dedicated experiments were performed in a scaled down model ofKobe University. The experiments were performed with air and water at atmospheric pressure and room temperature. At high flow rates, CCFL occurs and the discharge of water to the reactor pressure vessel simulator is limited by the formation of slugs carrying liquid back to the steam generator. The structure of the interface was observed from the side of the channel test section using a high-speed video camera. An algorithm was developed to recognise the stratified interface in the camera frames after background subtraction. This method allows extracting the water level at any position in the image as well as performing further statistical treatments. The evolution of the interfacial structure along the horizontal part of the hot leg is shown by the visualisation of the probability distribution of the water level and analysed in function of the liquid and gas flow rates. The data achieved are useful for the analysis of the flow conditions as well as for the validation of modelling approaches like computational fluid dynamics.

scholarly journals Countercurrent Air-Water Flow in a Scale-Down Model of a Pressurizer Surge Line

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Takashi Futatsugi ◽  
Chihiro Yanagi ◽  
Michio Murase ◽  
Shigeo Hosokawa ◽  
Akio Tomiyama
Keyword(s):  
Inclination Angle ◽  
Atmospheric Pressure ◽  
Room Temperature ◽  
Flow Direction ◽  
Reactor Core ◽  
Scale Model ◽  
Countercurrent Flow ◽  
Flow Limitation ◽  
Scale Down ◽  
Surge Line

Steam generated in a reactor core and water condensed in a pressurizer form a countercurrent flow in a surge line between a hot leg and the pressurizer during reflux cooling. Characteristics of countercurrent flow limitation (CCFL) in a 1/10-scale model of the surge line were measured using air and water at atmospheric pressure and room temperature. The experimental results show that CCFL takes place at three different locations, that is, at the upper junction, in the surge line, and at the lower junction, and its characteristics are governed by the most dominating flow limitation among the three. Effects of inclination angle and elbows of the surge line on CCFL characteristics were also investigated experimentally. The effects of inclination angle on CCFL depend on the flow direction, that is, the effect is large for the nearly horizontal flow and small for the vertical flow at the upper junction. The presence of elbows increases the flow limitation in the surge line, whereas the flow limitations at the upper and lower junctions do not depend on the presence of elbows.

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