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 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 in Slightly Inclined Pipes With Elbows

2015 ◽  
Vol 1 (4) ◽  
Author(s):  
Michio Murase ◽  
Ikuo Kinoshita ◽  
Takayoshi Kusunoki ◽  
Dirk Lucas ◽  
Akio Tomiyama
Keyword(s):  
Friction Coefficient ◽  
Single Phase ◽  
Wall Friction ◽  
Scale Model ◽  
Gas Flows ◽  
Countercurrent Flow ◽  
Flow Limitation ◽  
Adjustment Factor ◽  
Pressurized Water ◽  
Inclined Pipes

One-dimensional (1D) sensitivity computations were carried out for air–water countercurrent flows in a 1/15-scale model of the hot leg and a 1/10-scale model of the pressurizer surge line in a pressurized water reactor (PWR) to generalize the prediction method for countercurrent flow limitation (CCFL) characteristics in slightly inclined pipes with elbows. In the 1D model, the wall friction coefficient fwG of single-phase gas flows was used. The interfacial drag coefficient of fi=0.03, an appropriate adjustment factor of NwL=6 for the wall friction coefficient fwL of single-phase liquid flows (NwG=1 for fwG of single-phase gas flows), and an appropriate adjustment factor of Nde=6 for the pressure loss coefficient ζe of elbows in single-phase flows were determined to give good agreement between the computed and measured CCFL characteristics. The adjusted factors were used to compute and then discuss effects of the inclination angle and diameter on CCFL characteristics.

C111 Numerical Simulations of Countercurrent Flow Limitation at the Lower End of a Vertical Pipe

2013 ◽  
Vol 2013.18 (0) ◽  
pp. 71-72
Author(s):  
Michio MURASE ◽  
Yoichi UTANOHARA ◽  
Chihiro YANAGI ◽  
Takeshi TAKATA ◽  
Akira YAMAGUCHI ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Countercurrent Flow ◽  
Flow Limitation ◽  
Vertical Pipe

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.

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

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

Comparison of Countercurrent Flow Limitation Experiments Performed in Two Different Models of the Hot Leg of a Pressurized Water Reactor With Rectangular Cross Section

2010 ◽  
Vol 133 (5) ◽  
Author(s):  
Christophe Vallée ◽  
Tobias Seidel ◽  
Dirk Lucas ◽  
Akio Tomiyama ◽  
Michio Murase
Keyword(s):  
Cross Section ◽  
Flow Rate ◽  
Cross Sections ◽  
Characteristic Length ◽  
Rectangular Cross Section ◽  
Channel Height ◽  
Countercurrent Flow ◽  
Flow Limitation ◽  
Pressurized Water Reactor ◽  
Pressurized Water

In order to investigate the two-phase flow behavior during countercurrent flow limitation in the hot leg of a pressurized water reactor, two test models were built: one at the Kobe University and the other at the TOPFLOW test facility of Forschungszentrum Dresden-Rossendorf (FZD). Both test facilities are devoted to optical measurement techniques; therefore, a flat hot leg test section design was chosen. Countercurrent flow limitation (CCFL) experiments were performed, simulating the reflux condenser cooling mode appearing in some accident scenarios. The fluids used were air and water, both at room temperature. The pressure conditions were varied from atmospheric at Kobe to 3.0 bars absolute at TOPFLOW. According to the presented review of literature, very few data are available on flooding in channels with a rectangular cross section, and no experiments were performed in the past in such flat models of a hot leg. Commonly, the macroscopic effects of CCFL are represented in a flooding diagram, where the gas flow rate is plotted versus the discharge water flow rate, using the nondimensional superficial velocity (also known as Wallis parameter) as coordinates. However, the classical definition of the Wallis parameter contains the pipe diameter as characteristic length. In order to be able to perform comparisons with pipe experiments and to extrapolate to the power plant scale, the appropriate characteristic length should be determined. A detailed comparison of the test facilities operated at the Kobe University and at FZD is presented. With respect to the CCFL behavior, it is shown that the essential parts of the two hot leg test sections are very similar. This geometrical analogy allows us to perform meaningful comparisons. However, clear differences in the dimensions of the cross section (H×W=150×10 mm2 in Kobe, 250×50 mm2 at FZD) make it possible to point out the right characteristic length for hot leg models with rectangular cross sections. The hydraulic diameter, the channel height, and the Laplace critical wavelength (leading to the Kutateladze number) were tested. A comparison of our own results with similar experimental data and empirical correlations for pipes available in literature shows that the channel height is the characteristic length to be used in the Wallis parameter for channels with rectangular cross sections. However, some limitations were noticed for narrow channels, where CCFL is reached at lower gas fluxes, as already observed in small scale hot legs with pipe cross sections.

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 Numerical Simulation of Size Effects on Countercurrent Flow Limitation in PWR Hot Leg Models

2012 ◽  
Vol 2012 ◽  
pp. 1-7
Author(s):  
I. Kinoshita ◽  
M. Murase ◽  
A. Tomiyama
Keyword(s):  
Numerical Simulation ◽  
Size Effect ◽  
Numerical Simulations ◽  
Size Effects ◽  
Fluid Model ◽  
Flow Channel ◽  
Countercurrent Flow ◽  
Flow Limitation ◽  
Two Fluid Model ◽  
Two Fluid

We have previously done numerical simulations using the two-fluid model implemented in the CFD software FLUENT6.3.26 to investigate effects of shape of a flow channel and its size on CCFL (countercurrent flow limitation) characteristics in PWR hot leg models. We confirmed that CCFL characteristics in the hot leg could be well correlated with the Wallis parameters in the diameter range of0.05 m≤D≤0.75 m. In the present study, we did numerical simulations using the two-fluid model for the air-water tests withD=0.0254 m to determine why CCFL characteristics forD=0.0254 m were severer compared with those in the range,0.05 m≤D≤0.75 m. The predicted CCFL characteristics agreed with the data forD=0.0254 m and indicated that the CCFL difference betweenD=0.0254 m and0.05 mm≤D≤0.75 mm was caused by the size effect and not by other factors.

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