thermal engineering lab. , department of science and mechanical engineering , kansai university
DESCRIPTION
2011 / 01 / 06 - 07 (Thu.-Fri.). Seminar on neutron imaging @KURRI. 中性子ラジオグラフィを用いた 円管内沸騰二相流のボイド率定量評価. Quantitative evaluation of void fraction of boiling two-phase flow in a tube using neutron radiography. - PowerPoint PPT PresentationTRANSCRIPT
Thermal engineering Lab. , department of Science and Mechanical engineering , Kansai university
Seminar on neutron imaging @KURRI
谷口 斉 (関大院)
中性子ラジオグラフィを用いた円管内沸騰二相流のボイド率定量評価
Quantitative evaluation of void fraction of boiling two-phase flow in a tube using neutron radiography
2011 / 01 / 06 - 07 (Thu.-Fri.)
Contents
1. Background and objective
2. Experimental apparatus
3. Image processing method ( Consideration of measurement error )
4. Experimental result
5. Summary
Background
Bubbly flow Slug flow Annular flow
Isothermal two-phase flow
Boiling two-phase flowJ.G.Collier , J.R.Thome ( 1972 )
Bubbly flow
Slug flow
Churn flow
Annular flow
Drop flow
流動様式の予測相関式
限界熱流束の予測(液膜流モデル)
・・・断熱二相流のデータを基本とする.
壁面沸騰,環状流液膜の蒸発は再現不能.
Neutron radiography
・測定対象に非接触
・金属は透過し,水に対して強く減衰
⇒ 金属管内を流れる水の沸騰二相流の測定に適している.
Source Detector
Radiation
II0
mII exp0
0 20 40 60 80 10010-2
10-1
100
101
102
103
Atomic number ZM
ass
atte
nuat
ion
coef
fici
ent
m
cm
2 /g
X-ray(0.126 MeV) Thermal neutron
H
B
CN
O
FNa
AlSi
Cl
Ca
Ti
Cr
Fe
Ni
Cu
Ag
Cd
I
Xe
Pr
Gd
Pt
Au
Hg
Pb
Bi
U
H2O
・ Scatter・ Absorption・ Transmission
中性子ラジオグラフィを用いて沸騰二相流のボイド率定量評価,液膜測定に関する検討を行う.
Objective
Electrode
Electrode
Experimental apparatus ( flow loop and test section )
Experimental condition
ps 0.3 MPa
G 300 , 500 , 700 kg/m2s
xeq(outlet) ( Liquid )~ 0.20
Workingfluid
Water
Experimental apparatus ( imaging system )
Nuclear reactor KUR ( B4 port )Thermal output 1 MW
Guide tube length
11.7 m
Guide tubecross section
10 ( D ) ×75( D’ ) mm
Typical spectrum 1.2 A
Neutron flux 1×107 n/cm2s
o
Neutron source Beam port
Pit( Depth=1.0 m )
Camera box
Flamefor test loop
Experimental apparatus ( imaging system )
CCD camera “PIXIS 1024B”( Princeton Instruments )
Imaging array
1024×1024 pixels
Lens “APO MACRO 180mm F3.5”( SIGMA corporation )
Teleconverter “APO TELECONVERTER 2x EX DG”
( SIGMA corporation )Reproduction
ratio2x that of master lens
Converter “ZNSL-L100-AL1016”
( CHICHIBU FUJI co., ltd. )
Camera
Spatial resolution 0.030 mm
31.7 mm( 1024 pixel )
7.0 mmTest section
Thermocouple
Exposure 30 s
31.7 mm( 1024 pixel )
Image processing method
yxOyxyxGyxS
yxOyxGyxS
yxOyxGyxS
II
LLmLwmwwTP
wmwwG
LLmLwmwwL
m
,,1exp,,
,exp,,
,exp,,
exp0
ボイド率
S:輝度値, G:ゲイン, O:オフセット
w L G
液相透過厚さ と
気相透過厚さの比
yxOyxS
yxOyxS
yxOyxS
yxOyxS
yx
L
G
L
TP
,,
,,ln
,,
,,ln
,
Grid
Object
Converter
Grid
Object
Converter
Grid
Measurement error
Nondestructive Testing and Evaluation Vol.16, pp.345-354N. Takenaka ; H. Asano ; T. Fujii ; M. Matsubayashi
( 1 ) Scattered neutron
Grid Test section
Converter
Reactor 1MWExposure 30 s
Direct shadow method
Grid
Object
Converter
Grid
Object
Converter
Grid
Measurement error
Nondestructive Testing and Evaluation Vol.16, pp.345-354N. Takenaka ; H. Asano ; T. Fujii ; M. Matsubayashi
( 1 ) Scattered neutron -4 -3 -2 -1 0 1 2 3 40
2000
4000
6000
8000
x mm
Gra
y le
vel
Air only Liquid only
-4 -3 -2 -1 0 1 2 3 40
2000
4000
6000
8000
x mm
Gra
y le
vel
-4 -3 -2 -1 0 1 2 3 40
2000
4000
6000
8000
x mm
Gra
y le
vel
Air only Liquid only
-4 -3 -2 -1 0 1 2 3 40
2000
4000
6000
8000
x mm
Gra
y le
vel
Air only Liquid only
Non compensated
Compensated
Direct shadow method
Without teleconverter
Without teleconverter
Reactor 1MWExposure 30 s
0 1 2 3 4 5 610-1
100
L mm
Att
enua
tion
rat
io(S L
/SG)
non compensated value compensated value
2
,,,,,
yxSyxSyxSyxOyxS c
Measurement error
- =
SG SL Dynamic range
( 2 ) Gray scale
-4 -3 -2 -1 0 1 2 3 40
500
1000
1500
2000
2500
3000
3500
4000
x mm
Gra
y le
vel
"Gas only"-"Liquid only"
Exposure 0.1 s Exposure 5 s Exposure 10 s Exposure 30 s
10-3 10-2 10-1 100 1010
20
40
60
80
100
L mm
Mea
sure
men
t err
or
%
Dynamic range = 500 Dynamic range = 1000 Dynamic range = 3200
・ Dynamic range ⇒ 透過方向の分解能
・輝度は整数しか取れない ⇒測定誤差となる.
Without teleconverter
-4 -3 -2 -1 0 1 2 3 40
500
1000
1500
2000
2500
3000
3500
4000
x mm
Gra
y le
vel
"Gas only"-"Liquid only"
Exposure 0.1 s Exposure 5 s Exposure 10 s Exposure 30 s
Reactor 1MW
Measurement error
縦方向 Ig’ = 0.401 mm
( D’=75 mm , L/D’=62.3 )
DL
L
DL
LI g
'
/
'
( 3 ) Geometric unsharpness ( Vertical )
D’
D
Beam port ConverterTest section
Beam port
L=4675mm L’=25mm
D’
Ig’
Vertical
Measurement error
Converter
Test sectionBeam port
L=4675mm L’=25mm
DIg
( 3 ) Geometric unsharpness ( Horizontal )Without slit ( D=10 mm )
Converter
Test sectionBeam port
L=4675mm L’=25mm
DIg’
With Slit ( D=2.5 mm )
Ig = 0.054 mm Ig = 0.013 mm
Without slit With slit
LiF
・ L/D を上げることでボケを低減し平行度を上げることで(照射時間は長くなるが) Dynamic range を上げる.
Reactor 1MWExposure 30 s
Measurement error
Converter
Test sectionBeam port
L=4675mm L’=25mm
DIg
( 3 ) Geometric unsharpness ( Horizontal )Without slit ( D=10 mm )
Converter
Test sectionBeam port
L=4675mm L’=25mm
DIg’
With Slit ( D=2.5 mm )
Ig = 0.054 mm Ig’ = 0.013 mm
Without slit With slit
Without slit : 500
With slit : 120
-4 -3 -2 -1 0 1 2 3 40
100200300400500600700800900
x mm
Gra
y le
vel
Air only Liquid only without slit
with slit(2.5mm)
Reactor 1MWExposure 30 s
With teleconverter
□ NRG using high-speed camera in KUR
□ Development of void fraction
□ Point of net vapor generation ( PNVG )
□ Application to measurement of liquid film thickness
Experimental result
Discussion point
Experimental result
Isothermal two-phase flow ( Slug flow )( Reactor 5 MW )
jG = 0.40 m/s
jL = 0.23 m/s
( Playback speed : 1/5 )
Shading correction
2000 fps 500 fps 100 fps200 fps
Experimental result
-0.009 -0.002 0.004 0.050-0.110 -0.023
xeq (middle)
0.165
Void fraction
0.00 1.00
Boiling two-phase flow( Static image )
ps = 0.3 MPa G = 300 kg/m2s
Reactor 1MWExposure 30 s
-0.15 -0.1 -0.05 0 0.05 0.1 0.150
0.2
0.4
0.6
0.8
1
xeq
ave
Sekoguchi(1980) Bowring(1967) Drift flux model
ps=0.3 MPa G=500 kg/m2s
z=125 mm
Experimental result
Time averaged void fraction ( cross sectional average )( Effect of vertical position ) -0.15 -0.1 -0.05 0 0.05 0.1 0.15
0
0.2
0.4
0.6
0.8
1
xeq
ave
Sekoguchi(1980) Bowring(1967) Drift flux model
ps=0.3 MPa G=300 kg/m2s
z=125 mm
下流側に比べて沸騰開始点の xeq が高い.⇒気泡の発達や合体に伴う ボイド率の上昇が少ない.
= Constanteqx
-0.15 -0.1 -0.05 0 0.05 0.1 0.150
0.2
0.4
0.6
0.8
1
xeq
ave
Sekoguchi(1980) Bowring(1967) Drift flux model
ps=0.3 MPa G=500 kg/m2s
z=275 mm
-0.15 -0.1 -0.05 0 0.05 0.1 0.150
0.2
0.4
0.6
0.8
1
xeq
ave
Sekoguchi(1980) Bowring(1967) Drift flux model
ps=0.3 MPa G=500 kg/m2s
z=370 mm
PNVG
PNVG
PNVG
Experimental result
Time averaged void fraction ( cross sectional average )( Estimation of PNVG )
○高熱流束条件・ PNVG 以降のボイド率の発達⇒どの相関式も定量的には不一致.
○低熱流束条件・ PNVG は Sekoguchi による推算式が近い値.・ PNVG 以降のボイド率の発達⇒加熱部出口付近については Drift flux model がよく一致.
-0.15 -0.1 -0.05 0 0.050
0.1
0.2
0.3
0.4
0.5
0.6
0.7
xeq
ave
Sekoguchi(1980) Bowring(1962) Drift flux model
ps = 0.3 MPa G=500 kg/m2s q = 500 kW/m2
ln y=a + b xa=-5.85452263e-01b=6.43260764e+013.22313656e-01|r|=9.79487812e-01
PNVG(Sekoguchi)
PNVG(Bowring)
PNVG(Saha-Zuber)
-0.15 -0.1 -0.05 0 0.050
0.1
0.2
0.3
0.4
0.5
0.6
0.7
xeq
ave
Sekoguchi(1980) Bowring(1962) Drift flux model
ps = 0.3 MPa G=500 kg/m2s q = 500 kW/m2
ln y=a + b xa=-5.85452263e-01b=6.43260764e+013.22313656e-01|r|=9.79487812e-01
PNVG(Sekoguchi)
PNVG(Bowring)
PNVG(Saha-Zuber)
-0.15 -0.1 -0.05 0 0.05 0.1 0.150
0.10.20.30.40.50.60.70.80.9
1
xeq
ave
Sekoguchi(1980) Bowring(1967) Drift flux model
ps = 0.3 MPa G=500 kg/m2s q = 900 kW/m2
y=Σ an xn
a0=3.14922733e-01a1=7.47602227e+00a2=1.49994969e+01a3=-3.68705622e+022.36593801e-02|r|=9.97700419e-01
PNVG(Sekoguchi)
PNVG(Bowring)
PNVG(Saha-Zuber)
= Constantq
Experimental result
Time averaged liquid phase thickness( Center of the tube )
-0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.20
0.5
1
1.5
2
2.5
3
xeq
L
mm
z=370 mm z=275 mm z=125 mm
ps=0.3 MPa G=300 kg/m2s
Onset of annular flow
Film flow model
Tube radius
環状流中の液相⇒液膜と液滴液膜厚さ測定への応用
管中心のボイド率⇒液相透過厚さ
0 0.05 0.1 0.15 0.20
0.5
1
xeq
L
mm
z=370 mm z=275 mm z=125 mm
ps=0.3 MPa G=300 kg/m2s
Onset of annular flow(Wallis)
Film flow model
Tube radius
Summary
中性子ラジオグラフィを用いて沸騰二相流のボイド率測定を行い以下の結論を得た.
・熱出力 5MW 運転時において高速度カメラを用いて流れを撮影したところ, 500fps程度の撮影速度以上で定性的な評価を見込める動画が得られることを確認した.
・同じ熱流束条件において軸方向にボイド率分布を測定することで, PNVG の推定を行ったところ, PNVG 自体は既存の相関式と近い値を示すが, PNVG 以降のボイド率の発達の仕方について,従来の相関式と異なる特性を示した.
・沸騰流中の液相透過厚さを計測することで,液膜あるいは液滴の計測に応用が可能であると考えられる.