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Analysis of flow distribution in a PWR fuel rod bundle model containing a blockage - Part 2. A non-coplanar blockage
Nuclear Engineering and Design 108 (1988) 295-314 North-Holland, Amsterdam
295
ANALYSIS OF FLOW DISTRIBUTION IN A PWR FUEL ROD BUNDLE MODEL CONTAINING A BLOCKAGE
Part 2. A non-coplanar blockage M.L. A N G
Department of Chemical Engineering Loughborough University of Technology, Loughborough, Leicestershire LE11 3TU, United Kingdom an d A. A Y T E K I N , A . H . F O X
National Nuclear Corporation Limited, Warrington Road, Risley, Warrington, Cheshire WA3 5BZ, United Kingdom Received February 1988
An experimental investigation, covering a Reynolds number range from 1900 to 9800, was conducted to study the influence of a non-coplanar blockage on the velocity and turbulence intensity distributions in an unheated 7 × 7 rod bundle. Using the blockage sleeves from a previous 61% coplanar blockage study, the non-coplanarity was obtained by axially staggering these sleeves in a prescribed manner. The results showed that the introduction of non-coplanarity did not result in significant changes from the overall bundle flow behaviour with a coplanar blockage. The effect on the flow immediately upstream and downstream of the blockage and within the blockage was less pronounced, thereby resulting in a smaller degree of flow diversion. The blockage zone, despite being effectively longer than the coplanar geometry, did not seem to adversely influence the downstream flow recovery process. Indeed the recovery to an undisturbed flow profile was more rapidly established. Complete flow recovery was attained for both the non-coplanar and coplanar blockage geometries at the same axial location in the rod bundle. Predictions from the COBRA subchannel computer code again agreed reasonably with the experimental data.
1. Introduction A series of experiments were conducted at the National Nuclear Corporation (NNC) to study the effects of various blockages on the flow distribution in a pressurised water reactor (PWR) fuel rod bundle model. The basic model consisted of a 7 × 7 rod bundle with a deformed cluster configuration forming a 4 x 4 array. Initial experiments reported recently [1] examined the flow disturbance caused by an axially extensive blockage in which the central nine subchannels were each reduced in flow area by 90%. The blockage sleeve shape was such that from a total sleeve length of 38.3 × rod diameter, the 90% blockage zone occupied a length of 16.4 × rod diameter. Using the same basic test arrangement, the N N C
flow blockage study was extended to consider two other blockages, viz. a short 61% coplanar blockage and a non-coplanar blockage. The swelling shape adopted for these latter tests followed the FLECHT-SEASET reflood experiments [2]. These comparatively short blockage sleeves, with length of 6.8 × rod diameter, followed a cosine profile [3]. In the coplanar geometry, the sleeves were aligned axially to maximise the blockage within the bundle. This provided a maximum subchannel flow area reduction of 61%. The non-coplanar blockage was formed by axially staggering the same blockage sleeves in an order which is described later. Results of the flow distribution experimental study using the coplanar arrangement and subsequent comparison with COBRA (Coolant Boiling in Rod Arrays) computer code calculation were described in the previ-
0 0 2 9 - 5 4 9 3 / 8 8 / $ 0 3 . 5 0 © Elsevier Science Publishers B.V. ( N o r t h - H o l l a n d Physics Publishing Division)
296
M.L Ang A. Aytekin, A.H. Fox / Analysis of flow distribution (2) DATA POINT LOCATIONS
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Numbers shown on the bat|ooned pins represent the pin number and the axial movement in mrn of each pin relative to pins 3 and 8
Fig. 1. Axial position of ballooned pins for non-coplanar blockage geometry.
ous paper, Part 1 [3]. This paper, Part 2, examines the effects of using a non-coplanar blockage configuration on the flow distribution in a rod bundle.
2. Experimental method The basic test apparatus and the measurement method were similar to those described in Part 1. By axially staggering the same blockage sleeves in the manner shown in fig. 1, the non-coplanar configuration was formed. Numbers indicated in fig. 1 were the required downstream movement of the 14 rods relative to the two reference rods, rods 3 and 8. This specification was based on the results of the MT-3 Clad Deformarion experiment conducted in the National Research University (NRU) reactor [4]. The length of the resultant blockage zone was approximately twice the length of the coplanar blockage. Symmetry about the diagonal was maintained to simplify both the air flow measurements and the COBRA modelling. The axial flow area blockage distribution within the 4 × 4 deformed rod cluster is plotted in fig. 2 for both the non-coplanar and coplanar geometries.
The velocity data for this geometry were obtained for flow conditions similar to those of the 61% coplanar arrangement and at the same axial stations along the test section (fig. 1 [3]). Figs. 3-7 present the measured velocity profiles. A survey of these velocity distributions and also those measured in the coplanar blockage experiments showed it was only in the vicinity of the blockage that the profiles displayed notable differences. Further away from the blockage zone, the profiles for both geometries were very similar. The main features are summarised as follows: (i) A comparison of the velocity profiles at # 4 ( # denotes experimental station of fig. 1 [3]), given by fig. 3 and fig. 5 [3], showed that upstream of the blockage the influence of the coplanar arrangement was more pronounced than that of the non-coplanar geometry. This was not unexpected since considerably greater flow area was available between # 4 and # 5 in the non-coplanar configuration. At # 5 , an increase in flow area of 23% resulted with the introduction of non-coplanarity. (ii) At # 5 , the velocity profiles for both blockage geometries (fig. 4 and fig. 6 [3]) revealed higher velocities within the undistorted subchannels near the test channel walls for the coplanar geometry, exemplified by traverses 1, 2 and 8. This indicated that flow diversion from the coplanar rod bundle was greater than that from the non-coplanar bundle. (iii) The profiles at # 7 (fig. 5 and fig. 7 [3]) showed that the non-coplanar blockage velocities were lower since this station was still within the blockage zone. The full velocity profiles at # 5 and # 6 could not be obtained for the non-coplanar geometry because, as indicated in fig. 2, the diameters of the ballooned rods were still sufficiently high to prevent the insertion of the measurement probes. (iv) The minimum velocities downstream of the noncoplanar blockage at # 7 were measured in the locality of subchannels 1, 2 and 3 of fig. 1. This was consistent with the fact that these subchannels had the highest blockages amongst the nine subchannels as shown in fig. 2. (v) In the non-coplanar bundle, the flow disturbance was still significant at # 8 (fig. 8). This was illustrated by the much higher velocities measured at the rod gaps compared to the subchannel centreline velocities.
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M.L. Ang, A. Aytekin, A.H. Fox / Analysis of flow distribution (2)
both blocked geometries assumed similar appearances. Results at # 1 3 (fig. 7 and fig. 9 [3]) also suggested that flow recovery was achieved at this point. Therefore for both blockage geometries the recovery length from the flow disturbances was approximately 33 × rod diameter from the location marking the end of the coplanar blockage sleeve. The non-coplanar blockage zone, despite being effectively longer, did not adversely in-
The velocity distribution measured immediately downstream of the blockage again indicated that the downstream flow behaviour was Re dependent as was concluded in the 61% coplanar blockage study. Data at # 7 and # 8 displayed this effect although not as pronounced as the results of the coplanar blockage experiments. Further downstream the velocity profiles for
blockage zone
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0.6 i , 10
0.4
1 i 20
i , 30
I
l
n
50
40
i
n
70
60
i
i
80
90
I
l
100
Axial distance (ins) blockage zone _J
I_
flow
1= I
1.6
G
grid
I
L
1.4 0
Us
1.2(
o
o
0
.]i
0
0
O
/I •
o
o
1.0t
0
•
•
•
t'\. B°~B~
0,8
•
Oa = 3.16ft/s
•
Re : 2000
0.6 0.4
i
i
10
20
i
i
30
i
40
50
I
i
60
i
i
70
i
i
80
i
i
90
I
i
100
Axial distance (ins)
Fig. 13. Experimental and calculated axial velocity distributions for subchannel 22.
M.1, Ang, A. Aytekin, A.H. Fox / Analysis of flow distribution (2) fluence the downstream flow recovery process, indeed the recovery to an undisturbed profile appeared to be more rapidly achieved.
tion in the profiles and downstream, the redevelopment of these profiles followed the same pattern. Consistent with the velocity data, only in the immediate vicinity of the blockage zones did the turbulence intensity profiles showed marked differences. Immediately upstream, a comparison of the data for # 4 (fig. 8 and fig. 11 [3]) showed that the effect due to the coplanar blockage was much more pronounced with the flow being more turbulent. At # 5 , measurements in the subchannels sur-
3.2. Turbulence intensity profiles Generally, the turbulence intensity profiles for the coplanar and non-coplanar blockage geometries were similar. Upstream of the blockage there was little varia-
blockage zone grid
flow
I I
1.6
UB = 16.5 f t / s Re = 9800
1.~, 1.2
O \o
1.01
o oooo
-~---.IL.
O0 " ~ , , "
0
"~ .~,,~r
o
o
0 ~..,~.. *~ PI~
•
•
•
•
0.8
o experimental data • mean velocity estimated from o - - - - - COBRA calculation
0.6
OA.
I
I
10
!
,
i
20
30
,
I
,
/
40
,
I
50
,
60
I
i
70
80
I
,
.
l
90
100
Axiat distance (ins)
btockage zone flow
]<::~Z~>I"
I..-- grid
I 1.6
Us = 3.18 f t / s
I
Re - 2000
1.4
o ~
1.2
O
0 O0//
Us
o
"~-~.==! \ o ?...~._
i'
,
0
I
10
,
i
20
O
O
0 •
30
40
309
t
50
o
" I
!
60
I
L
I
70
80
90
i
I
100
Axiat distance (ins)
Fig. 14. Experimental and calculated axial velocity distributions for subchannel No. 23.
310
M.L. Ang~ A. Aytekin, A.H. Fox / Analysis of flow distribution (2)
rounding the 4 × 4 blockage (fig. 9 and fig. 12 [3]) showed remarkably similar levels of intensities. Downstream from the blockage at # 7 (fig. 10 and fig. 13 [3]), where some maximum intensity values were measured, unlike the coplanar case, the non-coplanar profiles displayed asymmetry. These profiles showed a shift towards the positions corresponding to subchannels 1, 2 and 3. This behaviour, due to the higher flow area restriction in these three subchannels, was consistent with the velocity data. At # 8 and # 9, the non-coplanar
profiles began to regain symmetry but still displayed relatively higher turbulence intensity values. Comparison of results for ~ : 1 0 - ~ 13 subsequently showed similar characteristics for both geometries• It can therefore be concluded that, similar to the results for the coplanar arrangement, the undisturbed turbulence intensity profiles were also regained at # 13 for the non-coplanar configuration. As in the previous studies [1,3], the turbulence intensity profiles were found to be influenced by the pres-
blockage zone
I--
flow
g,id I
1.6
Ua = 16.5 f t / s Re = 9800
1.4
0
O0
U. 1.2
0
0
O0
0
0
O0
0
0
O
O
I
. ~ .
0
1.0:
•
o experimental data • mean velocity estimated from o m COBRA calculation
0.8 _. 0.6 ,
0.4
I , 10
i
I
I , 30
20
I
I
I
40
I
50
I
I
60
70
i
I
I
80
I
]
I
~
~-~
i
I
90
Axial distance (ins)
100
blockage zone
-i
flow
t-
I
1.6
0
grid
:
Ua = 3.18 f t / s Re = 2000
1.4 O
UB
OOO
O
O
O
1.2
O
O
Oo
O
..i"_'~,.. • ,.=-.-..~ • ~...
1.0
•
O O
•
"=
•
•
.
0.8
0.6 0.4
, 0
I
I
I
10
20
30
i
I
40
L
I
I
l
I
50
60
70
80
i
I
90
100
AxiaL distance (ins)
Fig. 15. Experimental and calculated axial velocity distributions for subcharmel No. 29.
M.I.. Ang A. Aytekin, A.H. Fox / Analysis of flow distribution (2) ence of grids and more significantly at the lower Re. This grid effect was clearly demonstrated by profiles at # 1 and #12.
flow area for the nonmcoplanar arrangement, a description was also provided in the model to account for the variation in the gaps between the subchannels within the ballooned zone. In the following discussion, S denotes the subchannel sequencing specified in fig. 16 [3].
4. Comparison with COBRA computer code calculations The half bundle, 36 subchannel model used in the 61% coplanar study [3] was similarly used in this noncoplanar bundle flow calculation. Together with a specification of the axial distribution of subchannel
4.1. Velocity data comparison In addition to figs. 13-16, which show the comparison of axial velocity profiles for subchannels $22, $23,
blockage zone
flow
I--- grid
"
i
~ = 16.5 f t / s Re : 9600
J
1.6 1.~, O0
1.2
0
0 °/~m
0
O0
0
0
0
0
0
o
0
Ue m . ~
1.0
\.L.m"m--'ai'"
• ...i~l.
=
. •
o experimental data m mean velocity estimated from o m . _ _ COBRA calculation
0.6 0.6 0.~,
I
J
I
I
10
20
I
I
30
,
q
I
I
I
I
E0 50 60 Axial distance (ins)
I
70
I
I
80
I
I
:
90
100
blockage zone grid
I 1.6
Um : 3,18 f t / s Re : 2000
1.4
O
O O
0_ Ue
1.2 1.01
m 0
0 0
0
°A'=.
o
o
B
B
0
"---i'"~= • /
\ --.=-~..~ oO °
0
O
=
=
O
0.8 0.6
0.4
!
10
t
I
Z0
i
|
30
I
|
|
l
311
i
!
/,0 50 60 Axial distance (ins)
I
i
70
l
I
00
I
I
90
I
I
100
Fig. 16. Experimental and calculated velocity distributions for subchannel No. 24.
312
M.L Ang, A. Aytekin, A.H. Fox / Analysis of flow distribution (2) Coplanar blockage zone I~
1.6 _1
I
I r'---
I
Non-copla.nar blockage zone
1A
J_
grid
I Us : 16.5 f t / s Re = 9800
1.2
UB 1.0
i~
0.0
~ o e ~ _ . . ~ ~
.~"
-
SubchannelNo. o • •
Non-Coplanar
61% Copianar . . . . .
0.6
0./*
'
0
I
10
,
I
20
,
I
30
I
I
~,0
t
I
I
I
50 60 Axial distance (ins)
,
I
70
I
I
80
22 17 23
22
I
I
,
90
I
100
Fig. 17. Comparison of calculated axial velocities for some subchannels within the 4 × 4 blockage cluster.
$29 and $24, fig. 17 and fig. 18 are also included to highlight some of the departures from the coplanar flow distributions predicted by COBRA. The axial velocity comparison for the four selected subchannels showed that generally the COBRA predicted flow profiles agreed consistently with the experimental values. As in the coplanar bundle flow analysis [3], the calculation failed to predict the Re dependency characteristic of the downstream flow immediately after the blockage zone. Due to the uncertainty of this downstream flow redevelopment at the lower Re, the inadequacy in the modelling also led to less favourable comparison. As shown in fig. 17, COBRA predicted that the flow disturbance due to the presence of the non-coplanar blockage was less severe than the corresponding coplanar geometry. Velocities both immadiately upstream and downstream of the blockage were about 15% higher for the non-eoplanar geometry. The non-coplanarity caused less fluid to bypass the blockage thereby resulting in higher blocked subchannel mass flows of about 10%. Although the slightly lower magnitude of the maximum velocity within the non-coplanar blockage zone could not be experimentally verified, it was consistent with the data presented in fig. 2. Greater flow areas were available than for the corresponding coplanar geometry
thereby resulting in lower flow restriction. Although the non-coplanar blockage zone was effectively extended axially by a further 4 × rod diameter, the flow recovery process downstream of the blockage not only was unhindered but actually accelerated. The COBRA predictions were consistent with the experimental findings. Fig. 18 shows the predicted cross-sectional velocity profiles at two experimental stations to demonstrate the effect of non-coplanarity in the ballooned cluster. At # 5 , whilst the predicted velocity patterns at various traversing levels for the coplanar geometry remained essentially unchanged, those for the non-eoplanar case displayed significant variation. With the coplanar blockage terminating at # 6 , the velocity profiles differed markedly from those of # 5, indicating the start of the downstream flow recovery process. The results at # 6 for the non-coplanar bundle also differed appreciably from those of # 5 , reflecting the influence of the irregularly shaped and staggered flow paths. Consistent with the experimental evidence, the COBRA analysis showed that, the general effect on the flow profiles was small with the introduction of noncoplanarity. The effect on the velocity profiles immediately upstream and downstream of the blockage and within the blockage was less severe than for the
Us
o_.
Ua
u_
0.8
I ~,
0.4
4
I
Traverse
0
0
o---
8
I
. ~ _
I
I
i
- - - = _ _ .
0.4
0.8
1.2
4.
1
I 0.4 [ 12 Data point location /* 1.6
0.8
1.2
0.41
I 8
I 12
.....
I 12
I 12
1.6
0.4
0,0
1.2
0.4
0.6
~__ 1.2 Us=
Ua
_o
1.6
0.4,
0
0
Us= 0.0!
1.2
1.6
.,,
I
4
I
I
8
8
|
Traverse 6
I
8
I
Traverse 5
4
Traverse 4
COPLANAR
Fig. 18. Calculated velocity profiles at axial stations 5 and 6.
o - - .
I 6
I 6
___~ . . . . . .
NON-COPLANAR
12 Data point location 4 1.6
o.el-
1,2I~-
1.6
Data point location Axial station 5, Re = 9600
8
=
Traverse 6
° ~
I
Traverse S
COPLANAR
0.6
1.2
1,6
0.4
0.8
1.2
1.6
0A
Us=
0 1.2
1.6
8
8
4
I
I
I
I
6
I
0.4.
0.8
1.2
1.6
Data point location
0.4
0"8I
1.2
4
1
. - - -
___,..-
NON-COPLANAR
4 Data point location Axial station 6, Re = 9000
i
I
. . - - - -
0.4 Data point location 1.6[
- - - .
I
0.8
1.2
1.6
12
I
12
I
I
12
--..
314
M.L. An~ A. Aytekin, A.H. Fox / Analysis of flow distribution (2)
coplanar situation. The experimental and theoretical analyses further suggested that bundle flow behaviour was more strongly influenced by the severity of flow area restriction than the degree of non-concentricity and distortion of the flow passages.
from the end of the coplanar blockage sleeve. The results of this study further suggested that bundle flow behaviour was more strongly influenced by the severity of flow area restriction than the degree of non-coplanarity and distortion of the flow passages.
5. Conclusions
Nomenclature
This experimental programme has provided data related to the flow disturbance caused by a short noncoplanar blockage in a 7 × 7 rod bundle. The flow disturbance was found to display many features similar to those from a previous study using a short coplanar blockage. The COBRA computer code was shown to predict flow profiles consistent with the experimental data. This investigation showed that the introduction of non-coplanarity in a blockage did not result in significant deviation from the overall bundle flow behaviour due to a coplanar blockage. The effect on the flow immediately upstream and downstream of the blockage and within the blockage was less severe than for the coplanar configuration. As a result, the flow diversion from the non-coplanar blockage to the surrounding subchannels was less. The non-coplanar blockage zone, despite being effectively longer, did not adversely influence the downstream flow recovery process. Indeed the recovery to an undisturbed profile seemed more rapidly achieved. Complete flow recovery was achieved for both geometries at the same axial experimental location at a distance equivalent to 33 × rod diameter
Re Reynolds number based on the equivalent diameter of an unblocked subchannel, U local subchannel mean velocity, Un bundle average velocity, u fluctuating velocity in the axial direction.
References
[1] M.L. An8, A. Aytekin and A.H. Fox, Analysis of flow distribution in a PWR fuel rod bundle model containing a 90~ blockage, Nucl. Engrg. Des. 103 (1987) 165-188. [2] L.E. Hochreiter, R.A. Basel, R.J., Dennis, N. Lee, H.W. Massie, Jr, M.J. Loftus, E.R. Rosal and M.M. Dalkovic, PWR FLECHT SEASET 21 rod bundle flow blockage task: Task plan report, NRC/EPRI/Westinghouse Report No. 5, NUREG/CRo1370, NP-1382, WCAP-9658 (1980). [3] M.L. An8, A. Aytekin and A.H. Fox, Analysis of flow distribution in a PWR fuel rod bundle model containing a blockage, Part. 1, Nucl. Engrg. Des. 108 (1988) 275-294, preceding article in this issue. [4] I.H. Gibson, P. Coddington , T. Healey and C.A. Mann, The UK-MT-3 ballooning test in the Battelle NRU loop, Rept. No. AEEW-R-1506, AEE Winfrith (1982).
295
ANALYSIS OF FLOW DISTRIBUTION IN A PWR FUEL ROD BUNDLE MODEL CONTAINING A BLOCKAGE
Part 2. A non-coplanar blockage M.L. A N G
Department of Chemical Engineering Loughborough University of Technology, Loughborough, Leicestershire LE11 3TU, United Kingdom an d A. A Y T E K I N , A . H . F O X
National Nuclear Corporation Limited, Warrington Road, Risley, Warrington, Cheshire WA3 5BZ, United Kingdom Received February 1988
An experimental investigation, covering a Reynolds number range from 1900 to 9800, was conducted to study the influence of a non-coplanar blockage on the velocity and turbulence intensity distributions in an unheated 7 × 7 rod bundle. Using the blockage sleeves from a previous 61% coplanar blockage study, the non-coplanarity was obtained by axially staggering these sleeves in a prescribed manner. The results showed that the introduction of non-coplanarity did not result in significant changes from the overall bundle flow behaviour with a coplanar blockage. The effect on the flow immediately upstream and downstream of the blockage and within the blockage was less pronounced, thereby resulting in a smaller degree of flow diversion. The blockage zone, despite being effectively longer than the coplanar geometry, did not seem to adversely influence the downstream flow recovery process. Indeed the recovery to an undisturbed flow profile was more rapidly established. Complete flow recovery was attained for both the non-coplanar and coplanar blockage geometries at the same axial location in the rod bundle. Predictions from the COBRA subchannel computer code again agreed reasonably with the experimental data.
1. Introduction A series of experiments were conducted at the National Nuclear Corporation (NNC) to study the effects of various blockages on the flow distribution in a pressurised water reactor (PWR) fuel rod bundle model. The basic model consisted of a 7 × 7 rod bundle with a deformed cluster configuration forming a 4 x 4 array. Initial experiments reported recently [1] examined the flow disturbance caused by an axially extensive blockage in which the central nine subchannels were each reduced in flow area by 90%. The blockage sleeve shape was such that from a total sleeve length of 38.3 × rod diameter, the 90% blockage zone occupied a length of 16.4 × rod diameter. Using the same basic test arrangement, the N N C
flow blockage study was extended to consider two other blockages, viz. a short 61% coplanar blockage and a non-coplanar blockage. The swelling shape adopted for these latter tests followed the FLECHT-SEASET reflood experiments [2]. These comparatively short blockage sleeves, with length of 6.8 × rod diameter, followed a cosine profile [3]. In the coplanar geometry, the sleeves were aligned axially to maximise the blockage within the bundle. This provided a maximum subchannel flow area reduction of 61%. The non-coplanar blockage was formed by axially staggering the same blockage sleeves in an order which is described later. Results of the flow distribution experimental study using the coplanar arrangement and subsequent comparison with COBRA (Coolant Boiling in Rod Arrays) computer code calculation were described in the previ-
0 0 2 9 - 5 4 9 3 / 8 8 / $ 0 3 . 5 0 © Elsevier Science Publishers B.V. ( N o r t h - H o l l a n d Physics Publishing Division)
296
M.L Ang A. Aytekin, A.H. Fox / Analysis of flow distribution (2) DATA POINT LOCATIONS
2
3
t+ 5
6
I I I II
7
8
I II
9
I II
II
oooooo o gQQogo co
3. Experimental results and discussion
A
10 11 12 13 1& 15/
o
)oo
3.1. Velocity profiles
_~
m 3 o m 4
_
m 5
)oo
QQQQO0 ,/
Numbers shown on the bat|ooned pins represent the pin number and the axial movement in mrn of each pin relative to pins 3 and 8
Fig. 1. Axial position of ballooned pins for non-coplanar blockage geometry.
ous paper, Part 1 [3]. This paper, Part 2, examines the effects of using a non-coplanar blockage configuration on the flow distribution in a rod bundle.
2. Experimental method The basic test apparatus and the measurement method were similar to those described in Part 1. By axially staggering the same blockage sleeves in the manner shown in fig. 1, the non-coplanar configuration was formed. Numbers indicated in fig. 1 were the required downstream movement of the 14 rods relative to the two reference rods, rods 3 and 8. This specification was based on the results of the MT-3 Clad Deformarion experiment conducted in the National Research University (NRU) reactor [4]. The length of the resultant blockage zone was approximately twice the length of the coplanar blockage. Symmetry about the diagonal was maintained to simplify both the air flow measurements and the COBRA modelling. The axial flow area blockage distribution within the 4 × 4 deformed rod cluster is plotted in fig. 2 for both the non-coplanar and coplanar geometries.
The velocity data for this geometry were obtained for flow conditions similar to those of the 61% coplanar arrangement and at the same axial stations along the test section (fig. 1 [3]). Figs. 3-7 present the measured velocity profiles. A survey of these velocity distributions and also those measured in the coplanar blockage experiments showed it was only in the vicinity of the blockage that the profiles displayed notable differences. Further away from the blockage zone, the profiles for both geometries were very similar. The main features are summarised as follows: (i) A comparison of the velocity profiles at # 4 ( # denotes experimental station of fig. 1 [3]), given by fig. 3 and fig. 5 [3], showed that upstream of the blockage the influence of the coplanar arrangement was more pronounced than that of the non-coplanar geometry. This was not unexpected since considerably greater flow area was available between # 4 and # 5 in the non-coplanar configuration. At # 5 , an increase in flow area of 23% resulted with the introduction of non-coplanarity. (ii) At # 5 , the velocity profiles for both blockage geometries (fig. 4 and fig. 6 [3]) revealed higher velocities within the undistorted subchannels near the test channel walls for the coplanar geometry, exemplified by traverses 1, 2 and 8. This indicated that flow diversion from the coplanar rod bundle was greater than that from the non-coplanar bundle. (iii) The profiles at # 7 (fig. 5 and fig. 7 [3]) showed that the non-coplanar blockage velocities were lower since this station was still within the blockage zone. The full velocity profiles at # 5 and # 6 could not be obtained for the non-coplanar geometry because, as indicated in fig. 2, the diameters of the ballooned rods were still sufficiently high to prevent the insertion of the measurement probes. (iv) The minimum velocities downstream of the noncoplanar blockage at # 7 were measured in the locality of subchannels 1, 2 and 3 of fig. 1. This was consistent with the fact that these subchannels had the highest blockages amongst the nine subchannels as shown in fig. 2. (v) In the non-coplanar bundle, the flow disturbance was still significant at # 8 (fig. 8). This was illustrated by the much higher velocities measured at the rod gaps compared to the subchannel centreline velocities.
o_.~ °
m
O
8¢'3
10
20
30
40
50
60
AXIAL
/,Sy.,/./ ,
STATION
BLOCKAGE
COPLANAIR
t
100
"
AXIAL
~ \
DISTANCE
150 FROM
THE
200
'
Fig. 2. Axial variation of subchannel blockages for the non-coplanar geometry.
POSITIONS
"
r
PINS.
250 REFERENCE
-
48,8
3
28`6
( flg 1 ) 1 8` 9
(mm)
Subchonne( no.
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M.L An~ A. Aytekin, A.H. Fox / Analysis of flow distribution (2)
298 1.8
TRAVERSE
/..
~-6 +
,.2 V ~ ' , J , / ~
o.,-oI
L
1.6-
;
A/
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I
1'2
°'~o
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1.8.
TRAVERSE
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1.2
+
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~
,
1'2
0.8"
0"4.
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0'8.
0'8
0 '4 ~
0 "4
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1°1"1TRAVERSE ~ 11i. 0.8|
• ~
x
~
~ ~
+
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~
, 8
, 12
o
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;
1'2
0
L
8
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,
,
o
,.
8
,
~ DATA POINT LOCATIONS
(a) STATION 1
1,;X UB
o
L
&
0.4,
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(b) STATION 2
(c) S T A T I O N
.;,
0"8 0'4
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~:~
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i
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(d)STATION
DATA POINT LOCATIONS 151~ 11 g 7 s,3_1
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123 ~
o
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TRAVERSE ~ ~
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+ R e = 1.9 x 1 0 3 Fig. 3. V e l o c i t y profiles at axial stations 1, 2, 3 a n d 4.
~
v,~
x Re=
,
9 . 8 x I0 3
3
UB
0
UB
0
7 I'4
+
1-6
l x
12
I
10
/
3
I
1.4
÷
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-~:=
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POINT L O C A T I O N S
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+
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1.2
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TRAVERSE
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~x.
x-x
x
'L/x/
.x
~/'<
x -)~
x.×
x -x,
T R AVE RSE 8
'
xx
Fig. 4. Velocity profiles at axial station 5.
x
\÷-\r~,+,/,.<+~'<+'/'/
i
8
r
&
TRAVERSE 08
•
TRAVERSE
5
T
1400
~:~
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-LI_ ~ _ _ @ @ _(~[Q_I
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15 13 11 9 7 5
=
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DATA POINT LOCATIONS
STATION
MI--I&O0 ~ : ~
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/x
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x
16
1.2
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16
1-2
14
16
ARRAY
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p,
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POINT
LOCATIONS
(a) STATION
DATA
i
12
6
0
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8
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i
04
08
&
08
12
0
1.2
1.6
TRAVERSE 6 16
0
i
O4
&
OZ.
0-8
0
0-8
1.2
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1.2
1-6
TRAVERSE 5
O
li
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1.2
1-5
16
TRAVERSE 4
;
1'2
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i
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(b) S T A T I O N
2
i 8
~
7 Fig. 5. V e l o c i t y p r o f i l e s at a x i a l stations 6 and 7.
0
;.
•
1/,00 --~
Re= 1-9x10 3
x
/ee®ooee
Re=
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JBLOCKED
DATA POINT LOCATIONS
67
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ARRAY
1'2
8
L
6
6
6
(b) STATION
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*-
~
Fig. 6. Velocity profiles at axial stations 8 and 9.
04
04
STATION
08"
08
(o)
12
12
DATA POINT LOCATIONS
16.
6
16
TRAVERSE
04
04
o
o
0"8-
0"8"
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6
1-6-
0
1.6-
04
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UB 0.S
0
1.6
16
TRAVERSE 4
POINT
LOCATION
x
Re=
1400
9-8x!03
J~N~,,oc,Eo
4~ 1 ~ @ @ ~ I
151311 9 7 f) 3 1
DATA
° Re = 1 . 9 x 1 0 3
traverse
tt
1400 --m"~[~1400 ~
STATIONS 89
~ ' - 1400 ~
Ar.aY ~,
¢'
.=:
4.
302
+IT'R IAVERSE'
M.L. Ang, A. Aytekin, A.H. Fox / Analysis of flow distribution (2)
A,~\i ~+
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1'6 t + 1'2 ~'
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i
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i
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112
DATA POINT L O C A T I O N S
5UB
11 .6" t. • 2-1 ~'~
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(b) STATION 11
(o) STATION 10
/~ -~4.,'*
x
0,8" 0.4.
0
1 ,6]
;
8
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+
~:~
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DATA POINT L O C A T I O N S
o
;
~
t1.4-
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?2 ÷
le@e®e@ol
4.
TRAV,R,,41 te jtltIIIF ''°'c''D
~
0.8-
0.~
0
4
;
{d)STATION
1'2
13
+ Re= 1,9 x l 0 3
• Re = 9 . 8 x 1 0 3
Fig. 7. Velocity profiles at axial stations 10, 11, 12 and 13.
ARRAY
M.L Ang, A. Aytekin, A.H. Fox / Analysis of flow distribution (2) TRAVERSE
2/
/+
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;.
~
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,
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i
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-
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i
i
4.
@
i
12
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•,. R e =
19
x 103
x Re =
Fig. 8. Turbulence intensity profiles at axial stations 1, 2, 3 and 4.
9.8
x 103
10
0 "05
( U_~.~2 0.1
0.05
0.1
6
;
1
17
0.05
0.1
10
7 I'4
, ,'
DATA POINT LOCATIONS
I'4
;.
TRAVERSE
~,. v, x. -.,-x.:...yx.._~
÷
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8
TRAVERSE
8
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TRAVERSE
ii \x / \\ /g~x / \x /xx ~x /' x\~ x x x x ~,xI Xx
10
3
/
10
4
I'4
0.05 ~'/\~'~" 'ci!4 x-, x-X,x x
o.i
I l
10
•
Re =
2
~-9x10 3
• Re =
~4 112110/8|6/:/2/ $ ~'V # Vi' t,~ t' tF~t' t' V
9-8 xl0 3
POINT LOCATIONS
5
T 15 13 11 9 7 5 3 1
DATA
STATION
5
x" ~(x
x
I'4
/, o.o~ xX,+x.~,_,,~ \
o,]
~'-1400 ;:~- 1400 ~-:~ 14OO ~:¢ 1400 -'~
14
0-05 xx~x x~X~'X~x~X.~!
0I
Fig. 9. Turbulence intensity profiles at axial station 5.
00. c
0,1
0.05
0.1
0
4
o
i
;
1~
0.1
8
1'2
DATA POINT LOCATIONS
,~
(o) STATION 6
0
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(b)
0
0
8
8
STATION
4
;*
7
12
12
~
~ , y "'"%~..,.%
.
H
1400
leeeoeeol
15 13 11 9 7 5 3 1
N881
Re= 1.9x10 3
x Re= 9.8x10 3
/¢¢0¢¢eel
°q
44
DATA POINT LOCATIONS
!!
1400 .~:~ 1400 ~
STAT]O N
1400 ~
T'~AVE.SES 4 -tle¢86¢~l
N
Fig. 10. T u r b u l e n c e intensity profiles at axial stations 6 a n d 7.
0-4 03 02 0"1
0-4 03 02 01
0.4 03 0"2 01
p,
01
8
~
6
8
DATAP0,.T L0CAT,ONS
;/
TRAVERSE h.,,
f
5
12
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~. vL.A """", ',,,*.-\'.+.,
f%~++'~'~,
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o.,+-
02-
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TRAVERSE
o,, j,, 0.05..,,7"
02.
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o o~1 j
<+_ff,~ o~t/v,.-,-~ ot5~ f,...., \ ,o,,, o, t j; .........%, ~'
TRAVERSE L
;4
~
~7
,,+,
~
+'2
o, t i--'v'+ '.-....
~
4
8
9
12 * Re=
H
~;4 1400
H
/BLOCKED
LOCATION
l'i+v+~+li,tilit leeoeceo
POINT
15 13 11 9 7 5
DATA
SIATIONS
~
1400 --~+",,- 1400 -4"'~1400
× Re = 9 . 0 x 1 0 3
TRAVeRSeS~ W ~ @ ~ ) ( ~
H
Fig. l l . Turbulence intensity profiles at axial stations 8 and 9.
(b) S T A T I O N
0
oo1:.....7......7._..:::~
°o;~+t
o
01 t
+
,V" *~+../\.
021 o15/---v~ ....
o
*
/\/\+-*,
0 1 t +/+~
o 15
021
ARRAY
h
n.
r~
307
M.L Ang, A. Aytekin, A.H. Fox / Analysis of flow distribution (2)
~ 1'i20.201 2
TRAVERSE4
0.20
0.15..I
-c o.,ol
w.-
I
0.051;"
o!0
"
" "x"
,,-i-, ~
"
,
,
o.15
x÷
O.lO1+.. +-A x "ix." x" "~ 'x" x .'.+ "x 0'051 z""-~<,+,V,+'%.',/',
,",,
4
8
12
0.20 t
TRAVERSE 5
0451
+
+ + +.
0
/
\ /. % x
x- x -
+ x , • /+x",
+x
w~
*, . . . . ,
,
,
8
12
o/ o
TRAVERSE 6
o.2o t
0
o.20 t
Z
~
/+x-V .,+\.,.i-,4 "o:-x, . /+v +x'Fx ",.+.+.+, x
/
o.o~I;, .... o/ o
;.
..,...,\
-°17, o.o:1
o
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;
+
+
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+V~+
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8
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o.,,1 •
0.151 0.10 -]
0.,01 :.:,,
' 1'2
8
o.lo 1 ~,.+';,"~'- ".+" "x" 0.051 . .-;.,..,\,,+,t,,
/-,
I
0I
+
,f~
o.1oi +,'~. , + . . / \ / \ / ~ \ 0.051 ,/
I"
•
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I
i
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0'20
+
;
~
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+
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+:\ A
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+
o.,o, , . , . , . ,
'.'.~
o.O5o,t " " ,"" '"" ,"" '"'"" ," "
1'2
o
~.
8
12
DATA POINT LOCATIONS
(c) STATION 12
(b) STATION 11
(a) STATION 10
(t) o,o 112
0.15 1
/~"¢'~[N'/~'~+'%/~%/"~
0'0! t
o
;.
1'2
~
1400 ~
1400
~::
1400 ~
1400
0.20 t
o.151 ,,./\/%/<,/+,~/k/\ O.lOl
" " DATA POINT LOCATIONS
o
;.
~
15 13 11 g 7 5 3 1 1 1 1 6 4 2
I'2
0-20 t 0-15 "1 /
.,..
+
.I-
e
;t;.Eo
,i-
•l'x ~ x x, x, - "x,, , , ~ / ,./,+/,\+/+,.~: x" "x" "~" ~" x k+/.N+/~, x 'x
O,it, 00
o
;.
~
;2
(d) STATION 13
+ Re=
^
o.,,t i v`'+ wv\
..X\
~":"V*¢',:'~'
o
19
x10 3
• Re=
Fig. 12. Turbulence intensity profiles at axial stations 10, 11, 12 and 13.
9.8x10
3
308
M.L. Ang, A. Aytekin, A.H. Fox / Analysis of flow distribution (2)
both blocked geometries assumed similar appearances. Results at # 1 3 (fig. 7 and fig. 9 [3]) also suggested that flow recovery was achieved at this point. Therefore for both blockage geometries the recovery length from the flow disturbances was approximately 33 × rod diameter from the location marking the end of the coplanar blockage sleeve. The non-coplanar blockage zone, despite being effectively longer, did not adversely in-
The velocity distribution measured immediately downstream of the blockage again indicated that the downstream flow behaviour was Re dependent as was concluded in the 61% coplanar blockage study. Data at # 7 and # 8 displayed this effect although not as pronounced as the results of the coplanar blockage experiments. Further downstream the velocity profiles for
blockage zone
flow L
L.-- grid I I
1.6
o experimental data • mean velocity estimated from o - - - - COBRA calculation
1.4
G --
Ua
/I
1.2'
0
0
// O/
10t
O \ 0
0 0
0
0
0
0
- "
0.B
Ua : 16.5 f t / s Re : 9800
0.6 i , 10
0.4
1 i 20
i , 30
I
l
n
50
40
i
n
70
60
i
i
80
90
I
l
100
Axial distance (ins) blockage zone _J
I_
flow
1= I
1.6
G
grid
I
L
1.4 0
Us
1.2(
o
o
0
.]i
0
0
O
/I •
o
o
1.0t
0
•
•
•
t'\. B°~B~
0,8
•
Oa = 3.16ft/s
•
Re : 2000
0.6 0.4
i
i
10
20
i
i
30
i
40
50
I
i
60
i
i
70
i
i
80
i
i
90
I
i
100
Axial distance (ins)
Fig. 13. Experimental and calculated axial velocity distributions for subchannel 22.
M.1, Ang, A. Aytekin, A.H. Fox / Analysis of flow distribution (2) fluence the downstream flow recovery process, indeed the recovery to an undisturbed profile appeared to be more rapidly achieved.
tion in the profiles and downstream, the redevelopment of these profiles followed the same pattern. Consistent with the velocity data, only in the immediate vicinity of the blockage zones did the turbulence intensity profiles showed marked differences. Immediately upstream, a comparison of the data for # 4 (fig. 8 and fig. 11 [3]) showed that the effect due to the coplanar blockage was much more pronounced with the flow being more turbulent. At # 5 , measurements in the subchannels sur-
3.2. Turbulence intensity profiles Generally, the turbulence intensity profiles for the coplanar and non-coplanar blockage geometries were similar. Upstream of the blockage there was little varia-
blockage zone grid
flow
I I
1.6
UB = 16.5 f t / s Re = 9800
1.~, 1.2
O \o
1.01
o oooo
-~---.IL.
O0 " ~ , , "
0
"~ .~,,~r
o
o
0 ~..,~.. *~ PI~
•
•
•
•
0.8
o experimental data • mean velocity estimated from o - - - - - COBRA calculation
0.6
OA.
I
I
10
!
,
i
20
30
,
I
,
/
40
,
I
50
,
60
I
i
70
80
I
,
.
l
90
100
Axiat distance (ins)
btockage zone flow
]<::~Z~>I"
I..-- grid
I 1.6
Us = 3.18 f t / s
I
Re - 2000
1.4
o ~
1.2
O
0 O0//
Us
o
"~-~.==! \ o ?...~._
i'
,
0
I
10
,
i
20
O
O
0 •
30
40
309
t
50
o
" I
!
60
I
L
I
70
80
90
i
I
100
Axiat distance (ins)
Fig. 14. Experimental and calculated axial velocity distributions for subchannel No. 23.
310
M.L. Ang~ A. Aytekin, A.H. Fox / Analysis of flow distribution (2)
rounding the 4 × 4 blockage (fig. 9 and fig. 12 [3]) showed remarkably similar levels of intensities. Downstream from the blockage at # 7 (fig. 10 and fig. 13 [3]), where some maximum intensity values were measured, unlike the coplanar case, the non-coplanar profiles displayed asymmetry. These profiles showed a shift towards the positions corresponding to subchannels 1, 2 and 3. This behaviour, due to the higher flow area restriction in these three subchannels, was consistent with the velocity data. At # 8 and # 9, the non-coplanar
profiles began to regain symmetry but still displayed relatively higher turbulence intensity values. Comparison of results for ~ : 1 0 - ~ 13 subsequently showed similar characteristics for both geometries• It can therefore be concluded that, similar to the results for the coplanar arrangement, the undisturbed turbulence intensity profiles were also regained at # 13 for the non-coplanar configuration. As in the previous studies [1,3], the turbulence intensity profiles were found to be influenced by the pres-
blockage zone
I--
flow
g,id I
1.6
Ua = 16.5 f t / s Re = 9800
1.4
0
O0
U. 1.2
0
0
O0
0
0
O0
0
0
O
O
I
. ~ .
0
1.0:
•
o experimental data • mean velocity estimated from o m COBRA calculation
0.8 _. 0.6 ,
0.4
I , 10
i
I
I , 30
20
I
I
I
40
I
50
I
I
60
70
i
I
I
80
I
]
I
~
~-~
i
I
90
Axial distance (ins)
100
blockage zone
-i
flow
t-
I
1.6
0
grid
:
Ua = 3.18 f t / s Re = 2000
1.4 O
UB
OOO
O
O
O
1.2
O
O
Oo
O
..i"_'~,.. • ,.=-.-..~ • ~...
1.0
•
O O
•
"=
•
•
.
0.8
0.6 0.4
, 0
I
I
I
10
20
30
i
I
40
L
I
I
l
I
50
60
70
80
i
I
90
100
AxiaL distance (ins)
Fig. 15. Experimental and calculated axial velocity distributions for subcharmel No. 29.
M.I.. Ang A. Aytekin, A.H. Fox / Analysis of flow distribution (2) ence of grids and more significantly at the lower Re. This grid effect was clearly demonstrated by profiles at # 1 and #12.
flow area for the nonmcoplanar arrangement, a description was also provided in the model to account for the variation in the gaps between the subchannels within the ballooned zone. In the following discussion, S denotes the subchannel sequencing specified in fig. 16 [3].
4. Comparison with COBRA computer code calculations The half bundle, 36 subchannel model used in the 61% coplanar study [3] was similarly used in this noncoplanar bundle flow calculation. Together with a specification of the axial distribution of subchannel
4.1. Velocity data comparison In addition to figs. 13-16, which show the comparison of axial velocity profiles for subchannels $22, $23,
blockage zone
flow
I--- grid
"
i
~ = 16.5 f t / s Re : 9600
J
1.6 1.~, O0
1.2
0
0 °/~m
0
O0
0
0
0
0
0
o
0
Ue m . ~
1.0
\.L.m"m--'ai'"
• ...i~l.
=
. •
o experimental data m mean velocity estimated from o m . _ _ COBRA calculation
0.6 0.6 0.~,
I
J
I
I
10
20
I
I
30
,
q
I
I
I
I
E0 50 60 Axial distance (ins)
I
70
I
I
80
I
I
:
90
100
blockage zone grid
I 1.6
Um : 3,18 f t / s Re : 2000
1.4
O
O O
0_ Ue
1.2 1.01
m 0
0 0
0
°A'=.
o
o
B
B
0
"---i'"~= • /
\ --.=-~..~ oO °
0
O
=
=
O
0.8 0.6
0.4
!
10
t
I
Z0
i
|
30
I
|
|
l
311
i
!
/,0 50 60 Axial distance (ins)
I
i
70
l
I
00
I
I
90
I
I
100
Fig. 16. Experimental and calculated velocity distributions for subchannel No. 24.
312
M.L Ang, A. Aytekin, A.H. Fox / Analysis of flow distribution (2) Coplanar blockage zone I~
1.6 _1
I
I r'---
I
Non-copla.nar blockage zone
1A
J_
grid
I Us : 16.5 f t / s Re = 9800
1.2
UB 1.0
i~
0.0
~ o e ~ _ . . ~ ~
.~"
-
SubchannelNo. o • •
Non-Coplanar
61% Copianar . . . . .
0.6
0./*
'
0
I
10
,
I
20
,
I
30
I
I
~,0
t
I
I
I
50 60 Axial distance (ins)
,
I
70
I
I
80
22 17 23
22
I
I
,
90
I
100
Fig. 17. Comparison of calculated axial velocities for some subchannels within the 4 × 4 blockage cluster.
$29 and $24, fig. 17 and fig. 18 are also included to highlight some of the departures from the coplanar flow distributions predicted by COBRA. The axial velocity comparison for the four selected subchannels showed that generally the COBRA predicted flow profiles agreed consistently with the experimental values. As in the coplanar bundle flow analysis [3], the calculation failed to predict the Re dependency characteristic of the downstream flow immediately after the blockage zone. Due to the uncertainty of this downstream flow redevelopment at the lower Re, the inadequacy in the modelling also led to less favourable comparison. As shown in fig. 17, COBRA predicted that the flow disturbance due to the presence of the non-coplanar blockage was less severe than the corresponding coplanar geometry. Velocities both immadiately upstream and downstream of the blockage were about 15% higher for the non-eoplanar geometry. The non-coplanarity caused less fluid to bypass the blockage thereby resulting in higher blocked subchannel mass flows of about 10%. Although the slightly lower magnitude of the maximum velocity within the non-coplanar blockage zone could not be experimentally verified, it was consistent with the data presented in fig. 2. Greater flow areas were available than for the corresponding coplanar geometry
thereby resulting in lower flow restriction. Although the non-coplanar blockage zone was effectively extended axially by a further 4 × rod diameter, the flow recovery process downstream of the blockage not only was unhindered but actually accelerated. The COBRA predictions were consistent with the experimental findings. Fig. 18 shows the predicted cross-sectional velocity profiles at two experimental stations to demonstrate the effect of non-coplanarity in the ballooned cluster. At # 5 , whilst the predicted velocity patterns at various traversing levels for the coplanar geometry remained essentially unchanged, those for the non-eoplanar case displayed significant variation. With the coplanar blockage terminating at # 6 , the velocity profiles differed markedly from those of # 5, indicating the start of the downstream flow recovery process. The results at # 6 for the non-coplanar bundle also differed appreciably from those of # 5 , reflecting the influence of the irregularly shaped and staggered flow paths. Consistent with the experimental evidence, the COBRA analysis showed that, the general effect on the flow profiles was small with the introduction of noncoplanarity. The effect on the velocity profiles immediately upstream and downstream of the blockage and within the blockage was less severe than for the
Us
o_.
Ua
u_
0.8
I ~,
0.4
4
I
Traverse
0
0
o---
8
I
. ~ _
I
I
i
- - - = _ _ .
0.4
0.8
1.2
4.
1
I 0.4 [ 12 Data point location /* 1.6
0.8
1.2
0.41
I 8
I 12
.....
I 12
I 12
1.6
0.4
0,0
1.2
0.4
0.6
~__ 1.2 Us=
Ua
_o
1.6
0.4,
0
0
Us= 0.0!
1.2
1.6
.,,
I
4
I
I
8
8
|
Traverse 6
I
8
I
Traverse 5
4
Traverse 4
COPLANAR
Fig. 18. Calculated velocity profiles at axial stations 5 and 6.
o - - .
I 6
I 6
___~ . . . . . .
NON-COPLANAR
12 Data point location 4 1.6
o.el-
1,2I~-
1.6
Data point location Axial station 5, Re = 9600
8
=
Traverse 6
° ~
I
Traverse S
COPLANAR
0.6
1.2
1,6
0.4
0.8
1.2
1.6
0A
Us=
0 1.2
1.6
8
8
4
I
I
I
I
6
I
0.4.
0.8
1.2
1.6
Data point location
0.4
0"8I
1.2
4
1
. - - -
___,..-
NON-COPLANAR
4 Data point location Axial station 6, Re = 9000
i
I
. . - - - -
0.4 Data point location 1.6[
- - - .
I
0.8
1.2
1.6
12
I
12
I
I
12
--..
314
M.L. An~ A. Aytekin, A.H. Fox / Analysis of flow distribution (2)
coplanar situation. The experimental and theoretical analyses further suggested that bundle flow behaviour was more strongly influenced by the severity of flow area restriction than the degree of non-concentricity and distortion of the flow passages.
from the end of the coplanar blockage sleeve. The results of this study further suggested that bundle flow behaviour was more strongly influenced by the severity of flow area restriction than the degree of non-coplanarity and distortion of the flow passages.
5. Conclusions
Nomenclature
This experimental programme has provided data related to the flow disturbance caused by a short noncoplanar blockage in a 7 × 7 rod bundle. The flow disturbance was found to display many features similar to those from a previous study using a short coplanar blockage. The COBRA computer code was shown to predict flow profiles consistent with the experimental data. This investigation showed that the introduction of non-coplanarity in a blockage did not result in significant deviation from the overall bundle flow behaviour due to a coplanar blockage. The effect on the flow immediately upstream and downstream of the blockage and within the blockage was less severe than for the coplanar configuration. As a result, the flow diversion from the non-coplanar blockage to the surrounding subchannels was less. The non-coplanar blockage zone, despite being effectively longer, did not adversely influence the downstream flow recovery process. Indeed the recovery to an undisturbed profile seemed more rapidly achieved. Complete flow recovery was achieved for both geometries at the same axial experimental location at a distance equivalent to 33 × rod diameter
Re Reynolds number based on the equivalent diameter of an unblocked subchannel, U local subchannel mean velocity, Un bundle average velocity, u fluctuating velocity in the axial direction.
References
[1] M.L. An8, A. Aytekin and A.H. Fox, Analysis of flow distribution in a PWR fuel rod bundle model containing a 90~ blockage, Nucl. Engrg. Des. 103 (1987) 165-188. [2] L.E. Hochreiter, R.A. Basel, R.J., Dennis, N. Lee, H.W. Massie, Jr, M.J. Loftus, E.R. Rosal and M.M. Dalkovic, PWR FLECHT SEASET 21 rod bundle flow blockage task: Task plan report, NRC/EPRI/Westinghouse Report No. 5, NUREG/CRo1370, NP-1382, WCAP-9658 (1980). [3] M.L. An8, A. Aytekin and A.H. Fox, Analysis of flow distribution in a PWR fuel rod bundle model containing a blockage, Part. 1, Nucl. Engrg. Des. 108 (1988) 275-294, preceding article in this issue. [4] I.H. Gibson, P. Coddington , T. Healey and C.A. Mann, The UK-MT-3 ballooning test in the Battelle NRU loop, Rept. No. AEEW-R-1506, AEE Winfrith (1982).