Adding value through knowledge © NNC Limited September 2002International PHOENICS User Conference 1...

September 2002 International PHOENICS User Conference

1

Adding value through knowledgeAdding value through knowledge

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A PHOENICS model of the hotbox region of A PHOENICS model of the hotbox region of an advanced gas-cooled nuclear reactoran advanced gas-cooled nuclear reactor

byby

G HulmeG Hulme

NNC LtdNNC Ltd


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Content of presentationContent of presentation

Description of the problemDescription of the problem Description of the PHOENICS modelDescription of the PHOENICS model

– meshmesh

– modelling of complex standpipe regionmodelling of complex standpipe region Results for three cases are presentedResults for three cases are presented Comparison against experimental measurementsComparison against experimental measurements

– velocity fieldvelocity field

– trace gas concentrationtrace gas concentration


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The AGR hotbox regionThe AGR hotbox region

Hot gas from reactor fuel channels mixes before entering Hot gas from reactor fuel channels mixes before entering boilersboilers

Geometry Geometry

– cylindricalcylindrical

– square array of 332 fuel channel standpipes at centresquare array of 332 fuel channel standpipes at centre

– outer ring of 12 boilersouter ring of 12 boilers

– gas baffle domegas baffle dome NNC 1/8th scale modelNNC 1/8th scale model


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September 2002

Side view of NNC 1/8th scale modelSide view of NNC 1/8th scale model


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September 2002

Plan view of hotboxPlan view of hotbox

Boilers

Standpipes


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PHOENICS modelPHOENICS model

Cylindrical domain with multi-block meshCylindrical domain with multi-block mesh Uses GCV method to solve for Uses GCV method to solve for

– pressure,pressure,

– 3 velocity components,3 velocity components,

– k-k- turbulence model, turbulence model,

– trace gas concentrationtrace gas concentration SMART higher-order scheme for velocities and concentrationSMART higher-order scheme for velocities and concentration Initial development on single-quadrant modelInitial development on single-quadrant model Extended to 4-quadrant modelExtended to 4-quadrant model


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Computational meshComputational mesh

Multi-block mesh with body-fitted co-ordinatesMulti-block mesh with body-fitted co-ordinates Central square block allows modelling of standpipesCentral square block allows modelling of standpipes Outer blocks allow fitting of mesh to boilers and outer Outer blocks allow fitting of mesh to boilers and outer

shellshell Single-quadrant 3-block model Single-quadrant 3-block model 4-quadrant 5-block model 4-quadrant 5-block model Mesh is generated by Mesh is generated by SATELLITESATELLITE inter-active facility inter-active facility

followed by modification of followed by modification of XYZXYZ files by specially written files by specially written programs.programs.


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September 2002

Single quadrant mesh Single quadrant mesh - block arrangement- block arrangement

Boiler 5

Boiler 7

Boiler 6

Block 1

Block 3

Block 2


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September 2002

Mesh in horizontal plane, single Mesh in horizontal plane, single quadrant modelquadrant model


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Modelling of standpipe regionModelling of standpipe region

Approximate model of a complex regionApproximate model of a complex region Each standpipe modelled by 3Each standpipe modelled by 33 array of cells3 array of cells Mesh areas adjusted to match area of inlet jetsMesh areas adjusted to match area of inlet jets Cross-flow pressure drop modelled by resistance sources Cross-flow pressure drop modelled by resistance sources

with directional magnitudewith directional magnitude Turbulence modellingTurbulence modelling

– source term for source term for kk making making k~0.28vk~0.28v22

set to give length scale based on passage width so set to give length scale based on passage width so

that that L = 0.1(P-D)L = 0.1(P-D)

DP

VCS tk

k

2


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September 2002

Mesh in vertical plane through Mesh in vertical plane through standpipe regionstandpipe region


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September 2002

Mesh for 4 quadrant modelMesh for 4 quadrant model


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Calculations performedCalculations performed

A1A1 Symmetrical operation with trace gas injection at Symmetrical operation with trace gas injection at a single standpipe using single-quadrant modela single standpipe using single-quadrant model

A2A2 Symmetrical operation with enhanced flow from Symmetrical operation with enhanced flow from a single empty channel using single-quadrant modela single empty channel using single-quadrant model

BB 3-quadrant operation using the 4-quadrant model 3-quadrant operation using the 4-quadrant model with a coarse mesh.with a coarse mesh.


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September 2002

Results - Symmetrical operation, Results - Symmetrical operation, Vectors in plane between boilersVectors in plane between boilers


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September 2002

Results - Symmetrical operation, Results - Symmetrical operation, Vectors in plane through a boilerVectors in plane through a boiler


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September 2002

Results - Symmetrical operation, Results - Symmetrical operation, Vectors in horizontal plane below Vectors in horizontal plane below boiler inletboiler inlet


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September 2002

Comparison of radial velocity Comparison of radial velocity profiles in plane between boilersprofiles in plane between boilers

Radial velocity profiles in vertical plane at 32.1degrees, between boilers

0 200 400 600

Depth below roof mm

Rad

ial velo

cit

y in

terv

al 10 m

/sMeasurement 1208 mm radiusPHOENICS

Measurement 1165 mm radiusPHOENICS





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September 2002

Comparison of radial velocity Comparison of radial velocity profiles in plane through a boilerprofiles in plane through a boiler

Radial velocity profiles in vertical plane at 75 degrees, through centre of boiler

0 200 400 600

Depth below roof mm

Rad

ial velo

cit

y in

terv

al 10 m

/sMeasurement 1208 mm radiusPHOENICS






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Discussion of results - velocityDiscussion of results - velocity

Flow pattern well representedFlow pattern well represented Velocity fields in reasonable agreement with Velocity fields in reasonable agreement with

measurementsmeasurements Main discrepancy is underprediction of velocity of jet Main discrepancy is underprediction of velocity of jet

from top of standpipe region from top of standpipe region CausesCauses

– smearing of velocity distribution downstream of smearing of velocity distribution downstream of

standpipesstandpipes

– modelling of standpipe region flow distributionmodelling of standpipe region flow distribution


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September 2002

Results - Symmetrical operation, Results - Symmetrical operation, Trace gas injection at one standpipeTrace gas injection at one standpipe


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September 2002

Comparison of trace gas Comparison of trace gas concentration profilesconcentration profiles

Trace gas concentration variation with depth at 32 degrees, radius 823 mm

0

20

40

60

80

100

120

140

0 100 200 300 400 500 600

Distance below model roof mm

Co

nce

ntr

atio

n*1

000

Measurement PHOENICS model

Trace gas concentration variation with angle at depth of peak concentration

0

20

40

60

80

100

120

140

160

0 10 20 30 40 50Angle

Co

nce

ntr

atio

n*1

000

MeasurementPHOENICS


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September 2002

Results - symmetrical operation Results - symmetrical operation with empty channel flowwith empty channel flow

Distribution of empty channel flow at boilers

0

10

20

30

40

50

60

70

80

1 2 3 4 5 6a 6b 7 8

Boiler

Em

pty

ch

ann

el f

low

%Measured

Code


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Discussion of results - concentrationDiscussion of results - concentration

Trace gas plume fairly well modelled Trace gas plume fairly well modelled Main discrepancyMain discrepancy

– plume slightly too low plume slightly too low

– diffusion slightly too weak.diffusion slightly too weak. CausesCauses

– velocity field in jet from standpipe regionvelocity field in jet from standpipe region

– turbulence level in flow leaving standpipe regionturbulence level in flow leaving standpipe region Distribution of empty channel flow at boilers is well Distribution of empty channel flow at boilers is well

predictedpredicted


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ConclusionConclusion

A PHOENICS model of the AGR hotbox region has been A PHOENICS model of the AGR hotbox region has been described.described.

The model uses a multi-block mesh with body-fitted co-The model uses a multi-block mesh with body-fitted co-ordinates.ordinates.

An approximate model of the complex standpipe region is An approximate model of the complex standpipe region is used.used.

It has been shown that the model gives reasonably good It has been shown that the model gives reasonably good representations of representations of

– the velocity fieldthe velocity field

– the trace gas concentration fields.the trace gas concentration fields. The extension of the model to a four-quadrant asymmetric The extension of the model to a four-quadrant asymmetric

case has been demonstrated.case has been demonstrated.

Adding value through knowledge © NNC Limited September 2002International PHOENICS User Conference 1...

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Transcript of Adding value through knowledge © NNC Limited September 2002International PHOENICS User Conference 1...