Multiphase Flow Heat Transfer in Fuel Assemblies January 2014 ASCOMP; ASCOMP Inc. USA, ...
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![Page 1: Multiphase Flow Heat Transfer in Fuel Assemblies January 2014 ASCOMP; ASCOMP Inc. USA, transat@ascomp.ch.](https://reader038.fdocuments.in/reader038/viewer/2022110323/56649d8b5503460f94a72e09/html5/thumbnails/1.jpg)
Multiphase Flow Heat Transfer in Fuel Assemblies
January 2014ASCOMP; ASCOMP Inc. USA, www.ascomp.ch [email protected]
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The Westinghouse 24-rod mock-up of SVEA-96 fuel bundle Caraghiaur & Anglart (NED, 2009)
The Westinghouse 24-rod mock-up
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The Westinghouse 24-rod mock-up of SVEA-96 fuel bundle
• KTH Stockholm (CFX, 1.300.00 cells)
The Westinghouse 24-rod mock-up
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• ASCOMP (TransAT, IST MESH). From CAD (left) to OST grid (right). Note that the very coarse mesh shown in right is for illustration only.
The Westinghouse 24-rod mock-up
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• ASCOMP (TransAT, 1.400.00 cells)
The Westinghouse 24-rod mock-up
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• KTH Stockholm (CFX) • ASCOMP (TransAT)
-30 -20 -10 0 10 20 3015000
20000
25000
30000
35000
40000
45000 0º E xp.-135º E xp.Trans at s harp IS T dy40mm m1Trans at s harp IS T dy200mm m2Trans at s tandard IS T dy40mm m1
Dis tance from the middle of s pacer, [mm]
Pre
ssur
e, [k
Pa]
The Westinghouse 24-rod mock-up
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The OECD PSBT 5x5 Benchmark with 3 spacers (3 million cells, K-e model)
The OECD PSBT 5x5 Benchmark
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The OECD PSBT 5x5 Benchmark
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The OECD PSBT 5x5 Benchmark
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Flow field and heat contours downstream the 1st simple spacer
The OECD PSBT 5x5 Benchmark
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Flow field and heat contours downstream the 1st mixing vane
The OECD PSBT 5x5 Benchmark
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The OECD PSBT 5x5 Benchmark
![Page 13: Multiphase Flow Heat Transfer in Fuel Assemblies January 2014 ASCOMP; ASCOMP Inc. USA, transat@ascomp.ch.](https://reader038.fdocuments.in/reader038/viewer/2022110323/56649d8b5503460f94a72e09/html5/thumbnails/13.jpg)
NUPEC PWR Test Facility
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Problem Description (PSBT OECD)
Heat flux q”
Flow outletFuel Rod
L=1000 mm
flow cross section
r=5 mm
P=13.0 mm
Fig. 1. Computational domain: Dimensions & BC’s.
Benchmark definition within CASL: Lakehal & Buongiorno, 2011: main changes: length reduced to 1m from 3m, power to 1.6kW from 7 MW, and thus Re=GDe/ 4.8105 to 1.0104
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Pressure 15.5 MPaSaturation
temperature344.6C
Inlet temperature 290CMass flux 3333 kg/m2sHeat Flux 581 kW/m2
Power 7. MW
Pressure 15.5 MPaSaturation
temperature344.6C
Inlet temperature 290CMass flux 74.1 kg/m2s (or Re=300)Heat Flux 50 kW/m2
Power 1.57 kWTable 2: Downscaled operating flow Cdts. for LES
Table 1: Reference operating Cdts. for PSBT OECD cases (Rubin et al., 2010).
Problem Description (PSBT OECD)
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Ret=300
Number of nodes ResolutionGrid type
total number of cellsx-y z Dx+
--Dy+ N blocks
Grid Med
40-40
798 0.5-2.1 208 BFC1,317,40
0Grid Fine
60-60
1.600 0.4-1.5 832 BFC6,011,20
0
q=00
q=450
Figure 3. Medium (left) and fine (right) grids for LES (x-y). Arrows show 00 and 450 segments
Flow along a heated single rod at Re*=300
• SGS model: LES (Dynamic SGS model) • Schemes: Central 2nd order; RK 3rd order in time• Adaptive time-stepping ~ Dt = 0.0001s (CFL = 0.1-
0.3)• Days on the DOE Jaguar on 144 and 832 MPI // cores
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Figure 4. Fine vs. medium resolutions (non-scaled domain): Instantaneous cross-sectional velocities and temperature contours.
Results
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• Fine grid: instantaneous Fine grid: time average
• Medium grid: instantaneous Medium grid: time average
Results
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• Fine grid: instantaneous Fine grid: time average
• Medium grid: instantaneous Medium grid: time average
Results
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Medium grid Fine grid
Figure 7a. Mean velocity profiles across the subchannel (00 & 450) compared to the DNS of Eggels (1994).
Results (comparison with DNS of pipe flow)
Medium grid: 0 and 450 Fine grid: 0 & 450
Figure 7b. Time averaged normal-stresses profiles (<w’w’>)
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Quantity Medium grid Fine grid Analytical/Exp.
Pressure drop DP [Pa]
10.223 10.52 ~ 10.0
Heat transfer coefficient (HTC) at XONB
[kW/m2K]
1.495
1.535
1.62 (Colburn) 2.16 (Col-W*)
1.44 (Gnielinski) 1.99 (Gnlsk-W) 1.50 (Petukov)
2.00 (Ptkov-W)
Distance to XONB [m] Min-max0.49–0.57
Min-max0.49–0.6
~ 0.59 (Colburn)~ 0.79 (Col-W)
Thermal entry length [m]
Min-max0.21–0.28
Min-max0.21–0.29
~ 0.29–0.46
*W means with the Weisman (1959) correction factor
Global Results
=1.826p/D-1.043=1.33
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Convective boiling phenomenon: The physical reality of turbulent confined bubbly flow is way more complex than the idealized conditions considered in two-phase flow studies (smooth or sinusoidal wavy films, spherical or elliptic droplets and bubbles, etc.). Turbulence-bubbles interactions is mysterious!
Bubble layer in high-subcooling, high-mass-flux, high-pressure, flow boiling of Freon near the point of DNB. The situation is qualitatively similar to the PWR hot channel during a transient overpower event.
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Iso-contours of transport quantities, including liquid and vapour temperature. 2D Axisymmetric simulations TransAT.
Bubbly-flow boiling: Debora test case (CEA)
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Test Case: DEBORA Experiments of Manon et al (2000, 2001)
Pipe Length: 5mPipe Diameter: 19.2 mm
Bubbly-flow boiling: Debora test case (CEA)
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Void Fraction for Case 2 & 3: Tin = 58.4 C and 63.4 C
Void Fraction for Case 4 & 5: Tin = 67.9 C and 70.14 C
Void Fraction for Case 6 & 7: Tin = 72.6 C and 73.7 C
Bubbly-flow boiling: Debora test case (CEA)
There are differences between the 2-fluid & the N-phase homogeneous models. Same grid, same turbulence model, same comp. parameters.
All models fail near the wall for Tin=73.7 C
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Test Case: Experiments of Lee, Park & Lee (2002) and Tu & Yeoh (2003)
Bubbly-flow boiling: Lee et al. & Tu & Yeoh (KAERI)
Heat flux mass flux Tinlet Tsat
MW/ m2 kg/m2/s K K
0.1523 474 371.5 383
a
Norm. Radial distance
• Pipe Length: 2.376m• q=152.3 kW/m2
• Gl=474 kg/(m2s)• P=0.14 Mpa• ΔTsub=11.5 K.
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Bubbly-flow boiling: Bartolomei Test Case
Test Case: Experiments of Bartolomei et al (1982)
• Pipe Length: 1.4m• Heated Length = 1m• q =1.2 MW/m2
• Gl= 1500 kg/(m2s)• P = 6.89 Mpa• ΔTsub= 63 K.
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Heat transfer in tube buddle in a steam generator 3D Setup (SNERDI)
Geometry of the flow field
Location and size of tube and supports
Hot water
Cold water
Cold water
Cross-Sectional view of support * * Coarse grid is shown to illustrate
the cross-section
Conjugate heat transfer through the tube to heat the cold water where phase change occurs.
Cold water• P2=5.8MPa• Tf=259 ℃• va=0.63 m/s• Tsat = 271 ℃
Hot Water • P1=15.5MPa • Ti= 322℃• vi=5.3m/s
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Heat transfer in tube buddle in a steam generator 3D Results (SNERDI)
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Testcase
Pressure
[MPa]
Inlet Tem
p[°C]
Power
[kW]
Mass Flux
[kg m-2s-1]
1.2211 15295.
490 11
1.2223 15319.
670 11
1.2237 15329.
660 11
1.4411 10238.
960 5
1.4325 10253.
860 2
1.4326 10268.
860 5Cell
Size (in mm)
No. of Cells
No. of
Processors
Wall Clock Time
(in days)
5.31 9216 1 0.332.655
73728 8 0.75
1.328
1280000
108 1.5
0.885
2880000
128 4
NUPEC PWR Test Facility: Phase average
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a) ∆x = 2.65mm b) ∆x = 1.328mm ) ∆x = 0.885mm
Steady State void fraction profiles for different grids (Testcase: 1.2237).
NUPEC PWR Test Facility: Phase average