Transcript Experimental Verification of Gas-Cooled T

Update on Thermal
Performance of the GasCooled Plate-Type Divertor
M. Yoda, S. I. Abdel-Khalik,
D. L. Sadowski and M. D. Hageman
Woodruff School of Mechanical Engineering
Objective / Motivation
Objective
• Experimentally evaluate and validate thermal performance of
gas-cooled divertor designs in support of the ARIES team
Motivation
• Leading divertor designs rely on jet impingement cooling to
achieve desired performance
• Accommodate heat fluxes up to 10 MW/m2
• Performance is “robust” with respect to manufacturing
tolerances and variations in flow distribution
• Extremely high heat transfer coefficients (~50 kW/(m2K))
predicted by commercial CFD codes used for the design
• Experimentally validate such numerical predictions
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Approach
• Design and instrument test modules that closely
match divertor geometries
• Conduct experiments at conditions matching and
spanning expected non-dimensional parameters for
prototypical operating conditions
– Reynolds number Re
– Use air instead of He
• Measure temperature distributions and pressure drop
• Compare experimental data with predictions from
CFD software for test geometry and conditions
– Nu(Re), P*(Re)
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Some History
Investigated leading gas-cooled divertor designs
• FZK Helium-Cooled Multi-Jet (HEMJ) “Finger”
[Norajitra et al. 2005]
– Ihli et al. 2007; Crosatti et al. 2009
• ARIES-CS T-Tube
[Ihli et al. 2007; Raffray et al. 2008]
– Crosatti et al. 2007; Abdel-Khalik et al. 2008; Crosatti et al.
2009
• ARIES-Pathways Plate-Type Design
[Malang; Wang et al. 2009]
– Variant with metal open-cell foam: Gayton et al. 2009
[Sharafat et al. 2007]
– Variant with pin-fin array: In progress
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Outcomes
• Enhanced confidence in predicted performance by
commercial CFD codes at prototypical and offnormal operating conditions
– FLUENT®
• Use validated CFD codes to optimize/modify
divertor designs
• Predict sensitivity to changes in geometry and
operating conditions to define and establish
manufacturing tolerances
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Plate-Type Divertor Design
• Covers large area (2000 cm2 = 0.2 m2): divertor area
O(100 m2)
20
– HEMJ, T-tube
cool 2.5, 13 cm2
– Accommodates
up to 10 MW/m2
without exceeding
Tmax  1300 °C, max  400 MPa
Castellated
W armor
0.5 cm thick
100 cm
– 9 individual manifold units with ~3 mm
thick W-alloy side walls brazed together
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GT Test Module
Armor
• Jet issues from 0.5 mm slot, then
impinges on and cools underside
of W-alloy pressure boundary
In
Out
– Coolant flows along 2 mm gap,
exits via outlet manifold
– Original design [Malang 2007]
– Use air as coolant
– Reynolds number Re =
1.1104– 6.8104 (vs. 3.3104 at
nominal operating conditions)
– Nominal heat flux qnom = 0.2–
0.75 MW/m2
Heated brass shell
In
Out
Al inner cartridge
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Al Inner Cartridge
• Inlet, outlet manifolds embedded
inside Al cartridge
– Manifolds 19 mm  15 mm  76.2 mm
– 2 mm  76.2 mm slot
– Coolant enters outlet
manifold via holes
– Side wall bolted on
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Brass Outer Shell
• Models pressure boundary
– 5 TC in shell to measure cooled
surface temperature distribution: 2 in
center; (1,5) and (3,4) at same depth
0.5 mm from surface
– Brass shell heated
by heater block
– k for brass
similar to
that of W-alloy
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Pin-Fin Array
• Can thermal performance of leading
divertor designs be further improved?
– Mo open-cell foam in 2 mm gap increased
HTC by 40–50%, but also increased P* by
similar fraction
[Gayton et al. 2009]
– In HEMP, a variant of HEMJ, coolant
impinges on pin-fin array [Diegele et al. 2003]
• Combine plate with pin-fin array
– 808 1.0 mm  2.0 mm pin fins (nearly)
contacting Al cartridge on 1.2 mm pitch
– 2 mm “clear” area for impinging jet
– Pin fins EDM’ed into inside of brass shell
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Heated Test Section
Copper
heater block
Graphite
shim
Brass
outer shell
Gasket
Aluminum
cartridge
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GT Air Flow Loop
Outlet P, T
measurement
Inlet P, T
measurement
Cu heater block
• 3 cartridge heaters
• 6 TC in neck measure q
• 2 TC at top monitor max.
Cu temperature
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Effect of Pin Fins
• Nu from TC data
Nu
– Nearly uniform T along
slot
– Nu based on gap width, k
at 300K and effective
HTC (for pin fins)
Pin fins
Bare surface
• qnom = 0.2–0.75 MW/m2
 TC 1
 TC 2
 TC 3
 TC 4
 TC 5
Nominal
operating
condition
Re (/104)
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Comparison: Pins vs. Bare
Nup / Nu
Pp* / P *
• Ratio of Nu and P for
cooled surface with,
without pin-fins
• Pin-fins with ~260%
more surface area
improve cooling
performance by
~150%–200% while
increasing pressure drop
by ~40–70%
Mass flow rate [g/s]
Nominal
operating
condition
Re (/104)
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Summary
• Designed and studied experimental test modules
modeling leading He-cooled divertor designs
– T-tube, HEMJ “finger,” plate
– Conducted dynamically similar thermal-hydraulics
experiments matching and spanning expected prototypical
operating conditions
• Used commercial CFD software to predict
performance of experimental test modules
– Good agreement between experimental data and model
predictions (including those from other groups)
– Use validated codes to predict performance of gas-cooled
components with complex geometries
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Conclusions
• Plate-type divertor + pin-fin array promising design
– Smaller number of divertor modules required  reduced
cost, complexity
– Two- to three-fold enhancement by pin fins  can
accommodate heat fluxes much higher than 10 MW/m2
• Initial results for un-optimized configuration: use
CFD to suggest improvements to current experimental
design
– Effect of pin pitch, diameter
– Effect of slot width
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Next Steps
To complete ARIES-Pathways study:
• Validate CFD codes (e.g. FLUENT) and plate models
with experimental data
– Model pin-fin array
• Use validated CFD codes to optimize/modify pin-fin
layout
– Predict maximum heat flux that can be accommodated by
optimized pin-fin/plate-type divertor
– Predict pressure drop across optimized pin-fin array
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