Experimental Validation of Experimental Validation of Thermal Performance of Gas-Thermal Performance of Gas-

Cooled DivertorsCooled Divertors

ByByS. Abdel-Khalik, M. Yoda, L. Crosatti, S. Abdel-Khalik, M. Yoda, L. Crosatti,

E. Gayton, and D. SadowskiE. Gayton, and D. Sadowski

International HHFC Workshop, San Diego, CA International HHFC Workshop, San Diego, CA December 10-12, 2008December 10-12, 2008

22

Objective/MotivationObjective/Motivation

Primary objective:Primary objective: – To evaluate and experimentally-validate the thermal performance To evaluate and experimentally-validate the thermal performance

of leading Gas-Cooled Divertor Module Designsof leading Gas-Cooled Divertor Module Designs

Motivation:Motivation:– Leading gas-cooled divertor module designs rely on jet Leading gas-cooled divertor module designs rely on jet

impingement cooling to achieve the desired levels of performanceimpingement cooling to achieve the desired levels of performance

– Heat fluxes up to 10 MW/mHeat fluxes up to 10 MW/m22 can be accommodated can be accommodated

– Performance is “robust” with respect to manufacturing tolerances Performance is “robust” with respect to manufacturing tolerances and variations in flow distributionand variations in flow distribution

– Extremely high heat transfer coefficients (Extremely high heat transfer coefficients (~ 50 kW/m~ 50 kW/m22.K).K) predicted predicted by commercial CFD codes used for the designby commercial CFD codes used for the design

– It was deemed necessary to experimentally validate the numerical It was deemed necessary to experimentally validate the numerical results in light of the extremely high heat transfer coefficientsresults in light of the extremely high heat transfer coefficients

33

Approach/OutcomesApproach/Outcomes

Approach:Approach:– Design test modules that closely match the geometry of the proposed Design test modules that closely match the geometry of the proposed

leading divertor module designs leading divertor module designs

– Conduct experiments at conditions matching/spanning expected non-Conduct experiments at conditions matching/spanning expected non-dimensional parameter range for prototypical operating conditionsdimensional parameter range for prototypical operating conditions

– Measure detailed temperature distributionsMeasure detailed temperature distributions

– Compare experimental data to performance predicted by commercial CFD Compare experimental data to performance predicted by commercial CFD software for test geometry/conditionssoftware for test geometry/conditions

Outcomes:Outcomes:

– Enhanced confidence in predicted performance by CFD codes at Enhanced confidence in predicted performance by CFD codes at prototypical and off-normal operating conditionsprototypical and off-normal operating conditions

– Validated CFD codes can be confidently used to optimize/modify design Validated CFD codes can be confidently used to optimize/modify design

– Performance sensitivity to changes in geometry and/or operating Performance sensitivity to changes in geometry and/or operating conditions can be used to define/establish manufacturing tolerancesconditions can be used to define/establish manufacturing tolerances

44

All Leading Gas-Cooled Divertor DesignsAll Leading Gas-Cooled Divertor Designs

FZK Helium-Cooled Multi-Jet (HEMJ), FZK Helium-Cooled Multi-Jet (HEMJ), Norajitra, et al. (2005) Norajitra, et al. (2005)

ARIES-CS T-Tube Design, Ihli, et al. (2006)ARIES-CS T-Tube Design, Ihli, et al. (2006)

ARIES-TNS Plate Design, ARIES-TNS Plate Design, Malang, Wang, Wang, et al. (2008)– Metal-Foam-Enhanced Plate Design, Sharafat, Sharafat,

et al. (2007)et al. (2007)

ScopeScope

Case StudyCase Study

Plate-Type Divertor DesignPlate-Type Divertor Design

66

Plate Type Divertor DesignPlate Type Divertor Design

(Malang, Wang, et al., 2008)

Large modules

Only ~750 needed for ARIES-AT

Handles heat fluxes up to 10 MW/m2

High heat transfer coefficient: HTC w/slot jet impingement 3.9 x 104 W/(m2K)

Does not exceed temperature, stress limits

6

20 cm

100 cm

77

Open-cell Metallic Foam - promotes turbulent mixing and increases cooling Open-cell Metallic Foam - promotes turbulent mixing and increases cooling areaareaFoam is selectively located to minimize pressure dropFoam is selectively located to minimize pressure dropModular DesignModular DesignCan accommodate heat fluxes up to 10 MW/mCan accommodate heat fluxes up to 10 MW/m2 2 (predicted)(predicted)

(Sharafat et al., 2007)

SOFIT- SOFIT- SShort Flhort Floow-Path w-Path FFoam-oam-IIn-n-TTubeube

88

Test Module Design / VariationsTest Module Design / VariationsGT Test ModulesARIES Plate Design

(Malang 2007)

In

Out

Slot

2 mm

Slot w/ foamHoles

0.8 mm

5.86 mm

5.0 mm

Holes w/ foam

99

Test ModulesTest Modules

Al Inner Cartridge Brass Outer Shell

1010

Metal Refractory Open-Cell FoamMetal Refractory Open-Cell Foam

AdvantagesAdvantagesCustomizable pore size and porosity Customizable pore size and porosity – to optimize HTC/pressure dropto optimize HTC/pressure drop

High Surface AreaHigh Surface AreaLow Pressure DropLow Pressure Drop

GT specifics•Molybdenum•2 mm thick•45 ppi (70% porosity)•65 ppi (88% porosity)•100 ppi (86% porosity)

(Ultramet, 2008)

1111

Test Module AssemblyTest Module Assembly

1212

Five TCs (Five TCs (Ø 0.61 mm)Ø 0.61 mm) embedded just inside cooled brass surface to measure local embedded just inside cooled brass surface to measure local temperaturestemperaturesTC 2 at originTC 2 at origin

TCTC x x [mm][mm]

y y [mm][mm]

11 -4.5-4.5 -10-10

22 00 00

33 -8.5-8.5 1010

44 8.58.5 -5-5

55 4.54.5 55

z

3

2

14

5

14

53

2

Cooled Surface Temperature Cooled Surface Temperature MeasurementMeasurement

x

x

y

x

y

1313

Heat Flux MeasurementHeat Flux Measurement

Six TCs are embedded in Six TCs are embedded in the “neck” of the the “neck” of the concentrator to measure the concentrator to measure the incident heat flux.incident heat flux.

Two TCs are embedded in Two TCs are embedded in the top of the copper heater the top of the copper heater block to monitor the peak block to monitor the peak temperature of the copper.temperature of the copper.

1414

GT Air Flow LoopGT Air Flow Loop

Rotameter

RotameterPressure Gauge

DifferentialPressure

Transducer

Inlet

Tygon Tubing

ExitPressure Gauge

Outlet

Butterfly Valve

1515

ParameterParameterAir Air

(Holes)(Holes)Air Air

(Slot)(Slot)HeliumHelium(ARIES)(ARIES)

Operating PressureOperating Pressure[MPa][MPa] 0.1 0.1 –– 0.5 0.5 0.4 – 0.50.4 – 0.5 1010

Mass Flow Rate Mass Flow Rate [g/(s[g/(s··m)]m)] 61 – 34461 – 344 118 – 528118 – 528 702702

Inlet Temp. [Inlet Temp. [°C]°C] 23 23 2323 600600

Hydraulic Diameter Hydraulic Diameter DDhh [mm] [mm] 0.80.8 44 11

Re Re ((101044)) 1.1 – 6.81.1 – 6.8 1.3 – 6.8 1.3 – 6.8 3.3 3.3

PrPr 0.730.73 0.730.73 0.660.66

Thermal Hydraulic ParametersThermal Hydraulic Parameters

1616

0.0

50.0

100.0

150.0

200.0

250.0

-10 -5 0 5 10

x (mm)

Tem

per

atu

re (

C)

Holes-6 Slot-2

Slot vs. Holes Jet Geometry Slot vs. Holes Jet Geometry

(Reh = 66,000; Resl = 36,000)

havg_holes = 1.33*havg_slot

P’holes = 1.96*P’slot

MFR = 26 g/s

q” = 0.5 MW/m2

1717

Effect of 65 ppi Metal Foam Insert for Effect of 65 ppi Metal Foam Insert for

the the HolesHoles Test Configuration Test Configuration

0.0

50.0

100.0

150.0

200.0

250.0

-10 -5 0 5 10

x (mm)

Tem

per

atu

re (

C)

Holes-5

Holes-65-3

Holes-7

Holes-65-6

q” = 0.5 MW/m2

MFR = 13 g/s

MFR = 26 g/s

At MFR = 13 g/s, the avg. HTC enhancement with foam is 19%.

At MFR = 26 g/s, the avg. HTC enhancement with foam is only 7%

1818

Effect of 45, 65, and 100 ppi Metal Foam Effect of 45, 65, and 100 ppi Metal Foam Insert for the Slot Test ConfigurationInsert for the Slot Test Configuration

0.0

50.0

100.0

150.0

200.0

250.0

-10 -5 0 5 10

x (mm)

Tem

per

atu

re (

C)

Slot-2

Slot-45-3

Slot-65-2

Slot-100-2

Avg. HTC Increase

--

20%

42%

51%

1919

0.0

50.0

100.0

150.0

200.0

250.0

0.0 10.0 20.0 30.0 40.0 50.0

MFR (g/s)

Del

ta P

(kP

a) (R

esca

led

to

p_n

orm

= 4

14 k

Pa

Holes-65

Holes

Slot-100

Slot-45

Slot-65

Slot

Poly.(Holes)Poly. (Slot-65)Poly. (Slot)

Poly.(Holes-65)Poly. (Slot-100)Poly. (Slot-45)

Normalized Pressure DropNormalized Pressure Drop

R2 > 0.999 Decreasing ΔP'

2020

Comparison Between Test ConfigurationsComparison Between Test Configurations

MFR = 9 g/sMFR = 9 g/sΔΔP'P'

(kPa)(kPa)% Inc. % Inc. ΔΔP’P’

(-)(-)hhavgavg

(W/m(W/m22-K)-K)% Inc % Inc hhavgavg

(-)(-)

Slot-100Slot-100 14.814.8 136%136% 28752875 71%71%

Slot-65Slot-65 11.711.7 87%87% 25542554 52%52%

Holes-65Holes-65 32.432.4 415%415% 23632363 40%40%

HolesHoles 18.218.2 190%190% 20802080 24%24%

Slot-45Slot-45 13.013.0 107%107% 19451945 16%16%

SlotSlot 6.36.3 -- 16821682 --

MFR = 26 g/sMFR = 26 g/s

Slot-100Slot-100 106.2106.2 112%112% 44764476 51%51%

Holes-65Holes-65 223.6223.6 346%346% 43534353 47%47%

Slot-65Slot-65 73.173.1 46%46% 42074207 42%42%

HolesHoles 101.1101.1 102%102% 40814081 37%37%

Slot-45Slot-45 99.299.2 98%98% 35733573 20%20%

SlotSlot 50.250.2 -- 29702970 --

2121

Numerical ModelNumerical Model

Gambit® 2.2.30FLUENT® 6.2

Half-model via symmetry

1.67x106 cells 7.66x105 nodes

2222

Structured MeshSize Functions/Triangular Mesh

Structured Mesh

UnstructuredMesh

2323

Results – Temperature ContoursResults – Temperature Contours

Uniform incident heat flux in center of concentrator (Uniform incident heat flux in center of concentrator (Re Re = 35,000)= 35,000)

2424

Results - HTC & Temp. ProfilesResults - HTC & Temp. Profiles

hhmax_airmax_air = 2.82 kW/m = 2.82 kW/m22-K-K → → hhmax_Hemax_He = 34.1 kW/m = 34.1 kW/m22-K-K

hhavg_airavg_air = 1.25 kW/m = 1.25 kW/m22-K-K → → hhavg_Heavg_He = 15.1 kW/m = 15.1 kW/m22-K-K

Re = 35,000

q” = 0.5 MW/m2

2525

FLUENT vs. ExperimentalFLUENT vs. ExperimentalLow Flow/ Low Power Medium Flow/ Medium Power

•k-ε turbulence model overpredicts HTC by ~15% for the low flow case and ~20% for the medium flow case

•Spalart-Allmaras turbulence model overpredicts HTC by ~5% for low flow case and ~2% for the medium flow case

0.0

50.0

100.0

150.0

200.0

250.0

-10 -5 0 5 10

x (mm)

Tem

pera

ture

(C)

Experimental Holes-2

Std. k-eps./ Std. WF

Std. k-eps./ Non-Equil.WF

RNG k-eps./Non-Equil.WF

Spalart-Allmaras 0.0

50.0

100.0

150.0

200.0

250.0

-10 -5 0 5 10

x (mm)

Tem

pera

ture

(C)

Experimental Holes-5

Std. k-eps./ Std. WF

Std. k-eps./ Non-Equil.WF

Spalart-Allmaras

2626

Experimentally examined thermal performance Experimentally examined thermal performance of a prototypical flat-plate divertor moduleof a prototypical flat-plate divertor module

Six variations of the flat-plate divertor concept Six variations of the flat-plate divertor concept were studied and evaluated in terms of heat were studied and evaluated in terms of heat transfer coefficient and pressure drop transfer coefficient and pressure drop

These results provide a key dataset for These results provide a key dataset for validating commercial CFD codes and modelsvalidating commercial CFD codes and models

Summary – Flat Plate Divertor StudySummary – Flat Plate Divertor Study

2727

Conclusions and ContributionsConclusions and Contributions

Designed and constructed experimental test modules duplicating Designed and constructed experimental test modules duplicating complex geometries of leading three He-cooled divertor designscomplex geometries of leading three He-cooled divertor designs

Conducted experiments at dynamically-similar conditions Conducted experiments at dynamically-similar conditions matching/spanning expected prototypical operating conditions matching/spanning expected prototypical operating conditions

Constructed detailed numerical models with commercial CFD Constructed detailed numerical models with commercial CFD software to predict performance of experimental Apparatusessoftware to predict performance of experimental Apparatuses

Good agreement between experimental and numerical resultsGood agreement between experimental and numerical results– Results confirm validity of high heat transfer coefficients predicted in

preliminary design calculations– Confirmed that tConfirmed that these divertor designs can accommodate incident heat flux

values up to 10 MW/m2

Validated CFD Codes can be used with confidence to predict Validated CFD Codes can be used with confidence to predict performance of gas-cooled components with complex performance of gas-cooled components with complex geometriesgeometries– Optimize/modify design and/or operating conditionsOptimize/modify design and/or operating conditions– Quantify sensitivity of performance to changes in operating conditions Quantify sensitivity of performance to changes in operating conditions

and/or geometry due to manufacturing tolerances and/or geometry due to manufacturing tolerances