5931/34.05 3/4/20091

Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration

under contract DE-AC04-94AL85000.

Advanced Cooling Technologies for PFCs

ReNeW: Theme III Status & Challenges for helium-cooled refractories

D. YouchisonSandia National Laboratories

Los Angeles, CAMarch 5, 2009

5931/34.05 3/4/20092

Why helium-cooling?Advantages:

• inherently safe, inert chemical properties• lack of corrosion• single-phase heat transfer without the possibility of CHF->High Temps• lack of neutron activation• easy separation from tritium. • fluid of choice for a highly efficient, high temperature Brayton cycle exhibiting minimal wear and corrosion of gas turbines.

Disadvantages:• low thermal mass, Cp, that is less than 1% of water• high pressure systems -> high stored energy• compressible gas requiring higher pumping or blower power and larger supply and return piping compared to liquids• higher cost and sophistication of the turbomachinery such as compressors, high temperature turbines, and recuperators

5931/34.05 3/4/20093

Gaps in helium-cooling

1. Ductile W-alloy development, and other refractories: Mo, V

2. Low-cost fabrication techniques w/ integrated manifolding

3. Joining development, refractory armor and RAFS

4. Innovative, low-pressure-drop thermal designsCFD/HX modeling of porous media, jets

5. Flow instabilities in multi-channel devices

6. High temperature, high pressure testing capabilities

7. Tritium permeation into the coolant

8. Purity control and high temperature diagnostics

5931/34.05 3/4/20094

HELIUMCOOLER

PMTF WATERCOOLANTOUT

T & PRELIEFVALVE

SV1 RELIEFVALVE

CV1 BACKPRESSURE

VALVE

SV2

V1

VACUUMPUMPTEMP

SWITCH

DIVERTOR PLATETEST SECTION

V2V5

V4

EBTS

V3

HELIUM ACCUMULATORCIRCULATOR HOUSING

SV3 CV2

HeSUPPLY

HELIUMCIRCULATOR

S

T

T

S

P

S

T

PT

F

P

T

P

F

P

ELECTRON BEAM SOURCE

Sandia’s HeFL started operation in 1993. Tested 20 modules, 13 designs

30 kW Electron Beam Test SystemHelium Flow Loop for EBTS

5931/34.05 3/4/20095

• Oxygen gettering and gas analysis• in-line helium heaters• larger capacity blowers or compressors• high efficiency helium/water heat exchangers• fast actuating, high temperature valves• High temperature diagnostics• Niobium or super-alloy piping

Advances in helium HXs have surpassed current PMTF HeFL capabilities!

New Helium Flow Loops will be required for higher temperature (>600C), higher pressure (8-10 MPa), higher mass flow (1 kg/s) operation for both PFC and BM testing.

5931/34.05 3/4/20096

year Type of Test Article fabricator 1993 Cu Micro-channel HX (~100 channel size) Creare, Inc. Cu Divertor mockup A (0.46mm channels) General Atomics Cu Porous (40%) metal HX (0.43mm dia.) Thermacore, Inc. 1994 Cu Dual channel porous metal HX Thermacore, Inc. Cu Div. mockup A retest, higher heat loads General Atomics 1996 Cu Phase-II porous metal HX Creare, Inc. Vanadium spiral-tube HX General Atomic 1997 Cu Faraday shield A Thermacore, Inc. Cu Divertor mockup B Thermacore, Inc. 1998 Cu Faraday 2nd shield B Thermacore, Inc. Cu Divertor 2nd mockup C Thermacore, Inc. 1999 Div. mockup B retest, added diagnostics Thermacore, Inc. 2000 W tubes with W foam Ultramet, Inc. 2000 W FW module with W porous medium Thermacore, Inc. 2001 VPS W tube with VPS porous medium Plasma Processes2006 W tube with W foam in axial flow Ultramet, Inc. 2008 Sq. Mo w/ Mo foam, circumferential flow Ultramet, Inc. 2009 4-Channel, Larger Area Mo panel Ultramet, Inc 2009 W Tee-tube Jet impingement Plasma Processes

Background: Helium-cooled modules developed for PFCs

TR3

TR4

5931/34.05 3/4/20097

Helium divertor module design specifications

Parameter SpecificationCross-section dimensions and shape 4.45 cm x 3.18 cm, rectangularOuter shell material GlidCopTM Al-15 barPorous medium OFE copper powderParticle diameter 0.102 cm, 12HPInner tube material OFE copper D-shaped tubesNumber of channels 2Panel length 4.45 cmHeated area 6.45 cm2

Heat load 12.9 kWMaximum heat flux 2000 W/cm2

Maximum surface temperature 400 oCTest orientation HorizontalHelium pressure 4 MPaHelium flow rate per channel 2.5 g/sTotal helium flow rate 5.0 g/sBlower power 90 W

Helium divertor module is a dual channel, circumferential flow, porous metal device.

Pressure taps

RTD

A

A

SECTION A-A

Flow

Dual-channel, circumferential flow, porous metal helium divertor module was tested for evidence of flow instabilities under non-uniform heating.

0

10

20

30

40

50

60

70

80

0 5 10 15 20 25 30

channel #1channel #2channel #1 onlychannel #2 onlychannel #1 parallelchannel #2 parallel

Pres

sure

Dro

p (k

Pa)

Mass Flow (g/s)

to tal dual-channel flowsingle channel flow

Unexpected difference in pressure drop

Isothermal - no applied q”

• Unit cell design with manifolding• short flow paths• add power to helium very near the exit• avoid long flow paths that generate high -P and

flow instabilities

1997

5931/34.05 3/4/20098

0

100

200

300

400

500

600

700

0 5 10 15 20 25 30

21.6 sq. cm.2.0 sq. cm.

Surf

ace

Tem

pera

ture

(o C)

Heat Flux (MW/m 2)

uniform heating

q” max = 29.5 MW/m2

>208.5°C

<23.9°C

40.060.080.0

100.0120.0140.0160.0180.0200.0

Uniform HeatingChannel Heated Area

(cm 2)Heat Flux(MW/m 2)

Absorbed Power(W)

Mass Flow(g/s)

Surface Temperature(oC)

Channel #1 21.6 6 6437 7.8 680Channel #2 21.6 6 6488 11 680Channel #1 2 29.5 2774 11.05 691Channel #2 2 29.5 3125 8.05 691

Copper helium-cooled divertor module met performance goals.

heated area effect

5931/34.05 3/4/20099

1 2

A steady state temperature profile through the center plane of the divertor modulewas obtained by numerical modeling. A heat flux of of 227 W/cm2 applied to the topsurface revealed a constant heat transfer coefficient of 20,400 W/m2·K on the insidewall of channel #1 and 26,000 W/m2·K on the inside wall of channel #2.

Uniform heating case was used to determine heat transfer coefficients.

>208.5°C

<23.9°C

40.060.080.0

100.0120.0140.0160.0180.0200.0

205

206

207

208

209

210

0 0.25 0.5 0.75 1

Tem

pera

ture

(o C)

Distance

5931/34.05 3/4/200910

• goals: • investigate heat transfer analyses for porous media and jet

impingement - identify useful modeling approaches• demonstrate performance in medium scale test

(implies we have a test stand and a capable loop)• deploy helium-cooled module in toroidal facility

• needed development: • incorporate low-cost fabrication concepts for refractories including

manifolding and connectors• accommodate thermal stresses in face plates• adequate heat transfer analyses for porous media and jets

HHF He-Cooled PFC Development• all refractory metal heat sink• helium-cooled, high Delta-T heat sink, mCp T• high efficiency gas turbine technology• hydrogen production

Helium-cooling for DEMO

.

5931/34.05 3/4/200911

CY 2000: Three phase I SBIR projects started on helium-cooled refractories. Only one concluded with a successful test.

1. Thermacore Ni-brazed W pellet porous metalsmall scale EBTS mock-up - February 2000

2. Ultramet CVD W-Re foam porous metalsmall scale EBTS mock-up - March 2000

3. Saddleback W foil microlaminate porous metalsmall scale EBTS mock-up - March 2000

•refractory porous media– W, Mo, Ta, V, Zr ...

•fabrication or joining technique– fibrous foam– spherical pellets– micro-laminates

•operating parameters and design– mechanical and thermal stresses– flow distribution to unit cells– pumping power/pressure drop

ISSUES:Micro-channels• machined (difficult & expensive)• direct deposit e.g. spray cast, P.S., PVD(mandrel removal)• micro-laminates(Hip porosity and bond strength)

Porous media• variety of techniques(control porosity, bonding)

Micro-jets• fabrication-joining & manifolding

*All require high purity helium

OPTIONS:

1993 DSCu

5931/34.05 3/4/200912

•Previous copper test article dissipated 6MW/m2 with max surface temperature of 700°C (5.2 MW/m2 @ 450 °C). World record heat flux 108 MW/m2 on a stripe 0.2x8 cm2 Faraday shield. Effective heat transfer coefficient of 26,000 W/m2.K for He cooled divertor module. (DE-FG02-95ER82095) •Goal of program (DE-FG02-99ER82906) was to duplicate results using all low-activation refractory materials.•Dual parallel flow channels for testing of flow distribution with non-uniform heating.•Testing performed at SNL CY2000.

W pellets with Ni braze selected for porous matrix.

Cool Helium In Warm Helium Out

Heat Source

Well-Bonded PorousMetal Matrix

Heat In

Helium InletHe

E xit

Porous Metal Matrix

5931/34.05 3/4/200913

porousmedia

plugcup

tubebody

stainless steelbellows

end cap flow

The dual-channel PMHX consisted of two separate modules in parallel flow. Each module consisted of a tungsten cylindrical cup containing a hemispherical shell of brazed tungsten porous metal. This cup is brazed onto a tungsten cylindrical tube bottomed by a flat tungsten plate that facilitates the brazed attachment of 316 stainless steel supply tubes. The tungsten cylinder acts as the pressure boundary and entrance plenum for the cool helium. The helium flows into the tube plenum and enters a hemispherical shell of porous media along its perimeter. The helium then flows radially inward while moving closer to the backside of the heated faceplate. At the apex, the flow is redirected normally away from the faceplate along the vertical axis of the hemisphere where it exits the porous media. A stainless steel bellows connects the exit duct to the exit tube at the bottom of the heat exchanger and segregates the hot and cold gas.

**This design minimizes pressure drop by absorbing most of the heat near the exit duct, thus reducing the distance that hot gas must travel in the porous media and localizing the gas expansion near the exit.

Description

5931/34.05 3/4/200914

Pressure tapsRTD

External Top View

B

A

C

Flow

Orifice meter

Turbine meter2

1RTD

RTD

Experiment CY2000

Each channel was equipped for independent calorimetry by use of separateoutlet RTDs and pressure taps. Two flow meters were used with three valvesto deduce the helium mass flow rate in each channel. Two thermocoupleswere used on each module for pyrometer calibration. Surface temperatureswere measured with 2 pyrometers and a 3-12 m infrared camera.

5931/34.05 3/4/200915

0

200

400

600

800

1000

0 1 2 3 4 5 6

1-C low pyro1-C mid pyro

surf

ace

tem

pera

ture

(C)

absorbed heat flux (MW/m2)

Results

Thermal ResponseModule Heated Area

(cm2)Heat Flux(MW/m2)

Absorbed Power(W)

Mass Flow(g/s)

Surface Temperature(oC)

Module #1 4.9 5.9 2891 3.0 840Module #2 4.9 5.5 2698 1.1 934

Thermal Fatigue (>500 cycles 25s ON/10s OFF)Module Heated Area

(cm2)Heat Flux(MW/m2)

Absorbed Power(W)

Mass Flow(g/s)

Surface Temperature(oC)

Module #1 4.9 3.5 1715 3.4 476

0

200

400

600

800

1000

0 1 2 3 4 5 6

1-C low pyro1-C mid pyro1-C mid pyro w/ bypass

surf

ace

tem

pera

ture

(C)

absorbed heat flux (MW/m2)

Module #2 Module #1

5931/34.05 3/4/200916

Area1Min Mean Max910.3 1,010 1,119

Area1Min Mean Max910.3 1,010 1,119

*>1,233°C

*<160.6°C

200.0

400.0

600.0

800.0

1,000

1,200

Module #2 easily reachesenvisioned operating rangewith 1000 oC surface temperature.

CY2000

5931/34.05 3/4/200917

8.5

9

9.5

10

10.5

11

11.5

12

12.5

0

100

200

300

400

500

total mass flow (g/s)

bypass flow (g/s)

module pressure drop (kPa)bypass pressure drop (kPa)delta-T (C)

mas

s flo

w ra

te (g

/s)

pressure drop *10 (kPa)delta-T (C

)

time (s)0 60 120 180 240 300Bypass tube

Parallel flow instability seen only in worst case scenario.

5931/34.05 3/4/200918

564C

350C

0

5000

10000

15000

20000

25000

0 10 20 30 40 50 60 70 80 90Angular Position from Inlet (degrees)

Hea

t Tra

nsfe

r Coe

ffic

ient

(W/m

2 ·K)

porousmedia

0

90q”

Area1Min Mean Max 523.5 565.5 612.6

Area1Min Mean Max 523.5 565.5 612.6

*>682.5°C

*<345.8°C

350.0

400.0

450.0

500.0

550.0

600.0

650.0

Area1Min Mean Max 524.7 563.2 614.9

Area1Min Mean Max 524.7 563.2 614.9

*>682.5°C

*<345.8°C

350.0

400.0

450.0

500.0

550.0

600.0

650.0

module #1 in single channel flow, 4.4 MW/m2

Good thermal performance obtained for non-optimized design.

Modeling

module #1 in parallel channel flow, 4.4 MW/m2

5931/34.05 3/4/200919

•These heat exchangers exceeded design specifications and survived a maximum heat flux of almost 6 MW/m2 and a maximum surface temperature near 1000 oC.

•The heatsink survived over 500 thermal fatigue cycles at 3.5 MW/m2 with only minimal microcracking of the faceplate.

•No evidence of mass flow instabilities was observed for the two modules in parallel even for very high delta-Ts in the helium.

•This level of thermal performance is more than adequate for 2 MW/m2 first wall applications proposed for solid first walls in APEX.

•Better performance could be obtained if the porosity of the porous media could be doubled without a reduction in thermal conductivity. This would almost triple the mass flow and power handling capability.

•Such an innovation could open a design window into the divertor heat flux regime of 20 to 30 MW/m2 and make high temperature, helium-cooled refractory heatsinks a desirable alternative to liquid metal pfcs

Thermacore W Summary

5931/34.05 3/4/200920

Porous W Foam 38mm length

W Tube 12.7 mm ID x 16.2 mm OD

Nb Tube at ends

2006 Ultramet Phase-I geometry – single channel, round tubes

0.50” 0.62” 0.75” (for Swagelok)W Foam

CVD W Tube (0.060” wall)CVD Nb Sleeve (0.065” wall)

1.25”0.75”

8.5”

6.0”

2.0”

5931/34.05 3/4/200921

Before

After

PN1 failed due to thermal cycling above 2000 C at 4 MPa

•Hi-Temp Brayton cycle application.•More ductile refractory alloy at

pressure boundary required.•Foam HX performed well.

Achieved a maximum of 22.4 MW/m2 along the axial centerline of the top surface and an average absorbed heat flux of 14 MW/m2. The 4-MPa helium flowing at 27 g/s produced a pressure drop of 92 kPa and removed 7.2 kW at steady state.

5931/34.05 3/4/200922

PN-1 Thermal Response, 24 g/s, 4 MPa

0

500

1000

1500

2000

2500

0.0 500.0 1000.0 1500.0 2000.0 2500.0

Absorbed Heat Flux (W/cm2)

Surf

ace

Tem

pera

ture

(C)

Midrange 1-CMidrange 2-CHirange 2-CPN-4

reducedarea

2-3x performance enhancement with foam

~22* MW/m2

(EBTS)

5931/34.05 3/4/200923

Is W the only game in town?

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

2.00

0 200 400 600 800 1000 1200 1400

T (C)

kTH

(W/c

mK

)

WMoNbNb1ZrVTZM70Mo30WTa10WTa

Thermal conductivies of refractory alloys

5931/34.05 3/4/200924

4 Single4 Single--Channel Heat Exchangers Tested in EBChannel Heat Exchangers Tested in EB--6060

-- All Molybdenum All Molybdenum --

1. No foam2. 45 ppi 77% porosity3. 65 ppi 77% porosity4. 100 ppi 77% porosity

2008

DMS, Inc.

5931/34.05 3/4/200925

Ultramet single channel testing completed in EB-60

No foam, 127 mm x 2 mm slot

q”

FY08-FY09 testing campaign – Brayton cycle relevant (large DT)W DBTT <600C Mo DBTT <RTW recrystallization ~1100C Mo recrystallization 1180C

5931/34.05 3/4/200926

PN1 – No Foam

5931/34.05 3/4/200927

PN3 - 65 ppi

5931/34.05 3/4/200928

Ultramet to deliver larger panels for phase-II.

•Multiple channel (4)•Flat surface•All refractory•Short flow paths•600 C inlet temps

Investigate:•Larger heated areas•Flow instabilities

1concept

Testing in late summer 2009

5931/34.05 3/4/200929

Plasma Processes Tee-Tube Concept

• ARIES CS design

2concept

Testing in early 2010

5931/34.05 3/4/200930

HEMJ from FZK/Efremov (Norajitra)

600C, 10 MPa, 25 g/s

Tsefey2007

3concept

US testing in early 2010 as IEA NTFR collaboration

5931/34.05 3/4/200931

Small Thrust ($2-3M)

• International collaboration thru IEA NTFR to test 3 concepts• Test refractory pfcs for high power density applications

– Helium-cooled divertors– TBM heatsinks

• Deploy helium-cooled module on a toroidal facility (CMod?)TR4 TR6