Thermal Performance of the HEMJ Divertor J. D. Rader B. H. Mills - - PowerPoint PPT Presentation

Verification of the Thermal Performance

• f the HEMJ Divertor
• J. D. Rader
• B. H. Mills
• D. L. Sadowski
• S. I. Abdel-Khalik
• M. Yoda

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Objectives

Jordan Rader - rader@gatech.edu

 Update previous predictions of the thermal performance of the

helium-cooled multi-jet (HEMJ) modular divertor design

 Recent results on finger-type divertor  dynamic similarity requires

matching non-dimensional coolant flow rate Re and ratio of divertor to coolant thermal conductivities

 Perform experiments on steel and brass HEMJ-like test sections

cooled by helium, air, or argon

 Incident heat fluxes q ≤ 3 MW/m2

 Following previous approach, extrapolate results to prototypical

conditions to obtain parametric design curves for HEMJ

 Max. heat flux at given max. pressure boundary temperature  Pressure drop (loss coefficient KL) at prototypical Re

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 Experiments with He

and Ar to validate procedure

 He Nu did not match

air, Ar Nu

 Similarity not

achieved matching

• nly Re

 Account for changes

in conduction vs. convection

 Thermal conductivity

ratio, κ

Previous Experiments

Jordan Rader - rader@gatech.edu

■Air ♦Argon

• Helium

[Mills et al. (2012)]

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 Accommodate q > 10 MW/m2

[Ihli et al. 05; Weathers 07; Crosatti 08]

 Hot He enters at 10 MPa, cools W tile

as an array of impinging jets

 Require many modules (~5×105 for

HEMJ) to cover O(100 m2) divertor

W

HEMJ Divertor

Jordan Rader - rader@gatech.edu

W-alloy

18 mm

HEMJ

Tile Steel Hexagonal Tiles

Φ15 mm 18 mm Φ15 mm

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 Brass and steel thimbles (pressure

boundary) cooled by helium (He), air, argon (Ar) at near-ambient temperatures

 Prototypical conditions: Re = 2.16 104

(mass flow rate ṁ = 6.8 g/s), κ = 340

 Experiments: Re = 8103 − 6104

κ  ks / k = 360 − 7000

 Incident heat flux q ≤ 3.0 MW/m2 (torch),

q ≤ 0.9 MW/m2

(electrical)

 Measure temperatures near cooled surface

with embedded thermocouples (TC)  TC, pressure drop across module p

GT Test Module

Jordan Rader - rader@gatech.edu Thimble Jet Cartridge Φ15 Φ17

q

6 Φ9.54 0.9 TCs

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Nu v Re

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Nu Re / 104

100 200 300 400 1 2 3 4 5

Increasing κ

• Ar Brass, κ ≈ 7000

♦ Air Brass, κ ≈ 5000 ○ Ar Steel, κ ≈ 3000 ◊ Air Steel, κ ≈ 2000 ■ He Brass, κ ≈ 900 □ He Steel, κ ≈ 360

 Heat flux based on

energy balance of coolant

 HTC assumes all

heat absorbed through cooled surface

 Doesn’t take

conduction into account

 Each scenario

shows its own trend

 Cases arranged by κ

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Accounting for κ

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Nu/κ0.200

10 20 30 40 50 60 70 80 1 2 3 4 5

• Ar Brass, κ ≈ 7000

♦ Air Brass, κ ≈ 5000 ○ Ar Steel, κ ≈ 3000 ◊ Air Steel, κ ≈ 2000 ■ He Brass, κ ≈ 900 □ He Steel, κ ≈ 360

 Multilinear curve

fitting assuming power law

 Nearly all data fits

within ±10%

 Prototypical values:

 Re = 21,600  κ = 340

Re / 104

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Pressure Loss Coefficient

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 Pressure loss

coefficient KL

 Hydraulic

parameter independent of κ

 Correlate to Re

KL Re / 104

1 2 3 4 1 2 3 4 5

• Ar Brass, κ ≈ 7000

♦ Air Brass, κ ≈ 5000 ○ Ar Steel, κ ≈ 3000 ◊ Air Steel, κ ≈ 2000 ■ He Brass, κ ≈ 900 □ He Steel, κ ≈ 360

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Prototypical Conditions

Jordan Rader - rader@gatech.edu

 Use Nu = ƒ(Re, κ) and KL = ƒ(Re) to calculate performance

for a range of high pressure/temperature operating conditions

 Lines of constant pressure boundary temperature, Ts,

 Use Nu correlation to calculate qmax

 Tin = 600 °C  Ts = 1200 °C

 Area changes result in q focusing from tile to pressure boundary

 Loss coefficient KL gives pressure drop for prototype pp  Lines of constant pumping power as fraction of incident

thermal power, β

 Desire to have β < 10%

5 10 15 20 25 0.5 1.5 2.5 3.5 4.5

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Performance Curves

Jordan Rader - rader@gatech.edu

qmax [MW/m2] Re / 104

1200 °C 1100 °C 1300 °C 5% 10% 15% 20%

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Summary

 Seven experimental configurations  HEMJ shows similar conduction/convection characteristics as

the previous finger-type design

 Parametric design curves were created to aid in further design

iterations and to account for changes in operating conditions

 For β < 10% and Ts < 1200 °C → Re < 2.5104, q < 15.5

MW/m2 and qt < 13 MW/m2

 These studies show that thermal conductivity ratio

methodology can be applied to other divertor designs with similar geometries/heat transfer paths

 Performance verification with dynamically similar experiments

• ver a wide range of conditions

Jordan Rader - rader@gatech.edu