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

Verification of the Thermal Performance of the HEMJ Divertor J. D. Rader B. H. Mills D. L. Sadowski S. I. Abdel-Khalik M. Yoda

Objectives  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 K L ) at prototypical Re 2 Jordan Rader - rader@gatech.edu

Previous Experiments  Experiments with He and Ar to validate ■ Air procedure ♦ Argon ● Helium  He Nu did not match air, Ar Nu  Similarity not achieved matching only Re  Account for changes in conduction vs. convection [Mills et al. (2012)]  Thermal conductivity ratio, κ 3 Jordan Rader - rader@gatech.edu

HEMJ Divertor HEMJ  Accommodate q  > 10 MW/m 2 18 mm [Ihli et al. 05; Weathers 07; Crosatti 08] Tile  Hot He enters at 10 MPa, cools W tile W as an array of impinging jets Φ 15 mm  Require many modules (~5×10 5 for HEMJ) to cover O (100 m 2 ) divertor W-alloy 18 mm Steel Φ 15 mm Hexagonal Tiles 4 Jordan Rader - rader@gatech.edu

GT Test Module q  Φ 17 Φ 15  Brass and steel thimbles (pressure boundary) cooled by helium (He), air, Thimble 6 TCs argon (Ar) at near-ambient temperatures  Prototypical conditions: Re = 2.16  10 4 (mass flow rate ṁ = 6.8 g/s), κ = 340  Experiments: Re = 8  10 3 − 6  10 4 0.9 Φ 9.54 κ  k s / k = 360 − 7000  Incident heat flux q  ≤ 3.0 MW/m 2 (torch), Jet Cartridge q  ≤ 0.9 MW/m 2 (electrical)  Measure temperatures near cooled surface with embedded thermocouples (TC)  T C , pressure drop across module  p 5 Jordan Rader - rader@gatech.edu

Nu v Re  Heat flux based on energy balance of 400 coolant  HTC assumes all Increasing κ 300 heat absorbed Nu through cooled surface 200  Doesn’t take ● Ar Brass , κ ≈ 7000 ♦ Air Brass , κ ≈ 5000 conduction into 100 ○ Ar Steel , κ ≈ 3000 account ◊ Air Steel, κ ≈ 2000  Each scenario ■ He Brass , κ ≈ 900 □ He Steel , κ ≈ 3 60 shows its own trend 0 0 1 2 3 4 5  Cases arranged by κ Re / 10 4 6 Jordan Rader - rader@gatech.edu

Accounting for κ  Multilinear curve 80 fitting assuming 70 power law 60  Nearly all data fits Nu / κ 0.200 within ± 10% 50  Prototypical values: 40  Re = 21,600  κ = 340 ● Ar Brass , κ ≈ 7000 30 ♦ Air Brass , κ ≈ 5000 20 ○ Ar Steel , κ ≈ 3000 ◊ Air Steel, κ ≈ 2000 10 ■ He Brass , κ ≈ 900 □ He Steel , κ ≈ 3 60 0 0 1 2 3 4 5 Re / 10 4 7 Jordan Rader - rader@gatech.edu

Pressure Loss Coefficient  Pressure loss 4 coefficient K L 3  Hydraulic K L 2 parameter ● Ar Brass , κ ≈ 7000 independent of κ ♦ Air Brass , κ ≈ 5000 ○ Ar Steel , κ ≈ 3000  Correlate to Re 1 ◊ Air Steel, κ ≈ 2000 ■ He Brass , κ ≈ 900 □ He Steel , κ ≈ 3 60 0 0 1 2 3 4 5 Re / 10 4 8 Jordan Rader - rader@gatech.edu

Prototypical Conditions  Use Nu = ƒ( Re , κ ) and K L = ƒ( Re ) to calculate performance for a range of high pressure/temperature operating conditions  Lines of constant pressure boundary temperature, T s ,  Use Nu correlation to calculate q  max  T in = 600 ° C  T s = 1200 ° C  Area changes result in q  focusing from tile to pressure boundary  Loss coefficient K L gives pressure drop for prototype  p p  Lines of constant pumping power as fraction of incident thermal power, β  Desire to have β < 10% 9 Jordan Rader - rader@gatech.edu

Performance Curves 25 1300 °C 15% 20% 1200 °C 20 q  max [MW/m 2 ] 10% 1100 °C 5% 15 10 5 0 0.5 1.5 2.5 3.5 4.5 Re / 10 4 10 Jordan Rader - rader@gatech.edu

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 T s < 1200 °C → Re < 2.5  10 4 , q  < 15.5 MW/m 2 and q t  < 13 MW/m 2  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 over a wide range of conditions 11 Jordan Rader - rader@gatech.edu