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Update: HEMJ Experiments in the GT Helium Loop

Update: HEMJ Experiments in the GT Helium Loop. M. Yoda, S. I. Abdel-Khalik, D. L. Sadowski, B. H. Mills September 18, 2013. Gas-Cooled Divertors. Objectives Evaluate thermal performance of leading helium-cooled divertor designs at prototypical conditions

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Update: HEMJ Experiments in the GT Helium Loop

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  1. Update: HEMJ Experiments in theGT Helium Loop M. Yoda, S. I. Abdel-Khalik, D. L. Sadowski, B. H. Mills September 18, 2013

  2. Gas-Cooled Divertors • Objectives • Evaluate thermal performance of leading helium-cooled divertor designs at prototypical conditions • Determine design correlations from experimental data at near-prototypical conditions and numerical simulations • Use correlations to estimate how changes in operating conditions affect divertor thermal performance • Current Approach • Test a single helium-cooled divertor with multi-jet cooling (HEMJ) module in helium loop at prototypical pressures, near-prototypical temperatures • Estimate maximum heat flux and He pumping power requirements from cooled surface temperature and pressure drop data ARIES Mtg. (9/13)

  3. HEMJ Design • Divertor design proposed for DEMO • Jet impingement cooling: He at 600 °C (increased to 650-700 °C), 10 MPa exits from 25 (24 each 0.6 mm dia. + one 1.0 mm dia.) holes • He mass flow rate  6.8 g/s • KIT/Efremov experiments of 9-module unit at prototypical conditions show HEMJ can accommodate heat fluxes q > 10 MW/m2 • Cools very small area: need ~5105 modules to cool O(100m2) divertor 18 mm W Tile W-alloy 15 mm 18 mm Steel ARIES Mtg. (9/13)

  4. Background • Previous work: Dynamically similar studies of various divertor designs extrapolated to prototypical conditions • Study HEMJ, finger-type divertor with single impinging jet, He-cooled flat-plate (HCFP) and T-tube divertors • Cool with air, He and Ar at near-ambient temperatures • Match coolant mass flow rate (Re) and fraction of heat removed by convection, vs. conduction (Biot number Bi Nu/, where thermal conductivity ratio   ks/k) • Determine correlations for Nusselt number Nu= f(Re, ) [neglecting Prandtl number effects] and loss coefficient KL = g(Re) • Test at near-prototypical conditions in helium test loop •  10 g/s, inlet temperature Ti 400 °C, inlet pressure pi  10 MPa • Can accommodate test sections with pressure drops  0.7 MPa ARIES Mtg. (9/13)

  5. Average Nu and KL • Reynolds number from mass flow rate • Dj = 1 mm • Calculate average heat transfer coefficient • Heat flux from energy balance for He (Te exit temperature) • Avg. cooled surface temperature extrapolated from embedded TCs • Ac = 131.5 mm2 = area of cooled surface • Average Nusselt number from • coolant thermal conductivity • Loss coefficient from pressure drop p • average speed ARIES Mtg. (9/13)

  6. Helium Loop Schematic He source tanks Electric heater Recuperator Buffer tanks • Evacuate loop, then charge to 10 MPa with He from 41.3 MPa source tanks • Two buffer tanks increase He inventory and reduce flow pulsation • Mass flow rate adjusted using bypass • He supplied to test module is heated with recuperator and electric heater • Inline filters remove particulates larger than 7 μm Bypass Cooler Test section Vacuum pump Reciprocating compressor ARIES Mtg. (9/13)

  7. GT Helium Loop Recuperator/Preheater Buffer Tanks Test Section (in fume hood) Reciprocating Compressor ARIES Mtg. (9/13)

  8. HEMJ Experiments • HEMJ test section:J-1c design • D185 W-alloy (97% W + 2.1% Ni + 0.9% Fe) outer shell + brass C360 inner jets cartridge • Heat with oxy-acetylene torch: incident heat fluxes q 2.7 MW/m2 • Flow argon over flame impingement location to minimize oxidation (D185 “oxidation-resistant” up to 600 °C): maximum measured temperatures ~950 °C ARIES Mtg. (9/13)

  9. Current Status • HEMJ experiments in GT helium loop • Inlet temperatures Ti= 43 – 295 °C (pi = 10 MPa) • Mass flow rates = 2.9 – 6.9 g/s (fluctuations <3%): Re 1.4104  4.1104 (vs. 2.14104 at prototypical conditions) • Incident heat fluxes q = 0.72.7 MW/m2 • Minor oxidation + stress-induced fracture (at TC port 0.25 mm from heated surface) observed on outer shell • Based on pressure drop data loss coefficients KL= 2.4 – 2.5 over all measurements • Inconsistent results for Nu due to variations in gap between inner cartridge, outer shell (0.9 mm): machining tolerance (0.1 mm) + seating of cartridge inside shell ARIES Mtg. (9/13)

  10. Relaminarization Flow regime map: Square ducts • Focus of US-Japan collaboration PHENIX (Kyoto U., TUS) • Relaminarization/“Deteriorated turbulent heat transfer”  reduction in Nu due to variations in coolant properties • Based on available data (in simpler geometries), only occurs at low Re: potential issue for off-normal events • Use He loop to see if anomalous heat transfer behavior observed at low Re (  0.6 g/s with 6% fluctuation), smaller gaps • Hosting visitors in Aug., Sept. Nondimensional heat flux McEligot & Jackson 2004 Reynolds number ARIES Mtg. (9/13)

  11. Next Steps • HEMJ experiments • New test section: WL10 outer cartridge + stainless steel inner jets cartridge with adjustable gap • Measurements by ORNL  ks(T) for D185, brass   • Increase Tito ~400 °Cand q above 5 MW/m2 using 10 kW RF induction heater (loan from INL): avoid oxidation • Relaminarization experiments • Continue experiments at low mass flow rates • Vary gap width ARIES Mtg. (9/13)

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