Detailed Modeling of Passive Auto-Catalytic Recombiner Operational Behavior with the Coupled REKODIREKT-CFX Approach

Transcription

1 Mitglied der Helmholtz-Gemeinschaft Detailed Modeling of Passive Auto-Catalytic Recombiner Operational Behavior with the Coupled REKODIREKT-CFX Approach S. Kelm, E.-A.Reinecke, *Hans-Josef Allelein *Institute for Reactor Safety and Technology, RWTH Aachen University 46 th Annual Meeting on Nuclear Technology Project No

2 Outline Background & Motivation REKO-DIREKT model & development RD-CFX Coupling Validation strategy and selected results Summary and Outlook Slide 2

3 Task: Improved assessment of H 2 mixing and mitigation For a detailed simulation, it is essential to capture the direct interaction of flow and mitigation measure Slide 3

4 Motivation for a detailed modeling approach Motivation: Transfer of REKO-3 & 4 experimental database (project / ) and detailed modeling results (CFX, SPARK) to large scale application. Unified PAR modeling approach in different TH codes (testing of first implementation in COCOSYS ongoing) Extendable, mechanistic mode basis: New physics (CO conversion / poisoning, ignition, start-up behavior) Different PAR types (e.g. AECL, NIS) Reliable and numerically efficient modeling of PAR operational behavior Conservative and numerically stable coupling of RD and CFX Extension to a full PAR System (arbitrary number and PAR types) Validation against OECD/NEA THAI-1&2 hydrogen recombiner tests Slide 4

5 Outline Background & Motivation REKO-DIREKT model & development RD-CFX Coupling Validation strategy and results Summary and Outlook Slide 5

6 REKO-DIREKT D&V - Experimental Database REKO-3 REKO-4 5m³ THAI 60m³ Reaction kinetics H 2 Chimney, buoyant flow PAR atmosphere interaction Development Validation Slide 6

7 REKO-DIREKT code structure PAR Phenomena REKO-DIREKT PAR housing / chimney Buoyancy driven flow Thermal inertia and heat losses to the environment Catalyst section Reaction kinetics (Oxygen starvation, steam impact, parallel CO recombination..) by transport approach Heat distribution, thermal inertia ( Böhm, 2006) Slide 7

8 Outline Background & Motivation REKO-DIREKT model & development RD-CFX Coupling Validation strategy and selected results Summary and Outlook Slide 8

9 RD-CFX interface (1) Fully parallelizable, explicit Master (CFX) Slave (RD) coupling Data handling by means of program flow or data controlled USER Fortran subroutines Arbitrary number and types of PARs Output data: temperatures gas composition mass flow RD-run data: catalyst temperature field radiative view factor matrix Input data: temperatures gas composition system pressure CFX time step REKO-DIREKT ( Kelm et al., NURETH-14, 9/2011) Geometric information: box size catalyst size & numbers RD numerical grid Slide 9

10 RD-CFX interface (2) ANSYS CFX Memory Management System REKO-DIREKT First call Read Input & Mesh Start of Run Start of Time Step Start of Coefficient Loop Start of linear Solution Linear Solution End of linear Solution End of Coefficient Loop End of Time Step (createinput.f) Trigger RD exec. (writeout.f) (createinput.f) Execute REKO-Direkt: Read Initialisation & Input Values Update REKO-Direkt Results Write Results on Boundary Condition Update Input Values for REKO- DIREKT (rekodirekt.f) (rekodirekt.f) First call Read Input File Direct Solution Write Solution Start of Run Start of Time Step End of Time Step End of Run Loop over each PAR Write Solution End of Run Writing to MMS Reading from MMS ( Kelm et al., NURETH-14, 9/2011) Slide 10

11 RD Application in CFX large scale application, coarse mesh (e.g. PWR) small scale application (e.g. resolving the THAI ) m q q m m m Slide 11

12 Outline Background & Motivation REKO-DIREKT model & development RD-CFX coupling Validation strategy and selected results Summary and outlook Slide 12

13 Separation of Errors: RD-CFX Validation strategy Scenarios of systematically increasing complexity HR2 / HR3 / HR5 Effect of pressure HR12 Effect of humid atmosphere HR35 Effect of oxygen starvation ( Kanzleiter et al., QLR, 2/2009) ( Freitag & Sonnenkalb, HR35 comparison report, 12/2013) ( Kanzleiter et al., QLR, 9/2009) Test Pressure [bar] Temperature [ C] Steam Concentration [vol.-%] Oxygen Concentration [vol.%] HR HR HR HR < 8 HR < 2 Slide 13

14 Separation of Errors: RD-CFX Validation strategy Scenarios of systematically increasing complexity Three step validation approach RD stand-alone RD-CFX 2D test RD-CFX 3D THAI Fundamental validation [7] Project No CFX Verify coupling Reference for 3D simulation Integral validation of H 2 mixing and mitigation Slide 14

15 HR Experimental Setup and CFD Geometry Geometric model simplifications [2]: Injection lines: H2: 2D Inlet boundary condition PAR box: Zero thickness (in CFD model) Only active half considered Inlet and Outlet section conserved THAI internals neglected: Auxiliary fan Flanges, man holes Bearing rings and condensate trays at inner cylinder 0.5* AREVA FR90/380T H 2 feed line Measurement channel Kelm et al, CFD4NRS-4, Korea, 2012 Slide 15

16 HR Physical Model CFD (ANSYS CFX15) Model [2]: U-RANS equations Ideal gas equation of state Temperature dependent properties k- -SST model incl. buoyancy prod. & dissipation Sc t =Pr t =0.9 Conjugate heat transfer Thermal radiation: Monte Carlo, histories, participating media, steam =1.0, w =0.6 Gas sampling: 15 sink points Wall & bulk condensation Automatic wall treatment at inner walls REKODIREKT (RD) Model: H 2 & O 2 start concentration: 0.1vol.% PAR Startup time: according to experiment Kelm et al, CFD4NRS-4, Korea, Sept Slide 16

17 HR Numerics Numerical Model: High resolution advection scheme 2 nd order Euler-backward t ~0.2 s, ave CFL~2, max CFL<20 Max residual < 1E-3 (RMS<1E-5) 3..6 coefficient loops per time step Grid independent solution Computational Effort: 5000s ~ 10 days on 8 CPU s RD runtime < 70ms / time step ~ 0.5 h / total transient Slide 17

18 HR2 - Visualization of the PAR Operation Transient Slide 18

19 HR2 - Visualization of the PAR Operation Transient Slide 19

20 PAR-Atmosphere Interaction thermal stratification vs. H 2 injection! Hard to differentiate between single model errors Strong interaction between PAR operation (hot plume) and atmospheric mixing Slide 20

21 HR Validation Strategy Aim: Avoid elimination of errors (1) Detailed assessment of PAR performance: Prove consistent prediction of the conversion rate / heat source compared to experiment,,, Prove consistent thermal representation of the In-/outlet conditions Catalyst Temperature Inlet velocity (throughput) Rate & Efficiency (2) Comparison of atmospheric mixing: Analyse effect of PAR operation on H 2 distribution Pressure and gas temperature Slide 21

22 HR12 PAR Behavior Concentrations & Reaction Rate Consistent global balances (conversion & heat release to the vessel) Oxygen starvation captured O 2 starvation O 2 starvation Slide 22

23 HR12 PAR Behavior Thermal Aspects Reaction heat distribution is qualitatively and quantitatively well predicted PAR thermal inertia is a key issue for predicting the exhaust gas temperature Gas PAR inlet Slide 23

24 HR12 PAR Behavior Buoyant Flow Rate Qualitatively well predicted, but visible scattering among the different experiments / TH conditions Sensible parameter to reaction rate (mass transfer approach) Ongoing detailed CFD simulations of measurement channel / flow resistances v ave ~0.8 m/s vane wheel Slide 24

25 HR12 Atmospheric H 2 Mixing, Temperature & Pressure Overall consistent transport and mixing processes during full transient Vessel sump Slide 25

26 Outline Background & Motivation REKO-DIREKT model & development RD-CFX coupling Validation strategy and results Summary and future work Slide 26

27 Summary & Future Work Detailed mechanistic PAR model REKO-DIREKT, developed from small scale separate effect tests REKO-3 and REKO- 4, was implemented in CFX Systematic validation performed by means of technical scale OECD/NEA THAI hydrogen recombiner tests Validation results in overall consistent and plausible results Conversion rate and global heat and species mass balances Importance of PAR thermal inertia for prediction of the gas temperatures and resulting buoyant mass flow rate Significant impact of thermal radiation heat transfer on gas temperatures, pressure, thermal stratification and gas mixing Extension of the interface to parallel CO conversion Development of a model to predict PAR start-up Extension to other PAR types (AECL, NIS) Detailed CFD application to determine measurement uncertainties and model coefficients (e.g. flow resistances of chimney internals) Slide 27

28 Acknowledgements The continued development of CFD models for prediction of H2 mixing and mitigation is performed in close cooperation with RWTH Aachen University and funded by German Federal Ministry of Economic Affairs and Energy (Project No ) Parts of REKO-3 / 4 experimental programme and REKODIREKT code development are performed in close cooperation with RWTH Aachen University and funded by German Federal Ministry of Economic Affairs and Energy (Project No / ) The PAR performance test have been performed within the OECD/NEA THAI and THAI2 project. We acknowledge the support of all the countries and the international organizations participating in the projects and the staff of Becker Technologies for their effort for preparing, performing and documenting the experiments. Analytical investigations on PAR operational behaviour are performed in collaboration with the Institut de Radioprotection et de Sûreté Nucléaire (IRSN). Slide 28

29 References (1) Böhm, J.: Modelling of processes in catalytic recombiners, Forschungszentrum Jülich, Energy Technologies Vol 61 (2007). (2) Kelm et al.: Simulation of hydrogen mixing and mitigation by means of passive auto-catalytic recombiners Proc. 14th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-14), Toronto, Ontario, Canada, September 25-29, (3) Kelm et al.: Passive auto-catalytic recombiner operation - Validation of a CFD approach against OECD-THAI HR2-test, Proc. OECD/NEA & IAEA Workshop on Experiments and CFD Codes Application to Nuclear Reactor Safety (CFD4NRS), Deajon, South Korea, September 9-13, 2012 (4) Kanzleiter, T. et al.:quick Look Report Hydrogen Recombiner Tests - HR-1 to HR-5, HR-27 and HR-28 (Tests without steam, using an Areva PAR), Report No HR-QLR-1, OECD-NEA THAI Project, February 2009 (5) Kanzleiter, T. et al.:quick Look Report Hydrogen Recombiner Tests HR-6 to HR-13, HR-29 and HR-30 (Tests with steam, using an Areva PAR), Report No HR-QLR-2, OECD-NEA THAI Project, August 2009 (6) Freitag, M., Sonnenkalb, M.: Comparison Report for Blind and Open Simulations of HR 35 - Onset of PAR operation in case of extremely low oxygen concentration, Report No HR35 AWG (VB), OECD-NEA THAI2 Project, 17. December 2013 (7) Reinecke et al.: Validation of the PAR code REKO-DIREKT against large scale experiments performed in the frame of the OECD/NEA-THAI project, Proc. 7 th European Review Meeting on Severe Accident Research (ERMSAR-2015), Marseille, France, March 2015, Paper No. 060 Slide 29