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Study of turbulent mixing for thermal fatigue prediction at reactor conditions

This study examines turbulent mixing for thermal fatigue prediction at reactor conditions. It includes experiments, simulations, and conclusions on dominant frequencies, vortices, temperatures, and fatigue damage. Future work and journal articles on related topics are also discussed.

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Study of turbulent mixing for thermal fatigue prediction at reactor conditions

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  1. Study of turbulent mixing for thermal fatigue prediction at reactor conditions Mattia Bergagio bergagio@kth.se NuclearEngineering, KTH Supervisor: HenrykAnglart

  2. Overview • Introduction • Experiment • Simulation • Conclusions • Future work SKC • MATTIA BERGAGIO

  3. 1) Goals Industrial cases IHCP Experiments LES in the wall and on the wall FEA stresses Fatigue damage SKC • MATTIA BERGAGIO

  4. 1) Test section Inner tube Outer tube • A Turbulent thermal mixing High-cycle thermal fatigue Frequencies of interest = 0.01 – 5 Hz SKC ● Mattia Bergagio

  5. 1) Test section, inner tube & thermocouple discs Inner tube

  6. 2) Temps from Case 1 Homogeneous mixing Incipientmixing

  7. 2) Mixing inhomogeneity in Case 1 THEMFE ● Bergagio Mattia

  8. 2) Temperatures in Case 1 at THEMFE ● Bergagio Mattia

  9. 2) Spectral analysis in Case 1 at

  10. 2) Dominant frequencies and critical modes in Case 1 SKC ● Mattia Bergagio

  11. 3) Temps and mag(U) – LES (WALE, CHT) • a SKC • MATTIA BERGAGIO

  12. 3) Vortices – LES (WALE, CHT) • a SKC • MATTIA BERGAGIO

  13. 3) Mean, highest, and lowest temperatures • LES Experiment SKC • MATTIA BERGAGIO

  14. 3) Fatigue damage over 10 s D (m) Which frequencies and modes at SKC • MATTIA BERGAGIO

  15. 3) Dominant frequencies and critical modes - LES Highest peaks at 0.4 Hz < 10 times the inverse of the simulation time SKC • MATTIA BERGAGIO

  16. 4) Conclusions • One of the first times CFD simulations and experiments on mixing are run at BWR conditions ( = 216 K, p = 7.2 MPa) • CFD results and experimental data agree reasonably well • Fatigue crack after 97 h • Mixing inhomogeneity, stress ranges, and fatigue susceptibility seem correlated • The oscillation modes behind the highest spectral peaks often correspond to the largest time scales, in both LES and experiments • At high mixing inhomogeneity, dominant frequencies = 0.03-0.10 Hz < 10 times the inverse of the measurement time SKC • MATTIA BERGAGIO

  17. 5) Future work • CFD simulations with (Bo Alfredsson’s LSY project) • Vast dataset of high-quality CFD results heat transfer coefficient, buoyancy, inverse heat transfer etc. • Improve spectral analysis SKC • MATTIA BERGAGIO

  18. Journal articles • M. Bergagio and H. Anglart. 2017. Experimental investigation of mixing of non-isothermal water streams at BWR operating conditions. Nuclear Engineering and Design, 317:158–176. • M. Bergagio, R. Thiele, and H. Anglart. 2017. Analysis of temperature fluctuations caused by mixing of non-isothermal water streams at elevated pressure. International Journal of Heat and Mass Transfer, 104:979–992. • M. Bergagio, H. Li, and H. Anglart. 2018. An iterative finite-element algorithm for solving two-dimensional nonlinear inverse heat conduction problems. International Journal of Heat and Mass Transfer, 126:281–292. • M. Bergagio, W. Fan, R. Thiele, and H. Anglart. 2018. Large eddy simulation of thermal mixing with conjugate heat transfer at BWR operating conditions. Submitted to Nuclear Engineering and Design. SKC • MATTIA BERGAGIO

  19. Conference papers • M. Bergagio, S. Hedberg, S. Rydström, and H. Anglart. 2015. Instrumentation for temperature and heat flux measurement on a solid surface under BWR operating conditions. In Proceedings of the 16th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, volume 7, pages 5962–5975. • H. Anglart, M. Bergagio, S. Hedberg, S. Rydström, and W. Frid. 2015. Measurement of wall temperature fluctuations during thermal mixing of non-isothermal water streams. In Proceedings of the 16th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, volume 1, pages 807–818. SKC • MATTIA BERGAGIO

  20. Thank you! • Questions? • bergagio@kth.se SKC • MATTIA BERGAGIO

  21. 4) IHCP - Domains Test problem 1 Test problem 2 SKC • MATTIA BERGAGIO

  22. 4) Test problem 1 – Wall temperature

  23. 4) Test problem 2 – Wall temperature SKC • MATTIA BERGAGIO

  24. 5) IHCP - Conclusions • A robust, effective algorithm has been implemented to solve transient boundary inverse problems on 2D domains • No a priori knowledge of noise statistics • Qualitative agreement between the solutions to the direct and inverse problems • Less accuracy if strong heating, for and at the early stages of the transients • Time-integrated error 0.8% in Case 2 SKC • MATTIA BERGAGIO

  25. 1) Geometry and experimental avg(T) z = 1.00 m (outlets) z = 0.80 m (hot inlets) z = 0.65 m (mixing region) SKC • MATTIA BERGAGIO

  26. 2) Water temperature – LES (WALE, CHT)

  27. 2) 216B – Water: avg(T) & var(T) SKC • MATTIA BERGAGIO

  28. 2) 216B – Water: avg(T) SKC • MATTIA BERGAGIO

  29. 2) Vortices (a) View at (b) View at (c) View at (d) View at SKC • MATTIA BERGAGIO

  30. 2) (yPlus) SKC • MATTIA BERGAGIO

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