Wir schaffen Wissen heute für morgen

Transcription

1 Paul Scherrer Institut Torsten Th. Betschart Wir schaffen Wissen heute für morgen Two-phase flow hydrodynamis characterization for understanding the aerosol retention in liquid pools ERMSAR 15, 7th conference on SEVERE ACCIDENT RESEARCH

2 Outline of the Presentation Objectives Test Facility TRISTAN Measurement technique Overview and flow features Gas Phase Velocity and Bubble Reconstruction Summary

3 Objectives Open Safety Valve Relevant Severe Accident Sequence PWR Fuel Rod Damage & Steam Generator Tube rupture Open safety valve on top of SG SGTR Bypass of Containment and potentially direct pathway for radioactive matter into the environment FRD What is the retention potential of the SG?

4 Decontamination factor Objectives Motivation & Background Hydrodynamics of two-phase flow in tube bundle geometries and pools widely unknown compared with integral understanding ARTIST project Integral retention factors of typical aerosols were measured Used models underestimate retention Flooded bundle, submerg. 3 m Flooded bundle, submerg. 0.3 m Water pool, m 1 Stk x relative submergence

5 Objectives Motivation & Background Hydrodynamics of two-phase flow in tube bundle geometries and pools widely unknown compared with integral understanding ARTIST project Integral retention factors of typical aerosols were measured Used models underestimate retention Transfer processes depend on interfacial surface and kinetics Objectives of the PhD Deeper understanding of two-phase flows in channels and tube bundles Characterization of a break-down of sonic gas jets into a pool of water Establish database for two-phase flow parameters Experimental data for lumped parameter code model development

6 Test Facility TRISTAN TRISTAN: Tube Rupture In Steam generator multi-phaseflow investigations Single Tube Setup 500x500mm square duct Measurement area: 408x408mm square segment Central rod with Guillotine break

7 Test Facility TRISTAN TRISTAN: Tube Rupture In Steam generator multi-phaseflow investigations Tube-Bundle Setup Subchannel and Bundle P/D: 1.44

8 Test Facility TRISTAN TRISTAN: Tube Rupture In Steam generator multi-phaseflow investigations Tube-Bundle Setup Tube Break Simulators: Guillotine Breaks

9 Test Facility TRISTAN Wire-mesh sensor Measurement of the electrical conductivity of the fluid

10 Test Facility TRISTAN Wire-mesh sensor Measurement of the electrical conductivity of the fluid Intrusive, high resolution flow imaging technique - Measurement Frequency: 1250 Hz

11 Test Facility TRISTAN Wire-mesh sensor Measurement of the electrical conductivity of the fluid Intrusive, high resolution flow imaging technique In TRISTAN, two sensors mounted in a short distance after each other are used

12 Extraction Chord Overview and flow features Presented cases: Gas Injection: 250 kg/h Distances: 625mm and 2500mm Both Tube bundle and Single Tube Data Extraction for profiles: Used for both setups Presented quantities: Void Fractions Flow Structure Interfacial area concentration

13 Overview and flow features: Tube Bundle 2500 mm 625 mm PSI, Seite 13

14 Void Fraction [%] Void Fraction [%] Overview and flow features: Tube Bundle mm 2500 mm PSI, Seite 14

15 Overview and flow features: Single Tube 625 mm 2500 mm PSI, 13.June 2012 Seite 15

16 Overview and flow features: Single Tube 625 mm 2500 mm PSI, Seite 16

17 Standard Deviation [-] Standard Void Fraction Deviation [%] [-] Standard Deviation [-] Void Fraction [%] Standard Void Fraction Deviation [%] [-] Void Frac Overview and flow features: Comparison Void Fractions and Standard Deviations on the extraction chord 100mm 100mm 625mm 100mm 1250mm 625mm Distance 1250mm from 1250mm 625mm Break [mm] 1250mm 2500mm mm Tube Bundle Single Tube Tube Bundle Single Tube Distance 50Distance 100 from Break 150 [mm] Distance Distance from from from Break Distance 2500mm Break Break [mm] [mm] [mm] from Break [mm] mm 625mm 625mm 2500mm Tube Bundle Single Tube Distance 2500mm from 2500mm Break [mm] 2500mm Tube Tube Bundle Bundle Single Single Tube Tube Tube Bundle Single Tube Distance Distance Distance from from from Break Break Break [mm] [mm] [mm] PSI, Seite 17

18 Bubble Reconstruction: Gas Phase Velocity and Bubble Reconstruction Starting from 3D void fraction distributions Not divided into interconnected structures Bubbles are identified using recursive algorithms Only the lateral components are geometrical, the axial component is still temporal Therefore, an estimate of the gas phase velocity is needed!

19 141 mm Gas Phase Velocity and Bubble Reconstruction Bubble Reconstruction: Single Tube Example Well, Bubble 134 mm

20 Gas Phase Velocity and Bubble Reconstruction Bubble Reconstruction: Single Tube Example Well, Bubble Jet case (100mm)

21 Gas Phase Velocity and Bubble Reconstruction Bubble Reconstruction: Tube Bundle Example Well, Bubble

22 Gas Phase Velocity and Bubble Reconstruction Bubble Reconstruction: Tube Bundle Example Well, Bubble

23 Gas Phase Velocity and Bubble Reconstruction Gas Phase Velocity is estimated using time-of-flight estimation between the signals of the two Wire-Mesh sensors Three Dimensional Signal Cross Correlation is used for the evaluation of the frame shifts ψ AB u, v, w = V V f x, y, z f sx,sy,sz g x u, y v, z w g f x, y, z f sx,sy,sz 2 g x u, y v, z w g 2 V Results: A clear, distinct peak of the distributions can be seen (extracts on x-z plane) Subchannel 5 Subchannel 47 Subchannel PSI, Seite 23

24 Gas Phase Velocity and Bubble Reconstruction Interfacial Area Concentration: Definition: Interfacial Area is the amount of interfacial area per unit mixture volume Two Methods to calculate IAC: Full Bubble Reconstruction S bub,i V tot V bub,i a = N i=1 S bub,i V tot PSI, Seite 24

25 Gas Phase Velocity and Bubble Reconstruction Interfacial Area Concentration: Definition: Interfacial Area is the amount of interfacial area per unit mixture volume Two Methods to calculate IAC: Full Bubble Reconstruction Void Fraction Gradient V tot V bub,i S bub,i a i = α g x 2 + α g y 2 + α g z 2 a = N i=1 S bub,i V tot PSI, Seite 25

26 Gas Phase Velocity and Bubble Reconstruction Interfacial Area Concentration: Definition: Interfacial Area is the amount of interfacial area per unit mixture volume Two Methods to calculate IAC: Full Bubble Reconstruction Void Fraction Gradient V tot V bub,i S bub,i a i = α g x 2 + α g y 2 + α g z 2 a = N i=1 S bub,i V tot Axial Gradient Approximation: α g z = α g t t z α g t 1 v z PSI, Seite 26

27 Interfacial Area Concentration [1/m] Gas Phase Velocity and Bubble Reconstruction Interfacial Area Concentration for the two Experiments ST Rec ST Grad TB Rec TB Grad Break-Sensor Distance [mm] Gradient Method gives slightly smaller volues compared to the full reconstruction It is within the errors expected from the wire-mesh sensor measurement Proof of concept of this gradient approach shown in a semester thesis and a coming NURETH paper Interfacial Area Concentration in the bundle quite higher, but PSI, Seite 27

28 Summary Conceptual New Hydrodynamic Experimental data collected for tube bundle and large square channel Data can be used for the validation of hydrodynamic models New experience gained in understanding the phenomenology of two-phase flows a bit more concrete BUSCA code comparison with TRISTAN data (BSD and gas phase velocity) If someone would like to give it a try in CFD Follow-up Project in TRISTAN

29 Thank you for your attention Seite 29