NUMERICAL SIMULATION OF FLOW- INDUCED CORROSION DAMAGES Kaushik Das, Debashis Basu and Todd Mintz Center for Nuclear Waste Regulatory Analyses ® Southwest Research Institute ® San Antonio, TX, USA ANSYS Regional Conference August 31 - September 1, 2011 Houston, TX
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NUMERICAL SIMULATION OF FLOW- INDUCED … SIMULATION OF FLOW-INDUCED CORROSION DAMAGES Kaushik Das, Debashis Basu and Todd Mintz Center for Nuclear Waste Regulatory Analyses® Southwest
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NUMERICAL SIMULATION OF FLOW-INDUCED CORROSION DAMAGES
Kaushik Das, Debashis Basu and Todd Mintz
Center for Nuclear Waste Regulatory Analyses ®
Southwest Research Institute®
San Antonio, TX, USA
ANSYS Regional ConferenceAugust 31 - September 1, 2011 Houston, TX
OUTLINE
2
• Introduction
• Description of the Simulation Test Cases
• Results and Discussions for Test Case-1
• Results and Discussions for Test Case-2
• Summary
2011 ANSYS Regional Conference Houston, TX
INTRODUCTION
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• Background
• Flow Assisted Corrosion Mechanism
• Species Concentration: Role of Hydrazine
• Objective
2011 ANSYS Regional Conference Houston, TX
BACKGROUND
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Ruptured Condensate Feedwater Pump Pipeline at Mihama 3 Nuclear Power
Plant (Source:” International Atomic Energy Agency, Erosion Corrosion Including FAC and EAC Issues in Nuclear Power Plants.” 2003)
• Considered a major Contributor to Pipeline Integrity
• Power Plant Components• Pipelines
• Significant Accidents in Power Plants 2005 Mihima-3; Kansai Electric Power
Company 1999 Tsuruga-2 : Japan Atomic Power
Company 1986 Surrey-2: Dominion Power
• Petrochemical Industry and Pipelines Significant Loss Due to Downtime and
Maintenance
2011 ANSYS Regional Conference Houston, TX
FLOW ASSISTED CORROSION MECHANISM
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• Flow Assisted Corrosion Diffusion of Corrosive Agent to
Metal Electrochemical Reaction on Metal
Surface Effect of Solid Particles
• Influenced by a host parameters• Temperature• Chemical Condition (pH)• Localized Species Concentration• Pipe Geometry and Material• Flow and Phase Condition Base Metal
Inner OxideLayer
Outer OxideLayer
Species Boundary Layer
Diffusion of Corrosive
SpeciesRelease of Base Metal
Fluid Shear Erosion
Erosion Due to Particle Impact
Base Metal Inner OxideLayer Reaction
Fluid Outer OxideLayer Reaction
2011 ANSYS Regional Conference Houston, TX
SPECIES CONCENTRATION : ROLE OF HYDRAZINE
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2011 ANSYS Regional Conference Houston, TX
• Reduced Use in Fossil Fuel Power Plants• Used in Nuclear Power Plants• Primarily Used as Oxygen Scavenger
Stabilizes pH Acts as Alkalinizer Reduced Stress Corrosion Cracking (SCC) in Steam Generator Tubes
• Hydrogen-Hydrazine Co-injection in BWR Primary Coolant for SCC Reduction
• N2H4-O2 Reaction Important for Corrosion Condition Calculations
Affects Species Concentration Affects Electrochemical Corrosion Potential (ECP) Oxidation at Base Metal Form Protective Magnetite Layer
OBJECTIVE
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• Part of Ongoing Research on Development of CFD Modeling Framework to Assess Erosion-Corrosion Damage Supplement System Level Corrosion Analysis
• Presented Study Computational Assessment of Existing N2H4-O2 Chemistry Models
Reaction Kinetics Inclusion of Surface Reaction
Simulate Reaction And Wall Mass Transfer in U-Bend Pipe Component
• Assess Effect of Turbulence Models in Wall Mass Transfer
2011 ANSYS Regional Conference Houston, TX
DESCRIPTION OF THE SIMULATION TEST CASES
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• Case-Study-1: Straight Pipe• Case Setup• Description of Chemical Kinetics• Assumptions and Simulation Conditions
• Case-Study-2: U-bend Pipe• Case Setup• Model Development and Assumptions• Mass Transfer Calculation Method
2011 ANSYS Regional Conference Houston, TX
CASE-STUDY-1 SETUP
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2011 ANSYS Regional Conference Houston, TX
• Based on Experimental Study of Ishida et. al.• ANSYS-FLUENT® Solver Version 12.1 Used
Experimental Setup
Computational Domain
Computational Grid at a Cross Section
DESCRIPTION OF CHEMICAL KINETICS
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• Baseline Reaction N2H4 + O2-→ N2 + 2H2O
• General Expression of Reaction Rate
• Arrhenius Rate
• Inclusion of Surface Effect
• Experimental Rate Determined Through Experimental Study of Ishida et al. Dickinson et. al
Zone Based Approach: 25% of Volume Affected by Surface
CASE-STUDY-2 SETUP
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• U-bend Pipe Encountered Frequently in
Pipelines and Powerplants Experimentally (Chang et al.)
and Numerically Studied (Keating et. al)
1.38 m
253.65 m
44.5 × 44.5 mm
Wall Thinning and ErosionCorrosion Damage in
Evaporating Tubes(Source:”Guidelines on Pipe
Wall Thinning” Class NK Sept 2008)
2011 ANSYS Regional Conference Houston, TX
MODEL DEVELOPMENT AND ASSUMPTIONS
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• ANSYS-FLUENT® Solver Version 12.1 Steady State Turbulent Flow Shear Stress Transport (SST) k-ω model
• Laminar Finite Rate Chemistry Model Turbulence-Chemistry Interaction Neglected Effect Retained in Species Calculations through Turbulent Schmidt Number Further Studies should include Eddy Dissipation Concept Model
• Adiabatic Walls• Experimental Reynolds Number : 5.67×104
• Compressed Liquid: Inlet Temperature 280o C and Pressure 80 MPa• Inlet Concentration of Oxygen: 700 ppb
EFFECT OF TURBULENCE ON CORROSION RATE DISTRIBUTION
2011 ANSYS Regional Conference Houston, TX
Locations Along The U-bend Wall Used In Corrosion Calculations
Inner Wall Centerline Outer Wall Centerline Top Wall Centerline
y
z
Outer Line
Inner Line
Top Line
?
SUMMARY
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• A Two Part Study to Simulate Flow and Chemistry in NPR Secondary Coolant Pipelines
• In Part-1 Used Experimentally Obtained N2H4-O2 Reaction Kinetics in Numerical Simulations Baseline Simulation without Wall Effect Study Effect of Wall
Overall Averaged Kinetics Provide Better Results
• In Part-2 Simulated a U-Bend Pipe Mass Transfer Calculation Based on Simple Diffusion Based Model
Minimal Variation at the Inlet Section Significant Impact of Secondary Flows at the Bend
Choice of Turbulence Model Important• Affects Corrosion Rate Predictions