EXPERIMENTAL AND NUMERICAL INVESTIGATIONS OF FLOW-ACCELERATED CORROSION DOWNSTREAM ORIFICES

THESIS ABSTRACT (ENGLISH)

 

NAME:          MUFATIU MUSILIU BELLO

TITLE:          Experimental and Numerical Investigations                          of Flow-Accelerated Corrosion Downstream                         Orifices

MAJOR:        MECHANICAL ENGINEERING

DATE:           8th May, 2012

 

Flow-Accelerated Corrosion (FAC) is a form of corrosion that affects carbon steel or low-alloy steel piping and fittings in power plants. Piping degradation due to FAC, especially downstream of control valves and restricting orifices, is considered to be one of the major safety and reliability problems facing aging power plants, where piping rupture occurs in high pressure systems. Accurate prediction of the highest FAC wear rate locations enables the mitigation of sudden and catastrophic failures, and the improvement of the plant capacity factor. The objective of the present study is to evaluate the effect of the local flow and mass transfer parameters on flow accelerated corrosion downstream of orifices. Orifice to pipe diameter ratios of 0.25, 0.5 and 0.74 were investigated numerically, under single phase flow conditions, by solving the continuity and momentum equations at Reynolds number of Re = 20,000. Laboratory experiments, using test sections made of hydrocal (CaSO4.½H2O) were carried out under both single and two phase flow conditions, in order to determine the surface wear pattern and validate the numerical results. The maximum mass transfer coefficient found to occur at approximately 1- 4 pipe diameters downstream of the orifice. This location was also found to correspond to the location of elevated turbulent kinetic energy generated within the flow separation vortices downstream of the orifice. The FAC wear rates were correlated with the turbulence kinetic energy and wall mass transfer in terms of Sherwood number. The current study provides FAC engineers in power plants with very useful information for better preparation of plant inspection scope.

 

MASTER OF SCIENCE DEGREE

KING FAHD UNIVERSITY OF PETROLEUM & MINERALS

Dhahran, Saudi Arabia

Table of Contents

 

 

 

Contents

Page

Acknowledgement………………………………………………………

iv

List of Tables……………………………………………………………….

vii

List of Figures……………………………………………………………..

viii

Abstract (English)……………………………………………………….

xii

Abstract (Arabic)…………………………………………………………

xiii

1.0     Introduction………………………………………………………….

1.1     Background…………………………………………………………..

1.2     Flow-Accelerated Corrosion (FAC)…………………………………

1

1

2

2.0     Motivation and Objectives……………………………………….

2.1     Motivation……………………………………………………………

2.2     Objectives…………………………………………………………….

5

5

5

3.0     Literature Review…………………………………………………….

3.1     Experimental Investigations………………………………………….

   3.1.1 FAC In Single Phase Flows………………………………………

   3.1.2 FAC In Two Phase Flows…………………………………………

3.2     Numerical Investigations…………………………………………….

               3.2.1 Single Phase Flow Modelling For FAC   

                        Prediction..………………………………………………………

               3.2.2 Two Phase Flow Modelling For FAC   

                        Prediction…………………………………………………………

               3.2.3 Mass Transfer Modelling For FAC   

                        Prediction………………………………………………………….

               3.2.4 Flow and Mass Transfer Modelling……………………………….    

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4.0     MATHEMATICAL FORMULATION……………………………………..

4.1     Problem Statement…………………………………………………..

1.2     Governing Equations………………………………………………..

1.3     Mass Transfer Calculations…………………………………………..

1.4     Boundary Conditions………………………………………………..

 

 

 

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2.0     Numerical Solution…………………………………………………

2.1     Grids Independence Study………………………………………….. 

2.2     Model Validation…………………………………………………….

2.3     Numerical Results and Discussions………………………………….

      5.3.1 Flow Field……………………………………………………….

                  5.3.2  Mass Transfer…………………………………………………  

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48

3.0     Experimental Analysis……………………………………………

3.1     Materials…………………………………………………………….

3.2     Experimental Setup and Procedure…………………………………..

3.3     Measurement techniques…………………………………………….

3.4     Experimental Results and Discussions……………………………….

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4.0     Validation OF Results………………………………………………

4.1     Comparison of Numerical With Correlation…………………………

4.2     Comparison of Numerical Results With Single Phase Experimental Results………………………………………………………………

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89

5.0     CONCLUSION AND RECOMMENDATIONS……………………………

5.1     Conclusions…………………………………………………………..

5.2     Recommendations and Future Work…………………………………

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NOMENCLATURE………………………………………………………………

96

References……………………………………………………………………

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