Flow Accelerated Corrosion in Single Bends Under Annular Two Phase Flow Conditions

2012 ◽  
Author(s):  
H. Mazhar ◽  
D. Ewing ◽  
J. S. Cotton ◽  
C. Schefski ◽  
C. Y. Ching
Keyword(s):  
Mass Transfer ◽  
Local Maximum ◽  
Outer Wall ◽  
Water Velocity ◽  
Maximum Mass ◽  
Flow Conditions ◽  
Air Velocity ◽  
Two Phase ◽  
Accelerated Corrosion ◽  
Flow Accelerated Corrosion

The distributions of the mass transfer coefficient in horizontal 90 degree bends were measured under a range of two phase annular flow conditions. A dissolving wall technique at a high Schmidt number (Sc = 1280) is used for the measurements. The maximum mass transfer occurred on the centerline of the bend outer wall at an angle of approximately 50 degrees from the bend inlet under all tested conditions. The area of maximum mass transfer was found to span approximately 30 degrees in the circumferential direction. A second region of enhanced mass transfer occurred on the latter part of the bend with a local maximum occurring slightly off the bend centerline in some cases. Changing the air and water superficial velocities (Jν = 20 to 30 m/s, JL = 0.17 to 0.41 m/s) showed that the air velocity had a larger effect on the mass transfer than the water velocity; however the effect of the water velocity on the mass transfer was not insignificant.

Mass Transfer in Single Bends Under Annular Two Phase Flow Conditions

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
H. Mazhar ◽  
D. Ewing ◽  
J. S. Cotton ◽  
C. Y. Ching
Keyword(s):  
Mass Transfer ◽  
Mass Transfer Rate ◽  
Local Maximum ◽  
Outer Wall ◽  
Water Velocity ◽  
Maximum Mass ◽  
Flow Conditions ◽  
Air Velocity ◽  
Two Phase ◽  
Transfer Rates

The distributions of the mass transfer coefficient in horizontal 90 deg bends were measured under a range of two phase annular flow conditions. A dissolving wall technique at a high Schmidt number (Sc = 1280) is used for the measurements. The maximum mass transfer occurred on the centerline of the bend outer wall at an angle of approximately 50 deg from the bend inlet under all tested conditions. The area of maximum mass transfer rate was found to span approximately 30 deg in the circumferential direction. A second region of enhanced mass transfer occurred on the latter part of the bend with a local maximum occurring slightly off the bend centerline in some cases. Changing the air and water superficial velocities (Jv = 22–30 m/s, JL = 0.17–0.41 m/s) showed that the air velocity had a larger effect on the mass transfer rates than the water velocity; however, the effect of the water velocity on the mass transfer was not insignificant.

Flow and Mass Transfer in Bends Under Flow-Accelerated Corrosion Wall Thinning Conditions

2009 ◽  
Author(s):  
John M. Pietralik ◽  
Chris S. Schefski
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Flow Conditions ◽  
Ferrous Ions ◽  
Local Flow ◽  
Accelerated Corrosion ◽  
Flow Effects ◽  
Flow Accelerated Corrosion

The three groups of parameters that affect flow-accelerated corrosion (FAC) are flow conditions, water chemistry, and materials. Nuclear power plant (NPP) data and laboratory tests confirm that under alkaline water chemistry there is a close relationship between local flow conditions and FAC rates in piping components. The knowledge of local flow effects can be useful for developing targeted inspection plans for piping components, predicting the location of the highest FAC rate for a given piping component, and determining what piping components should be replaced. A similar evaluation applies also to FAC in heat transfer equipment such as heat exchangers and steam generators. The objective of this paper is to examine the role of flow and mass transfer in bends under FAC conditions. Bends experience increased FAC rates compared to straight pipes, and are the most common components in piping systems. When the flow effects are dominant, the FAC rate is proportional to the mass flux of ferrous ions, which, in turn, is proportional to the mass transfer coefficient in the flowing water. The mass transfer coefficient describes the intensity of the transport of corrosion products (ferrous ions) from the oxide-water interface into the bulk water. Therefore, this parameter can be used for predicting the local distribution of the FAC rate. The current paper presents plant and laboratory evidence of the relationship between local mass transfer conditions and the FAC rate in bends. It shows correlations for mass transfer coefficients in bends and reviews the most important flow parameters affecting the mass transfer coefficient. The role of bend geometry and, in particular, the short and long radii, surface roughness, wall shear stress, and local turbulence is discussed. Computational fluid dynamics calculations and plant artefact measurements for short-radius and long radius bends are presented. The effect of the close proximity of two bends on FAC rate is also examined based on CANDU™ NPP inspection data and compared with literature data.

Experimental investigation of flow accelerated corrosion under two-phase flow conditions

2014 ◽  
Vol 267 ◽  
pp. 34-43 ◽  
Author(s):  
Wael H. Ahmed ◽  
Mufatiu M. Bello ◽  
Meamer El Nakla ◽  
Abdelsalam Al Sarkhi ◽  
Hassan M. Badr
Keyword(s):  
Experimental Investigation ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Flow Conditions ◽  
Two Phase ◽  
Accelerated Corrosion ◽  
Flow Accelerated Corrosion

scholarly journals Experimental investigation of hydrodynamic phenomena in vertical-upward adiabatic two-phase flow conditions

2021 ◽  
Vol 10 (3) ◽  
pp. 49-59
Author(s):  
Dinh Anh Tuan ◽  
Pham Tuan Nam ◽  
Nguyen Tu Oanh
Keyword(s):  
Experimental Investigation ◽  
Atmospheric Pressure ◽  
Two Phase Flow ◽  
Water Velocity ◽  
Phase Flow ◽  
Flow Conditions ◽  
Air Velocity ◽  
Two Phase ◽  
Single Flow ◽  
Flow Experiments

In order to investigate hydrodynamic phenomena in two-phase flow conditions in nuclear safety analysis, a series of two-phase flow experiments were conducted using a single flow channel in which air and water were simultaneously injected into the test section. The experiments under atmospheric pressure conditions were carried out with the water velocity and the air velocity covering the ranges from 0.2 to 1.5 m/s and 0.05 to 0.2 m/s, respectively. The technique of two-sensor conductivity probe was used for the measurement of bubble parameters. The experimental results presented and analyzed in this study are the local time-averaged void fraction and bubble velocities at three axial positions L/D = 14.4, 51.2 and 71.3.

Disturbed Flow and Flow-Accelerated Corrosion in Oil and Gas Production

1998 ◽  
Vol 120 (1) ◽  
pp. 72-77 ◽  
Author(s):  
K. D. Efird
Keyword(s):  
Mass Transfer ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Oil And Gas ◽  
Steel Corrosion ◽  
Flow Conditions ◽  
Accelerated Corrosion ◽  
Disturbed Flow ◽  
Wall Shear ◽  
Flow Accelerated Corrosion

The effect of fluid flow on corrosion of steel in oil and gas environments involves a complex interaction of physical and chemical parameters. The basic requirement for any corrosion to occur is the existence of liquid water contacting the pipe wall, which is primarily controlled by the flow regime. The effect of flow on corrosion, or flow-accelerated corrosion, is defined by the mass transfer and wall shear stress parameters existing in the water phase that contacts the pipe wall. While existing fluid flow equations for mass transfer and wall shear stress relate to equilibrium conditions, disturbed flow introduces nonequilibrium, steady-state conditions not addressed by these equations, and corrosion testing in equilibrium conditions cannot be effectively related to corrosion in disturbed flow. The problem in relating flow effects to corrosion is that steel corrosion failures in oil and gas environments are normally associated with disturbed flow conditions as a result of weld beads, pre-existing pits, bends, flanges, valves, tubing connections, etc. Steady-state mass transfer and wall shear stress relationships to steel corrosion and corrosion testing are required for their application to corrosion of steel under disturbed flow conditions. A procedure is described to relate the results of a corrosion test directly to corrosion in an operation system where disturbed flow conditions are expected, or must be considered.

Flow and Mass Transfer in Bends Under Flow-Accelerated Corrosion Wall Thinning Conditions

2010 ◽  
Vol 133 (1) ◽  
Author(s):  
John M. Pietralik ◽  
Chris S. Schefski
Keyword(s):  
Mass Transfer ◽  
Water Chemistry ◽  
Nuclear Power ◽  
Flow Conditions ◽  
Transfer Coefficients ◽  
Ferrous Ions ◽  
Local Flow ◽  
Accelerated Corrosion ◽  
Flow Accelerated Corrosion

The three groups of parameters that affect flow-accelerated corrosion (FAC) are the flow conditions, water chemistry, and materials. Nuclear power plant (NPP) data and laboratory tests confirm that, under alkaline water chemistry, there is a close relationship between local flow conditions and FAC rates in the piping components. The knowledge of the local flow effects can be useful for developing targeted inspection plans for piping components and predicting the location of the highest FAC rate for a given piping component. A similar evaluation applies also to the FAC in heat transfer equipments such as heat exchangers and steam generators. The objective of this paper is to examine the role of the flow and mass transfer in bends under alkaline FAC conditions. Bends experience increased FAC rates compared with straight pipes, and are the most common components in piping systems. This study presents numerical simulations of the mass transfer of ferrous ions and experimental results of the FAC rate in bends. It also shows correlations for mass transfer coefficients in bends and reviews the most important flow parameters affecting the mass transfer coefficient. The role of bend geometry and, in particular, the short and long radii, surface roughness, wall shear stress, and local turbulence, is discussed. Computational fluid dynamics calculations and plant artifact measurements for short- and long-radius bends are presented. The effect of the close proximity of the two bends on the FAC rate is also examined based on CANDU (CANDU is a registered trademark of the Atomic Energy of Canada Limited) NPP inspection data and compared with literature data.

Flow and mass transfer downstream of an orifice under flow accelerated corrosion conditions

2012 ◽  
Vol 252 ◽  
pp. 52-67 ◽  
Author(s):  
Wael H. Ahmed ◽  
Mufatiu M. Bello ◽  
Meamer El Nakla ◽  
Abdelsalam Al Sarkhi
Keyword(s):  
Mass Transfer ◽  
Accelerated Corrosion ◽  
Flow Accelerated Corrosion

Numerical Calculation of Shear Stress Distribution on the Inner Wall Surface of CANDU Reactor Feeder Pipe Conveying Two-Phase Coolant

2007 ◽  
Author(s):  
Jong Chull Jo ◽  
Dong Gu Kang ◽  
Kyung Wan Roh
Keyword(s):  
Shear Stress ◽  
Stress Distribution ◽  
Wall Thickness ◽  
Shear Stress Distribution ◽  
Cfd Analysis ◽  
Two Phase ◽  
Accelerated Corrosion ◽  
Wall Thinning ◽  
Local Areas ◽  
Flow Accelerated Corrosion

Two-phase flow fields inside feeder pipes of a CANDU reactor have been simulated numerically using a CFD (computational fluid dynamics) code to calculate the shear stress distribution which is the most important factor to be considered in predicting the local areas of feeder pipes highly susceptible to FAC (flow-accelerated corrosion)-induced wall thinning. The CFD approach with schemes used in this study to simulate the turbulent flow situations inside the CANDU feeder pipes had been verified by showing a good agreement between the investigation results for the failed feedwater pipe at Surry Unit 2 plant in U.S. and the CFD calculation. Sensitivity studies of the three geometrical parameters such as angle of the 1st and 2nd bends, length of the 1st span between the grayloc hub and the 1st bend, and length of the 2nd span between the 1st and the 2nd bends had already been performed. In this study, the effects of void fraction of the primary coolant coming out from the exit of pressure tubes containing nuclear fuels on the fluid shear stress distribution at the inner surface of feeder pipe wall have been investigated to find out the local areas of feeder pipes conveying two-phase coolant, where are highly susceptible to FAC (flow-accelerated corrosion)-induced wall thinning. As the results of CFD analysis, it is seen that the local regions of feeder pipes of the operating CANDU reactors in Korea, on which the wall thickness measurements have been performed so far, are not coincided with the worst regions predicted by the present CFD analysis where is the connection region of straight & bend pipe near the inlet part of the bend intrados. Finally, based on the results of the present CFD analysis a guide to the selection of the weakest local positions where the measurement of wall thickness should be performed with higher priority has been provided.

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