Validation of Code System DRAWTHREE-FAC for Evaluation of Wall Thinning due to Flow Accelerated Corrosion by PWR Feed Water Piping Analysis

2011 ◽  
Author(s):  
Masanori Naitoh ◽  
Shunsuke Uchida ◽  
Hidetoshi Okada ◽  
Seiichi Koshizuka
Keyword(s):  
Boundary Layer ◽  
Mass Transfer ◽  
Flow Behavior ◽  
Feed Water ◽  
Code System ◽  
Transfer Coefficients ◽  
Mass Transfer Coefficients ◽  
Accelerated Corrosion ◽  
Wall Thinning ◽  
Flow Accelerated Corrosion

The code system DRAWTHREE-FAC for evaluation of pipe wall thinning due to flow accelerated corrosion was validated by comparison of calculations with measurements at the secondary piping of a PWR plant. Distributions of flow velocity and temperature along the whole piping were calculated with the system code RELAP5 and corrosive conditions were calculated by a N2H4-O2 reaction analysis code. Precise flow turbulence at major parts of the piping was analyzed with a 3D computational fluid dynamics (CFD) code to obtain mass transfer coefficients at structure surfaces. In the CFD calculation, the κ-ε method was applied. Since the κ-ε method can not give detailed flow behavior in a boundary layer, the results were extrapolated with a wall function, a power law, and analogy of non-dimensional numbers to obtain mass transfer coefficients in the boundary layer. Then, wall thinning rates were calculated by coupling models of static electrochemical and dynamic oxide layer growth. The wall thinning calculation was focused on T-junction portions of a PWR feed water line. The wall thickness of the PWR secondary piping was measured by the ultrasonic testing. The calculated residual wall thicknesses after thinning agreed with the measurements within ±20% difference.

Evaluation of Wall Thinning of PWR Feed Water Piping With the Coupled Model of Static Electrochemical Analysis and Dynamic Double Oxide Layer Analysis

2010 ◽  
Author(s):  
Masanori Naitoh ◽  
Shunsuke Uchida ◽  
Hidetoshi Okada ◽  
Taku Ohira ◽  
Seiichi Koshizuka
Keyword(s):  
Mass Transfer ◽  
Oxide Layer ◽  
Large Scale ◽  
Electrochemical Analysis ◽  
Turbulence Energy ◽  
Feed Water ◽  
Transfer Coefficients ◽  
Oxygen Injection ◽  
Mass Transfer Coefficients ◽  
Wall Thinning

In order to confirm applicability and accuracy of FAC evaluation methods based on the coupled FAC model of static electrochemical analysis and dynamic oxide layer growth analysis, wall thinning rates calculated with the proposed methods were compared with those measured for the secondary piping of a PWR plant. Flow turbulence at major parts of the system was calculated with 3D CFD codes and extrapolated to the very surface of piping wall to obtain mass transfer coefficients at boundary layers of the structure surfaces. Then, wall thinning rates were calculated with the coupled FAC model by applying the mass transfer coefficients. Major conclusions are as follows: 1) Flow distribution calculated with 3D CFD codes could be extrapolated by applying 2/7 power law of turbulence energy as a function of distance from the surface to those at the very surface of the piping to obtain a precise distribution of mass transfer coefficients. 2) Wall thinning rates calculated for large scale piping of a PWR by applying the obtained mass transfer coefficients agreed with the measured rates within a factor of 2. 3) As a result of demonstration of the FAC evaluation model, it was confirmed that suitable amount of oxygen injection into the feed water resulted sufficient mitigation of FAC without any serious adverse effect on steam generator tubing.

The Effect of Model Parameters on CFD Simulation of a Thermosyphon

2019 ◽  
Author(s):  
Huiyu Wang ◽  
D. Keith Walters ◽  
Keisha B. Walters
Keyword(s):  
Mass Transfer ◽  
Phase Change ◽  
Change Process ◽  
Flow Behavior ◽  
Density Ratio ◽  
Model Parameters ◽  
Special Focus ◽  
Transfer Coefficients ◽  
Mass Transfer Coefficients ◽  
Phase Change Process

Abstract Both numerical and experimental studies have previously been carried out to investigate the heat transfer performance of the two-phase closed thermosyphon (TPCT). This paper investigates the performance of a commercially available computational fluid dynamics (CFD) solver (Ansys FLUENT) to predict the complex flow behavior of TPCTs, with special focus on modeling of the mass transfer phase change process. The present study uses four different sets of mass transfer coefficients for condensation and evaporation within a previously documented phase change model to determine their impact on the simulation results. The mass transfer coefficients effectively control the rate of transfer from liquid to vapor phase during evaporation and vice versa during condensation. The choice of coefficients is assumed to represent a balance between numerical accuracy and stability. A baseline simulation is performed for which both the evaporation and condensation coefficients are equal and set to default values. Three additional simulations vary the magnitude of the coefficients and adopt relative values based on density ratio following a recommended method that has been previously found to be effective for these simulations. Initial results show that the case with the highest coefficient of evaporation and coefficient for condensation based on the density ratio is in good agreement with available experimental data of overall thermal resistance of the TPCT., with predictive capability degrading as the values of the coefficients are reduced. Additionally, the 3D CFD models implemented in this study appear to successfully predict the phase change process and vital flow behavior inside the TPCTs, at least in a qualitative sense.

scholarly journals Some hydrodynamic boundary layer influences on mass transfer coefficients

1984 ◽  
Vol 19 (3) ◽  
pp. 289-308 ◽  
Author(s):  
G.L. Flynn ◽  
A.B. French ◽  
N.F.H. Ho ◽  
W.I. Higuchi ◽  
E.A. Ostafin ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Mass Transfer ◽  
Transfer Coefficients ◽  
Mass Transfer Coefficients ◽  
Hydrodynamic Boundary Layer

scholarly journals Measurements of Mass Transfer Coefficient and Effectiveness in the Recovery Region of a Film-Cooled Surface

1986 ◽  
Author(s):  
W. P. Webster ◽  
S. Yavuzkurt
Keyword(s):  
Boundary Layer ◽  
Mass Transfer ◽  
Turbulent Boundary Layer ◽  
Film Cooling ◽  
Transfer Coefficients ◽  
Large Area ◽  
Mass Transfer Equation ◽  
Mass Transfer Coefficients ◽  
Film Cooling Effectiveness ◽  
Naphthalene Sublimation Technique

Mass transfer coefficients and the film cooling effectiveness are measured downstream of a single row of holes inclined 30 degrees with the surface and inline with the main turbulent boundary layer flow. The mass transfer coefficients (based on the difference between the free stream and the surface concentrations) are measured using a naphthalene sublimation technique. The effectiveness is determined through the injection of a trace gas into the secondary (cooling jets) flow and measuring its concentration at the impermeable wall. Experiments are carried out in a subsonic, zero pressure gradient turbulent boundary layer, under isothermal conditions with three blowing ratios (Uj/U∞): 0.4, 0.8, and 1.2. The data is collected in a region 7 to 80 jet diameters downstream of the injection location. From the data on mass transfer coefficients and effectiveness obtained under the same flow conditions a general mass transfer equation is derived. This paper presents extensive data and discussions; and is believed to be one of the few studies in which both of these variables are measured on the same surface and in a large area in the recovery region.

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.

Laminar Boundary Layer Development Around a Circular Cylinder: Fluid Flow and Heat-Mass Transfer Characteristics

2010 ◽  
Vol 132 (12) ◽  
Author(s):  
A. Alper Ozalp ◽  
Ibrahim Dincer
Keyword(s):  
Boundary Layer ◽  
Mass Transfer ◽  
Circular Cylinder ◽  
Moisture Diffusivity ◽  
Front Face ◽  
Cylinder Surface ◽  
Transfer Coefficients ◽  
Mass Transfer Coefficients ◽  
Practical Applications ◽  
Transfer Characteristics

This paper presents a comprehensive computational work on the hydrodynamic, thermal, and mass transfer characteristics of a circular cylinder, subjected to confined flow at the cylinder Reynolds number of Red=40. As the two-dimensional, steady and incompressible momentum and energy equations are solved using ANSYS-CFX (version 11.0), the moisture distributions are computed by a new alternating direction implicit method based software. The significant results, highlighting the influence of blockage (β=0.200–0.800) on the flow and heat transfer mechanism and clarifying the combined roles of β and moisture diffusivity (D=1×10−8–1×10−5 m2/s) on the mass transfer behavior, are obtained for practical applications. It is shown that the blockage augments the friction coefficients (Cf) and Nusselt numbers (Nu) on the complete cylinder surface, where the average Nu are evaluated as Nuave=3.66, 4.05, 4.97, and 6.51 for β=0.200, 0.333, 0.571, and 0.800. Moreover, the blockage shifts separation (θs) and maximum Cf locations (θCf−max) downstream to the positions of θs=54.10, 50.20, 41.98, and 37.30 deg and θCf−max=51.5, 53.4, 74.9, and 85.4 deg. The highest blockage of β=0.800 encourages the downstream backward velocity values, which as a consequence disturbs the boundary layer and weakens the fluid-solid contact. The center and average moisture contents differ significantly at the beginning of drying process, but in the last 5% of the drying period they vary only by 1.6%. Additionally, higher blockage augments mass transfer coefficients (hm) on the overall cylinder surface; however, the growing rate of back face mass transfer coefficients (hm−bf) is dominant to that of the front face values (hm−ff), with the interpreting ratios of h¯m−bf/h¯m=0.50 and 0.57 and h¯m−ff/h¯m=1.50 and 1.43 for β=0.200 and 0.800.

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