Prediction of the Depletion Zone due to Selective Oxidation of P91 Steel

2005 ◽  
Vol 237-240 ◽  
pp. 965-970 ◽  
Author(s):  
Marek Danielewski ◽  
Robert Filipek ◽  
Barbara Kucharska
Keyword(s):  
Selective Oxidation ◽  
Computer Modelling ◽  
Average Concentration ◽  
Concentration Profiles ◽  
Unique Determination ◽  
Measured Concentration ◽  
P91 Steel ◽  
Calculated Concentration ◽  
Key Factor ◽  
Limitation Method

Experimental measurements do not allow for a unique determination of the concentration profiles, e.g., in case of multi-layer systems. The measured concentration of the elements at the alloy/scale interface is an average concentration in an alloy and in a scale near the spot of the beam [1]. The knowledge of the concentration of the elements at the boundary is necessary for the understanding corrosion of alloys. This essential obstacle of experimental techniques can be overcome by computer modelling. Namely, by combining the different methods (non-unique measurement with unique modelling). The Danielewski-Holly model of interdiffusion has a unique solution. This model enables to predict the evolution of component distributions in the reacting alloy. The model is valid for time dependent boundary conditions and consequently can be used for modelling the more complex reactions, eg., the formation of complex oxides. To avoid the nonphysical values of fluxes in reacting alloy the kinetic constraint on all fluxes was introduced, i.e., the flux limitation method. The results of the selective oxidation of the P91 steel (0,1 wt.% C, 8,6 wt.% Cr, 0,25 wt.% Ni) are presented. Calculated concentration profiles are compared with the experimental data. We show the evolution of chromium distribution in oxidizing steel up to 3 000 hours. The computations demonstrate that chromium depletion is the key factor determining the scale composition.

scholarly journals Experimental investigation and computer simulation of diffusion in Pt-coated bulk Ni

2010 ◽  
Vol 46 (2) ◽  
pp. 153-160 ◽  
Author(s):  
W. Gong ◽  
L. Zhang ◽  
M. Ode ◽  
H. Murakami ◽  
C. Zhou
Keyword(s):  
Thin Film ◽  
Experimental Investigation ◽  
Electron Probe ◽  
Bulk Diffusion ◽  
Concentration Profiles ◽  
Atomic Mobility ◽  
Measured Concentration ◽  
Calculated Concentration ◽  
Higher Temperature ◽  
Interdiffusion Coefficients

The concentration profiles of thin-film Pt/bulk Ni coatings annealed at 1150, 1250 and 1300?C for different time were measured by means of electron probe microanalysis. The corresponding interdiffusion coefficients were then determined using the thin-film solution. The calculated concentration profiles based on the presently obtained interdiffusion coefficients agree well with the experimental ones, but better at a higher temperature or a longer time. The comparison between the presently measured concentration profiles and the DICTRA simulated ones indicates that it is promising to apply the well-established atomic mobility databases due to bulk diffusion information in coating systems with some simple modifications for diffusivities.

scholarly journals Influence of Gating System Parameters of Die-Cast Molds on Properties of Al-Si Castings

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3755
Author(s):  
Štefan Gašpár ◽  
Tomáš Coranič ◽  
Ján Majerník ◽  
Jozef Husár ◽  
Lucia Knapčíková ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Computer Modelling ◽  
Permanent Deformation ◽  
Surface Hardness ◽  
Technological Parameters ◽  
Inlet System ◽  
Die Cast ◽  
Key Factor ◽  
Fine Grained Structure ◽  
Design Solutions

The resulting quality of castings indicates the correlation of the design of the mold inlet system and the setting of technological parameters of casting. In this study, the influence of design solutions of the inlet system in a pressure mold on the properties of Al-Si castings was analyzed by computer modelling and subsequently verified experimentally. In the process of computer simulation, the design solutions of the inlet system, the mode of filling the mold depending on the formation of the casting and the homogeneity of the casting represented by the formation of shrinkages were assessed. In the experimental part, homogeneity was monitored by X-ray analysis by evaluating the integrity of the casting and the presence of pores. Mechanical properties such as permanent deformation and surface hardness of castings were determined experimentally, depending on the height of the inlet notch. The height of the inlet notch has been shown to be a key factor, significantly influencing the properties of the die-cast parts and influencing the speed and filling mode of the mold cavity. At the same time, a significant correlation between porosity and mechanical properties of castings is demonstrated. With the increasing share of porosity, the values of permanent deformation of castings increased. It is shown that the surface hardness of castings does not depend on the integrity of the castings but on the degree of subcooling of the melt in contact with the mold and the formation of a fine-grained structure in the peripheral zones of the casting.

Validation of a Two-Pool Model for the Kinetics of ß2-Microglobulin

2002 ◽  
Vol 25 (5) ◽  
pp. 411-420 ◽  
Author(s):  
S. Stiller ◽  
X.Q. Xu ◽  
N. Gruner ◽  
J. Vienken ◽  
H. Mann
Keyword(s):  
Standard Deviation ◽  
Plasma Concentrations ◽  
Generation Rate ◽  
Secondary Amyloidosis ◽  
Concentration Profiles ◽  
Dialysis Dose ◽  
Measured Concentration ◽  
Pool Model ◽  
Efficacy Parameters ◽  
Beta 2 Microglobulin

Secondary amyloidosis due to beta-2-microglobulin (ß2-m) is a serious long-term complication in patients on regular dialysis therapy. ß2-m can be considered a middle-molecule marker used to facilitate the assessment of dialysis efficacy. For this purpose, a validated model that calculates characteristic efficacy parameters, such as Kt/V, TAC and generation rate, is needed. There is general agreement that ß2-m-kinetics should be described by a two-pool model, but little has been published to validate such an approach. We measured the ß2-m concentration profiles of eight stable patients during hemodialysis (HD) at the start of treatment, after 30 minutes, after 60 minutes, and every hour until the end. Thereafter they were measured at 10-minute intervals for an hour. The dialyser clearances were determined from the plasma concentrations in front of and behind the dialyser twice during each session – after 1 hour, and 4 hours from the start of treatment. The kinetic parameters of a two-pool model (e.g. the compartment volumes V1 and V2, the mass transfer coefficient K12 and the generation rate G) were determined from the optimal fit of the measured concentration profile. The table below summarises the results by giving the mean and standard deviation for each parameter: V (liters) V1/V2 V % TBW K12 m(ml/min) G (mg/kg/day) 10.0 ± 1.6 4.60 ± 1.8 28.4 ± 3.1 56.3 ± 25.2 2.50 ± 0.66 Inter-individual differences in V1/V2 and K12 were high, ranging from 2.5 to 10.0 for V1/V2 and from 26 to 140 for K12. Error analysis suggested that these wide ranges were due to the method and that in reality the probable range of V is 25–36% of TBW, of V1/V2 3.5–5.3, and of K12 30–80 ml/min. With standard values for these three parameters (V = 30% of TBW, V1/V2 = 4.4 and K12 = 55 ml/m), equal for all patients, and their respective ranges, Kt/V can be calculated with a standard deviation of 13%. Kt/V > 1.2 secures the maximum possible ß2-m removal with three HD treatments a week. Conclusions The parameters of a two-pool model of ß2-m kinetics can be derived from concentration profiles obtained under routine dialysis conditions, but accuracy is not completely satisfactory. Similar to the dialysis dose for urea (Kt/Vurea) the dialysis dose for ß2-m (Kt/Vß2-m) can be calculated from the pre- and post-dialysis concentrations of ß2-m, body weight, ultrafiltration and dialysis time. Kt/Vß2-m > 1.2 secures the maximum possible removal of ß2-m in HD with three sessions per week.

scholarly journals MEASUREMENT OF SEDIMENT SUSPENSION IN COMBINATIONS OF WAVES AND CURRENTS

1972 ◽  
Vol 1 (13) ◽  
pp. 55
Author(s):  
J. Kirkegarrd Jensen ◽  
Torben Sorenson
Keyword(s):  
Thin Layer ◽  
Concentration Profile ◽  
Field Data ◽  
Concentration Profiles ◽  
Sediment Suspension ◽  
Calculated Concentration ◽  
Waves And Currents ◽  
The Mean ◽  
Mean Concentration ◽  
Good Agreement

The paper describes a procedure for obtaining field data on the mean concentration of sediments in combination of waves and currents outside the breaker zone, as well as some results of such measurements. It is assumed that the current turbulence alone is responsible for the maintenance of the concentration profile above a thin layer close to the bottom, in which pick-up of sediments due to wave agitation takes place. This assumption gives a good agreement between field data and calculated concentration profiles.

Non-axisymmetric turbulent mass transfer in a circular tube

1969 ◽  
Vol 38 (3) ◽  
pp. 457-472 ◽  
Author(s):  
Alan Quarmby ◽  
R. K. Anand
Keyword(s):  
Mass Transfer ◽  
Circular Tube ◽  
Eddy Diffusivity ◽  
Concentration Profiles ◽  
Tracer Gas ◽  
Direct Evaluation ◽  
Measured Concentration ◽  
Eddy Diffusivities ◽  
Fluid Properties ◽  
Fully Developed Turbulent Flow

Theory and experiment are presented for mass transfer into a fully developed turbulent flow in a plain circular tube in two non-axisymmetric cases. The cases studied are a diametral line source and a discontinuous ring source, in which there is a uniform mass flux over rectangular areas of the tube wall. A comparison is made between the concentration profiles predicted by the solutions of the diffusion equation and experiments using nitrous oxide, Schmidt number S = 0·77, as a tracer gas in air. The range of experiments covers Reynolds numbers R from 20,000 to 120,000.In the analysis, the assumption is made that the tangential and radial eddy diffusivities of mass are equal at a point. The radial diffusivity of mass, which is a function of radial position, is related to the radial eddy diffusivity of momentum by a ratio, which takes account of fluid properties and the value of the radial eddy diffusivity of momentum. The satisfactory agreement between analysis and experiment establishes the correctness of this assumption. Further confirmation was obtained by direct evaluation of the tangential eddy diffusivity of mass from the measured concentration profiles.

Measurements of coastal dispersion in Ontario lakes

1976 ◽  
Vol 3 (1) ◽  
pp. 156-162 ◽  
Author(s):  
Merv. D. Palmer
Keyword(s):  
Cross Sections ◽  
Coastal Waters ◽  
Relative Dispersion ◽  
Concentration Profiles ◽  
Two Dimensional ◽  
Dispersion Coefficients ◽  
Measured Concentration ◽  
Power Growth ◽  
Constant Rate ◽  
Vertical Dispersion

A series of dye injection experiments were carried out near the surface in the coastal waters of lakes Erie, Ontario, and Simcoe. The purpose of the experiments was to determine whether the relative dispersion in these regions was similar to that obtained in other oceanographical experiment. Rhodamine BA dye was injected at a constant rate (approximately 150 mg/s) at a depth 1 m below the surface from a raft anchored in 9 m of water (approximately 1.5 km offshore) for 6 to 8 h. Two-dimensional dye plume concentrations were measured at cross sections 60 to 830 m from the source. Relative dispersion coefficients were determined numerically from the measured concentration profiles. The horizontal dispersion coefficients (80 to 4100 cm2/s) were comparable to oceanographical values and exhibited a 1.33 power growth with distance from the source. Vertical dispersion coefficients were very small (less than 1 cm2/s) and relatively independent of distance from the source.

scholarly journals Adsorption capacity of chosen sandy ground with respect to contaminants relocating with groundwater

2017 ◽  
Vol 43 (1) ◽  
pp. 27-33
Author(s):  
Andrzej Aniszewski
Keyword(s):  
Transport Equation ◽  
Adsorption Capacity ◽  
Contaminant Transport ◽  
Cross Sections ◽  
Measured Concentration ◽  
Calculated Concentration ◽  
Dimensionless Concentration ◽  
Sandy Ground ◽  
Measurement Series ◽  
Definition Of

Abstract One of the most important problems concerning contaminant transport in the ground is the problem related to the definition of parameters characterizing the adsorption capacity of ground for the chosen contaminants relocating with groundwater. In this paper, for chloride and sulfate indicators relocating in sandy ground, the numerical values of retardation factors (Ra) (treated as average values) and pore groundwater velocities with adsorption (ux/Ra) (in micro-pore ground spaces) are taken into consideration. Based on 2D transport equation the maximal dimensionless concentration values (C*max c) in the chosen ground cross-sections were calculated. All the presented numerical calculations are related to the unpublished measurement series which was marked in this paper as: October 1982. For this measurement series the calculated concentration values are compared to the measured concentration ones (C*max m) given recently to the author of this paper. In final part of this paper the parameters characterizing adsorption capacity (Ra, ux/Ra) are also compared to the same parameters calculated for the two earlier measurement series. Such comparison also allowed for the estimation of a gradual in time depletion of adsorption capacity for the chosen sandy ground.

scholarly journals A MODEL OF ION TRANSPORT IN CONJUGATED POLYMERS

2009 ◽  
Vol 50 (3) ◽  
pp. 355-364
Author(s):  
JOHN BURNELL
Keyword(s):  
Ion Transport ◽  
Conjugated Polymers ◽  
Conjugated Polymer ◽  
Experimental Studies ◽  
Cation Transport ◽  
Concentration Profiles ◽  
Measured Concentration ◽  
Micro Actuator ◽  
Micro Pump ◽  
Good Agreement

AbstractUnderstanding ion transport in conjugated polymers is essential for developing mathematical models of applications of these materials. Previous experimental studies have suggested that cation transport in a conjugated polymer could be either diffusion or drift controlled, with debate over which dominates. In this paper we present a new model of cation transport that explains most of the features seen in a set of recent experiments. This model gives good agreement with measured concentration profiles, except when the profile has penetrated the polymer by more than 60%. The model shows that both diffusion and drift processes can be present. An application of a micro-actuator based on a conjugated polymer is presented to demonstrate that this technology could be used to develop a micro-pump.

scholarly journals Description and Verification of the Contaminat Transport Models in Groundwater (Theory And Practice)

2013 ◽  
Vol 39 (3) ◽  
pp. 3-21 ◽  
Author(s):  
Andrzej Aniszewski
Keyword(s):  
Mathematical Models ◽  
Contaminant Transport ◽  
Organic Contaminants ◽  
Radioactive Decay ◽  
Theory And Practice ◽  
Transport Models ◽  
Measured Concentration ◽  
Calculated Concentration ◽  
Dimensionless Concentration ◽  
Measurement Series

Abstract This paper presents a general overview of 2D mathematical models for both the inorganic and the organic contaminants moving in an aquifer, taking into consideration the most important processes that occur in the ground. These processes affect, to a different extent, the concentration reduction values for the contaminants moving in a groundwater. In this analysis, the following processes have been taken into consideration: reversible physical non-linear adsorption, chemical and biological reactions (as biodegradation/biological denitrification) and radioactive decay (for moving radionuclides). Based on these 2D contaminant transport models it has been possible to calculate numerically the dimensionless concentration values with and without all the chosen processes in relation to both the chosen natural site (piezometers) and the chosen contaminants.In this paper, it has also been possible to compare all the numerically calculated concentration values to the measured concentration ones (in the chosen earlier piezometers) in relation to both the new unpublished measurement series of May 1982 and the new set of parameters used in these 2D contaminant transport models (as practical verification of these models).

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