Steel pipe corrosion under flow conditions—II. Mass transfer correlation with temperature effects

1968 ◽  
Vol 8 (10) ◽  
pp. 737-749 ◽  
Author(s):  
B.K. Mahato ◽  
F.R. Steward ◽  
L.W. Shemilt
Keyword(s):  
Mass Transfer ◽  
Temperature Effects ◽  
Steel Pipe ◽  
Flow Conditions ◽  
Mass Transfer Correlation

Modeling of mass transfer in biofilms in oscillatory flow conditions using k-ɛ turbulence model

2003 ◽  
Vol 3 (1-2) ◽  
pp. 201-207
Author(s):  
H. Nagaoka ◽  
T. Nakano ◽  
D. Akimoto
Keyword(s):  
Numerical Simulation ◽  
Mass Transfer ◽  
Turbulence Model ◽  
Uptake Rate ◽  
Oscillatory Flow ◽  
Substrate Uptake ◽  
Flow Conditions ◽  
Mass Transfer Mechanism ◽  
Substrate Uptake Rate ◽  
Good Agreement

The objective of this research is to investigate mass transfer mechanism in biofilms under oscillatory flow conditions. Numerical simulation of turbulence near a biofilm was conducted using the low Reynold’s number k-ɛ turbulence model. Substrate transfer in biofilms under oscillatory flow conditions was assumed to be carried out by turbulent diffusion caused by fluid movement and substrate concentration profile in biofilm was calculated. An experiment was carried out to measure velocity profile near a biofilm under oscillatory flow conditions and the influence of the turbulence on substrate uptake rate by the biofilm was also measured. Measured turbulence was in good agreement with the calculated one and the influence of the turbulence on the substrate uptake rate was well explained by the simulation.

Liquid Mixing in Static Micro Mixers With Various Cross Sections

2003 ◽  
Author(s):  
Norbert Kockmann ◽  
Michael Engler ◽  
Claus Fo¨ll ◽  
Peter Woias
Keyword(s):  
Mass Transfer ◽  
Laminar Flow ◽  
Cross Sections ◽  
A Priori ◽  
Channel Length ◽  
Convective Transport ◽  
Geometrical Parameters ◽  
Flow Conditions ◽  
Wide Range ◽  
Mixing Quality

Micro mixers are an integral part of several micro fluidic devices like micro reactors or analytical equipment. Due to the small dimensions, laminar flow is expected a priori in those devices while the mass transfer is supposed to be dominated by diffusion. A detailed numerical CFD-study by CFDRC-ACE+ of simple static mixers shows a significant deviation from strictly laminar flow in a wide range of Reynolds numbers Re, channel dimensions, and types of cross sections (square, rectangular, trapezoidal). With increasing flow velocity and Re number the flow starts to form vortexes at the entrance of the mixing channel. The vortexes are symmetrical to the symmetry planes of the mixing channel, both for the rectangular and the trapezoidal cross sections investigated here. With further increasing velocity the flow tends to instabilities, which causes a breakup of the flow symmetry. These instabilities are generally found in T-shape mixers with symmetrical flow conditions, but not always in Y-shape mixers or with asymmetrical flow conditions. Within the laminar flow regime diffusive mass transfer is dominant. In this case the mixing quality at constant channel length becomes worse with increasing velocity. This effect can almost be equalized by the onset of the vortex regime, which enhances the mass transfer by convective transport. This paper shows the mixing quality at a certain length for different geometrical parameters and flow conditions.

Mass Transfer Mechanisms in a Heterotrophic Biofilm

1985 ◽  
Vol 17 (8) ◽  
pp. 1469-1471
Author(s):  
H. Siegrist ◽  
W. Gujer
Keyword(s):  
Mass Transfer ◽  
Molecular Diffusion ◽  
Tap Water ◽  
Pure Water ◽  
Background Electrolyte ◽  
Chemical Species ◽  
Eddy Diffusion ◽  
Donnan Potential ◽  
Flow Conditions ◽  
Transfer Mechanisms

The diffusion coefficient of three different chemical species in naturally grown, heterotrophic biofilms have been measured. The mechanical structure of the biofilm matrix reduces the molecular diffusion to about 50 to 60 % of the value in pure water. Depending on the roughness of the biofilm surface and the flow conditions eddy diffusion increased the mass transfer into the biofilm near the surface. The influence of the diffusion potential and the donnan potential on the ions have been evaluated by comparing the diffusion coefficients of a positively and negatively charged ion and a neutral molecule in experiments with different background electrolyte concentrations. Mass transfer effects by electrostatic forces are negligible at the ionic strength of waste water and tap water.

Effect of Metallic Additives On Mercury Corrosion of Titanium

CORROSION ◽  
1965 ◽  
Vol 21 (2) ◽  
pp. 57-61 ◽  
Author(s):  
JAMES Y. N. WANG
Keyword(s):  
Mass Transfer ◽  
Thermal Convection ◽  
Outer Layer ◽  
Transformation Temperature ◽  
Temperature Effects ◽  
Nickel Content ◽  
Solubility Limit ◽  
Titanium Sample ◽  
Surface Layers

Abstract Mass transfer of nickel to the hot leg (454 C, 850 F) of a mercury thermal convection loop in which titanium samples were exposed has been observed. This involved dissolution of nickel in mercury at 320 C (608 F), its transfer to the surface of the sample in the hot leg, and subsequent interdiffusion of nickel and titanium. Microprobe study of surface layers on the titanium sample indicated stratification of nickel. Outer layer contained two materials with compositions closely approximating those of TiNi and TiNi3, and an inner layer a material with nickel content close to the reported solubility limit for nickel in β-Ti, even though the reaction was conducted below α-β transformation temperature. Effects of other metallic additives are also discussed.

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.

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