Rapid, Steady-State Measurement of the Effective Diffusion Coefficient of Gases in Closed-Cell Foams

1988 ◽  
Vol 110 (2) ◽  
pp. 500-506 ◽  
Author(s):  
A. G. Ostrogorsky ◽  
L. R. Glicksman
Keyword(s):  
Diffusion Coefficient ◽  
Steady State ◽  
Diffusion Coefficients ◽  
Effective Diffusion Coefficient ◽  
Effective Diffusion ◽  
Polyurethane Foams ◽  
New Technique ◽  
Closed Cell ◽  
State Technique

A rapid steady-state technique was developed to measure the effective permeability and diffusion coefficients of closed-cell foam insulation. To test the new technique, N2 data were first obtained by the long-term steady-state technique, and then reproduced ten times faster by the rapid steady-state technique. By using the new technique, reference values of effective diffusion coefficients of N2, O2, and Fluorocarbon 11 in closed-cell polyurethane foams were obtained at different temperatures. Data for Fluorocarbon 11 were obtained 30 times faster than data could be obtained by long-term steady-state tests. To estimate when steady-state has been achieved, the transient diffusion equation was solved, and the solution was given in the form of a chart. The time needed to achieve steady-state mass flux in a foam sample was found to depend strongly on the ratio of the partial pressures imposed on the surface of a tested sample. By use of the solution, the value of the foam effective diffusion coefficient can be obtained before steady-state conditions are achieved within the sample.

scholarly journals Field Validation of Concrete Transport Property Measurement Methods

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1166 ◽  
Author(s):  
Ahmed Abd El Fattah ◽  
Ibrahim Al-Duais ◽  
Kyle Riding ◽  
Michael Thomas ◽  
Salah Al-Dulaijan ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Diffusion Coefficients ◽  
Effective Diffusion Coefficient ◽  
Corrosion Inhibitors ◽  
Effective Diffusion ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Chloride Diffusion ◽  
Chloride Ingress ◽  
Exposure Site

Reinforcing steel corrosion, caused by chloride ingress into concrete, is the leading cause of reinforced concrete deterioration. One of the main findings in the literature for reducing chloride ingress is the improvement of the durability characteristics of concrete by the addition of supplementary cementitious materials (SCMs) and/or chemical agents to concrete mixtures. In this study, standard ASTM tests—such as rapid chloride permeability (RCPT), bulk diffusion and sorptivity tests—were used to measure concrete properties such as porosity, sorptivity, salt diffusion, and permeability. Eight different mixtures, prepared with different SCMs and corrosion inhibitors, were tested. Apparent and effective chloride diffusion coefficients were calculated using bound chloride isotherms and time-dependent decrease in diffusion. Diffusion coefficients decreased with time, especially with the addition of SCMs and corrosion inhibitors. The apparent diffusion coefficient calculated using the error function was slightly lower than the effective diffusion coefficient; however, there was a linear trend between the two. The formation factor was found to correlate with the effective diffusion coefficient. The results of the laboratory tests were compared and benchmarked to their counterparts in the marine exposure site in the Arabian Gulf in order to identify laboratory key tests to predict concrete durability. The overall performance of concrete containing SCMs, especially fly ash, were the best among the other mixtures in the laboratory and the field.

Gas Diffusion and Re-Diffusion in Polyethylene Foams

2009 ◽  
Vol 283-286 ◽  
pp. 583-588
Author(s):  
J. Escudero ◽  
J. Lázaro ◽  
E. Solórzano ◽  
Miguel A. Rodríguez-Pérez ◽  
Jose A. de Saja
Keyword(s):  
Diffusion Coefficient ◽  
Diffusion Process ◽  
Static Loading ◽  
Effective Diffusion Coefficient ◽  
Effective Diffusion ◽  
Gas Diffusion ◽  
Low Density Polyethylene ◽  
Low Density ◽  
Compressive Creep ◽  
Closed Cell

In this work, the effective diffusion coefficient of the gas contained in closed cell polyethylene foams under static loading is measured. To do this, compressive creep experiments were performed on low density polyethylene foams produced under a gas diffusion process. Density dependence of this coefficient has been analysed as well as the variation of pressure with time inside the cells. Finally, immediately after compressive creep, the recovery behaviour of the foams was also characterised. Different abilities for recovering were observed depending on the density of the foam and the absolute recovery resulted independent of the initial stress applied.

scholarly journals Impact of Pore Geometry and Water Saturation on Gas Effective Diffusion Coefficient in Soil

2018 ◽  
Vol 8 (11) ◽  
pp. 2097 ◽  
Author(s):  
Wulong Hu ◽  
Yao Jiang ◽  
Daoyi Chen ◽  
Yongshui Lin ◽  
Qiang Han ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Power Law ◽  
Diffusion Coefficients ◽  
Effective Diffusion Coefficient ◽  
Pore Diameter ◽  
Water Saturation ◽  
Knudsen Diffusion ◽  
Effective Diffusion ◽  
Pore Geometry ◽  
Effective Diffusion Coefficients

Gas flow in soil plays a crucial role in terrestrial ecosystems, and numerical simulation of their movement needs to know their effective diffusion coefficients. How pore structure influences the effective diffusion coefficient has been studied intensively for dry porous media, but much remains unknown for unsaturated soils. Here, we employed the X-ray tomography technique at the pore scale to directly obtain the soil structures, the geometry of their pores and the water distribution under different water saturation levels were calculated using a morphological model. The results show that pore structures including porosity, interface area of gas–solid–water and pore diameter are closely related to water saturation. The increase of mean pore diameter with gas saturation can be fitted into a power law. We also investigated the impact of pore geometry and water saturation on the effective diffusion coefficients, which is independent of the molecular mass of gas after normalization. As the normalized effective Knudsen diffusion coefficient increases with average pore diameter following a power law, with the scaling factor related to pore geometry and the exponent is a constant, we explained and proved that the Knudsen diffusion coefficient increases with gas saturation, also following a power law.

scholarly journals Diffusion Coefficients from the Rate of Decay of Meteor Trails

1955 ◽  
Vol 8 (2) ◽  
pp. 279 ◽  
Author(s):  
AA Weiss
Keyword(s):  
Diffusion Coefficient ◽  
Diffusion Coefficients ◽  
Effective Diffusion Coefficient ◽  
Effective Diffusion ◽  
Upper Atmosphere ◽  
Absolute Value ◽  
Meteor Trail ◽  
Rate Of Decay ◽  
Meteor Trails ◽  
Rates Of Decay

The effective diffusion coefficient for a meteor trail is calculated from the theory of ambipolar diffusion and the physical constants of the upper atmosphere. The absolute value of the diffusion coefficient so calculated, and also its gradient with height, are confirmed by measurement of the rates of decay of a large number of meteor echoes of known heights.

Estimation of oxygen effective diffusion coefficient in a non-steady-state biofilm based on response time

2018 ◽  
Vol 25 (10) ◽  
pp. 9797-9805 ◽  
Author(s):  
Jian-Hui Wang ◽  
Hai-Yan Li ◽  
You-Peng Chen ◽  
Shao-Yang Liu ◽  
Peng Yan ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Steady State ◽  
Response Time ◽  
Effective Diffusion Coefficient ◽  
Effective Diffusion

Diffusion of Neptuiyl(V)- and Pertechnetate Ions in Marine Sediments

1981 ◽  
Vol 6 ◽  
Author(s):  
F. Schreiner ◽  
S. Fried ◽  
A. Friedman
Keyword(s):  
Diffusion Coefficient ◽  
Marine Sediments ◽  
Diffusion Coefficients ◽  
Deep Sea ◽  
Effective Diffusion Coefficient ◽  
Atmospheric Oxygen ◽  
Effective Diffusion ◽  
Anoxic Conditions ◽  
Effective Diffusion Coefficients ◽  
Reducing Properties

ABSTRACTThe diffusion of the 235NpO2+ and 95m TCo4− -ions has been measured directly in sample cylinders of two different sediments from the floor of the deep sea. In smectiterich sediment not shielded from contact with atmospheric oxygen the following values were obtained for the effective diffusion coefficients of neptunyl- and pertechnetateions, respectively: Deff(NpO2+) = 1.5 × 10−12 m2 s−1 and Deff(TcO4−) = 3.2 × 10−10 m2 s−1. Under anoxic conditions in sediment with known reducing properties, the pertechnetate ion appears to undergo slow reduction and the effective diffusion coefficient of the reduced species of Deff(Tc,red)= 1.1 × 1014 m2 s−1 reflects a substantial decrease of the mobility of the lower-valent technetium.

scholarly journals The Dependency of Diffusion Coefficients and Geometric Factor on the Size of the Diffusing Molecule: Observations for Different Clay-Based Materials

Geofluids ◽  
2017 ◽  
Vol 2017 ◽  
pp. 1-16 ◽  
Author(s):  
Elke Jacops ◽  
Marc Aertsens ◽  
Norbert Maes ◽  
Christophe Bruggeman ◽  
Rudy Swennen ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Diffusion Coefficients ◽  
Effective Diffusion Coefficient ◽  
Tritiated Water ◽  
Effective Diffusion ◽  
Geometric Factor ◽  
Opalinus Clay ◽  
Dissolved Gases ◽  
Exponential Relationship ◽  
Boom Clay

In order to investigate in more detail the relation between the size of diffusing molecules and their diffusion coefficients (and geometric factors), diffusion experiments with gases of different size and tritiated water (HTO) have been performed on different clayey samples (Boom Clay, Eigenbilzen Sands, Opalinus Clay, Callovo-Oxfordian Clay, and bentonite with different dry densities). We observed that, for unreactive gases in clayey materials, the effective diffusion coefficient varies with the size of the diffusing molecule and this variation can be described by an exponential or a power law function. The variation of the geometric factor can also be described by an exponential function. The observed experimental relations can be used to estimate diffusion coefficients; by measuring experimentally in clay the effective diffusion coefficient of two unreactive dissolved gases with a different size, the diffusion coefficients of other dissolved gases (with a size in between the two measured gases) can be estimated by using the fitted exponential relationship.

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