Surface relaxation and the long-time diffusion coefficient in porous media: Periodic geometries

1994 ◽  
Vol 49 (1) ◽  
pp. 215-225 ◽  
Author(s):  
Pabitra N. Sen ◽  
Lawrence M. Schwartz ◽  
Partha P. Mitra ◽  
Bertrand I. Halperin
Keyword(s):  
Porous Media ◽  
Diffusion Coefficient ◽  
Surface Relaxation ◽  
Long Time

PERMEABILITY AND DIFFUSION COEFFICIENT PREDICTION OF FRACTAL POROUS MEDIA WITH NANOSCALE PORES FOR GAS TRANSPORT

2018 ◽  
Vol 21 (12) ◽  
pp. 1253-1263
Author(s):  
Ruifei Wang ◽  
Hongqing Song ◽  
Jiulong Wang ◽  
Yuhe Wang
Keyword(s):  
Porous Media ◽  
Diffusion Coefficient ◽  
Gas Transport ◽  
And Diffusion

scholarly journals Experimental study of the supercritical CO 2 diffusion coefficient in porous media under reservoir conditions

2019 ◽  
Vol 6 (6) ◽  
pp. 181902 ◽  
Author(s):  
Junchen Lv ◽  
Yuan Chi ◽  
Changzhong Zhao ◽  
Yi Zhang ◽  
Hailin Mu
Keyword(s):  
Porous Media ◽  
Diffusion Coefficient ◽  
Oil Recovery ◽  
Carbon Capture ◽  
Carbon Capture And Storage ◽  
Elevated Pressure ◽  
Experimental Results ◽  
Saturated Porous Media ◽  
Reservoir Conditions ◽  
The Impact

Reliable measurement of the CO 2 diffusion coefficient in consolidated oil-saturated porous media is critical for the design and performance of CO 2 -enhanced oil recovery (EOR) and carbon capture and storage (CCS) projects. A thorough experimental investigation of the supercritical CO 2 diffusion in n -decane-saturated Berea cores with permeabilities of 50 and 100 mD was conducted in this study at elevated pressure (10–25 MPa) and temperature (333.15–373.15 K), which simulated actual reservoir conditions. The supercritical CO 2 diffusion coefficients in the Berea cores were calculated by a model appropriate for diffusion in porous media based on Fick's Law. The results show that the supercritical CO 2 diffusion coefficient increases as the pressure, temperature and permeability increase. The supercritical CO 2 diffusion coefficient first increases slowly at 10 MPa and then grows significantly with increasing pressure. The impact of the pressure decreases at elevated temperature. The effect of permeability remains steady despite the temperature change during the experiments. The effect of gas state and porous media on the supercritical CO 2 diffusion coefficient was further discussed by comparing the results of this study with previous study. Based on the experimental results, an empirical correlation for supercritical CO 2 diffusion coefficient in n -decane-saturated porous media was developed. The experimental results contribute to the study of supercritical CO 2 diffusion in compact porous media.

scholarly journals Исследование коэффициента диффузии в тонких изделиях из пористых материалов

2019 ◽  
Vol 89 (10) ◽  
pp. 1630
Author(s):  
В.П. Беляев ◽  
С.В. Мищенко ◽  
П.С. Беляев
Keyword(s):  
Mass Transfer ◽  
Porous Media ◽  
Diffusion Coefficient ◽  
Transfer Process ◽  
Noise Immunity ◽  
Measurement Accuracy ◽  
High Sensitivity ◽  
Mass Transfer Process ◽  
Static Characteristic ◽  
Rapid Diffusion

A new method for studying mass transfer process in porous media has been considered, which allows the rapid diffusion coefficient control in thin products without destroying them and without the preliminary calibration of the diffuser concentration meter. The method provides an increase in the measurement accuracy due to the possibility of choosing the measured parameters included in the design expression. Parameters are taking from the segments of converter static characteristic. The converter has high sensitivity and noise immunity.

scholarly journals Exploring particle escape in supernova remnants through gamma rays

2019 ◽  
Vol 490 (3) ◽  
pp. 4317-4333 ◽  
Author(s):  
S Celli ◽  
G Morlino ◽  
S Gabici ◽  
F A Aharonian
Keyword(s):  
Diffusion Coefficient ◽  
Power Law ◽  
Supernova Remnants ◽  
Gamma Ray ◽  
Phenomenological Approach ◽  
Maximum Energy ◽  
Shock Acceleration ◽  
Middle Aged ◽  
The Galaxy ◽  
Long Time

ABSTRACT The escape process of particles accelerated at supernova remnant (SNR) shocks is one of the poorly understood aspects of the shock acceleration theory. Here we adopt a phenomenological approach to study the particle escape and its impact on the gamma-ray spectrum resulting from hadronic collisions both inside and outside of a middle-aged SNR. Under the assumption that in the spatial region immediately outside of the remnant the diffusion coefficient is suppressed with respect to the average Galactic one, we show that a significant fraction of particles are still located inside the SNR long time after their nominal release from the acceleration region. This fact results into a gamma-ray spectrum that resembles a broken power law, similar to those observed in several middle-aged SNRs. Above the break, the spectral steepening is determined by the diffusion coefficient outside of the SNR and by the time dependence of maximum energy. Consequently, the comparison between the model prediction and actual data will contribute to determining these two quantities, the former being particularly relevant within the predictions of the gamma-ray emission from the halo of escaping particles around SNRs, which could be detected with future Cherenkov telescope facilities. We also calculate the spectrum of runaway particles injected into the Galaxy by an individual remnant. Assuming that the acceleration stops before the SNR enters the snowplow phase, we show that the released spectrum can be a featureless power law only if the accelerated spectrum is ∝ p−α with α > 4.

Moisture Effective Diffusivity in Porous Media with Different Physical Properties

2006 ◽  
Vol 258-260 ◽  
pp. 207-212
Author(s):  
Miranda M.N.N. ◽  
M.A. Silva
Keyword(s):  
Porous Media ◽  
Diffusion Coefficient ◽  
Moisture Content ◽  
Mass Transport ◽  
Physical Properties ◽  
Pore Size ◽  
Structural Properties ◽  
Effective Diffusivity ◽  
Nay Zeolite ◽  
Moisture Effective Diffusivity

In the drying of porous media, the mass transport occurs in the pores as well as on the surface of the solid. The mechanisms involved can take place simultaneously, influenced by the predominant one and can change depending on the moisture content. In this work, the moisture effective diffusivity was estimated in solids with distinct structural properties in order to verify the predominant mechanisms according to the moisture content, analyzing the influence of the physical properties. The materials studied were NaY Zeolite, Kaolin, Silica and Alumina. The results of diffusion coefficient present a minimum at low moisture content that can be related to pore size.

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