scholarly journals Laws of Gas Diffusion in Coal Particles: A Study Based on Experiment and Numerical Simulation

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Yongjiang Hao ◽  
Xiaofeng Ji ◽  
Jiewen Pang
Keyword(s):  
Methane Emission ◽  
Darcy’S Law ◽  
Correlation Coefficients ◽  
Gas Diffusion ◽  
Darcy's Law ◽  
Coal Particles ◽  
Rate Functions ◽  
Methane Desorption ◽  
Initial Adsorption ◽  
Methane Emission Rate

In order to research on the law of methane released through the pore in coal particles, the methane desorption experiments were conducted, respectively, on four types of particle size of coal samples under three different initial adsorption pressures. The cumulative methane desorption quantity (CMDQ) with time increasing was obtained to show that the reciprocal of CMDQ was in linear relation with the reciprocal of the square root of time, and the correlation coefficients were all above 0.99, on basis of which an empirical formula of CMDQ was established. Then, according to Fick diffusion law and Darcy percolation law, the mathematical models of methane emission from the spherical coal particles were created, respectively, and the corresponding calculating software was programmed by the finite difference method to obtain the simulated CMDQ of each sample under different conditions. The methane emission rate functions (MERF) of the simulation and the experiment were also calculated, respectively. Comparative analysis between the numerically simulated outcomes and the assay results reveals that the simulation outcomes as per Darcy’s law match the experimental data better, while the simulated results by Fick’s law deviate greatly, which indicates that the methane flowing through coal particles is more in accordance with Darcy’s law.

Investigation of Porous Gas Diffusions Layer Modeling in PEM Fuel Cells

2008 ◽  
Author(s):  
Zhongying Shi ◽  
Xia Wang
Keyword(s):  
Fuel Cell ◽  
Darcy’S Law ◽  
Transport Phenomena ◽  
Gas Diffusion ◽  
Darcy's Law ◽  
Porous Electrodes ◽  
Cell Performance ◽  
Momentum Transport ◽  
Brinkman Equation ◽  
Fuel Cell Performance

Darcy’s law, the Brinkman Equation and the modified N-S equation describe the momentum transport phenomena occurring in porous gas diffusion layer. This paper proposes to compare the differences in applying aforementioned models to describe the transport phenomena in porous gas diffusion layers, and evaluate their effects on the fuel cell performance. A two dimensional isothermal single phase PEM fuel cell model is developed, in which Darcy’s law, the Brinkman equation and the modified N-S equation are applied separately in porous electrodes. These three models show no visible effects on the fuel cell performance characterized by the polarization curves. The polarization curve shows a sharp potential drop when calculated by the pure diffusion model. Three values of GDL permeability are investigated here. The order of the magnitude of each term in the modified N-S equation is numerically evaluated. The inertial term is found much smaller than other terms, and can be dropped in the Navier-Stokes equation. Considering the boundary condition setting problem of Darcy’s law and the convergence problem of the modified N-S equation, the Brinkman equation is recommended by this paper to describe the momentum transport in porous electrodes.

scholarly journals An extension of Darcy’s law incorporating dynamic length scales

2019 ◽  
Vol 129 ◽  
pp. 70-79 ◽  
Author(s):  
Yuhang Wang ◽  
Saman A. Aryana ◽  
Myron B. Allen
Keyword(s):  
Darcy’S Law ◽  
Darcy's Law ◽  
Length Scales ◽  
Dynamic Length

scholarly journals The Use of Nonlinear Constitutive Equations to Evaluate Draw Resistance and Filter Ventilation

2001 ◽  
Vol 19 (4) ◽  
pp. 177-188
Author(s):  
B Eitzinger ◽  
G Ederer
Keyword(s):  
Pressure Drop ◽  
Differential Equations ◽  
Ordinary Differential Equations ◽  
Constitutive Equations ◽  
Darcy’S Law ◽  
Stationary Flow ◽  
Darcy's Law ◽  
Nonlinear Behaviour ◽  
Cigarette Paper ◽  
Drop Flow

AbstractThis study investigates by nonlinear constitutive equations the influence of tipping paper, cigarette paper, filter, and tobacco rod on the degree of filter ventilation and draw resistance. Starting from the laws of conservation, the path to the theory of fluid dynamics in porous media and Darcy's law is reviewed and, as an extension to Darcy's law, two different nonlinear pressure drop-flow relations are proposed. It is proven that these relations are valid constitutive equations and the partial differential equations for the stationary flow in an unlit cigarette covering anisotropic, inhomogeneous and nonlinear behaviour are derived. From these equations a system of ordinary differential equations for the one-dimensional flow in the cigarette is derived by averaging pressure and velocity over the cross section of the cigarette. By further integration, the concept of an electrical analog is reached and discussed in the light of nonlinear pressure drop-flow relations. By numerical calculations based on the system of ordinary differential equations, it is shown that the influence of nonlinearities cannot be neglected because variations in the degree of filter ventilation can reach up to 20% of its nominal value.

scholarly journals Simulation of Water Filtration in Porous Zone Based on Darcy's Law

2013 ◽  
Vol 36 ◽  
pp. 163-168
Author(s):  
Mohammed Amine Kendouci ◽  
Benali Kharroubi ◽  
Rachid Khelfaoui ◽  
Ali Bendida ◽  
Brahim Dennai ◽  
...  
Keyword(s):  
Darcy’S Law ◽  
Darcy's Law ◽  
Water Filtration ◽  
Porous Zone
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