scholarly journals Phenomenological Model of Nonlinear Dynamics and Deterministic Chaotic Gas Migration in Bentonite: Experimental Evidence and Diagnostic Parameters

2022 ◽  
Author(s):  
Boris Faybishenko ◽  
Yifeng Wang ◽  
Jon Harrington ◽  
Elena Tamayo-Mas ◽  
Jens Birkholzer ◽  
...  
Keyword(s):  
Nonlinear Dynamics ◽  
Phenomenological Model ◽  
Gas Diffusion ◽  
Transport Processes ◽  
Chaotic Advection ◽  
Coupled Processes ◽  
Series Data ◽  
Gas Migration ◽  
Diagnostic Parameters ◽  
Clay Materials

AbstractUnderstanding gas migration in compacted clay materials, e.g., bentonite and claystone, is important for the design and performance assessment of an engineered barrier system of a radioactive waste repository system, as well as many practical applications. Existing field and laboratory data on gas migration processes in low-permeability clay materials demonstrate the complexity of flow and transport processes, including various types of instabilities, caused by nonlinear dynamics of coupled processes of liquid–gas exchange, dilation, fracturing, fracture healing, etc., which cannot be described by classical models of fluid dynamics in porous media. We here show that the complexity of gas migration processes can be explained using a phenomenological concept of nonlinear dynamics and deterministic chaos theory. To do so, we analyzed gas pressure and gas influx (i.e., input) and outflux (i.e., output), recorded during the gas injection experiment in the compact Mx80-D bentonite sample, and calculated a set of the diagnostic parameters of nonlinear dynamics and chaos, such a global embedding dimension, a correlation dimension, an information dimension, and a spectrum of Lyapunov exponents, as well as plotted 2D and 3D pseudo-phase-space strange attractors, based on the univariate influx and outflux time series data. These results indicate the presence of phenomena of low-dimensional deterministic chaotic behavior of gas migration in bentonite. In particular, during the onset of gas influx in the bentonite core, before the breakthrough, the development of gas flow pathways is characterized by the process of chaotic gas diffusion. After the breakthrough, with inlet-to-outlet movement of gas, the prevailing process is chaotic advection. During the final phase of the experiment, with no influx to the sample, the relaxation pattern of gas outflux is resumed back to a process of chaotic diffusion. The types of data analysis and a proposed phenomenological model can be used to establish the basic principles of experimental data-gathering, modeling predictions, and a research design.

scholarly journals A Kernel for Calculating PEM Fuel Cell Distribution of Relaxation Times

2021 ◽  
Vol 9 ◽  
Author(s):  
Andrei Kulikovsky
Keyword(s):  
Fuel Cell ◽  
Oxygen Transport ◽  
Relaxation Times ◽  
Catalyst Layer ◽  
Pem Fuel Cell ◽  
Negative Real Part ◽  
Gas Diffusion ◽  
Transport Processes ◽  
Transport Layer ◽  
Cathode Side

Impedance of all oxygen transport processes in PEM fuel cell has negative real part in some frequency domain. A kernel for calculation of distribution of relaxation times (DRT) of a PEM fuel cell is suggested. The kernel is designed for capturing impedance with negative real part and it stems from the equation for impedance of oxygen transport through the gas-diffusion transport layer (doi:10.1149/2.0911509jes). Using recent analytical solution for the cell impedance, it is shown that DRT calculated with the novel K2 kernel correctly captures the GDL transport peak, whereas the classic DRT based on the RC-circuit (Debye) kernel misses this peak. Using K2 kernel, analysis of DRT spectra of a real PEMFC is performed. The leftmost on the frequency scale DRT peak represents oxygen transport in the channel, and the rightmost peak is due to proton transport in the cathode catalyst layer. The second, third, and fourth peaks exhibit oxygen transport in the GDL, faradaic reactions on the cathode side, and oxygen transport in the catalyst layer, respectively.

Local Entropy Production Rates in a Polymer Electrolyte Membrane Fuel Cell

2017 ◽  
Vol 42 (1) ◽  
pp. 1-30 ◽  
Author(s):  
Marc Siemer ◽  
Tobias Marquardt ◽  
Gerardo Valadez Huerta ◽  
Stephan Kabelac
Keyword(s):  
Fuel Cell ◽  
Entropy Production ◽  
Polymer Electrolyte ◽  
Polymer Electrolyte Membrane ◽  
Gas Diffusion ◽  
Transport Processes ◽  
Local Entropy ◽  
Equilibrium Thermodynamics ◽  
Electrolyte Membrane ◽  
Non Equilibrium

AbstractA modeling study on a polymer electrolyte membrane fuel cell by means of non-equilibrium thermodynamics is presented. The developed model considers a one-dimensional cell in steady-state operation. The temperature, concentration and electric potential profiles are calculated for every domain of the cell. While the gas diffusion and the catalyst layers are calculated with established classical modeling approaches, the transport processes in the membrane are calculated with the phenomenological equations as dictated by the non-equilibrium thermodynamics. This approach is especially instructive for the membrane as the coupled transport mechanisms are dominant. The needed phenomenological coefficients are approximated on the base of conventional transport coefficients. Knowing the fluxes and their intrinsic corresponding forces, the local entropy production rate is calculated. Accordingly, the different loss mechanisms can be detected and quantified, which is important for cell and stack optimization.

Computational Modelling and Simulation of Proton-Exchange Membrane Fuel Cells (Keynote)

2002 ◽  
Author(s):  
N. Djilali ◽  
T. Berning
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Proton Exchange Membrane ◽  
Transport Phenomena ◽  
Computational Modelling ◽  
Ambient Air ◽  
Gas Diffusion ◽  
Transport Processes ◽  
Proton Exchange ◽  
Exchange Membrane

Fuel cells (FC’s) are electrochemical devices that convert directly into electricity the chemical energy of reaction of a fuel (usually hydrogen) with an oxidant (usually oxygen from ambient air). The only by-products in a hydrogen fuel cell are heat and water, making this emerging technology the leading candidate for quiet, zero emission energy production. Several types of fuel cell are currently undergoing intense research and development for applications ranging from portable electronics and appliances to residential power generation and transportation. The focus of this lecture is Proton-Exchange Membrane Fuel Cells (PEMFC’s). An electrolyte consisting of a “solid” polymer membrane, low operating temperatures (typically below 90 °C) and a relatively simple design combine to make PEMFC’s particularly well suited to automotive and portable applications. The operation of a fuel cell relies on electrochemical reactions and an array of coupled transport phenomena, including multi-component gas flow, two phase-flow, heat and mass transfer, phase change and transport of charged species. The transport processes take place in variety of media, including porous gas diffusion electrodes and polymer membranes. The fuel cell environment makes it impossible to measure in-situ the quantities of interest to understand and quantify these phenomena, and computational modelling and simulations are therefore poised to play a central role in the development and optimization of fuel cell technology. We provide an overview of the role of various transport phenomena in fuel cell operation and some of the physical and computational modelling challenges they present. The processes will be illustrated through examples of multi-dimensional numerical simulations of Proton-Exchange Membrane Fuel Cells. We close with a perspective on some of the many remaining challenges and future development opportunities.

scholarly journals A parallelization scheme to simulate reactive transport in the subsurface environment with OGS#IPhreeqc

2015 ◽  
Vol 8 (3) ◽  
pp. 2369-2402
Author(s):  
W. He ◽  
C. Beyer ◽  
J. H. Fleckenstein ◽  
E. Jang ◽  
O. Kolditz ◽  
...  
Keyword(s):  
Message Passing ◽  
Reactive Transport ◽  
Message Passing Interface ◽  
Transport Processes ◽  
Coupled Processes ◽  
Scientific Software ◽  
Geochemical Reactions ◽  
Optimized Allocation ◽  
And Performance ◽  
The One

Abstract. This technical paper presents an efficient and performance-oriented method to model reactive mass transport processes in environmental and geotechnical subsurface systems. The open source scientific software packages OpenGeoSys and IPhreeqc have been coupled, to combine their individual strengths and features to simulate thermo-hydro-mechanical-chemical coupled processes in porous and fractured media with simultaneous consideration of aqueous geochemical reactions. Furthermore, a flexible parallelization scheme using MPI (Message Passing Interface) grouping techniques has been implemented, which allows an optimized allocation of computer resources for the node-wise calculation of chemical reactions on the one hand, and the underlying processes such as for groundwater flow or solute transport on the other hand. The coupling interface and parallelization scheme have been tested and verified in terms of precision and performance.

The Dynamics of a Flexible Levitated Droplet

2001 ◽  
Author(s):  
Mihai Dupac ◽  
Dan B. Marghitu ◽  
David G. Beale
Keyword(s):  
Nonlinear Dynamics ◽  
Time Series ◽  
Lyapunov Exponent ◽  
Time Series Data ◽  
Simulated Data ◽  
Series Data ◽  
Largest Lyapunov Exponent ◽  
Dynamics Analysis ◽  
Attractor Dimension ◽  
Levitated Droplet

Abstract In this paper, a nonlinear dynamics analysis of the simulated data was considered to study the time evolution of an electro-magnetically levitated flexible droplet. The main goals of this work are to study the behavior of the levitated droplet and to investigate its stability. Quantities characterizing time series data such as attractor dimension or largest Lyapunov exponent were computed.

An X-Ray Tomography Based Lattice Boltzmann Simulation Study on Gas Diffusion Layers of Polymer Electrolyte Fuel Cells

2010 ◽  
Vol 7 (3) ◽  
Author(s):  
Pratap Rama ◽  
Yu Liu ◽  
Rui Chen ◽  
Hossein Ostadi ◽  
Kyle Jiang ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Polymer Electrolyte ◽  
Lattice Boltzmann ◽  
Gas Diffusion ◽  
Transport Processes ◽  
Polymer Electrolyte Fuel Cell ◽  
Absolute Permeability ◽  
Carbon Paper ◽  
X Ray ◽  
Microscale Transport

This work reports a feasibility study into the combined full morphological reconstruction of fuel cell structures using X-ray computed micro- and nanotomography and lattice Boltzmann modeling to simulate fluid flow at pore scale in porous materials. This work provides a description of how the two techniques have been adapted to simulate gas movement through a carbon paper gas diffusion layer (GDL). The validation work demonstrates that the difference between the simulated and measured absolute permeability of air is 3%. The current study elucidates the potential to enable improvements in GDL design, material composition, and cell design to be realized through a greater understanding of the nano- and microscale transport processes occurring within the polymer electrolyte fuel cell.

Fundamental Research Needs in Combined Water and Thermal Management Within a Proton Exchange Membrane Fuel Cell Stack Under Normal and Cold-Start Conditions

2009 ◽  
Vol 6 (4) ◽  
Author(s):  
Satish G. Kandlikar ◽  
Zijie Lu
Keyword(s):  
Fuel Cell ◽  
Proton Exchange Membrane ◽  
Cold Start ◽  
Gas Diffusion ◽  
Transport Processes ◽  
Proton Exchange ◽  
Operating Conditions ◽  
Automotive Application ◽  
Current Status ◽  
Exchange Membrane

Each fuel cell component of a proton exchange membrane fuel cell (PEMFC) used in automotive application operates most effectively (from performance and durability standpoints) within specific ranges of water content and temperature. The water and heat transport processes are coupled and present a challenge in providing the right balance over the entire range of operating conditions. Another important related aspect is CO poisoning of the electrocatalyst, which adversely affects the fuel cell performance. Freezing and cold-start present additional challenges for automotive PEMFCs. A critical review of the recent developments on these topics is presented in this paper. The study covers both the microscopic and macroscopic aspects of the transport within membrane, catalyst layers, gas diffusion layers, and gas channels, and an overview of the current PEMFC cooling technology. After discussing the current status, suggestions for future work on the above topics are presented.

scholarly journals Pore-Scale Modeling of Air–Water Two Phase Flow and Oxygen Transport in Gas Diffusion Layer of Proton Exchange Membrane Fuel Cell

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3812
Author(s):  
Chongbo Zhou ◽  
Lingyi Guo ◽  
Li Chen ◽  
Xin Tian ◽  
Tiefeng He ◽  
...  
Keyword(s):  
Liquid Water ◽  
Reactive Transport ◽  
Proton Exchange Membrane ◽  
Water Saturation ◽  
Gas Diffusion ◽  
Transport Processes ◽  
Proton Exchange ◽  
Scale Model ◽  
Pore Scale ◽  
Two Phase

Understanding multiphase flow and gas transport occurring in electrodes is crucial for improving the performance of proton exchange membrane fuel cells. In the present study, a pore-scale model using the lattice Boltzmann method (LBM) was proposed to study the coupled processes of air–water two-phase flow and oxygen reactive transport processes in porous structures of the gas diffusion layer (GDL) and in fractures of the microscopic porous layer (MPL). Three-dimensional pore-scale numerical results show that the liquid water generation rate is gradually reduced as the oxygen consumption reaction proceeds, and the liquid water saturation in the GDL increases, thus the constant velocity inlet or pressure inlet condition cannot be maintained while the results showed that at t = 1,200,000 iterations after 2900 h running time, the local saturation at the GDL/MPL was about 0.7, and the maximum value was about 0.83, while the total saturation was 0.35. The current density reduced from 2.39 to 0.46 A cm-2. Effects of fracture number were also investigated, and the results showed that for the fracture numbers of 8, 12, 16, and 24, the breakthrough point number was 4, 3, 3, and 2, respectively. As the fracture number increased, the number of the water breakthrough points at the GDL/GC interface decreased, the liquid water saturation inside the GDL increased, the GDL/MPL interface was more seriously covered, and the current density decreased. The pore-scale model for the coupled multiphase reactive transport processes is helpful for understanding the mechanisms inside the porous electrodes of PEMFC.

Sign in / Sign up

Export Citation Format

Share Document