Bulletin of the American Physical Society
66th Annual Meeting of the APS Division of Fluid Dynamics
Volume 58, Number 18
Sunday–Tuesday, November 24–26, 2013; Pittsburgh, Pennsylvania
Session E31: Porous Media Flows IV: Electrochemical and Heat Transfer Devices |
Hide Abstracts |
Chair: Ying Sun, Drexel University Room: 402 |
Sunday, November 24, 2013 4:45PM - 4:58PM |
E31.00001: Capacitive Charging and Desalination with Porous Electrodes Howard Hu, Mengying Li, Haim Bau Electrochemical capacitors (ECs) are attractive storage devices with many advantages over traditional batteries. In contrast to batteries, ECs store energy in the electric double layer and do not undergo electrochemical reactions during charging and discharging. In this work, we examine the charging/discharging process of an EC cell consisting of a conductive, granular medium confined between two parallel, current collecting, electrodes. The granular particles are porous, assembled by aggregation, and saturated with an electrolyte solution. They are separated into two compartments with an ion-permeable, electrically insulating membrane. The Debye screening length around and within porous particles is small compared to the characteristic size of the pores. We will present a mathematical model based on Poisson-Nernst-Planck equations to describe the charging/discharging process in the EC cell. Using this model, the ion distribution and potential variation within the cell are solved numerically as functions of time when the current collecting electrodes are subjected to a step change and to time-periodic alternations in electrodes' potentials. The same model can be also used for potential desalination applications. [Preview Abstract] |
Sunday, November 24, 2013 4:58PM - 5:11PM |
E31.00002: GPU-enabled Computational Model of Electrochemical Energy Storage Systems Charles Andersen, Gang Qiu, Nagarajan Kandasamy, Ying Sun We present a computational model of a Redox Flow Battery (RFB), which uses real pore-scale fiber geometry obtained through X-ray computed tomography (XCT). Our pore-scale approach is in contrast to the more common volume-averaged model, which considers the domain as a homogenous medium of uniform porosity. We apply a finite volume method to solve the coupled species and charge transport equations. The flow field in our system is evaluated using the Lattice Boltzmann method (LBM). To resolve the governing equations at the pore-scale of carbon fibers, which are on the order of tens of microns, is a highly computationally expensive task. To overcome this challenge, in lieu of traditional implementation with Message Passing Interface (MPI), we employ the use of Graphics Processing Units (GPUs) as a means of parallelization. The Butler-Volmer equation provides a coupling between the species and charge equations on the fiber surface. Scalability of the GPU implementation is examined along with the effects of fiber geometry, porosity, and flow rate on battery performance. [Preview Abstract] |
Sunday, November 24, 2013 5:11PM - 5:24PM |
E31.00003: Simulation of water splitting reaction in porous media using Random Walk particle tracking method Nima Rahmatian, J\"org Petrasch, Renwei Mei, James Klausner Water splitting using iron-based looping process is a well-known method to produce high purity hydrogen. A stable porous structure is best suited for the reaction over many cycles due to high surface area. In order to simulate the reacting flow in the porous structure Random Walk method is used due to its ability to handle stiff reaction kinetics and varying hydrodynamic dispersion tensor caused by pore-level velocity fluctuations. Because of significant variation in bulk density during conversion of steam to hydrogen, Random Walk formulation needs to be modified to account for bulk density variations and source term due to chemical reaction. The species transport equation is recast in the form of Fokker-Planck equation and the trajectories of fluid particles are obtained by solving an appropriate Langevin equation that has additional drift terms due to spatial variations in bulk density and dispersion tensor. The source term is accounted for by changing the number or the composition of fluid particles based on the reaction kinetics. The treatment for each new term is validated using highly resolved finite difference solution. A bench-scale reactor for hydrogen production is simulated and excellent agreement with the measured hydrogen production rate is obtained. [Preview Abstract] |
Sunday, November 24, 2013 5:24PM - 5:37PM |
E31.00004: Estimation of Porous Medium Tortuosity Directly from Flow Path Lines Suryanarayana Pakalapati, Ismail Celik A thorough understanding of transport processes inside porous materials is vital for improving the efficiency of energy devices such as fuel cells and batteries. Continuum simulations of porous media make use of parameters such as porosity and tortuosity to account for the influence of the actual pore geometry and orientation on the transport processes. In most studies the tortuosity is treated as an adjustable parameter which is calibrated to match the predictions with the experiments. In this study a direct method is utilized to estimate the tortuosity of a porous medium. The actual geometry of a fuel cell electrode is obtained from an experimental study where the porous structure is reconstructed from slice images. The detailed geometry of porous medium is used to simulate fully resolved fluid flow through the pores. Stream lines are then generated which show the actual paths taken by the fluid flowing through the porous medium. The lengths of these path lines are then used to calculate the tortuosity of the porous medium by employing the actual definition of the tortuosity. It is shown that the tortuosities obtained in this way are smaller than the typical values reported in literature. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700