The Impact of Fiber Arrangement and Advective Transport in Porous Electrodes for Silver-Based Thermally Regenerated Batteries

2021 ◽  
pp. 138527
Author(s):  
Nicholas R. Cross ◽  
Derek M. Hall ◽  
Serguei N. Lvov ◽  
Bruce E. Logan ◽  
Matthew J. Rau
Keyword(s):  
Porous Electrodes ◽  
Advective Transport ◽  
Fiber Arrangement ◽  
The Impact

scholarly journals How marine emissions of bromoform impact the remote atmosphere

2019 ◽  
Vol 19 (17) ◽  
pp. 11089-11103 ◽  
Author(s):  
Yue Jia ◽  
Susann Tegtmeier ◽  
Elliot Atlas ◽  
Birgit Quack
Keyword(s):  
Dispersion Model ◽  
Hot Spot ◽  
Open Ocean ◽  
Advective Transport ◽  
Localized Source ◽  
Mixing Ratios ◽  
Low Wind Speed ◽  
Uniform Background ◽  
Lagrangian Dispersion ◽  
The Impact

Abstract. It is an open question how localized elevated emissions of bromoform (CHBr3) and other very short-lived halocarbons (VSLHs), found in coastal and upwelling regions, and low background emissions, typically found over the open ocean, impact the atmospheric VSLH distribution. In this study, we use the Lagrangian dispersion model FLEXPART to simulate atmospheric CHBr3 resulting from assumed uniform background emissions, and from elevated emissions consistent with those derived during three tropical cruise campaigns. The simulations demonstrate that the atmospheric CHBr3 distributions in the uniform background emissions scenario are highly variable with high mixing ratios appearing in regions of convergence or low wind speed. This relation holds on regional and global scales. The impact of localized elevated emissions on the atmospheric CHBr3 distribution varies significantly from campaign to campaign. The estimated impact depends on the strength of the emissions and the meteorological conditions. In the open waters of the western Pacific and Indian oceans, localized elevated emissions only slightly increase the background concentrations of atmospheric CHBr3, even when 1∘ wide source regions along the cruise tracks are assumed. Near the coast, elevated emissions, including hot spots up to 100 times larger than the uniform background emissions, can be strong enough to be distinguished from the atmospheric background. However, it is not necessarily the highest hot spot emission that produces the largest enhancement, since the tug-of-war between fast advective transport and local accumulation at the time of emission is also important. Our results demonstrate that transport variations in the atmosphere itself are sufficient to produce highly variable VSLH distributions, and elevated VSLHs in the atmosphere do not always reflect a strong localized source. Localized elevated emissions can be obliterated by the highly variable atmospheric background, even if they are orders of magnitude larger than the average open ocean emissions.

scholarly journals Groundwater flow below construction pits and erosion of temporary horizontal layers of silicate grouting

2020 ◽  
Vol 28 (8) ◽  
pp. 2821-2832
Author(s):  
Joris M. Dekker ◽  
Thomas Sweijen ◽  
Alraune Zech
Keyword(s):  
Hydraulic Conductivity ◽  
Groundwater Flow ◽  
Analytical Solutions ◽  
Mass Flux ◽  
Approximate Solutions ◽  
Sensitivity Study ◽  
Advective Transport ◽  
Dilution Ratio ◽  
The Impact ◽  
Horizontal Layers

AbstractInjection of silicate grouting materials is widely used to create temporary horizontal layers for reducing inflow of groundwater at construction sites, in regions with shallow water tables. The erosion of a grouting layer was investigated by means of analytical solutions for groundwater flow and transport within a pit after construction finished. Erosion is assumed to occur by dissolution of the temporary injection layer and subsequent advective transport. Thereby, the hydraulic conductivity changes with time. This paper presents novel analytical solutions and approximate solutions for the major fluxes in the construction pit as a function of the domain settings, aquifer gradient and hydraulic conductivity. In addition, the mass flux and the dilution ratio of erosion-related components leaving the construction pit and entering the aquifer are quantified. Derived solutions are verified against numerical simulations. A sensitivity study shows the impact of domain settings on fluxes and dilution ratio. The results confirm that mass flux of grout components increases with ongoing erosion. Thus, its effect on groundwater quality increases with time after construction ceased.

Combining CFD and Stress Models for PEM Cells: Initial Development

2004 ◽  
Author(s):  
Carlos Martinez-Baca ◽  
Rowland Travis
Keyword(s):  
Fuel Cell ◽  
Polymer Electrolyte ◽  
Single Channel ◽  
Polymer Electrolyte Membrane ◽  
Pem Fuel Cell ◽  
Porous Electrodes ◽  
Membrane Electrode ◽  
Initial Development ◽  
Electrolyte Membrane ◽  
The Impact

The aim of this work is to determine the relationship between the operational characteristics of a Polymer Electrolyte Membrane (PEM) fuel cell, and the relevant materials issues and in particular mechanical stresses that develop. A three dimensional, non-isothernal, single phase model of a single channel PEM fuel cell is developed to investigate the impact of temperature variation on the Membrane Electrode Assembly (MEA). The model accounts for heat transfer in solids as well as in the multi-component mixture of gases, convection and diffusion of different species in the porous electrodes and the channels, electrochemical reactions and transport of water and ions through the PEM. This model has been numerically implemented in a commercial Computational Fluid Dynamic (CFD), finite volume based code. Temperature contours derived from the model were then exported to a commercial Finite Element (FE) code to analyse the relevant mechanical issues of the PEM and in particular thermomechanical stresses that develop. Initial results verify that, even considering the polymer electrolyte membrane in isolation with mechanically free boundary conditions, there is a significant temperature difference leading to tensile stresses of up to 2.1 MPa within the membrane.

scholarly journals Modeling the impact of soil aggregate size on selenium immobilization

2013 ◽  
Vol 10 (3) ◽  
pp. 1323-1336 ◽  
Author(s):  
M. F. Kausch ◽  
C. E. Pallud
Keyword(s):  
Reactive Transport ◽  
Temporal Dynamics ◽  
Transport Model ◽  
Soil Aggregates ◽  
Aggregate Size ◽  
Soil Aggregate ◽  
Drainage Water ◽  
Rate Equations ◽  
Advective Transport ◽  
The Impact

Abstract. Soil aggregates are mm- to cm-sized microporous structures separated by macropores. Whereas fast advective transport prevails in macropores, advection is inhibited by the low permeability of intra-aggregate micropores. This can lead to mass transfer limitations and the formation of aggregate scale concentration gradients affecting the distribution and transport of redox sensitive elements. Selenium (Se) mobilized through irrigation of seleniferous soils has emerged as a major aquatic contaminant. In the absence of oxygen, the bioavailable oxyanions selenate, Se(VI), and selenite, Se(IV), can be microbially reduced to solid, elemental Se, Se(0), and anoxic microzones within soil aggregates are thought to promote this process in otherwise well-aerated soils. To evaluate the impact of soil aggregate size on selenium retention, we developed a dynamic 2-D reactive transport model of selenium cycling in a single idealized aggregate surrounded by a macropore. The model was developed based on flow-through-reactor experiments involving artificial soil aggregates (diameter: 2.5 cm) made of sand and containing Enterobacter cloacae SLD1a-1 that reduces Se(VI) via Se(IV) to Se(0). Aggregates were surrounded by a constant flow providing Se(VI) and pyruvate under oxic or anoxic conditions. In the model, reactions were implemented with double-Monod rate equations coupled to the transport of pyruvate, O2, and Se species. The spatial and temporal dynamics of the model were validated with data from experiments, and predictive simulations were performed covering aggregate sizes 1–2.5 cm in diameter. Simulations predict that selenium retention scales with aggregate size. Depending on O2, Se(VI), and pyruvate concentrations, selenium retention was 4–23 times higher in 2.5 cm aggregates compared to 1 cm aggregates. Under oxic conditions, aggregate size and pyruvate concentrations were found to have a positive synergistic effect on selenium retention. Promoting soil aggregation on seleniferous agricultural soils, through organic matter amendments and conservation tillage, may thus help decrease the impacts of selenium contaminated drainage water on downstream aquatic ecosystems.

scholarly journals Modeling the impact of soil aggregate size on selenium immobilization

2012 ◽  
Vol 9 (9) ◽  
pp. 12047-12086 ◽  
Author(s):  
M. F. Kausch ◽  
C. E. Pallud
Keyword(s):  
Reactive Transport ◽  
Temporal Dynamics ◽  
Transport Model ◽  
Soil Aggregates ◽  
Aggregate Size ◽  
Soil Aggregate ◽  
Drainage Water ◽  
Rate Equations ◽  
Advective Transport ◽  
The Impact

Abstract. Soil aggregates are mm- to cm-sized microporous structures separated by macropores. Whereas fast advective transport prevails in macropores, advection is inhibited by the low permeability of intra-aggregate micropores. This can lead to mass transfer limitations and the formation of aggregate-scale concentration gradients affecting the distribution and transport of redox sensitive elements. Selenium (Se) mobilized through irrigation of seleniferous soils has emerged as a major aquatic contaminant. In the absence of oxygen, the bioavailable oxyanions selenate, Se(VI), and selenite, Se(IV), can be microbially reduced to solid, elemental Se, Se(0), and anoxic microzones within soil aggregates are thought to promote this process in otherwise well aerated soils. To evaluate the impact of soil aggregate size on selenium retention, we developed a dynamic 2-D reactive transport model of selenium cycling in a single idealized aggregate surrounded by a macropore. The model was developed based on flow-through-reactor experiments involving artificial soil aggregates (diameter: 2.5 cm) made of sand and containing Enterobacter cloacae SLD1a-1 that reduces Se(VI) via Se(IV) to Se(0). Aggregates were surrounded by a constant flow providing Se(VI) and pyruvate under oxic or anoxic conditions. In the model, reactions were implemented with double-Monod rate equations coupled to the transport of pyruvate, O2, and Se-species. The spatial and temporal dynamics of the model were validated with data from experiments and predictive simulations were performed covering aggregate sizes between 1 and 2.5 cm diameter. Simulations predict that selenium retention scales with aggregate size. Depending on O2, Se(VI), and pyruvate concentrations, selenium retention was 4–23 times higher in 2.5-cm-aggregates compared to 1-cm-aggregates. Under oxic conditions, aggregate size and pyruvate-concentrations were found to have a positive synergistic effect on selenium retention. Promoting soil aggregation on seleniferous agricultural soils, through organic matter amendments and conservation tillage, may thus help decrease the impacts of selenium contaminated drainage water on downstream aquatic ecosystems.

scholarly journals Subsurface flow mixing in coarse, braided river deposits

2015 ◽  
Vol 12 (9) ◽  
pp. 9295-9316 ◽  
Author(s):  
E. Huber ◽  
P. Huggenberger
Keyword(s):  
Flow Field ◽  
Subsurface Flow ◽  
Three Dimensional ◽  
Small Scale ◽  
Braided River ◽  
Advective Transport ◽  
Open Framework ◽  
Flow Mixing ◽  
River Deposits ◽  
The Impact

Abstract. Coarse, braided river deposits show a large hydraulic heterogeneity at the metre scale. One of the main depositional elements found in such deposits is a trough structure filled with open-framework–bimodal gravel couplet cross-beds. Several studies investigated the impact of the highly permeable open-framework gravel texture mainly in terms of concentration breakthrough curves. However, although the trough fills are expected to be significant mixing agents for the subsurface flow, their impact on the three-dimensional flow field has not draw much attention. This study aims to evaluate the subsurface flow mixing caused by overlapping trough fills embedded in a poorly-sorted gravel matrix. Below the river bed of the Tagliamento River (northeast Italy), trough fills were identified with ground-penetrating radar (GPR) probing. Based on field observations of coarse, braided river deposits, a simple three-dimensional geometrical model with associated hydraulic properties was fitted to the interpreted GPR reflectors. Then, steady-state subsurface flow and advective transport simulations were performed on the small-scale, high-resolution model (size: 45 m × 50 m × 10.26 m). The impact of trough fills on the flow field is visualised by the injection of a conservative tracer at three different depths.

scholarly journals The impact of advective transport by the South Indian Ocean Countercurrent on the Madagascar plankton bloom

2012 ◽  
Vol 39 (6) ◽  
pp. n/a-n/a ◽  
Author(s):  
F. Huhn ◽  
A. von Kameke ◽  
V. Pérez-Muñuzuri ◽  
M. J. Olascoaga ◽  
F. J. Beron-Vera
Keyword(s):  
Indian Ocean ◽  
Advective Transport ◽  
The South ◽  
South Indian Ocean ◽  
South Indian ◽  
Plankton Bloom ◽  
The Impact

scholarly journals Analyzing the Sensitivity of WRF’s Single-Layer Urban Canopy Model to Parameter Uncertainty Using Advanced Monte Carlo Simulation

2011 ◽  
Vol 50 (9) ◽  
pp. 1795-1814 ◽  
Author(s):  
Zhi-Hua Wang ◽  
Elie Bou-Zeid ◽  
Siu Kui Au ◽  
James A. Smith
Keyword(s):  
Monte Carlo ◽  
Parameter Uncertainty ◽  
Single Layer ◽  
Urban Canopy ◽  
Mitigation Strategies ◽  
Urban Atmosphere ◽  
Advective Transport ◽  
Surface Parameters ◽  
Input Parameters ◽  
The Impact

AbstractSingle-layer physically based urban canopy models (UCM) have gained popularity for modeling urban–atmosphere interactions, especially the energy transport component. For a UCM to capture the physics of conductive, radiative, and turbulent advective transport of energy, it is important to provide it with an accurate parameter space, including both mesoscale meteorological forcing and microscale surface inputs. While field measurement of all input parameters to a UCM is rarely possible, understanding the model sensitivity to individual parameters is essential to determine the relative importance of parameter uncertainty for model performance. In this paper, an advanced Monte Carlo approach—namely, subset simulation—is used to quantify the impact of the uncertainty of surface input parameters on the output of an offline modified version of the Weather Research and Forecasting (WRF)-UCM. On the basis of the conditional sampling technique, the importance of surface parameters is determined in terms of their impact on critical model responses. It is found that model outputs (both critical energy fluxes and surface temperatures) are highly sensitive to uncertainties in urban geometry, whereas variations in emissivities and building interior temperatures are relatively insignificant. In addition, the sensitivity of the model to input surface parameters is also shown to be very weakly dependent on meteorological parameters. The statistical quantification of the model’s sensitivity to input parameters has practical implications, such as surface parameter calibrations in UCM and guidance for urban heat island mitigation strategies.

The Impact of Fiber Arrangement on Power Density and Electrodeposition in Porous Ag-Trab Electrodes

2021 ◽  
Vol MA2021-01 (1) ◽  
pp. 28-28
Author(s):  
Nicholas Cross ◽  
Derek M Hall ◽  
Serguei Lvov ◽  
Bruce Logan ◽  
Matthew Rau
Keyword(s):  
Power Density ◽  
Fiber Arrangement ◽  
The Impact
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