scholarly journals Fully Developed Flow of a Nanofluid through a Circular Micropipe in the Presence of Electroosmotic Effects

2020 ◽  
Vol 2020 ◽  
pp. 1-15 ◽  
Author(s):  
Muhammad D. K. Niazi ◽  
Hang Xu
Keyword(s):  
Double Layer ◽  
Electrical Double Layer ◽  
Microelectromechanical Systems ◽  
Flow Behavior ◽  
Fluid Viscosity ◽  
Buongiorno’S Model ◽  
Flow Models ◽  
Similarity Transformations ◽  
Modern Engineering ◽  
Wide Range

Microscale heat sinks based on channels or pipes are designed to restrict the temperatures of microelectromechanical systems, which have a wide range of applications in the modern engineering and mechanics. In this context, this work aims to study heat convection and entropy generation of a fully developed nanofluid flow in a circular micropipe in the presence of an electrical double layer. Buongiorno’s model is employed to exhibit the nanofluid behavior. The governing equations are reduced to a system of nonlinear ordinary differential equations through appropriate similarity transformations. Particularly, we rectify the pressure term as an unknown constant, which makes our flow model compatible with those well-known fluid flow models in macrosize. Highly accurate solutions are obtained and verified. Analysis for physical properties of electric field, velocity field, temperature, and nanoparticle distributions is discussed followed by an investigation of the entropy evolution in the flow. The results show that flow behavior and total entropy of the system depend on the electroosmosis, thermophoresis, and fluid viscosity. However, the influence of the electrical double layer on the flow and system entropy is negligible when the electroosmotic parameter exceeds a maximum value.

scholarly journals Fabricating Silicon Resonators for Analysing Biological Samples

Micromachines ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1546
Author(s):  
Momoko Kumemura ◽  
Deniz Pekin ◽  
Vivek Anand Menon ◽  
Isabelle Van Van Seuningen ◽  
Dominique Collard ◽  
...  
Keyword(s):  
Double Layer ◽  
Biological Samples ◽  
Electrical Double Layer ◽  
Biomedical Applications ◽  
Microelectromechanical Systems ◽  
Layer Formation ◽  
Wide Range ◽  
Experimental Approaches ◽  
Silicon Based ◽  
Microelectromechanical Resonators

The adaptability of microscale devices allows microtechnologies to be used for a wide range of applications. Biology and medicine are among those fields that, in recent decades, have applied microtechnologies to achieve new and improved functionality. However, despite their ability to achieve assay sensitivities that rival or exceed conventional standards, silicon-based microelectromechanical systems remain underutilised for biological and biomedical applications. Although microelectromechanical resonators and actuators do not always exhibit optimal performance in liquid due to electrical double layer formation and high damping, these issues have been solved with some innovative fabrication processes or alternative experimental approaches. This paper focuses on several examples of silicon-based resonating devices with a brief look at their fundamental sensing elements and key fabrication steps, as well as current and potential biological/biomedical applications.

scholarly journals Avalanche dynamics by Newton. Reply to comments on avalanche flow models based on the concept of random kinetic energy

2018 ◽  
Vol 64 (243) ◽  
pp. 165-170 ◽  
Author(s):  
PERRY BARTELT ◽  
OTHMAR BUSER
Keyword(s):  
Flow Behavior ◽  
Practical Applications ◽  
Flow Models ◽  
Size Dependent ◽  
Drag Forces ◽  
Gravity Flows ◽  
Wide Range ◽  
Avalanche Dynamics ◽  
Avalanche Flow ◽  
Model Equations

ABSTRACTThe critique by Issler and other (2017) of our avalanche dynamics model maintains that we disregard well-established results of particulate gravity flows. Here we show that the arguments of Issler and others (1) violate Newton's laws of motion in the avalanche core and (2) ignore size-dependent drag forces on snow particles (Stokes law) that lead to the formation of avalanche suspension layers. We explain why we cannot amend our model equations to accommodate their suggestions. The goal of our approach is to describe highly non-stationary processes in the avalanche core that lead to a wide range of avalanche flow types and therefore different flow behavior. This is important for practical applications.

scholarly journals Real-time Characterization of Chemical Structure and Dynamics of Electrical Double Layer at Electrode-electrolyte Interfaces

2020 ◽  
Author(s):  
Yanyan Zhang ◽  
Jilin Tang ◽  
Zhigang Ni ◽  
Yao Zhao ◽  
Feifei Jia ◽  
...  
Keyword(s):  
Double Layer ◽  
Electrode Surface ◽  
Electrical Double Layer ◽  
Gold Electrode ◽  
Chemical Structure ◽  
Secondary Ion Mass Spectrometry ◽  
Supporting Electrolyte ◽  
Ion Pairs ◽  
Electrochemical Reactions ◽  
Wide Range

The chemisorption of species from supporting electrolytes on electrode surfaces is ubiquitous in electrochemical systems and affects the dynamics and mechanism of various electrochemical reactions. The understanding of chemical structure and property of the resulting electrical double layer is vital but limited. In this work, we operando probed the electrochemical interface between a gold electrode surface and a common supporting electrolyte, phosphate buffer, using our newly developed in situ liquid secondary ion mass spectrometry during dynamic potential scanning. We surprisingly found that on the positively charged gold electrode surface sodium cations coexisted within the inner Helmholtz layer to form ion pairs with the accumulated phosphate anions, resulting in a strong and dense adsorption phase which was further revealed to retard the electro-oxidation reaction of ascorbate. This finding addressed one major gap in the fundamental science of the electrode-electrolyte interface that where and how the cations exactly reside in the double layer to impose effects on electrochemical reactions, providing insights into engineering of better electrode-electrolyte interfaces in a wide range of fields such as electrochemical conversion and storage of energy, electrocatalysis, and electrodeposition.

scholarly journals Real-time Characterization of Chemical Structure and Dynamics of Electrical Double Layer at Electrode-electrolyte Interfaces

2020 ◽  
Author(s):  
Yanyan Zhang ◽  
Jilin Tang ◽  
Zhigang Ni ◽  
Yao Zhao ◽  
Feifei Jia ◽  
...  
Keyword(s):  
Double Layer ◽  
Electrode Surface ◽  
Electrical Double Layer ◽  
Gold Electrode ◽  
Chemical Structure ◽  
Secondary Ion Mass Spectrometry ◽  
Supporting Electrolyte ◽  
Ion Pairs ◽  
Electrochemical Reactions ◽  
Wide Range

The chemisorption of species from supporting electrolytes on electrode surfaces is ubiquitous in electrochemical systems and affects the dynamics and mechanism of various electrochemical reactions. The understanding of chemical structure and property of the resulting electrical double layer is vital but limited. In this work, we operando probed the electrochemical interface between a gold electrode surface and a common supporting electrolyte, phosphate buffer, using our newly developed in situ liquid secondary ion mass spectrometry during dynamic potential scanning. We surprisingly found that on the positively charged gold electrode surface sodium cations coexisted within the inner Helmholtz layer to form ion pairs with the accumulated phosphate anions, resulting in a strong and dense adsorption phase which was further revealed to retard the electro-oxidation reaction of ascorbate. This finding addressed one major gap in the fundamental science of the electrode-electrolyte interface that where and how the cations exactly reside in the double layer to impose effects on electrochemical reactions, providing insights into engineering of better electrode-electrolyte interfaces in a wide range of fields such as electrochemical conversion and storage of energy, electrocatalysis, and electrodeposition.

URBAN FACADE GEOMETRY ON OUTDOOR COMFORT CONDITIONS: A REVIEW

2020 ◽  
Vol 4 (1) ◽  
pp. 45
Author(s):  
Elahe Mirabi ◽  
Nasrollahi Nazanin
Keyword(s):  
Thermal Comfort ◽  
Urban Areas ◽  
Natural Ventilation ◽  
Flow Behavior ◽  
Air Flow ◽  
Urban Geometry ◽  
Wide Range ◽  
Low Energy Buildings ◽  
Outdoor Comfort ◽  
Solar Access

<p>Designing urban facades is considered as a major factor influencing issues<br />such as natural ventilation of buildings and urban areas, radiations in the<br />urban canyon for designing low-energy buildings, cooling demand for<br />buildings in urban area, and thermal comfort in urban streets. However, so<br />far, most studies on urban topics have been focused on flat facades<br />without details of urban layouts. Hence, the effect of urban facades with<br />details such as the balcony and corbelling on thermal comfort conditions<br />and air flow behavior are discussed in this literature review. <strong>Aim</strong>: This<br />study was carried out to investigate the effective factors of urban facades,<br />including the effects of building configuration, geometry and urban<br />canyon’s orientation. <strong>Methodology and Results</strong>: According to the results,<br />the air flow behavior is affected by a wide range of factors such as wind<br />conditions, urban geometry and wind direction. Urban façade geometry<br />can change outdoor air flow pattern, thermal comfort and solar access.<br /><strong>Conclusion, significance and impact study</strong>: In particular, the geometry of<br />the facade, such as indentation and protrusion, has a significant effect on<br />the air flow and thermal behavior in urban facades and can enhance<br />outdoor comfort conditions. Also, Alternation in façade geometry can<br />affect pedestrians' comfort and buildings energy demands.</p>

Modeling the Electrical Double Layer to Understand the Reaction Environment in a CO2 Electrocatalytic System

2019 ◽  
Author(s):  
Divya Bohra ◽  
Jehanzeb Chaudhry ◽  
Thomas Burdyny ◽  
Evgeny Pidko ◽  
wilson smith
Keyword(s):  
Electric Field ◽  
Double Layer ◽  
Electrical Double Layer ◽  
Surface Reaction ◽  
Catalyst Surface ◽  
Local Reaction ◽  
Reaction Diffusion ◽  
Alkali Metal Cations ◽  
Applied Potential ◽  
Critical Aspect

<p>The environment of a CO<sub>2</sub> electroreduction (CO<sub>2</sub>ER) catalyst is intimately coupled with the surface reaction energetics and is therefore a critical aspect of the overall system performance. The immediate reaction environment of the electrocatalyst constitutes the electrical double layer (EDL) which extends a few nanometers into the electrolyte and screens the surface charge density. In this study, we resolve the species concentrations and potential profiles in the EDL of a CO<sub>2</sub>ER system by self-consistently solving the migration, diffusion and reaction phenomena using the generalized modified Poisson-Nernst-Planck (GMPNP) equations which include the effect of volume exclusion due to the solvated size of solution species. We demonstrate that the concentration of solvated cations builds at the outer Helmholtz plane (OHP) with increasing applied potential until the steric limit is reached. The formation of the EDL is expected to have important consequences for the transport of the CO<sub>2</sub> molecule to the catalyst surface. The electric field in the EDL diminishes the pH in the first 5 nm from the OHP, with an accumulation of protons and a concomitant depletion of hydroxide ions. This is a considerable departure from the results obtained using reaction-diffusion models where migration is ignored. Finally, we use the GMPNP model to compare the nature of the EDL for different alkali metal cations to show the effect of solvated size and polarization of water on the resultant electric field. Our results establish the significance of the EDL and electrostatic forces in defining the local reaction environment of CO<sub>2</sub> electrocatalysts.</p>

Thin structure of heterogeneous and multiphase fluid flows

2012 ◽  
Vol 9 (1) ◽  
pp. 175-180
Author(s):  
Yu.D. Chashechkin
Keyword(s):  
Large Scale ◽  
Fundamental System ◽  
Fluid Flows ◽  
Regular Solutions ◽  
Flow Models ◽  
Group Methods ◽  
Wide Range ◽  
Thin Structure ◽  
Multiphase Fluid ◽  
Complete Solutions

According to the results of visualization of streams, the existence of structures in a wide range of scales is noted: from galactic to micron. The use of a fundamental system of equations is substantiated based on the results of comparing symmetries of various flow models with the usage of theoretical group methods. Complete solutions of the system are found by the methods of the singular perturbations theory with a condition of compatibility, which determines the characteristic equation. A comparison of complete solutions with experimental data shows that regular solutions characterize large-scale components of the flow, a rich family of singular solutions describes formation of the thin media structure. Examples of calculations and observations of stratified, rotating and multiphase media are given. The requirements for the technique of an adequate experiment are discussed.

Electrical Double Layer Formation on Glassy Carbon in Aqueous Solution

2021 ◽  
pp. 138416
Author(s):  
Sofia B. Davey ◽  
Amanda P. Cameron ◽  
Kenneth G. Latham ◽  
Scott W. Donne
Keyword(s):  
Aqueous Solution ◽  
Double Layer ◽  
Glassy Carbon ◽  
Electrical Double Layer ◽  
Layer Formation

Enzyme Immobilization Behavior on the Surface of Hydroxyapatite Capsules under Alkaline Condition

2018 ◽  
Vol 782 ◽  
pp. 21-26
Author(s):  
Takeshi Yabutsuka ◽  
Masaya Yamamoto ◽  
Shigeomi Takai ◽  
Takeshi Yao
Keyword(s):  
Enzyme Immobilization ◽  
Double Layer ◽  
Isoelectric Point ◽  
Electrical Double Layer ◽  
Alkaline Condition ◽  
Bicarbonate Buffer

We prepared hydroxyapatite (HA) capsules encapsulating maghemite particles. In order to evaluate enzyme immobilization behavior of the HA capsules under alkaline condition, we immobilized five kinds of enzymes with different isoelectric point in carbonate/bicarbonate buffer (CBB, pH 10.0). When the enzymes in CBB were moderately charged, immobilization efficiency on the HA capsules showed the highest value. It was suggested that immobilization efficiency was affected according to both pI of enzyme and pH of the surrounding solution and that enzyme immobilized on the HA capsules by not only electrical double layer interactions but also ion interaction and other interactions.

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