Diffusion Polarization in Air Channels

1969 ◽  
pp. 83-94
Author(s):  
HENRI J. R. MAGET ◽  
EUGENE A. OSTER
Keyword(s):  
Diffusion Polarization ◽  
Air Channels

Diagnostics Development for E-Beam-Excited Air Channels

1985 ◽  
Author(s):  
D. J. Eckstrom ◽  
M. N. Spencer ◽  
J. S. Dickinson
Keyword(s):  
Air Channels

A novel approach in numerical simulation of contaminant removal by air sparging

2007 ◽  
Vol 7 (3) ◽  
pp. 163-170
Author(s):  
N. Jacimovic ◽  
T. Hosoda ◽  
M. Ivetic ◽  
K. Kishida
Keyword(s):  
Mass Transfer ◽  
Deterministic Model ◽  
Water Phase ◽  
Air Sparging ◽  
Order Kinetic ◽  
Contaminant Removal ◽  
Water Compartments ◽  
Novel Approach ◽  
Adopted Model ◽  
Air Channels

The paper presents a mechanistic/deterministic model for simulation of mass removal during air sparging. From the point of numerical modeling, there are two issues considering air sparging: modeling of air flow and distribution and modeling of mass transport and transfer. Several processes, which are commonly neglected, such as air channeling and pollutant advection by the water phase, are taken into account. The numerical model presented in this paper considers all relevant for mass transfer during the air sparging. Model includes hydrodynamics of air and water phase; calculated air volume content is divided into a number of air channels surrounded by the water phase, which is divided into two compartments. First compartment is immobile and it is in contact with air phase, while the second compartment is mobile. This “mobile-immobile” formulation is a common approach for description of solute transport by groundwater. Mass transfer between two water compartments is modeled as a first order kinetic, where the mass transfer coefficient, representing diffusion and advection in the water phase towards the air channels, is parameter needed to be calibrated. Sorption for both water compartments is considered. The adopted model of contaminant evaporation at the air-water interface is verified by comparison with experimental results available from published sources. Model is used for simulation of two-dimensional air sparging laboratory experiment. Good overall agreement is observed. It is showed that the efficiency of air sparging can be influenced by natural groundwater flow.

scholarly journals Design of Thermal Insulation Materials with Different Geometries of Channels

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2217
Author(s):  
Daniela Șova ◽  
Mariana Domnica Stanciu ◽  
Sergiu Valeriu Georgescu
Keyword(s):  
Thermal Conductivity ◽  
Porous Structure ◽  
Base Material ◽  
Cost Effective ◽  
Heat Radiation ◽  
Average Temperature ◽  
Temperature Regimes ◽  
The Face ◽  
Inclined Channels ◽  
Air Channels

Investigating the large number of various materials now available, some materials scientists promoted a method of combining existing materials with geometric features. By studying natural materials, the performance of simple constituent materials is improved by manipulating their internal geometry; as such, any base material can be used by performing millimeter-scale air channels. The porous structure obtained utilizes the low thermal conductivity of the gas in the pores. At the same time, heat radiation and gas convection is hindered by the solid structure. The solution that was proposed in this research for obtaining a material with porous structure consisted in perforating extruded polystyrene (XPS) panels, as base material. Perforation was performed horizontally and at an angle of 45 degrees related to the face panel. The method is simple and cost-effective. Perforated and simple XPS panels were subjected to three different temperature regimes in order to measure the thermal conductivity. There was an increase in thermal conductivity with the increase in average temperature in all studied cases. The presence of air channels reduced the thermal conductivity of the perforated panels. The reduction was more significant at the panels with inclined channels. The differences between the thermal conductivity of simple XPS and perforated XPS panels are small, but the latter can be improved by increasing the number of channels and the air channels’ diameter. Additionally, the higher the thermal conductivity of the base material, the more significant is the presence of the channels, reducing the effective thermal conductivity. A base material with low emissivity may also reduce the thermal conductivity.

scholarly journals Reflections on iridescent neck and breast feathers of the peacock, Pavo cristatus

2018 ◽  
Vol 9 (1) ◽  
pp. 20180043 ◽  
Author(s):  
Pascal Freyer ◽  
Bodo D. Wilts ◽  
Doekele G. Stavenga
Keyword(s):  
Three Dimensional ◽  
Refractive Indices ◽  
Rectangular Lattice ◽  
Pavo Cristatus ◽  
Feather Coloration ◽  
Air Channels ◽  
Difference Time ◽  
Modelling Methods ◽  
Reflection Characteristics ◽  
Reflectance Measurements

The blue neck and breast feathers of the peacock are structurally coloured due to an intricate photonic crystal structure in the barbules consisting of a two-dimensionally ordered rectangular lattice of melanosomes (melanin rodlets) and air channels embedded in a keratin matrix. We here investigate the feather coloration by performing microspectrophotometry, imaging scatterometry and angle-dependent reflectance measurements. Using previously determined wavelength-dependent refractive indices of melanin and keratin, we interpret the spectral and spatial reflection characteristics by comparing the measured spectra to calculated spectra by effective-medium multilayer and full three-dimensional finite-difference time-domain modelling. Both modelling methods yield similar reflectance spectra indicating that simple multilayer modelling is adequate for a direct understanding of the brilliant coloration of peacock feathers.

Experimental Study of Notoginseng Drying Based on a Solar Air Heating System

2011 ◽  
Vol 71-78 ◽  
pp. 2073-2076
Author(s):  
Fen E Hu ◽  
Zhi Juan Wang
Keyword(s):  
Winter Season ◽  
Heating System ◽  
Solar Drying ◽  
Mass Rate ◽  
Drying Time ◽  
Air Heating ◽  
Solar Air Collector ◽  
Air Blower ◽  
Drying System ◽  
Air Channels

A solar air drying system including solar air collector, drying cabinet and air blower for notoginseng drying has been constructed and tested. Two identical air solar collectors with two air channels, V-groove absorption heat plates and a single glass cover have been employed. The results of test show that the solar air collectors can obtain a good thermal performance in winter season. When the air flow mass rate is fixed at 0.0597kg·s-1, the maximum values of thermal efficiency and outlet air temperature are 76.0% and 62.2°C, respectively. The experimental analysis between two sampling notoginseng drying suggests that the solar drying is very effective, and the drying time has been shorten to about 440 minutes from 990 minutes of the traditional drying by sun. It is also observed that using the solar drying system notoginseng has a higher quality than traditional drying method.

Light propagation mechanism switching in a liquid crystal infiltrated microstructured polymer optical fibre

2015 ◽  
Vol 23 (4) ◽  
Author(s):  
K.A. Rutkowska ◽  
K. Milenko ◽  
O. Chojnowska ◽  
R. Dąbrowski ◽  
T.R. Woliński
Keyword(s):  
Liquid Crystal ◽  
Optical Fibre ◽  
Total Internal Reflection ◽  
Light Propagation ◽  
Propagation Mechanism ◽  
External Temperature ◽  
Air Channels ◽  
Propagation Properties ◽  
Infiltration Method ◽  
Light Guidance

AbstractIn this work studies on propagation properties of a microstructured polymer optical fibre infiltrated with a nematic liquid crystal are presented. Specifically, the influence of an infiltration method on the LC molecular alignment inside fibre air-channels and, thus, on light guidance is discussed. Switching between propagation mechanisms, namely the transition from modified total internal reflection (mTIR) to the photonic bandgap effect obtained by varying external temperature is also demonstrated.

Migration of air channels: An instability of air flow in mobile saturated porous media

2009 ◽  
Vol 64 (7) ◽  
pp. 1528-1535 ◽  
Author(s):  
Xiang-Zhao Kong ◽  
Wolfgang Kinzelbach ◽  
Fritz Stauffer
Keyword(s):  
Porous Media ◽  
Air Flow ◽  
Saturated Porous Media ◽  
Air Channels

Modeling and analysis of solar air channels with attachments of different shapes

2019 ◽  
Vol 29 (5) ◽  
pp. 1815-1845 ◽  
Author(s):  
Younes Menni ◽  
Ahmed Azzi ◽  
A. Chamkha
Keyword(s):  
Heat Transfer ◽  
Stokes Equations ◽  
Research Work ◽  
Convection Heat Transfer ◽  
Navier Stokes ◽  
Transfer Coefficients ◽  
Navier Stokes Equations ◽  
Content Type ◽  
Modeling And Analysis ◽  
Air Channels

Purpose This paper aims to report the results of numerical analysis of turbulent fluid flow and forced-convection heat transfer in solar air channels with baffle-type attachments of various shapes. The effect of reconfiguring baffle geometry on the local and average heat transfer coefficients and pressure drop measurements in the whole domain investigated at constant surface temperature condition along the top and bottom channels’ walls is studied by comparing 15 forms of the baffle, which are simple (flat rectangular), triangular, trapezoidal, cascaded rectangular-triangular, diamond, arc, corrugated, +, S, V, double V (or W), Z, T, G and epsilon (or e)-shaped, with the Reynolds number changing from 12,000 to 32,000. Design/methodology/approach The baffled channel flow model is controlled by the Reynolds-averaged Navier–Stokes equations, besides the k-epsilon (or k-e) turbulence model and the energy equation. The finite volume method, by means of commercial computational fluid dynamics software FLUENT is used in this research work. Findings Over the range investigated, the Z-shaped baffle gives a higher thermal enhancement factor than with simple, triangular, trapezoidal, cascaded rectangular-triangular, diamond, arc, corrugated, +, S, V, W, T, G and e-shaped baffles by about 3.569-20.809; 3.696-20.127; 3.916-20.498; 1.834-12.154; 1.758-12.107; 7.272-23.333; 6.509-22.965; 8.917-26.463; 8.257-23.759; 5.513-18.960; 8.331-27.016; 7.520-26.592; 6.452-24.324; and 0.637-17.139 per cent, respectively. Thus, the baffle of Z-geometry is considered as the best modern model of obstacles to significantly improve the dynamic and thermal performance of the turbulent airflow within the solar channel. Originality/value This analysis reports an interesting strategy to enhance thermal transfer in solar air channels by use of attachments with various shapes

IP interpretation in environmental investigations

Geophysics ◽  
2002 ◽  
Vol 67 (1) ◽  
pp. 77-88 ◽  
Author(s):  
Lee D. Slater ◽  
David Lesmes
Keyword(s):  
Field Experiments ◽  
Low Frequency ◽  
Environmental Parameters ◽  
Clay Content ◽  
Chemistry Laboratory ◽  
Frequency Effect ◽  
Resistivity Method ◽  
Surface Polarization ◽  
Capacitive Properties ◽  
Diffusion Polarization

The induced polarization (IP) response of rocks and soils is a function of lithology and fluid conductivity. IP measurements are sensitive to the low‐frequency capacitive properties of rocks and soils, which are controlled by diffusion polarization mechanisms operating at the grain‐fluid interface. IP interpretation typically is in terms of the conventional field IP parameters: chargeability, percentage frequency effect, and phase angle. These parameters are dependent upon both surface polarization mechanisms and bulk (volumetric) conduction mechanisms. Consequently, they afford a poor quantification of surface polarization processes of interest to the field geophysicist. A parameter that quantifies the magnitude of surface polarization is the normalized chargeability, defined as the chargeability divided by the resistivity magnitude. This parameter is proportional to the quadrature conductivity measured in the complex resistivity method. For nonmetallic minerals, the quadrature conductivity and normalized chargeability are closely related to lithology (through the specific surface area) and surface chemistry. Laboratory and field experiments were performed to determine the dependence of the standard IP parameters and the normalized chargeability on two important environmental parameters: salinity and clay content. The laboratory experiments illustrate that the chargeability is strongly correlated with the sample resistivity, which depends on salinity, porosity, saturation, and clay content. The normalized chargeability is shown to be independent of the sample resistivity and it is proportional to the quadrature conductivity, which is directly related to the surface polarization processes. Laboratory‐derived relationships between conductivity and salinity, and normalized chargeability and clay content, are extended to the interpretation of 1‐D and 2‐D field‐IP surveys. In the 2‐D survey, the apparent conductivity and normalized chargeability data are used to segment the images into relatively clay‐free and clay‐rich zones. A similar approach can eventually be used to predict relative variations in the subsurface clay content, salinity and, perhaps, contaminant concentrations.

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