Enhancement of fog-collection efficiency of a Raschel mesh using surface coatings and local geometric changes

2016 ◽  
Vol 508 ◽  
pp. 218-229 ◽  
Author(s):  
Mithun Rajaram ◽  
Xin Heng ◽  
Manasvikumar Oza ◽  
Cheng Luo
Keyword(s):  
Collection Efficiency ◽  
Surface Coatings ◽  
Fog Collection ◽  
Geometric Changes

On the aerodynamic fog collection efficiency of fog water collectors via three-dimensional numerical simulations

2020 ◽  
Vol 245 ◽  
pp. 105123
Author(s):  
Danilo Carvajal ◽  
Luis Silva-Llanca ◽  
Dante Larraguibel ◽  
Bastián González
Keyword(s):  
Numerical Simulations ◽  
Collection Efficiency ◽  
Three Dimensional ◽  
Fog Water ◽  
Fog Collection

scholarly journals Controlled transportation of droplets and higher fog collection efficiency on a multi-scale and multi-gradient copper wire

RSC Advances ◽  
2017 ◽  
Vol 7 (47) ◽  
pp. 29606-29610 ◽  
Author(s):  
Yan Xing ◽  
Sijie Wang ◽  
Shile Feng ◽  
Weifeng Shang ◽  
Siyan Deng ◽  
...  
Keyword(s):  
Anodic Oxidation ◽  
Collection Efficiency ◽  
Copper Wire ◽  
Scale Structure ◽  
Multi Scale ◽  
Fog Collection ◽  
One Step

Via a one-step gradient anodic oxidation, copper wire with a multi-scale structure and a multi-gradient was fabricated and controlled self-propelling of droplet was achieved.

Fog harvesting from cooling towers using metal mesh: Effects of aerodynamic, deposition, and drainage efficiencies

2019 ◽  
Vol 234 (7) ◽  
pp. 994-1014 ◽  
Author(s):  
Ritwick Ghosh ◽  
Ranjan Ganguly
Keyword(s):  
Fresh Water ◽  
Cooling Tower ◽  
Collection Efficiency ◽  
Fluid Dynamic ◽  
Tangential Velocity ◽  
Cooling Towers ◽  
Metal Mesh ◽  
Computational Fluid Dynamic Analysis ◽  
Fog Collection ◽  
Energy Penalty

Fog harvesting is recognized as an important alternate source of fresh water. Industrial fog can supplement water for industrial requirement. Collection of fog (drift droplets) from cooling tower plumes is a viable mode of industrial fog harvesting. The present study delves deeper into the findings of our earlier pilot investigation, on cooling tower fog harvesting and unravels how the collection efficiency depends on interaction of the mesh with the oncoming flow and the deposited fog droplets. Herein, we quantify the fog collection and explain the rationale of the individual contributions of aerodynamic, deposition, and drainage efficiencies on the overall collection efficiency. The effect of the mesh orientations and the tangential velocity component of the cooling tower plume (arising out of the cooling tower-fan rotation) are considered. Aerodynamic efficiency of the mesh and pressure drop across is estimated through computational fluid dynamic analysis. Also, an analysis of the force interaction between the mesh wires, deposited droplet, and the fog stream is carried out to identify the salient deterring factors like re-entrainment, clogging, and premature dripping of collected water droplets, based on which the regime of collection is mapped. The best collection configuration is found at an inclination of 15° with the vertical, with an overall collection efficiency of about 16%. The best configuration would allow recovery of re-usable fresh water at a nominal energy penalty of ∼3.9 kWh/m3. Our results offer the design bases for developing full-scale fog harvesting setups for industrial cooling towers.

Improving the Operation of a Cyclone Coupled With an Ejector

2008 ◽  
Author(s):  
Wayne Strasser
Keyword(s):  
Collection Efficiency ◽  
Physical Space ◽  
Solid Particles ◽  
Transient Pressure ◽  
Strain Formulation ◽  
Particle Orbit ◽  
Polyethylene Production ◽  
Ejector System ◽  
Dense Vapor ◽  
Geometric Changes

The dynamics of a plant-scale cyclone/ejector system have been studied numerically. The purpose of said system is to separate and evacuate solid particles from a highly dense vapor stream involved in polyethylene production. Complexity arises from the fact that the transient pressure field within the Lappel cyclone governs the operation of the annular ejector, and vice versa. Specifically, the cyclone’s asymmetrically dancing vortex dips well into the ejector suction; therefore the two units cannot be computationally uncoupled. Compressible, time-dependent CFD results were surprisingly sensitive to the pressure discretization approach. Results had a mixed dependency on the slow pressure strain formulation in the differential Reynolds Stress calculations, while they were insensitive to the pressure-velocity coupling routine. Interesting results from earlier researchers regarding particle orbit radius, as well as particle bypassing were confirmed. Six geometric configurations for improving the system operation were evaluated. Pressure differential and solids collection efficiency were the two primary measures. Since said system is an integral part of a complex commercial operation, cost and physical space constraints severely limit the extent to which the geometry can be modified. Simple geometric changes were shown numerically to make operational improvements while only incrementally improving particle collection efficiency.

scholarly journals Aerodynamics-assisted, efficient and scalable kirigami fog collectors

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Jing Li ◽  
Ranjiangshang Ran ◽  
Haihuan Wang ◽  
Yuchen Wang ◽  
You Chen ◽  
...  
Keyword(s):  
Collection Efficiency ◽  
Three Dimensional ◽  
Surface Characteristics ◽  
Water Shortage ◽  
Viscous Drag ◽  
Flow Forming ◽  
Low Wind Speed ◽  
Fog Collection ◽  
Outdoor Setting ◽  
Structural Length

AbstractTo address the global water shortage crisis, one of the promising solutions is to collect freshwater from the environmental resources such as fog. However, the efficiency of conventional fog collectors remains low due to the viscous drag of fog-laden wind deflected around the collecting surface. Here, we show that the three-dimensional and centimetric kirigami structures can control the wind flow, forming quasi-stable counter-rotating vortices. The vortices regulate the trajectories of incoming fog clusters and eject extensive droplets to the substrate. As the characteristic structural length is increased to the size of vortices, we greatly reduce the dependence of fog collection on the structural delicacy. Together with gravity-directed gathering by the folds, the kirigami fog collector yields a collection efficiency of 16.1% at a low wind speed of 0.8 m/s and is robust against surface characteristics. The collection efficiency is maintained even on a 1 m2 collector in an outdoor setting.

scholarly journals Importance of Body Stance in Fog Droplet Collection by the Namib Desert Beetle

Biomimetics ◽  
2019 ◽  
Vol 4 (3) ◽  
pp. 59 ◽  
Author(s):  
Unmeelan Chakrabarti ◽  
Roberto Paoli ◽  
Souvick Chatterjee ◽  
Constantine M. Megaridis
Keyword(s):  
Gas Flow ◽  
Volume Fraction ◽  
Collection Efficiency ◽  
Three Dimensional ◽  
Stream Velocity ◽  
Feedback Effects ◽  
Carrier Fluid ◽  
Microphysical Properties ◽  
Fog Collection ◽  
Biomimetic Approach

The fog-basking behavior of the Onymacris unguicularis, a beetle species living in the coastal regions of the Namibian desert, has recently caught the attention of the engineering community, as suggesting a viable biomimetic approach to address the problem of harvesting water in arid regions of the globe. Previous research has focused on observation and analysis of the beetle’s elytron properties and how these affect fog-collection rates. The head stance taken by the Onymacris unguicularis when fog basking is well documented. However, how this stance affects droplet collection has not been studied up to now. The present paper addresses this problem from a computational fluid dynamics perspective, where three-dimensional numerical simulations are used to characterize the fog flow properties around a simplified geometry mimicking the beetle’s body. The simulations employ two-way coupling between the gas flow and the dispersed fog phase to account for feedback effects of fog droplets on the carrier fluid (air), and assume that droplets are captured after hitting the elytron surface. The study considers several combinations of free-stream velocity and droplet volume fraction. The analysis reveals that there is a range of head-stance angles, corresponding to an inclination of the beetle between 35 deg and 45 deg with respect to the horizon, that maximizes water collection on the beetle’s back, in qualitative agreement with observations in nature and laboratory experiments. A rationale is proposed to explain this phenomenon, finding that the specific head stance corresponds to the maximum residence time of fluid particles above the beetle’s elytron surface. This, in turn, designates the maximum likelihood for water droplets to be captured in the boundary layer developing over the beetle and subsequently hit the surface where they get captured. The results reveal the importance of the fluid flow pattern around the beetle’s body in addition to the microphysical properties of the elytron when reliable predictions of the water droplet collection efficiency are sought.

To What Extent are Inelastically Scattered Electrons Useful in the Stem?

1973 ◽  
Vol 31 ◽  
pp. 286-287 ◽  
Author(s):  
H. Rose
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Electron Correlation ◽  
Quantum Noise ◽  
Collection Efficiency ◽  
Scanning Transmission Electron Microscope ◽  
Electron Cloud ◽  
Scanning Time ◽  
Transmission Electron ◽  
Scanning Transmission

The scanning transmission electron microscope offers the possibility of utilizing inelastically scattered electrons. Use of these electrons in addition to the elastically scattered electrons should reduce the scanning time (dose) Which is necessary to keep the quantum noise below a certain level. Hence it should lower the radiation damage. For high resolution, Where the collection efficiency of elastically scattered electrons is small, the use of Inelastically scattered electrons should become more and more favorable because they can all be detected by means of a spectrometer. Unfortunately, the Inelastic scattering Is a non-localized interaction due to the electron-electron correlation, occurring predominantly at the circumference of the atomic electron cloud.

High energy resolution spectrometer for the dedicated STEM

1984 ◽  
Vol 42 ◽  
pp. 558-559 ◽  
Author(s):  
P.E. Batson
Keyword(s):  
Collection Efficiency ◽  
Core Loss ◽  
Beam Current ◽  
High Energy ◽  
High Energy Resolution ◽  
Acquisition Time ◽  
Good Definition ◽  
Loss Analysis ◽  
Definition Of ◽  
Acceleration Voltage

Use of the STEM to obtain precise electronic information has been hampered by the lack of energy loss analysis capable of a resolution and accuracy comparable to the 0.3eV energy width of the Field Emission Source. Recent work by Park, et. al. and earlier by Crewe, et. al. have promised magnetic sector devices that are capable of about 0.75eV resolution at collection angles (about 15mR) which are great enough to allow efficient use of the STEM probe current. These devices are also capable of 0.3eV resolution at smaller collection angles (4-5mR). The problem that arises, however, lies in the fact that, even with the collection efficiency approaching 1.0, several minutes of collection time are necessary for a good definition of a typical core loss or electronic transition. This is a result of the relatively small total beam current (1-10nA) that is available in the dedicated STEM. During this acquisition time, the STEM acceleration voltage may fluctuate by as much as 0.5-1.0V.

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