Influence Of Electrostatic Charge Research Articles

Velocity measurement of pneumatically conveyed particles via a simple current signal technique and the influence of electrostatic charge

Particle velocity in pulse feeding pneumatic conveying was measured utilizing current signal analysis and video imaging. Glass beads and silica particles were conveyed in a conductive tube (ID of 4.57 × 10 −3 m) at gas velocities of 7, 15, and 30 m/s. To measure particle velocity, electrical current signal method was used with a new approach that uses raw current data and eliminates signal conditioning and cross-correlation analysis. This technique was successful and results were comparable to video imaging results. The conveyed particles' charge was measured to determine its influence on particle velocity. 30 m/s gas velocity resulted in a turbulent flow and greater charge generation causing more deviations between particle and gas velocity due to the enhancement of particles' radial motion. Finally, the comparison of results with predictions of existing models revealed that further research is necessary to better understand the effect of particles' motion and charge on their conveying velocity. Video imaging and current signal measurement techniques and the acquired electrostatic charge during pneumatic conveying. • Particle velocity in pneumatic conveying was measured based on particles charge. • A simplified technique based on electrical current signal method was proposed. • Influence of particles electrostatic charge on their velocity was investigated. • Existing models overestimated particle velocity in the presence of electrostatics. • Existing models predictions were not in agreement to the measurements at high gas velocities.

Case study on the influence of electrostatic charges on particle concentration in turbulent duct flows

Preferential concentration of inertial particles in wall-bounded turbulent flows is of paramount importance and, thus, subject of fundamental research. In practical applications of confined particle-laden flows the particles experience frequent collisions with the piping system which may result in an unwanted electric charge separation through triboelectric effects. The consequential occurrence of electrostatic forces alters the particle trajectories and their distribution. In this work the influence of charges on the averaged concentration of inertial particles in a fully developed turbulent duct flow was investigated by means of a combined numerical and experimental approach. The order of magnitude of the potential charge accumulation was estimated and imposed in a parametric study to the particulate phase in the simulations. Also, a new numerical approach based on the stochastic parcel method is introduced that allows to handle a large number of charged particles in a Lagrangian framework. This new approach extends standard formulations by including the effect of electrostatic forces on each parcel. The simulations demonstrate that the concentration profiles are for the most part independent of the prescribed charge except in the region close to the walls. The peaks of the particle number density at the walls caused by turbophoresis are strongly reduced through the local increase of repelling electrostatic forces. The comparison of numerical with experimental data indicates that the particles in the experimental setup could be affected by a surface charge density of the order of 100 C/m2. The presented results aim to elucidate the impact of electrostatic forces in the particle distribution in wall-bounded particle-laden flows.

The Influence of Electrostatic Charge on the Stability of Electronic and Electrical Equipment

In discharge of static electricity caused by friction, the voltage can reach 25 kV and the discharge current can reach up to tens of amperes with a rise time from fractions of nanoseconds. Electrostatic discharge can lead to malfunctions of electronic equipment or even to its being damaged. The regulations require checking the operation of electronic equipment under the influence of electrostatic discharges. Tests for resistance to such discharges can be performed using specially developed test generators (simulators) of electrostatic discharges. During the tests, the influence of discharge, the parameters of which are regulated in accordance with the basic standards for test methods, is simulated. At the design stage of electronic equipment, it is proposed to use the model of electrostatic discharge simulator to evaluate the expected voltages on the equipment case and its components for prediction of test results.

The role of electrostatic charge in the adhesion of spherical particles onto planar surfaces in atmospheric systems

• Surface charge and humidity play strong roles in the adhesion of two surfaces. • Changes in adhesive force are greater for surfaces with higher charge densities. • The role of capillary force in surface adhesion is stronger for larger particles. • Humidity effects on the electrostatic force depend on surface hydrophobicity. The influence of electrostatic charge on the adhesive force between spherical particles and planar surfaces in atmospheric systems was studied using atomic force microscopy. Electrical bias was applied to modify the surface charge, and it was found that application of a stronger positive bias to a particle induces a stronger total adhesive force. The sensitivity of the system to changes in the bias depended on the surface charge density. For larger-size particles, the contribution of the electrostatic force decreased, and the capillary force became the major contributor to the total adhesive force. The influence of water adsorption on the total adhesive force and, specifically, on the contribution of the electrostatic force depended on the hydrophobicity of interacting surfaces. For a hydrophilic surface, water adsorption either attenuated the surface charge or screened the effect of surface potential. An excessive amount of adsorbed water provided a path to surface charge leakage, which might cancel out the electrostatic force, leading to a reduction in the adhesive force. Theoretically calculated forces were comparable with measured adhesive forces except for mica which has a highly localized surface potential. The results of this study provide information on the behavior of charged colloidal particles in atmospheric systems.

Influence of Electrostatic Charge on Recombination Lifetime and Native Oxide Growth on HF-Treated Silicon Wafers

This paper reports on the influence of electrostatic charge on the time-dependent change in the hydrogen-terminated surface of HF-treated silicon wafers. The change in the hydrogen-terminated silicon surfaces were evaluated from the changes in recombination lifetime and the rate of native oxide growth. It is known that electrostatic charges are generated on silicon wafers by wet processing, such as HF treatment. This study notes that the electrostatic charge on wafers is modified over time to achieve an equilibrium, resulting from the interactions between charged wafers and the ambient. Using these characteristics of the electrostatic charge, the conditions under which changes in recombination lifetime and native oxide growth could be controlled were found. Furthermore, this mechanism was considered to influence the electrostatic charge on the band structure of p-type silicon. Using this phenomenon, native oxide growth on a silicon surface could be suppressed and HF treatment would provide a simple surface passivation method for recombination lifetime measurement.

Prediction of air filter efficiency and pressure drop in air filtration media using a stochastic simulation

In this paper, we discussed the relationship of filter efficiency and pressure drop with the porosity, fiber diameter and filter thickness by Geodict®. We found that filter efficiency has exponential relationship with filter porosity, fiber diameter and thickness. Furthermorethe pressure drop has a linear relationship with filter thickness and exponential relationship with filter porosity and fiber diameter, respectively. The influence of electrostatic charge on the particle deposition has been investigated. Simulation results were compared with the actual test results by TSI 3160.

Influence of electrostatic charges and non-electrostatic components on the adsorption of an aspartyl protease to lipid interfaces

The influence of electrostatic charges and non-electrostatic components on the adsorption of an aspartyl protease to lipid membranes was determined by measuring the zeta and the monolayer potentials of phosphatidylcholine and phosphatidylcholine-stearylamine membranes with and without cholesterol and correlated with the aggregation of liposomes. A significant change in zeta potential was found in lipid bilayers with net charges, which was affected by cholesterol. This adsorption also affected the dipole potential of monolayers with a similar composition, but in this case, it was not dependent on cholesterol. The reduction of the electrostatic and the dipole potential barrier caused an increase in the aggregation of liposomes covered by the protein, and this was dependent on the saturation level of the phospholipid hydrocarbon chains.

The importance of electrostatic charge and dielectric constant in conformational analysis of biologically active dipeptides

Our aim was to use molecular modeling to determine the solution conformations of small peptides (2–6 residues), which are substrates for both peptide transporters and peptidases, and can be clinically important as the basis of various therapeutic agents including β-lactams and ACE inhibitors. We evaluated two conformational search strategies and, in particular, the influence of electrostatic charge and dielectric constant on the results. AlaAla (uncharged), AlaAla (charged), N-acetyl-Ala-Ala-O-methyl and N-acetyl-Ala-Ala-methylamide were modeled using grid search and random search as implemented within SYBYL 6.4 using distance-dependent dielectric constants of between 1 (in vacuo) and 80 (water). The two search procedures located similar energy minima for both forms of AlaAla at any given dielectric constant, indicating that random searches sample conformational space sufficiently well for dipeptides at least. Analyses of the minimum-energy conformers computed for each molecule showed that, whereas the dielectric constant had minimal effect for AlaAla (uncharged), N-acetyl-Ala-Ala-O-methyl and N-acetyl-Ala-Ala-methylamide, for AlaAla (charged), as the dielectric constant approached 1 (in vacuo), this conformer had a cis peptide bond and was the only conformer present. We conclude that it is essential to model peptides in their charged forms at dielectric constants of approximately 80 to be able to determine the solution conformations of peptides recognized by peptidases and peptide transporters.

On the influence of electrostatic charging on coagulation of dust and ice particles in the upper mesosphere

The upper mesosphere, at heights above about 80 km, is the region of the atmosphere in which most ablation of incoming meteoric material takes place, and is thought to contain tiny nanometer‐size smoke and dust particles with concentrations of several thousand per cubic centimeter. In the extremely cold summer conditions at high latitudes, these particles probably form the condensation nuclei on which ice particles grow, giving rise to a variety of unique phenomena, including noctilucent clouds and localized electron depletions (“biteouts”). Recent work has shown that the particles become electrically charged by scavenging free electrons and positive ions from the background ionosphere. Under normal daytime conditions, calculations of charge balance have shown that most of the particles will carry a single negative charge, and it has been pointed out that electrostatic repulsion will inhibit coagulation of the particles, which would otherwise be an important mechanism for their growth. It is shown here that the opposite is true when ionization rates are very low, for example at night in the absence of energetic‐particle precipitation. In this case, positively and negatively charged particles tend to exist in equal numbers, and coagulation is enhanced by charging, instead of being inhibited. Because of the major unknown factors other than charging that affect coagulation, only idealized semi‐quantitative estimates of coagulation rates can be made. Electrical charging, however, appears to be a much less serious barrier to coagulation than had been thought, and may actually be a powerful stimulant.

The Influence of Electrostatic Charge on the Performance of 10-mm Nylon Cyclones

The 10-mm nylon cyclone is commonly used for measuring the respirable aerosol concentration of airborne dust. Under some conditions, the measured respirable aerosol concentration may be lower than the actual value due to electrostatic charge. An ideal solution to this inaccuracy is a cyclone, identical to the nonconducting type but molded of conducting, graphite-filled nylon, which performs the same as the nonconducting nylon cyclone under electrically neutral conditions. When exposed to conditions which tend to produce electrostatic charge, the performance of the conducting cyclone is unaffected, but aerosol penetration of the nonconducting cyclone decreases as a function of charge. Relatively high electrostatic charges are used in this study for demonstration purposes since the magnitudes of charges found in the field are hard to predict. Using the conducting cyclone gives consistent measurements, resulting in more accurate representation of deposition in the human respiratory tract.

The Influence of Electrostatic Charge on the Performance of 10-mm Nylon Cyclones

The Influence of Electrostatic Charge on the Performance of 10-mm Nylon Cyclones

Similarity in Gas-Borne Flowing Particulate Suspensions

Examination is made of similar conditions concerning transport phenomena in the conveyance of particulate suspensions by gases. The paper, in large part, concerns conveyance in straight ducts. Pressure loss and heat transfer are considered together with the influence of electrostatic charging in fully developed flow. The case of suspensions of fine particles is considered from the point of view of a continuum. The different natures of flow both near and away from the duct wall are elucidated. The influence of agglomerative tendencies and particle/particle contact is also considered. The importance of the flow regime concept is illustrated for more involved situations where several factors contribute to overall transport phenomena.