Journal of Electrostatics最新文献

This paper presents numerical and experimental investigations of electrohydrodynamic (EHD) flow and solid extraction during melting of phase-change materials (PCMs) in a rectangular cavity under constant temperature boundary conditions. It was found that EHD generated electroconvection cells in the liquid PCM between each pair of electrodes. The fluid velocity increased with applied voltage and decreased under higher temperature gradients across the liquid region due to buoyancy suppression. In the experimental study, the high-speed imaging at the solid-liquid interface showed that dendrites were extracted from the mushy zone during EHD melting and moved upwards into the liquid bulk under the action of the interfacial EHD forces.

Electrospray deposition (ESD) was utilized for targeted nutrient and water delivery to the roots of lettuce plants. Compatibility of ESD with nutrient solutions was confirmed; however, detrimental effects of ESD electric fields/current on plant growth were observed. To overcome this, a novel approach called “Staticaponics" was introduced by separating current and mass transport of ESD using a grounded metal mesh surrounding the root zone. This combination of ESD along with aeroponic and hydroponic concepts was shown to have higher nutrient solution use efficiency than either hydroponic or aeroponic growth alone, with acceptable plant nutrient content in the resulting plant tissue.

The present study examines the use of a two-stage electrohydrodynamic (EHD) gas pump with its electrodes assembly anchored at one corner of a square channel to modify the characteristics of flow inside the channel. Specifically, the proposed EHD pump is examined for its effectiveness in enhancing flow mixing as well as reducing the power requirement. The present study is also aimed at confirming one of the important conclusions drawn from the authors’ earlier works that, given the same number of emitting electrodes, the performance of an EHD pump can be specifically tailored by rearranging the location and orientation of the electrodes so that the modified characteristics of flow can achieve the desired effect. To evaluate the effectiveness of the proposed electrode configuration, the performance of the pump is compared with that of a previous study in which a two-stage gas pump utilizes an electrode assembly mounted on the two parallel walls. For both pumps, the emitting electrodes are flush mounted on the channel walls so that the air flow produced is similar to that of a wall jet. Through the performance assessment, the results obtained from the present study can provide useful information for practical applications of EHD gas pumps.

the mathematical models of glow discharge in transverse (y-direction) and axial (z-direction) magnetic fields are established in this paper. Firstly, Paschen's law is modified for different cross fields. The results show that the breakdown voltage first decreases and then increases with the increase of y-direction magnetic field at the same pressure. The breakdown voltage of glow discharge in z-direction magnetic field increases with the increase of magnetic field. Secondly, the effects of y-magnetic field and z-magnetic field on glow discharge are compared and analyzed by using the modified ionization coefficient. The results show that the plasma density has an extreme value under the combined action of y-direction magnetic field and air pressure. At the same pressure, the plasma density first increases and then decreases with the increase of magnetic field. The larger the magnetic field, the more obvious the plasma attenuation. In the z-direction magnetic field, the plasma density increases with the increase of air pressure or magnetic field.

The recent emphasis on environmental justice by the U.S. EPA has motivated the aerosol research community to develop innovative and cost-effective particulate matters (PMs) control technologies for subpopulations who are frequently exposed to indoor PMs. PM collection by electrostatic precipitation (ESP) has been proposed for indoor usage because it provides advantageous features over conventional fabric filters, such as lower energy consumption and being filterless. However, further research is needed before ESP can be used in indoor spaces, as ESPs suffer from low collection efficiency of submicron particles due to lower particle charging rates. Electrostatic particle clustering can potentially improve the shortcoming of ESPs if electrohydrodynamic (EHD) flow can be manipulated and controlled. A large-scale electrohydrodynamic (EHD) vortex flow was experimentally observed in the streamwise direction of a cylindrical ESP due to variation in current density. The objective of this study is to numerically characterize this novel large-scale EHD vortex flow for drag reduction and its potential ability to induce electrostatic particle clustering for submicron particles. The numerical model developed in COMSOL Multiphysics® solves the large-scale EHD vortex flow by coupling electrostatic physics with RANS k-$\varepsilon$ turbulent flow physics, involving three numerical domains. The results show that increasing the inlet velocity by one order of magnitude increases the maximum velocity near the discharge electrode by 1.25%. In addition, under negligible inlet velocity, the ionic flow dominates, leading to pulsated EHD/Re² numbers $\sim$ 1000 in the regions near the discharge and collection electrodes. The peak EHD$\#$ can be increased by 1.75% as the discharge voltage increases from 20 to 26 kV. The large-scale EHD vortex flow can modify the turbulent boundary layer and result in reduction in viscous drag near the collection electrode under low inlet velocity and high discharge voltage, which can potentially lead to prolonged entrainment of submicron particles for electrostatic particle clustering.

To establish an evaluation technique of the degradation degree of silicone rubber (SiR) surfaces, we first fabricated artificially degraded SiR surfaces. The fabrication process consisted of 5 steps and a 1-cycle test required 24 h. We fabricated the degraded SiR surfaces by a 1-cycle or a 2-cycle test. Next, the artificially degraded SiR surface was exposed to surface discharge (SD). The hydrophobicity recovery time on artificially degraded SiR surface increased with the increase in SD treatment time. It was found that the degradation degree of the SiR surface can be evaluated by hydrophobicity recovery time after SD treatment.

Electrostatic precipitators (ESP) are an effective means of reducing particulate matter emissions from biomass combustion. This study presents a comprehensive evaluation of the performance of an ESP integrated in a 240 kW wood chip boiler. The boiler-integrated ESP is commercially available and is evaluated in-situ using two types of wood chips, unlike previous studies, which mainly focuses on prototypes or lab-based constructions. The obtained results indicate a mass-based ESP efficiency of 94%–96%, surpassing previously reported values for small-scale boiler-integrated ESPs. Furthermore, the number-based ESP efficiency is 83%–92%, which is in line with values reported in literature. Despite the promising performance, the widespread adoption of integrated ESPs in small-scale appliances faces challenges due to the lack of financial, regulatory and energetic incentives. Nevertheless, the application of ESPs in this context remains crucial in addressing local air pollution and reducing the overall environmental impact of small-scale biomass combustion. To facilitate broader implementation, further research and policy initiatives are necessary. This study provides valuable insights into the true effectiveness of a small-scale ESP in mitigating particulate matter emissions.

The leader discharge is the primary process in long air gap discharge. However, there is currently a lack of detailed observation of the development process of leader discharge in equipotential live-line work (EPLW) gaps. Therefore, this study utilizes an electrical and optical synchronous observation platform to measure the key parameters of leader discharge in two typical EPLW gaps with gap distance of 2 m–3.5 m. Research results indicates that the worker's posture has significant effect on the leader characteristics of EPLW gaps. The longer the length of the worker's body-parts stretch out the bundle conductor and the small diameter of the discharge part is, the lower the leader inception voltage and inception current are. The average leader velocity of worker facing the tower is 5.93–7.67 cm/μs, however the leader velocity of worker facing the conductor is 7.43–9.59 cm/μs. The bending frequency of the leader channel of these two typical EPLW gaps both rise with the increase of gap distance. The axial deflection angle of worker facing the conductor gap is 27.87°, which is larger and more dispersive than that of worker facing the test tower gap. These test results can provide important references for determination of minimum approach distance and optimization of equipotential entering path for live-line work.

The aim of this study is to investigate the wettability control performance of a fluorocarbon-coated nanofiber membrane under the electrowetting process. The outcome nanofiber membrane was evaluated for chemical composition, morphology, surface roughness, and wettability. Through the electrowetting process, we give an estimate of some major effects as fine nanofibers, small liquid volume, low anode-cathode separation distance, and polar molecular droplets. We simply used COMSOL Multiphysics with finite element electrostatic mode to simulate electric field distribution changes for some different situations. The results of this study should assist in understanding the electrowetting on nanofiber membrane surfaces.

The presence of electric charges within liquid is relatively unexplored despite its role in electrochemical energy storage and industrial safety. Quantifying charge distribution in liquids and at solid/liquid interfaces is therefore crucial to the efficiency and longevity of devices. Over time, metrologies using stimulus to measure space charges in solids have been transposed to liquids. The stimulus disturbs electrostatic equilibrium to induces electrical response. This study builds upon measuring electric charges in the Electrical Double Layer (EDL) using the Pressure-Wave-Propagation (PWP) method. It presents how the pressure wave amplitude, the liquid conductivity and the liquid nature impact the electrical response.