Flat Plate Electrodes Research Articles

Detection of Moisture Adsorption on Joining Surface Using Static Electricity Distribution

A new method using the static electricity distribution is proposed for noncontact detection of moisture adsorption on an object surface. The static electricity distribution with high spatial resolution over a short period of time was measured by scanning a vibrating array sensor with 30 parallel flat-plate electrodes along the object surface. Measurement of the local charge was demonstrated by using the sensor. It is possible to detect the influence of moisture adsorption over an entire object surface by observing the changes in the static electricity distribution over time.

Mass and heat transfer behaviour of catalytic and electrochemical stirred tank reactors employing metallic screens lining as a reaction surface

AbstractLiquid‐solid mass transfer behaviour of a rectangular stirred tank reactor lined with single screens and stacks of closely packed screens was studied in relation to catalytic and electrochemical reactor design by the electrochemical technique. Variables studied were impeller rotation speed, mesh number, and wire diameter of the screen, as well as physical properties of the solution, number of screens per stack, and impeller geometry. The rate of mass transfer increased with increasing impeller rotation speed and decreased with increasing screen mesh number and number of screens per stack. Radial flow turbine impellers produced higher rates of mass transfer than axial flow impellers. The data were correlated by dimensionless mass transfer equations. A comparison between the volumetric mass transfer coefficient at a stirred single‐screen electrode and at a stirred flat plate electrode shows that the volumetric mass transfer coefficient at the single screen is higher than that at the flat plate by a factor ranging from 7.3–22.5, depending on the operating conditions. For screen stacks, the ratio between the stack volumetric mass transfer coefficient and the flat plate value ranges from 2–46 depending on the operating conditions.The importance of the present results in the design and operation of catalytic and electrochemical reactors used to conduct diffusion‐controlled reactions was highlighted. The possibility of using screens as turbulence promoters to enhance the rate of heat transfer between the reactor wall and the surrounding cooling jacket was noted.

Numerical simulation and design optimization of an electrohydrodynamic pump for dielectric liquids

With an ever increasing demand for more effective heat sinks, liquid based electronic cooling has become a new prospect in the field. The present study introduces an electrohydrodynamic (EHD) pump with a simple design for dielectric liquids which have potential applications for electronic cooling. The pump consists of an eccentrically sandwiched wire electrode placed at the horizontal centerline between two parallel flat-plate electrodes. The EHD flow of dielectric liquid induced by the space charge generated due to the Onsager effect was obtained by the numerical solution of the Poisson–Nernst–Planck equations for ion transport and the Navier–Stokes equations for fluid flow. Good agreement obtained in the comparison of the numerical and the experimental results of velocity for the centrally sandwiched wire electrode case confirmed the validity of the numerical results. For a fixed voltage, the pump flow rate depends on the eccentricity of the wire electrode with respect to the plate electrodes and also with the electrode dimensions. By using the Taguchi method an optimum design for the EHD pump is obtained considering the wire electrode diameter, the flat plate electrode length and the eccentricity (the horizontal distance between the centers of wire and flat-plate electrodes) as the design parameters for fixed channel dimensions.

Modification of the tree root electrical capacitance method under laboratory conditions.

For many years, scientists have been searching for nondestructive methods for the measurement of plant root system parameters. The measurement of electrical capacitance (EC) across the root has been proposed as one such nondestructive method. This article presents a study on the determination of relationships between EC measurement and the shape and size of the electrodes immersed in medium that are used for measurement. Measurement of EC and the parameters characterizing root systems of 1-year-old seedlings of the common beech Fagus sylvatica L. was conducted under laboratory conditions. The measurements of EC were performed between seedling root systems and two different electrodes in the form of a cylinder or a rectangular plate. Statistically significant correlations were found between the capacitance and root system parameters in both the variants; however, the correlations were higher in the case of the flat rectangular plate. Correlation coefficient (r) between EC and total root length was 0.688 for cylindrical electrode and 0.802 for rectangular plate, for total root area 0.641 and 0.818, and for dry weight of root system 0.502 and 0.747. The best-fitted linear regression relationships between the EC and the measured parameters were characterized by low determination coefficients in variants with cylindrical electrodes, and higher with flat rectangular plate electrodes. The results indicated that a two-dielectric media concept is a better model than Dalton's model when attempting to interpret the behavior of root and soil capacitance. The different electrodes probably allow root capacitance measurements to be interpreted from different aspects. However, this hypothesis requires further verification.

Discharge and flow characteristics using magnetic fluid spikes for air pollution control

This paper presents an investigation of the atmospheric discharge and flow characteristics using a magnetic fluid (MF) for an air cleaning device. High-voltage ac is applied between MF spikes formed under a magnetic field and a flat-plate electrode. These MF-spikes are stretched upward to the opposing electrode sharpening its tip until discharge is generated. Furthermore, MF droplets are ejected from the tips of the spikes (a phenomenon known as electrospray) depending on the MF properties and operating conditions. The atmospheric discharge characteristics were investigated by measuring the discharge current. The cleaning ability of the system was evaluated by measuring the produced ozone concentrations.

Electrodeposition of PbO2 on Reticulated Vitreous Carbon for Organic Electrooxidation

The problems caused by the growing of the environmental contamination by organics have been calling the attention of researches, authorities, and population in general since their effects have been more present in our lives. Environmental contamination can be avoided by using, in most cases, biological treatments; however, some classes of compounds are refractory to this kind of treatment and require different technologies to oxidize the organic compound. In this context, the electrochemical technology emerged as an alternative environmentally, technically, and economically viable. Advantages of electrochemical technology are elimination of transport and storage of hazardous chemicals, reduction of the workmanship, and ease to automatization. Despite these advantages, for the effective use of the electrochemical technology for effluent treatment some drawbacks must be overcome, mainly mass transfer limitations resulting of the low concentrations in industrial effluents, which affect the current efficiency and the energy consumption. As an attempt to improve mass transfer, in this work we address the electrochemical oxidation using three-dimensional electrodes of reticulated vitreous carbon (RVC) covered by PbO2film as the electroactive material. The RVC/PbO2 electrode was prepared in a flow electrochemical reactor. The PbO2 film was electrodeposited on RVC applying different charges by varying the current density and electrolysis time. The porosities (in pores per inch) of the RVC substrates were 45, 60, and 80 ppi. The electrode was characterized by electrochemical techniques and scanning electronic microscopy. The decolorization reaction of the reactive blue 19 dye was used to evaluate the electrocatalytic power of the RVC/PbO2and compared to the flat plate electrode. The results for the 45 ppi RVC showed that the PbO2electrodeposition was not uniform within RVC due to non-uniform current penetration (Fig. 1 and 2). The best electrodeposit morphology and uniformity was obtained applying low current densities for longer electrolysis time (Fig 1c). Contrary, fast decolorization rate was obtained using the films deposited applying high current density (Fig. 2). A comparison between the flat plate and RVC/PbO2electrodes in Fig. 3 shows that the three-dimensional electrode was very effect to remove color. In order to increase the electrode specific surface area, PbO2 films were electrodeposited on RVC with 60 ppi and 80 ppi. After current density optimization, the PbO2 film was successfully deposited on the 60 ppi RVC. On the other hand, an optimum current density cannot be found in order to obtain a uniform deposit on the 80 ppi RVC. Moreover, the low porosity of this electrode and the high hydrophobic nature of RVC led to low surface wettability, thus contributing for the uneven PbO2 film. Figure 1

Polypyrrole-Coated Jute Substrate for Electromagnetic Shielding

In this study, electrically conductive polypropylene (PP) and jute nonwoven fabrics were synthesized by a chemical oxidative polymerization process using pyrrole as a monomer and iron chloride hexahydrate as an oxidant. After fabric production, electrical, morphological, and electromagnetic properties were determined. The deposition of polypyrrole (PPy) on nonwoven fabrics was confirmed by scanning electron microscopy (SEM) analysis. Electrical properties were evaluated as surface resistivity using two probe flat plate electrode systems. The electromagnetic interference shielding of PPy-coated fabrics (PP and jute nonwovens) and composites was measured as shielding effectiveness (SE) in the frequency range of 100 MHz to 1.5 GHz using the co-axial transmission line method.

Optimization of copper electrowinning from synthetic copper sulfate solution using a pulsed bed electrode

This paper concludes a series of investigations concerning the use of pulsed bed electrodes (PBEs) for copper electrowinning. In previous papers, the main operational parameters affecting the current efficiency (CE), space–time yield (Y), and energy consumption (EC) were identified and their effects on the performance of the process were analyzed. In light of the results, the fluidized bed time was set at 2s and it was found that the electrode thickness should be reduced in order to achieve values of CE and EC lower than those obtained in conventional industrial processes using flat plate electrodes. In this work, the electrode thickness was reduced from 3.4 to 2.4cm and the process was optimized using factorial experimental design and the Derringer desirability method to obtain current density (i), acid concentration (Cac), and pulsed bed time (tp) values that maximized CE and Y and minimized EC. The best Cac value was 100mgL−1 (a low level), while the optimum i and tp values were 2600Am−2 and 60s, respectively (high levels). Use of these values avoided short circuit and minimized copper dissolution during fluidization. The overpotential distribution within the porous cathode was improved using the 2.4cm electrode, and values of 100% (CE), 102kgm−3h−1 (Y), and 1.7kWhkg−1 (EC) were achieved under the optimized conditions. These values are better than those found for flat plate electrodes.

Electrohydrodynamic flow of dielectric liquid around a wire electrode - effect of truncation of onsager function

Electrohydrodynamic flow of a dielectric liquid around a wire electrode sandwiched between two parallel flat-plate electrodes is studied both numerically and experimentally. The Poisson-Nernst-Planck equations for the ion transport and the Navier-Stokes equations for the fluid flow are solved numerically by using a commercial code. Charge generation in a dielectric liquid (dodecane + 0.5% wt Span 80) due to Onsager effect is considered in the ion transport equations. Numerical results well predict the experimental ones both qualitatively and quantitatively. At high electric field the numerical approach slightly over-predicts the flow velocity measured from the experiment, but the level of discrepancy can be further lowered by using a truncated series for the Onsager function.

Irreversible Electroporation Ablation: Is All the Damage Nonthermal?

To determine whether high-dose irreversible electroporation (IRE) ablation induces thermal effects in normal liver tissue. Animal care and use committee approval was obtained prior to the experiments. IRE ablation (n = 78) was performed by a single four-person team in vivo in 22 porcine livers by applying electric current to two 1.3-cm-diameter circular flat-plate electrodes spaced 1 cm apart. Cardiac-gated IRE pulses (n = 40-360) were systematically applied at varying voltages (1500-2900 V). End temperatures at the ablation zone center were measured and were correlated with ablation time, energy parameters, and resultant treatment effect as determined at gross pathologic and histopathologic examination. Temperatures were then monitored at the center and periphery of four ablations created by using a four-electrode IRE array (3000 V, 90 pulses per electrode pair). Data were analyzed by using multivariate analysis of variance with multiple comparisons and/or paired t tests and regression analysis, as appropriate. Temperature rose above the 34°C baseline after IRE in all flat-plate experiments and correlated linearly (R(2) = 0.39) with IRE "energy dose" (product of voltage and number of pulses) and more tightly in univariate analysis with both voltage and number of pulses. Thus, mean temperatures as high as 86°C ± 3 (standard deviation) were seen for 2500 V and 270 pulses. Ablations of 90 pulses or more at 2500 V produced temperatures of 50°C or greater and classic gross and histopathologic findings of thermal coagulation (pyknotic nuclei and streaming cytoplasm). For lower IRE doses (ie, 2100 V, 90 pulses), temperatures remained below 45°C, and only IRE-associated pathologic findings (ie, swollen sinusoids, dehydrated cells, and hemorrhagic infiltrate) were seen. For the four-electrode arrays, temperatures measured 54.2°C ± 6.1 at the electrode surfaces and 38.6°C ± 3.2 at the ablation zone margin. In some conditions of high intensity, IRE can produce sufficient heating to induce "white zone" thermal coagulation. While this can be useful in some settings to increase tumor destruction, further characterization of the thermal profile created with clinical electrodes and energy parameters is therefore needed to better understand the best ways to avoid unintended damage when ablating near thermally sensitive critical structures.

Faster Time Response by the Use of Wire Electrodes in Capacitive Salinity Gradient Energy Systems

Capacitive energy extraction based on Donnan potential (CDP) and capacitive energy extraction based on double layer expansion (CDLE) are novel electroctrochemical processes to convert the potential free energy of mixing sea and river water into electric work. This is done by the use of supercapacitor electrodes with and without ion exchange membranes. Currently, these techniques rely on improved mass transport in order to become more efficient and give higher power output. In this paper we evaluate the transport phenomena by diffusion and the electrode geometry when switching between sea and river water at open circuit potential (OCP). By changing the electrode geometry from a flat plate to a cylindrical one, experiments and analytical models in combination show that mass transport by diffusion is increased. This is demonstrated without any changes in the hydrodynamic conditions. Improving mass transport without changing the hydrodynamic conditions breaks with what has been the convention in the scientific community of salinity gradient power. Moreover, in sea water the transport phenomena appear to be controlled by diffusion, and the response time for building open circuit potential in CDP and CDLE under this condition is reduced by a factor of 2 when using wire electrodes instead of flat plate electrodes. In river water, the trend is similar though the response time is generally larger.

Numerical simulation of mass transport in a filter press type electrochemical reactor FM01-LC: Comparison of predicted and experimental mass transfer coefficient

This paper studies flow characteristics and their effect on local mass transfer rate to a flat plate electrode in a FM01-LC electrochemical reactor. 3D reactor simulations under limiting current and turbulent flow conditions were performed using potassium ferro-ferricyanide electrochemical system with sodium sulfate as supporting electrolyte. The model consists of mass-transport equations coupled to hydrodynamic solution obtained from Reynolds-averaged Navier–Stokes equations using standard k–ɛ turbulence model, where the average velocity field, the turbulence level given by the eddy kinetic energy and the turbulent viscosity of the hydrodynamic calculation were used to evaluate the convection, turbulent diffusion and the concentration wall function. The turbulent mass diffusivity was evaluated by Kays–Crawford equation using heat and mass transfer analogies, while wall functions, for mass transport, were adapted from Launder–Spalding equations. Simulation results describe main flow properties, concentration profiles throughout the entire volume of the reactor and local diffusion flux over the electrode. Overall mass transfer coefficients estimated by simulation, without fitting parameters, agree closely with experimental coefficients determined from limiting current measurements (1.85% average error) for Re between 187 and 1407.

The use and optimization of stainless steel mesh cathodes in microbial electrolysis cells

Microbial electrolysis cells (MECs) provide a high-yield method for producing hydrogen from renewable biomass. One challenge for commercialization of the technology is a low-cost and highly efficient cathode. Stainless steel (SS) is very inexpensive, and cathodes made of this material with high specific surface areas can achieve performance similar to carbon cathodes containing a platinum catalyst in MECs. SS mesh cathodes were examined here as a method to provide a higher surface area material than flat plate electrodes. Cyclic voltammetry tests showed that the electrochemically active surface area of certain sized mesh could be three times larger than a flat sheet. The relative performance of SS mesh in linear sweep voltammetry at low bubble coverages (low current densities) was also consistent with performance on this basis in MEC tests. The best SS mesh size (#60) in MEC tests had a relatively thick wire size (0.02 cm), a medium pore size (0.02 cm), and a specific surface area of 66 m 2/m 3. An applied voltage of 0.9 V produced a high hydrogen recovery (98 ± 4%) and overall energy efficiency (74 ± 4%), with a hydrogen production rate of 2.1 ± 0.3 m 3H 2/m 3d (current density of 8.08 A/m 2, volumetric current density of 188 ± 19 A/m 3). These studies show that SS in mesh format shows great promise for the development of lower cost MEC systems for hydrogen production.

J0101-2-5 二相流を考慮した圧縮機翼に対する電気化学加工プロセスの数値的研究(エネルギーと環境問題におけるマルチフィジィックスCFDシミュレーション(2))

Electro-Chemical Machining (ECM) is an advanced machining technology and has been applied to highly specialized fields, such as aerospace, aeronautics, and medical industries, However, some problems remain to be solved The efficient tool-design, electrolyte processing, and disposal of metal hydroxide sludge are typical problems. In the previous study, we presented models to calculate the flow fields in an ECM process based on one- and two-way coupling simulation for interactions between gas and liquid phase. And we verified the presented models by comparing the numerical results with the experimental data for a flat plate electrode configuration. In this study, we apply the models for an ECM process for a compressor blade and compare the blade geometry.

Numerical and analytical studies of non-linear gravity capillary waves in fluid layers under normal electric fields

Non-linear gravity-capillary waves travelling at constant speed are considered in the presence of a normal electric field. The fluid, which is assumed to be inviscid, irrotational and a perfect dielectric, is bounded below by a solid plate electrode held at constant voltage, and the region above the free surface is a hydrodynamically passive perfect dielectric, e.g. air. A second parallel flat plate electrode is placed laterally far away and drives a uniform normal electric field there. Electrohydrodynamic coupling occurs at the free surface through the Maxwell stresses which act to modify the normal stress balance and consequently the Bernoulli equation boundary condition there. Three harmonic problems in deforming domains need to be solved, one for the hydrodynamics and one each for the electrostatics above and below the free surface, respectively. We derive and implement an accurate boundary integral method to compute travelling waves of arbitrary wavelength and amplitude. In addition, we consider a long-wave non-linear model of the full problem and compare solutions with the direct simulations. In both cases, we establish the existence of multiple families of solutions extending the classical theory of gravity-capillary waves. An asymptotic theory is also developed to construct periodic waves with ripples. These are used in comparisons with the numerical calculations and the agreement is very good.

Combined electrochemical and biological treatment of industrial wastewater using porous electrodes

AbstractZn2+, Ni2+ and propylene glycol methyl ether were simultaneously removed from simulated wastewater in a column consisting of an aerated packed bed and an electrochemical cell with a porous aluminium foam cathode and a porous stainless steel anode. After 48 h of sole electrochemical treatment at a liquid rate of 0.00183 m3 m−2 s−1, Zn2+ and Ni2+ were reduced by 95 and 80% respectively. In the turbulent flow regime with liquid rates varied from 0.0137 to 0.0366 m3 m−2 s−1, both Zn2+ and Ni2+ removal decreased by about 15% rather than increased as expected for a mass transfer‐controlled process. This can be attributed to bubble formation at the cathode surface under turbulent flow, which led to a lower active surface area for the electrodeposition of metal ions. Porous electrodes enhanced the metal removal by 17 and 60% for Zn2+ and Ni2+ respectively as compared with flat plate electrodes. Using combined biological and electrochemical treatment at a water rate of 0.00183 m3 m−2 s−1 and an air rate of 0.0518 m3 m−2 s−1, 99% of Zn2+ and 95% of Ni2+ were removed. In addition, the 5 day biological oxygen demand (BOD5) was reduced by 58% concurrently over 72 h of treatment. Copyright © 2006 Society of Chemical Industry

In vivo electroporation and ubiquitin promoter – a protocol for sustained gene expression in the lung

Gene therapy applications require safe and efficient methods for gene transfer. Present methods are restricted by low efficiency and short duration of transgene expression. In vivo electroporation, a physical method of gene transfer, has evolved as an efficient method in recent years. We present a protocol involving electroporation combined with a long-acting promoter system for gene transfer to the lung. The study was designed to evaluate electroporation-mediated gene transfer to the lung and to analyze a promoter system that allows prolonged transgene expression. A volume of 250 microl of purified plasmid DNA suspended in water was instilled into the left lung of anesthetized rats, followed by left thoracotomy and electroporation of the exposed left lung. Plasmids pCiKlux and pUblux expressing luciferase under the control of the cytomegalovirus immediate-early promoter/enhancer (CMV-IEPE) or human polyubiquitin c (Ubc) promoter were used. Electroporation conditions were optimized with four pulses (200 V/cm, 20 ms at 1 Hz) using flat plate electrodes. The animals were sacrificed at different time points up to day 40, after gene transfer. Gene expression was detected and quantified by bioluminescent reporter imaging (BLI) and relative light units per milligram of protein (RLU/mg) was measured by luminometer for p.Pyralis luciferase and immunohistochemistry, using an anti-luciferase antibody. Gene expression with the CMV-IEPE promoter was highest 24 h after gene transfer (2932+/-249.4 relative light units (RLU)/mg of total lung protein) and returned to baseline by day 3 (382+/-318 RLU/mg of total lung protein); at day 5 no expression was detected, whereas gene expression under the Ubc promoter was detected up to day 40 (1989+/-710 RLU/mg of total lung protein) with a peak at day 20 (2821+/-2092 RLU/mg of total lung protein). Arterial blood gas (PaO2), histological assessment and cytokine measurements showed no significant toxicity neither at day 1 nor at day 40. These results provide evidence that in vivo electroporation is a safe and effective tool for non-viral gene delivery to the lungs. If this method is used in combination with a long-acting promoter system, sustained transgene expression can be achieved.

The addition of red lead to flat plate and tubular valve regulated miners cap lamp lead–acid batteries

The study looked at the use of red lead in the manufacturing of valve regulated lead acid (VRLA) miners cap lamp (MCL) batteries that were made with either flat plate or tubular positive electrodes. A problem with using only grey oxide in the manufacture of thick flat plate or tubular electrodes is the poor conversion of the active material to the desired lead dioxide. The addition of red lead to the initial starting material improves the formation efficiency but is considerably more expensive thereby increasing the cost of manufacturing. The study showed that by carefully controlling the formation conditions in terms of the voltage and temperature of a battery, good capacity performance can be achieved for cells made with flat plate electrodes that contain up to 25% red lead. The small amount of red lead in the active cured material reduces the effect of electrode surface sulphate formation and allows the battery to achieve its rated capacity within the first few cycles. Batteries made with flat plate positive electrodes that contained more that 50% red lead showed good initial capacity but had poor structural active material bonding. The study showed that MCL batteries made with tubular positive electrodes that contained less than 75% red lead resulted in a poorly formed electrode with limited capacity utilization. Pickling and soaking times of the tubular electrodes should be kept at a minimum thereby allowing higher active material utilization during subsequent capacity cycling. The study further showed that it is beneficial to use higher formation rates in order to reduce manufacturing time and to improve the active material characteristics.

Assessment of high power HEV lead-acid battery advancements by comparative benchmarking with a European test procedure

The technical and practical suitability of lead-acid batteries for applications in vehicles with electrical drivetrains (battery-powered or hybrid electric) has been experimentally investigated in a variety of testing programmes. Under the direction and funding support of the Commission of the European Community, since early 1990s, the R&D Organisation EUCAR, a collaborative partnership of most European car manufacturers, has been conducting battery technological assessment projects, through bench tests carried out by different independent laboratories throughout Europe, using agreed test procedures. In this framework, ENEA acted as independent testing institute and tested, among others, three high power lead-acid batteries of various technologies (flat plate electrodes and spiral wound) for EV and HEV applications. In addition, different battery sizes and operating conditions have been tested at ENEA in a separate collaboration with ALTRA-IRISBUS.This paper intends to trace technological and performance improvements of high power lead-acid battery technology through the analysis of experimental data during parameter and life cycle tests, including the effects of battery sizes, charge/discharge profiles and testing procedures, with special emphasis on the reduction of the internal resistance and the variation of peak power and cycle life.

Development of a Pumping Module Using EHD Fluid.

Electro Hydro Dynamics (EHD) fluid is a kind of intelligent fluid. The fluid has the property that a fluid jet flow is generated between two electrodes when a high voltage is applied. DBDN (Di n-butyl dodecandioate) is a kind of EHD fluid and a dielectric organic liquid. The main purpose of this study is to develop a lightweight and compact fluid actuator which makes use of such properties of EHD fluid. We think that it is useful to apply EHD actuators to a micro actuating System as a lightweight actuator. In order to develop such an actuator, we first investigated the characteristics, the relation between the generated pressure and applied voltage to DBDN fluid. In this study, we tested two kinds of pumping module ; a direct type and a suction type. The direct type module consists of two doughnut shaped electrodes. The suction type module consists of a flat plate electrode and a cylindrical electrode. We investigated the relation between applied voltage and generated differential pressure using these modules. Further, we investigated the influence of geometric parameters on the characteristics of the module.