Electrical Conductivity Of Liquid Research Articles

Eulerian-Eulerian-VOF multifluid modelling of liquid–gas reacting flow for hydrogen generation in an alkaline water electrolyser

Alkaline water electrolysis is a promising technology for hydrogen production. However, its efficiency drops considerably at high current densities due to the mass transfer limitation and the increase in electrical resistivity arising from the complexity of the liquid–gas reacting flow behaviour within the electrolyser cell. In this work, a computational fluid dynamics (CFD) model is developed to describe the liquid–gas reactive flow behaviour. The model integrates the Eulerian-Eulerian two-fluid model and the multifluid Volume of Fluid (VOF) model, allowing the mathematical model to capture the electrochemical reaction effect on hydrogen gas formation and bulk flow bubble behaviour. The model is validated against prior experimental results. The simulation results suggest that, at higher current densities, the electrical performances and the mass transfer rates are highly influenced by the formation of gas bubbles, which may block the active sites for the electrochemical reaction to occur. Quantitatively, at 4000 A/m2, the mass transfer rate is reduced by 50% at regions above the cathode compared to electrode region, while electrical conductivity near the flow channel wall, drops by 17% compared to the bulk liquid electrical conductivity. The predicted electrical conductivity is comparable to the Bruggemann correlation with an average relative error of less than 2%, confirming the model’s validity in predicting the reacting flow behaviour and performance of the electrolyser. The numerical model offers a cost-effective tool for insightful understanding and refining the design and operation of hydrogen generation systems.

PCB-C4D coupled with paper-based microfluidic sampling for the rapid detection of liquid conductivity.

The detection of liquid electrical conductivity has board applications in food safety testing, water quality monitoring, and agricultural soil analysis. Electrodes used in traditional liquid electrical conductivity detection come into direct contact with liquid, leading to electrode contamination and affecting the accuracy of the detection results. The capacitively coupled contactless conductivity detection (C4D) method effectively addresses this issue. However, impurity particles present in the solution can compromise the consistency and repeatability of detection results. This study combines paper-based microfluidic technology with printed circuit board-capacitively coupled contactless conductivity detection (PCB-C4D) to address this issue. Prior to sample detection, in situ rapid filtration is employed to remove impurity particles from the raw solution sample, significantly enhancing detection consistency and reliability. Simultaneously, Optimization of PCB-C4D parameters, channel size, filtration time, and solution drop rate ensures optimal detection conditions. A compact kit design facilitates reliable assembly of the PCB-C4D electrodes and paper-based channel, enhancing practicality. Practical measurements on the conductivity of orange juice, cucumber, and soil solution further validate the method's accuracy, rapidity, and effectiveness in in situ conductivity detection. This work advances the practical application of PCB-C4D technology.

Electrospray characteristics and cooling performance of dielectric fluid HFE-7100

Electrospray (ES) cooling is a promising route of efficient heat removal for electronic components with powerful cooling capacity, a small liquid supply, and precise temperature control. In this study, we experimentally investigated the electrohydrodynamic (EHD) disintegration and ES cooling performance of the dielectric fluid HFE-7100. The stainless-steel capillary nozzle was connected to a high voltage direct current (DC) power supply, whereas the hot copper surface was grounded. A high-speed camera was used to capture the spray morphology of the coolant. The results indicated that a small amount of ethanol significantly improved the charging performance of HFE-7100 by increasing the liquid electrical conductivity. An uncharged column liquid jet was stretched into a thin liquid film by the EHD forces, generating numerous ultrafine droplets along the lower edge. The ES cooling heat flux was increased by about 2.2 times compared with the neutral condition. In addition, the influences of the applied voltage, flow rate, spray height, liquid subcooling, and ethanol concentration on the ES cooling capacity were discussed. Finally, correlations of the ES cooling heat transfer based on the Reynolds number, Weber number, Prandtl number, electric Weber number, Jacob number, and normalized surface temperature were established.

Electrohydrodynamic disintegration of dielectric fluid blended with ethanol

Engineered fluid HFE-7100 is an outstanding detergent and coolant with excellent thermal and chemical stability. Electrohydrodynamic jet disintegration and subsequent droplet formation of HFE-7100 dielectric liquid mixed with ethanol were experimentally investigated in this study. Contact-type charging was employed with the capillary nozzle directly connected to a negative high-voltage power supply, while the counter electrode was grounded. High-speed photography was utilized to capture the liquid breakup and droplet formation behaviors. The results showed that an ethanol content of 8% by volume visibly improved the charging performance of HFE-7100 due to the increase in the liquid electrical conductivity. In addition, with the increase in the applied voltage, the jet breakup was found to transform from the dripping/jetting mode to the ramified mode, which is characterized by a steady liquid sheet with fine droplets forming at the edge. Two distinct ramified breakup configurations, called the pudgy-ramified and lanky-ramified modes, are proposed, and their detailed structural parameters and droplet size distributions are discussed. The diameters of the droplets produced under the permanent ramified configuration could be as small as a few micrometers. Finally, a jet breakup regime map based on the Reynolds number Re and electric bond number BoE was established. Overall, the electrospray technique has shown promise for spray cooling enhancement, and the main results of this paper may be useful for the development of electrospray cooling with a dielectric coolant.

Практические аспекты реализации кондуктивного датчика электропроводности жидкости

Практические аспекты реализации кондуктивного датчика электропроводности жидкости

Deuterium–hydrogen ratios, electrical conductivity and nitrate for high-resolution dating of polar ice cores

In order to support the very high time resolution required to observe short-term variations in nitrates and all other ions represented by electrical conductivity in polar ice, a Fourier transform infrared spectrometer was developed for measurement of deuterium concentration in ice samples, as an additional support for the timescale of ultra-high resolution. The portable instrument provided the possibility to measure deuterium concentration on exactly the same samples as used for measuring nitrate concentrations and liquid electrical conductivity, thus verifying that the original dating of the annual variations in nitrate was correct. We present basic information about how the high-resolution data were obtained and discuss their reliability and significance.

Get 132–2018: State Primary Standard of the Unit of Specific Electrical Conductivity of Liquids in Range from 0.1 TO 50 mho/m

Results of studies carried out in the period from 2015 to 2017 as part of efforts to improve GET 132–99, the State Primary Standard of the unit of specific electrical conductivity of liquids, are presented. The structure of GET 132–2018, the new approved State Primary Standard of the unit of specific electrical conductivity of liquids in the range from 0.1 to 50 mho/m is described. Solutions by means of which the metrological characteristics of the primary standard may be improved are presented.

MEASUREMENT OF LIQUID LEVEL IN PARTIALLY-FILLED PIPES USING A NOISE OF ELECTROMAGNETIC FLOWMETER

This paper investigates the measurement of liquid level in partially filled pipes utilizing an electrical noise signal (transformer signal) generated in electromagnetic flowmeter namely, transformer signal. The study was conducted by experiments and the collected data were analyzed statistically using Artificial Neural Network (ANN). The experimental study was achieved by building a laboratory rig containing the main parts of electromagnetic flowmeter. The main parameters which have been studied were the liquid level, magnetic field strength (  = 0.00809T, 0.03308T, 0.05301T), liquid temperature (  = 11º  to 21.5º ) and liquid electrical conductivity (  = 0.11225, 3.08, 210, mS/cm). The collected data were analyzed using the back propagation neural network technique included in Matlab software 2009. The results show that the transformer signal is greatly influenced by variations of the liquid level inside partially filled electromagnetic flowmeter. The electrode position of (  = 160º) has had the strongest response to liquid level. The electrode position effect on the transformer signal is the greatest compared with that of the liquid temperature and the strength of the magnetic field. Generally, the transformer signal was found to be an increasing function with decreasing of liquid level.

Measuring Transducers of Electrical Conductivity of Liquids

We describe a measuring transducer of electrical conductivity of liquids, used both under laboratory conditions and also for the study of ocean processes (under natural conditions). The transducer is represented in the form of a separate unit for laboratory investigations, which can be used as part of a deep-water hydraulic probe. For an example of different processes and flows, at the IPMekh RAN laboratory of fluid mechanics it has been shown that a small-scale transducer has a high speed and high spatial resolution.

Temperature Dependent Properties of Silicon Carbide Nanofluid in Binary Mixtures of Glycerol-Ethylene Glycol

Nanofluids are a new class of engineered thermal fluids with enhanced thermal properties and heat transfer capabilities exceeding those of the base liquid. Studies related to the effect of temperature on the thermophysical and rheological properties of ethylene glycol and glycerol nanofluids have been documented in various articles. In this paper, the thermal and physio-chemical behavior of SiC nanofluid dispersed in glycerol and ethylene mixture of 60:40wt.% ratio was determined. The influence of temperature on the pH, viscosity, electrical and thermal conductivity of nanofluid was undertaken for a maximum concentration of 1.0 vol.% in the temperature range of 15-75oC. It was found that, the base liquid electrical conductivity and pH were unaffected by temperature; whereas the nanofluid electrical and thermal conductivity increased with temperature. The viscosity of the base liquid and nanofluid decreased significantly while the decrease in pH is not significant with temperature.

Fluidic dielectrophoresis: The polarization and displacement of electrical liquid interfaces.

Traditional particle-based dielectrophoresis has been exploited to manipulate bubbles, particles, biomolecules, and cells. In this work, we investigate analytically and experimentally how to utilize Maxwell-Wagner polarization to initiate fluidic dielectrophoresis (fDEP) at electrically polarizable aqueous liquid-liquid interfaces. In fDEP, an AC electric field is applied across a liquid electrical interface created between two coflowing fluid streams with different electrical properties. When potentials as low as 2 volts are applied, we observe a frequency-dependent interfacial displacement that is dependent on the relative differences in the electrical conductivity (Δσ) and dielectric constant (Δɛ) between the two liquids. At low frequency this deflection is independent of dielectric constant, while at high frequency it is independent of electrical conductivity. At intermediate frequencies, we observe an fDEP cross-over frequency that is independent of applied voltage, sensitive to both fluid electrical properties, and where no displacement is observed. An analytical fDEP polarization model is presented that accurately predicts the liquid interfacial cross-over frequency, the dependence of interfacial displacement on liquid electrical conductivity and dielectric constant, and accurately scales the measured fDEP displacement data. The results show that miscible aqueous liquid interfaces are capable of polarizing under AC electric fields, and being precisely deflected in a direction and magnitude that is dependent on the applied electric field frequency.

Electrostatic hand pressure knapsack spray system with enhanced performance for small scale farms

Electrostatic force fields have been employed and enhanced in the design of an electrostatic knapsack spray system for increasing the deposition efficiency and reducing the drift of pesticides. The designed induction charge based electrostatic sprayer offers optimum electrode position and electrical conductivity of liquid. The experiments were conducted in ambient conditions for liquid feed rate 340 ml/min at hand pressure of 30 psi. The charge-to-mass ratio was found to be 0.419 mC/kg at 3.25 kV by a spray liquid of conductivity 10.25 mS/cm. There has been 2–3 fold increase of chemical deposition with better uniformity on the target (potted plant).

Water film motor driven by alternating electric fields: Its dynamical characteristics

The "liquid film motor," a novel device with important implications for basic research and technology, is analyzed. It works perfectly with both direct current (dc) and alternating current (ac) fields. We develop a mathematical model describing electrohydrodynamical (EHD) motions induced by ac fields, which are more complex and have wider technological applications than those produced by dc fields. The main characteristics of these motions, derived in our paper and in full agreement with the experimental ones, are as follows: (i) Rotation of the film requires that the frequencies of the ac fields are exactly the same and their magnitudes surpass a threshold, which depends on their phase difference. (ii) Vibrations may be induced by fields with different frequencies. (iii) The EHD motions strongly depend on the polarization induced by the external electric field. However, these motions are little affected by the liquid's electrical conductivity, viscosity, dielectric constant, and density. Our model also predicts several features, which have yet to be experimentally verified.

Experimental investigation of electrosprayed droplets behaviour of water and KCl aqueous solutions in silicone oil

Electrostatic atomization of liquids is now considered as a well established technique for creating finely mono-dispersed liquid droplets. One of the techniques in producing stable emulsion is to make finer droplets of dispersed liquids using electrohydrodynamic actuators. This work is to investigate the hydrodynamics of dispersed droplets of water and aqueous solutions of KCl in a continuum dielectric fluid of silicone 100 cSt. The effects of dispersed liquid flow rate, applied voltage and electrical conductivity of liquids on droplet motion and its diameter were considered. By means of a nozzle with inner diameter of 0.8 mm, water and KCl solution droplets were generated and forwarded into the dielectric silicone oil as a base of quiescence medium. In order to produce fine droplets, EHD was applied using high voltage nozzle and grounded ring. By this method, stable water and KCl solution droplets were produced in oil without any surfactants. It was observed that increasing dispersed liquid flow rate reduces the effect of EHD leading to droplet size increment. The conductivity of dispersed media has significant effects on droplet size and stability of them. For KCl solution with more conductivity than water, the direct effects of this property on droplet size and their stability were studied.

Role of the effective electrical conductivity of nanosuspensions in the generation of TiO 2 agglomerates with electrospray

Suspensions with varying volume fraction of TiO 2 nanoparticles and ionic strength were electrosprayed to obtain agglomerates of different characteristics, which were then deposited to produce films with tailored morphology, thickness, and porosity. The role of the nanoparticle volume fraction in both the effective electrical conductivity of TiO 2 nanosuspensions and the control of the size of agglomerates produced by electrospray was investigated. A simple modified equation for the effective electrical conductivity of TiO 2 nanoparticle suspensions was derived. The equation, which accounted for nanoparticles' diffuse ionic layer and their agglomeration in a liquid, showed that the effective electrical conductivity is not only a function of the liquid and particle conductivities, and the particle volume fraction but also a function of both the thickness of the adsorbed ionic layer on the particles and the particle size. Gradual increase of particle volume fraction resulted in an increase in the suspension's effective electrical conductivity, when the initial liquid conductivity was in the range of 10 −4–10 −3 S m −1. When the liquid conductivity was in the range of 10 −3–10 −2 S m −1; however, addition of particles did not have any significant effect on the effective electrical conductivity. Control over the size of the TiO 2 nanoparticle agglomerates was achieved by electrospraying suspensions with liquid electrical conductivity of the order of 10 −3 S m −1 and by varying the particle volume fraction. Electrospray deposition of suspensions with TiO 2 volume fraction=0.04% resulted in a more compact film with lower porosity and showed better water-splitting performance.

Propagation Modes of an Electrical Discharge Along a Liquid Jet

This paper deals with the investigation of an electrical discharge propagated along a thin liquid jet. The propagation modes were studied. Three discharge areas were found out. The continuous degenerated glow discharge between an electrode and jet appeared at small current lower than ~5 mA and then transformed into a sliding surface pulse discharge propagated along the jet by increasing the current. The relative discharge pulse period was inversely proportional to the transit time for the jet. The surface discharge degenerated to an arc over the jet at a current above 20 mA. The surface discharge area was narrowed down at the increase of the electrical conductivity of liquid.

On the theory of dielectric liquid electric conductivity in a field of injecting electrodes (concentration dependence)

Calculation of the free electron concentration in a weakly conducting liquid at injection of electrons from high voltage needle electrodes on the liquid surface is given. Methods of solid state physics have been substantiated and applied. The concentration of free electrons does not depend on the electric field intensity up to prebreakdown voltages.

Ion evaporation from Taylor cones of propylene carbonate mixed with ionic liquids

A combined experimental and numerical approach is used to extract information on the kinetics of ion evaporation from the region of high electric field around the tip of a Taylor cone of the neutral solvent propylene carbonate (PC) mixed with two ionic liquids. On the numerical side, the electric field on the surface of the liquid is computed in the absence of evaporation by solving the electrohydrodynamic problem in this region within the framework of the leaky dielectric model. These computations justify the approximate (2% max error) scaling Emax = β Ek for the maximum electric field on the surface, with Ek = γ1/2 ϵ0−2/3 (K/Q)1/6 for 0.111 < K < 0.888 S m−1 and a numerical value of β ≈ 0.76. Here γ is the surface tension of PC, ϵ0 is the electrical permittivity of vacuum, and K and Q are the liquid electrical conductivity and flow rate. On the experimental side, 16 different propylene carbonate solutions with either of the ionic liquids 1-ethyl-3-methylimidazolium tetrafluoroborate (EMI-BF4) or EMI-bis(trifluoro-methylsulfonyl)imide (EMI-Im) are electrosprayed in a vacuum from a single Taylor cone, and their emissions of charged drops and ions are analysed by time-of-flight mass spectrometry at varying liquid flow rates Q. The sprays contain exclusively drops at large Q, both for small and for large electrical conductivities K, but enter a mixed ion–drop regime at sufficiently large K and small Q. Interestingly, the mixtures containing 10% and 15% (vol) EMI-Im exhibit no measurable ion currents at high Q, but approach a purely ionic regime (almost no drops) at small Q. The charge/mass ratio for the drops produced in these two mixtures increases continuously with decreasing Q, and gets very close to ionic values. Measured ion currents are represented versus computed maximum electric fields Emax on the liquid surface to infer ion evaporation kinetics. Comparison of measured ion currents with predictions from ion evaporation theory yields an anomalously low activation energy (~1.1 eV). This paradox appears to be due to alteration of the pure conj–eet electric field in the scaling laws used for the pure cone–jet regime, due to the substantial ion current density arising even when the ion current is relatively small. Elimination of this interference would require future ion current measurements in the 10–100 pA level. The electrical propulsion characteristics of the emissions from these liquids are determined and found to be excellent, particularly for 10% and 15% (vol) EMI-Im.

Influence of difference in specific electrical conductivities of liquids on the process of displacement in a porous medium

The results of experimental investigation of the influence of the specific electrical conductivity of liquids on the process of displacement in a porous medium have been given. It has been established that, for cofiltered aqueous electrolyte solutions of virtually the same viscosity, an increase in the ratio of the electrical conductivities of the displacing and displaced liquids leads to a decrease in the displacement coefficient before the breakthrough of the displacing liquid. It has been found that, in displacement of a nonpolar liquid by aqueous systems close in viscosity, an increase in the specific electrical conductivity of the displacing liquid causes a reduction in the displacement efficiency.

Ratios of Mg2+/Na+ in snowpack and an ice core at Austfonna ice cap, Svalbard, as an indicator of seasonal melting

AbstractSnowpack and ice-core samples were collected from the dome of Austfonna ice cap, Svalbard, in the spring of both 1998 and 1999. The samples were analyzed for anions, cations, pH, liquid electrical conductivity and oxygen isotopes. Concentrations of chemical components in snowpack with a history of melting were much lower than those in unmelted snowpack. There was a clear difference between Mg2+/Na+ ratios previously in melted snowpack (0.03 ± 0.02) and in unmelted snowpack (0.11 ± 0.02). We propose that the Mg2+/Na+ ratio can be used as an indicator of whether or not firn or bubbly ice in the Austfonna ice core has experienced melt percolation. The Mg2+/Na+ ratio indicates that firn or bubbly ice prior to AD 1920 was much less affected by melt percolation than firn or bubbly ice formed after 1920.