Electrothermal Process Research Articles

Sustainable Recovery of Gaseous Mercury by Adsorption and Electrothermal Desorption Using Activated Carbon Fiber Cloth.

The present work aims to develop a novel and sustainable approach to adsorb and recover low-concentration Hg0 in the off-gas downstream a distillation/condensation system in the recycling processes for waste Hg-containing devices. Hg0 adsorption and regeneration efficiencies of raw and HNO3-treated activated carbon fiber cloth (ACFC) were examined. The adsorption experiments were conducted with an initial Hg0 concentration of 260-300 μg/m3 at room temperature. The regeneration of ACFC was done by an electrothermal swing process with 20, 40, and 60 W direct currents. The experimental results showed that the Hg0 adsorption efficiency of raw ACFC increased to approximately 90% after the 60 W electrothermal regeneration. After HNO3 treatment, the content of oxygen functional groups on HNO3-treated ACFC increased, which enhanced the Hg0 adsorption performance and resulted in over 90% adsorption efficiency for the samples before and after electrothermal regeneration. Importantly, both raw and HNO3-treated ACFCs retained the high adsorption efficiency after nine cycles of adsorption/regeneration, indicating that both raw and HNO3-treated ACFCs were effective and renewable adsorbents for low-concentration Hg0 adsorption and recovery. A Hg adsorption/regeneration mechanism was proposed to explain the increasing adsorption efficiency after electrothermal regeneration and the great adsorption efficiency of HNO3-treated ACFC.

Study of electrothermically treated metal materials

Scatter of hardness and electrical resistivity of ferromagnetic (steels 25, 50KhFA, 65G, 9KhF, ShKh15, 6KhS, 8Kh6NFT), paramagnetic (titanium alloy VT16) and diamagnetic alloys (D16 and AMg2) after the electrophysical process of high-speed heating for quenching with high density current (108 А/m2) with rapid cooling in oil or in water is studied. Effect of electrophysical parameters of materials on the result (hardness and electric resistivity) of electrothermal processing is determined. Effect of chemical composition, coercive force and Joule component of electric current of metallic materials on variation of hardness is studied. The results can be used in development of technology for treatment of metallic materials by heating with high-density current.

Investigation of heat effects in pulse electric field treatment of cellular materials

The paper deals with modeling and analysis of coupled electro-thermal processes during the pulsed electric field treatment of cellular materials for extraction of bioactive compounds. Subject of consideration is evaluation of heat effects: appearance of local thermal spots and high temperature gradients in the treated tissue. The presence of these phenomena is important for the processing: it aids the process of electroporation and thereby is useful for the extraction, but also could cause overheating and deterioration of the product quality. The analysis is provided using the finite element method, applied to the coupled time-dependent electric and transient thermal field problem. The mechanisms of heat transfer are studied by numerical simulations corresponding to the parameters (type and duration of electric pulses) of experimental examination of the processes of extraction of substances from vegetable seeds. Two steps are considered in the modeling: before and after electroporation. The field analysis after electroporation is carried out for correspondingly changed size and properties of the contact area between the cells. The obtained results can be used for adjustment of the process parameters in order to improve the yield of the extracted substances, without risk of overheating and degrading the quality of extracted product.

A Thermal Failure Model for MOSFETs Under Repetitive Electromagnetic Pulses

A thermal failure model for MOSFETs under repetitive electromagnetic pulses is investigated in this paper. The analytic equation to analyze the relationship between the temperature rise and pulse parameters is given by a theoretical derivation. The electro-thermal process of a 180 nm MOSFET is simulated as an example. It shows that the model agrees well with the technology computer aided design (TCAD) results. Some discussions on the influence of the dissipation performance and on the electro-thermal coupled effect are given. Both the theoretical model and the TCAD results indicate that most of the failures occur in 1 or 2 cycles. Further increase in the pulse number does not change the failure probability. Influence of heat dissipation performance of the substrate is discussed. This work is useful for further failure analysis, and is also helpful in protection design for the MOSFET device and circuit under HPMs and other repetitive electromagnetic pulses.

Последние научные исследования в сфере электротермической металлургической обработки

A wide range of industrial metallurgical heating and melting processes are carried out using electrothermal technologies. The application of electrothermal processes offers many advantages from technological, ecological and economical point of view. Although the technology level of the electro heating and melting installations and processes used in the industry today is very high, there are still potentials for improvement and optimization due to the increasing complexity of the applications and the strong requirements regarding the performance and quality of the products but also regarding the reduction of time and costs for the development of new processes and technologies.In this paper recent applications and future development trends for efficient heating and melting by electrothermal technologies in metallurgical processes are described along selected examples like induction heating for forging or rolling of billets, heat treatment of strips and plates, press-hardening processes, induction surface hardening of complex geometries, induction welding as well as induction melting processes.

Parallel Simulation of Fully Coupled Electrothermal Processes in Large-Scale Phase-Change Memory Arrays

Numerical simulation of fully coupled electrothermal processes in phase-change memory (PCM) arrays is performed in this article. For realizing the ability in simulating the electrothermal responses of large-scale PCM arrays, an in-house parallel simulator based on domain decomposition method (DDM) and time-domain finite element method (FETD) is developed, with its performance evaluated in terms of accuracy and scalability. Then, thermal crosstalk in the PCM array is investigated using the developed simulator, and a diamond layer is introduced to suppress thermal crosstalk. Furthermore, the scaling effects of PCM arrays on their electrothermal performance are examined. A scheme for multibit PCM design is proposed, and the electrothermal characteristics of proposed 2-bit PCM cells and arrays are studied numerically.

Combined alternating current electrothermal and dielectrophoresis-induced tunable patterning to actuate on-chip microreactions and switching at a floating electrode

A unique platform to fabricate tunable micropatterns at an electrically floating electrode has been developed via an enhanced combination of dielectrophoresis (DEP) and alternating current electrothermal (ACET) processes. The design of the platform uses two pairs of driving electrodes to generate a tunable electric field at a floating electrode, which in turn allows for the formation of patterned cells and fluids with desired features. By regulating the input configuration of the ac signals, yeast cells can be either patterned at the field stagnant region by a synergistic combination of negative DEP and ACET flow, or partially captured at the electrode edges subjected to a strong positive DEP, to form varying cell patterns. Additionally, nanoparticles were used to characterize the ACET-based flow pattern formation. Furthermore, the patterns were successfully exploited as an electrokinetic actuator to actuate continuous droplet switching, fluid mixing and microreactions. Implementing the simultaneous nanoparticle synthesis and guiding demonstrated that the combined field pattern is capable of manipulating both particulate samples and fluids. The proposed micropatterning technique may provide new insights for sample manipulation, on-chip function development and integration with other analytical components (i.e., biochemical sensors, chemical detectors, cell culture bioreactors) owing to a facile operation, easy integration and multifunctionality.

Electrothermal and Overload Performance of Metal-Oxide Varistors

The energy absorption capability of metal-oxide varistors, decidedly influenced by the electrothermal processes occurring within their microstructures, is a vital parameter for the effective surge protection. This paper proposes a numerical model for the simulation of the electrothermal phenomena occurring in metal-oxide varistors. The model is based on a 3D representation of the varistor's polycrystalline microstructure and the finite element method analysis. With the aid of the proposed model, the interdependence of the varistor's energy absorption capability, nonuniform current conduction, and the thermal behavior is investigated. Results are in good alignment with experimental data and discussed in the context of electrothermal properties of the varistor's microstructure. An unambiguous dependency of the varistor's energy handling capability on the applied overvoltage is shown to exist. A quantitative evaluation of the effective volume decrease due to the severe current localization at temporary overvoltages is demonstrated. The presented work analyses varistor's current conduction under temporary overvoltages and provides the means for extension of the varistors IV characteristics into the time domain so as to accurately predict their dynamic electrothermal behavior. The introduced dynamic (IV t) model may have significant implications in energy absorption requirements and design principles for surge protective devices.

Unsteady simulation of aircraft electro-thermal deicing process with temperature-based method

Considering the mass and energy sources carried by the accumulated ice layer, an unsteady heat and mass transfer model of the runback water film on the deicing surface is established to simulate aircraft electro-thermal deicing process. With the extension of the freezing coefficient to the transient calculation, the coupled heat transfer of the runback water and the solid skin is solved at each time step by a temperature-based method. Unsteady numerical simulation is carried out for the electro-thermal deicing system of a NACA 0012 airfoil. The temperature variations with time are in acceptable agreement with the literature data, and the unsteady temperature-based deicing model is verified. The calculation results of temperature, runback water flux and ice thickness on the deicing surface are analyzed at different time points, and it is shown that the unsteady electro-thermal deicing model can capture the main features of the icing, ice melting and re-freezing processes in the transient deicing simulations.

On-chip Mixing, Pumping and Concentrating Effects by Using AC Electrothermal Flow

Background:Microfluidic manipulation (including: pumping, mixing and concentrating effects) is highly challengeable for bioengineering and on-chip analysis applications such as point-of-care immune-detection systems. In this research we propose a configurable electrode structure to form various manipulation effects including pumping, mixing and concentrating processes by applying an Alternate Current (AC) electrokinetically-driven flow.Methods:By applying an inhomogeneous electric field causes temperature rise accompanied by temperature gradients generation inside the microchannel. As a result, an AC electrothermal flow generates inside the channel, which is efficient to generate mixing, pumping and concentrating effects.Results:The proposed system is studied numerically by Finite-Element-Method, Based on the results, a) bulk fluid velocity of 100 µm/s is achieved by exciting the electrodes in pumping mode, b) complete mixing efficiency is observed in mixing mode, c) for antibody-antigen binding process (concentrating mode), the surface reaction increases by the factor of 9 after 5 seconds of sample loading. Results reveal that the system is highly efficient for bio-fluid mediums.Conclusion:AC electrothermal fluid manipulation process was investigated numerically inside a microchannel for biological buffers. Back and forth fluid motions, clockwise/counter-clockwise rotational vortexes and also antibody-antigen linking enhancement were achieved by engineering the specific electrode patterns. The manipulation efficiency improves by increasing both the amplitude of electric potential and the ionic strength of biofluid. As a result, our proposed configurable device is of interest for onchip immunoassays and point-of-care devices.

Electrothermal processing of tantalum capacitor powders

A low-pressure arc discharger with the hollow cathode is a newly developed electrotechnological device for finely dispersed powders of particles having dimensions 50 micron and less. The discharger is useful for putting powder into a high reactive zone of a plasma column and for thermal and mechanical action on particles. In the NSTU, the plain scales of the splinter tantalum powder were gained experimentally. Based on the results of the experiments, several constructive solutions are proposed for the heating of powders with subsequent deformation of tantalum powder particles on the target.

Experimental investigation on a shield and magnetic assisted EDM of EN24 steel

Electric discharge machining is a non-traditional method of machining and also it is an electro-thermal machining process where an electric spark is generated by electrical energy. In the EDM process, workpiece material needs to be electrically conductive. In EDM machining any type of workpiece material which is conductive can be machined also can be cut into any profile. An electrode which is generally used as a tool must be a good conductor of electricity. Both the electrode and workpiece material are immersed in a dielectric medium and connected to the DC power source. An electric field is generated within the gap between the electrode and the workpiece is retained based on the potential difference applied. There will be a big amount of electrons flowing from the tool to the job and ions from the job to the tool such electron and ion movement can be seen visually as a spark. The electrical energy is thus dissipated as the spark's heat energy. But in the above process, there is a problem associated with the energy utilization produced in the spark. As just a little extent of the energy created in the spark is utilized for melting and evaporating of the workpiece material, the rest of the energy is dispersed in the dielectric liquid. In this present work, an attempt has been made to restrict the energy dissipation in the dielectric fluid and for this purpose, an enclosure is attached around the cathode with the plan to make a back pressure in this manner confining the development of the plasma in the EDM procedure. This the enclosure is also called as a shield and again to remove debris from the workpiece, the magnetic field generated by the magnets is used around the machining region.

СОВЕРШЕНСТВОВАНИЕ МАТЕМАТИЧЕСКОЙ МОДЕЛИ РАСЧЕТА ЭЛЕКТРОТЕПЛОВЫХ ПРОЦЕССОВ В КОНТАКТНОЙ ПОДВЕСКЕ ПОСТОЯННОГО ТОКА

СОВЕРШЕНСТВОВАНИЕ МАТЕМАТИЧЕСКОЙ МОДЕЛИ РАСЧЕТА ЭЛЕКТРОТЕПЛОВЫХ ПРОЦЕССОВ В КОНТАКТНОЙ ПОДВЕСКЕ ПОСТОЯННОГО ТОКА

Self-Similar Solutions With Electrothermal Processes for Plasmas of Arbitrary Beta

Self-similar magnetohydrodynamic (MHD) solutions are developed for a cold planar wall next to a hot plasma with an embedded magnetic field parallel to the wall, including the relevant electrothermal terms. Velikovich et al. (Phys. Plasmas, vol. 22, no. 4, 042702, 2015) studied the Nernst electrothermal effect in the induction equation for such a problem under the assumption that the ratio of thermal to magnetic pressure ( $\beta$ ) was large. Other electrothermal processes, such as the Ettingshausen and plasma Thomson effects, vary inversely with $\beta$ , as does Joule heating, and may impact the plasma evolution at low $\beta$ . To study all these processes, we have extended the self-similar formulation to allow for an arbitrary $\beta$ . The self-similar ansatz requires constant total pressure, i.e., thermal plus magnetic. Self-similar solutions are presented with the density and temperature boundary conditions characteristic of the plasma immediately following laser preheat in the Magnetized Liner Inertial Fusion experiment, and with the far-field magnetic field equal to that at the wall. Four cases are examined: two with a large $\beta$ and two with a moderate $\beta$ , and for each of these with and without electrothermal terms. Solutions for the density, temperature, and velocity depend on the choice of $\beta$ but are largely insensitive to the electrothermal effects. However, for the same value of $\beta$ , whether large or moderate, the profile of the magnetic field changes significantly when the electrothermal effects are included. In the case of moderate $\beta$ and electrothermal effects, the magnetic field profile has two extrema. This interesting case is further simulated with a 1-D MHD code that allows for total pressure changes through the momentum equation. Comparison with the self-similar solution shows that the simulation results approach the self-similar solution between the wall and an outward propagating rarefaction wave. The solutions are proposed as verification tests for advanced, multiphysics MHD codes.

Effect of electrical breakdown modes on shock wave intensity in water

Shock waves generated by underwater pulsed discharge have been applied to industrial and bio-medical treatments, and the key technology is to induce high intensity shock waves. Based on the underwater pulsed discharge platform, the effect of the electrical breakdown modes on the shock wave intensity in water is discussed in the positive pin-to-plane configuration. Experimental results demonstrate that the amplitude of applied voltage have a significant influence on the breakdown modes as well as the shock wave intensity. Based on the analysis of discharge images captured by a high-speed camera, it can be concluded that the breakdown modes are classified as subsonic bush-like streamers or supersonic filamentary streamers. The mechanism of subsonic streamer in lower applied voltage is more likely an electro thermal process. The micro-bubbles are firstly generated, and then discharge occurs in the bubble cluster. The bubble volume grows until a breakdown of the underwater gap, and the shock wave is the generated. The time to breakdown of subsonic streamers is commonly within hundreds of microseconds at the experimental condition. In higher applied voltage, the energy loss in the pre-breakdown process is reduced significantly as well. In our experiment, a threshold value of 22.5 kV is necessary for the subsonic streamer mode transition into supersonic streamer mode. The energy conversion efficiency, the time to breakdown and the influence of the applied voltage are discussed at different breakdown modes. The shock wave intensity differs 2–4 times in different breakdown modes even in the same applied voltage, thus increasing the applied voltage may be a remarkable way to enhance the shock wave intensity.

Research of Electro-Thermal Aging Process of Cross-Linked Polyethylene

Cable XLPE-insulation operation capability and reliability highly depends on its insulation condition. Statistical analysis showed that more than 70% of cable technological disturbances are insulation breakdowns, caused by insulation aging or poor quality of cable jointing. This paper is devoted to the cable XLPE-insulation aging under the influence of electro-thermal stress. The goal of the research is to develop the technique of cable insulation residual life calculation. Theoretical and experimental research was carried out for this goal. During theoretical research Kuchinsky insulation aging model was considered and statistical research of cable insulation breakdown was performed. Experimental research of cable insulation accelerated electro-thermal aging was carried out. XLPE-insulated cable samples were exposed to the influence of temperature and voltage above rated. The results of theoretical and experimental research showed that partial discharge dependence on electric field has variable coefficients and requires an additional research, taking all possible influencing factors into account.

Electrothermally actuated moving contact line dynamics over chemically patterned surfaces with resistive heaters

In this paper, we explore the moving contact line dynamics of two Newtonian immiscible fluids over substrates patterned with two different alternative chemical patches. The bulk fluid motion is actuated using electrothermal kinetics where the thermal field is generated by incorporating resistive heaters on the substrate. The electrothermal forces, which arise from the local gradient in electrical conductivity and permittivity, strongly depend on the local temperature and potential distributions. The thermal field and the potential distribution can be modulated by altering the heater characteristics and electrode patterning. The contact line motion and its intricate physics can be effectively tuned by altering the geometrical parameters of the heaters and electrode arrangement. Further, a comparison is executed between conventional electrothermal and heater-assisted electrothermal processes. The interfacial dynamics of the immiscible binary fluids is greatly affected by the present electrothermal mechanism and shows advantages over the conventional electrothermal process. The results presented here are effective for developing various smart devices involving multiphase flow dynamics within an electrokinetic paradigm.

COMPUTER SIMULATION OF ELECTROMAGNETIC FIELD WITH APPLICATION THE FREQUENCY ADAPTATION METHOD

Context. A modern stage of powerful radio-electronic and electrotechnical systems development, with a power more than 1 MW, imposes increased requirements to their energy equipment, uninterrupted operation and power supply reliability in various operational modes. Field simulation of such systems class is based on modern numerical realization methods of boundary value problems for Helmholtz and Maxwell equations, both in single-connected and multi-connected domains. It imposes increased requirements to resources, computer hardware speed and software computing efficiency, defining the relevance of a new mathematical apparatus development or its elaboration, including combinations of analytical and approximate numerical methods.Objective. The purpose of work is the elaboration a new numerical realization methods of field models taking into account ACelectrophysical processes with high frequency on the basis of Helmholtz equations in frequency formulations, adapted to software packagesuse with a free license.Method. A new method of frequency adaptation is elaborated, which provides systems of Helmholtz equations reduction in vectormagnetic potential formulations to the recurrent modified Maxwell’s equations, in analogies of DC formulation, and also provides highprecision and field simulation efficiency.Results. The generalized spatial mathematical model of interrelated electromagnetic and electrothermal processes AC energy conversionin current-conducting wires of powerful radio-electronic and electrotechnical systems is offered. This model considers operational modes, nonlinear dependences of electrophysical properties in electrotechnical materials, replacement effects and outer superficial effects, self- and mutual induction. A new method of frequency adaptation is elaborated, based on Helmholtz system of equations reduction in the vector magnetic potential formulations, in frequency domain, to the recurrent modified Maxwell’s equations, in analogies of DC formulation, and also provides high precision and field simulation efficiency. At numerical realization of frequency adaptation methods and finite elements, the number of freedom degrees decreases twice. It is caused by step-by-step solution the recurrent modified Maxwell’s equations, in analogies of DC formulations, for real and imaginary components of electric and vector magnetic potentials.Conclusions. The elaborated new frequency adaptation method significantly expands possibilities of production design preparation forpowerful radio engineering systems. It allows using the software packages with a free license, reduces requirements to computing resources, reduces time costs and provides high precision in electromagnetic fields simulation.

Dynamic simulation and analysis of thermal decomposition of binary particles with composite textures

CaC2 production via oxygen-thermal heating by combustion of coals or chars presents advantages over the conventional electro-thermal process and is increasingly gaining interest for effective use of carbon resources. In this investigation, with a particular focus on the reactor design aspect of the oxygen-thermal process, a one-dimensional unsteady pyrolysis model of bituminous coal-calcium containing composite pellets is established to describe the coupled external and internal heat transfer and decomposition rate steps. It is demonstrated by simulation that calcium hydroxide is a suitable calcium source and preferably used in a pseudo-homogeneous composite form with coal; in decomposition, the endothermic effect of calcium hydroxide is greater than that of the coal, and the endothermic effect of evaporation can be ignored; the relative importance of the involving rate steps is in the order of internal thermal resistance > external thermal resistance> reaction kinetics.

Electromembrane Extraction Using a Round-Headed Platinum Wire as the Inner Electrode: A Simple and Practical Way to Enhance the Performance of Extraction

Electromembrane extraction (EME) was carried out using a round-headed platinum wire as the inner electrode. The round-headed platinum electrode was prepared by a simple electrothermal process based on discharging of the electrical energy stored in a capacitor bank. The effect of the experimental parameters on the recovery of the extraction was investigated for amlodipine (AMP), verapamil (VPL) and clomipramine (CLP) as the model analytes and 2-ethyl hexanol as the supported liquid membrane solvent. It was found that the application of round-headed electrode (RHE) significantly improves the performance and stability of EME in comparison to a classical electrode. It was found that the improvement factor greatly depends on the sample properties such as the ionic strength and matrix complexity. The improvement factors for the extraction of AMP, VPL and CLP from standard solutions were 39.7, 54.4 and 43.2%, respectively. Higher improvement factors were recorded during extraction from real samples or saline solutions. Also, the application of RHE changed the extractability of AMP and VPL from complex matrices such as human plasma. The model analytes were successfully extracted from wastewater, human plasma and human urine samples with recoveries ranging from 36.3 to 88.7%. The relative standard deviations of the determinations were in the range of 8.2–14.8%.