Electrothermal Methods Research Articles

Piston reactor for chemical energy storage: Modeling study to explore electro-mechanical conversion route using propane feedstock

Within the context of renewables and chemical energy storage, this work aims to explore chemical reaction conversion through the electro-mechanical route which is different from the commonly employed electro-thermal and electro-chemical conversion methods. Piston reactor is a novel equipment concept that can couple the rotational movement from an electric motor to a reciprocating piston within an enclosed reaction chamber resembling the operation of an internal combustion engine. Exploration of a reactor technology still in the laboratory stage requires an assessment of reaction intermediate mixtures to identify potential leads. This work uses a systematic methodology to assess these intermediate mixtures beyond typical reactor yield metrics to include economic values as part of the decision-making toward identifying lead candidates. Rather than focusing on a specific target reaction or product, this work is carried out as a model-driven study to cover a wider range of conditions and product scenarios. Propane as the main feedstock is selected because it is easier to trigger in the piston reactor, it is not a complex feed, a detailed kinetic mechanistic model is available to study it, and most importantly it can generate a wide range of industrially relevant products to serve the purpose of this study. The study revealed that the highly endothermic propane pyrolysis reaction requires intake temperatures larger than 950 K which is impractical. Diluting the feed with argon is one way to lower this intake temperature and achieve desirable conversion. This however is impractical because of additional separation steps and reduced production capacity. Thermal coupling of propane pyrolysis with exothermic side reactions by co-feeding oxygen, water, or carbon dioxide are investigated and showed promising results. A diverse range of products are produced such as hydrogen, carbon monoxide, ethylene, and propylene, achieving high conversions (>90 %), while simultaneously generating useful work and process heat. Unconventional triggers such as using ozone to generate radicals and trigger ignition are investigated to further lower the intake temperature requirements. The explored solution space is then evaluated considering a new reactor metric as the value of products mixture stream. Regions of high-value products do not match those obtained using the traditional yield metrics. This shows the importance of what metrics to use for assessing reactors with wide range of reaction mixture intermediates as the piston reactor. Full economic analysis and optimization are the right direction in the future to properly assess the potential of piston reactor technology.

Accessibilité et qualité de l’eau dans la commune de Mboro (Sénégal) : étude exploratoire

In a context of demographic growth in coastal areas, access to drinking water remains a major challenge. The aim of this work is to contribute to the study of the population's perception of the accessibility and quality of water, as well as the hydro-chemical characterisation of water samples from the commune of Mboro. A questionnaire was administered to a sample of 150 households out of 3,455 for the perception survey. Two borehole water samples (MBORO F1 and MBORO F2), one from a traditional well (PUITS TRAD) and one from a pond (THI) were analysed using volumetric, electrothermal and spectrophotometric methods. The results show that the pH values of the water samples comply with WHO standards, and that the conductivity values and chloride, sodium, sulphate, magnesium, calcium, bicarbonate and potassium levels are below the regulatory thresholds. However, the PUITS TRAD (185.7 mg/l) and THI (117.5 mg/l) samples had nitrate concentrations above the guide value (50 mg/l). The iron content of the PUITS TRAD and THI samples is equal to the guide value (0.2 mg/l). The survey on the supply of drinking water revealed that 67% of households have domestic taps, 4% use standpipes, 16% draw water from their neighbours and 13% of the population use water from wells. 77% of the population say they have easy access to a water source. However, 47% of households are not satisfied with the management and operation of the commune's water facilities. This work shows that the commune of Mboro is facing difficulties in supplying quality water. Concerted, sustainable action is therefore needed to improve the situation for the local population.

Mechanically Robust Interface at Metal/Muscovite Quasi van der Waals Epitaxy.

Quasi van der Waals epitaxy is an approach to constructing the combination of 2D and 3D materials. Here, we quantify and discuss the 2D/3D interface structure and the corresponding features in metal/muscovite systems. High-resolution scanning transmission electron microscopy reveals the atomic arrangement at the interface. The theoretical results explain the formation mechanism and predict the mechanical robustness of these metal/muscovite quasi van der Waals epitaxies. The evidence of superior interface quality is delivered according to the outstanding performance of the designed systems in both retention (>105 s) and cycling tests (>105 cycles) through electromechanical measurements. With high-temperature X-ray reciprocal space mapping, the unique anisotropy of thermal expansion is discovered and predicted to sustain the thermal stress with a sizable thermal actuation. A maximum bending curvature of 264 m-1 at 243 °C can be obtained in the silver/muscovite heteroepitaxy. The electrothermal and photothermal methods show a fast response to thermal stress and demonstrate the interface robustness.

Study of foreign experience in dealing with ice and frost deposits on the wires of overhead power lines

The means and technologies for predicting and preventing frost and ice deposits on the wires of overhead power lines in the power grids of foreign countries are presented. The focus is on such systems as Meteo, dynamic thermal rating, online monitoring of China Southern Power Grid, Variable resistance cable de-icing system and mobile ice melting units. The advantages and disadvantages of these systems are analyzed and it is found that such approaches require energy consumption and are relevant only for the relevant region of the power grid, depending on weather conditions and the distance of electricity transmission. The mechanical, electromechanical, electrothermal, and physicochemical methods of predicting frost and ice deposits on the wires of overhead power lines are considered. It was found that the consideration of dynamic processes is essential and effective in the study of power grids in extreme weather conditions, and the data on frost and ice deposits on overhead line wires are characterized by high dimensionality, nonlinearity, multimodality, and heterogeneity, which makes it impossible to create an accurate forecasting model using traditional methods of evaluation and decision-making. The method of time series analysis and the method of Ensemble Empirical Mode Decomposition are proposed to solve this problem. The basis of these methods is to maximize the use of inherent regularities represented by frequency and time characteristics for effective data analysis and to create the basis for subsequent models and improve their forecasting accuracy. On the basis of the research, the author proposes ways to adapt and integrate the experience of foreign countries into the power grids of Ukraine. The necessity of creating integrated information systems for monitoring meteorological parameters and operating modes of power grids using specialized forecasting models and IT systems is substantiated, which will automate the process of assessing the current state of overhead power lines based on meteorological data in order to timely prevent emergencies in power grids provoked by frost and ice deposits.

A Closed Cavity Ultrasonic Resonator Formed by Graphene/PMMA Membrane for Acoustic Application

A graphene/poly(methyl methacrylate) (PMMA) closed cavity resonator with a resonant frequency at around 160 kHz has been fabricated. A six-layer graphene structure with a 450 nm PMMA laminated layer has been dry-transferred onto the closed cavity with an air gap of 105 μm. The resonator has been actuated in an atmosphere and at room temperature by mechanical, electrostatic and electro-thermal methods. The (1,1) mode has been observed to dominate the resonance, which suggests that the graphene/PMMA membrane has been perfectly clamped and seals the closed cavity. The degree of linearity of the membrane’s displacement versus the actuation signal has been determined. The resonant frequency has been observed to be tuned to around 4% by applying an AC voltage through the membrane. The strain has been estimated to be around 0.08%. This research puts forward a graphene-based sensor design for acoustic sensing.

Development and digital twin of an experimental opto-electrothermal bench in the perspective of thin films thermal characterization

This work aims to widen the application of the front Flash methods to dielectric materials with thermal conduction times ranging from seconds to a few tens of nanoseconds. In this perspective, the design and characteristics of an experimental opto-electrothermal bench are presented here: its principle is based on the Flash methods (short optical excitation) however combined with an electrothermal measurement. The development of direct models acting as digital twins of the bench is also described. They allow considering its electrothermal behaviour, by taking into account the 1D thermal diffusion in a multilayer sample and the non-ideal frequency response of the acquisition chain (signal conditioner and the measuring devices) according to the sample thermal dynamics – which is little discussed in the literature to the authors’ knowledge. The methodology proposed here for the sizing and consideration of the acquisition chain can be applied to other electrothermal measurements methods such as the 3ω methods.

Study of the effect of continuous loading and compaction on the electrical resistance of powder materials

The electrical conductivity of powder media depends on the composition, impurities, oxide films, morphology and the nature of the contact surface. We present the results of studying the electrical resistance of powder materials and their compounds under continuous loading by the four-contact method. The electrical resistance is determined using a special experimental cell. Industrial powders Al (ASD-1), Ti (PTK), Hf (GFM-1), soot and their mixtures, as well as TaC and HfC powders obtained by self-propagating high-temperature synthesis were studied. It is shown that an increase in the mechanical pressure up to 80 MPa leads to a decrease in the electrical resistance of the materials under study. The morphology of the particles (spherical or fragmentary shape), their dispersion affects the quality of the contact surface and, accordingly, the magnitude of the electrical resistance. Moreover, the electrical resistance of the material depends on the degree of cleaning of the particle surface from oxide films. The proposed method in combination with other analytical methods used for studying powder media allows us to reveal the regularities of this relationship, characteristic of all morphological features, composition and electrophysical properties of powders of various compositions under loading conditions. The results obtained can be used to select the optimal characteristics of consolidation by electric current depending on the initial pressure, as well as in case of high-voltage electric pulse consolidation of powder materials by spark plasma sintering and electrothermal explosion methods.

Temperature-Dependent Characterization of Power Amplifiers Using an Efficient Electrothermal Analysis Technique

In this paper, we propose an efficient methodology for the electrothermal characterization of power amplifier (PA) integrated circuits. The proposed electrothermal analysis method predicts the effect of temperature variations on the key performances of PAs, such as gain and linearity, under realistic dynamic operating conditions. A comprehensive technique for identifying an equivalent compact thermal model, using data from 3-D finite element method thermal simulation and nonlinear curve fitting algorithms, is described. Two efficient methods for electrothermal analysis applying the developed compact thermal model are reported. The validity of the methods is evaluated using commercially available electrothermal computer-aided design (CAD) tools and through extensive pulsed RF signal measurements of a PA device under test. The measurement results confirm the validity of the proposed electrothermal analysis methods. The proposed methods show significantly faster simulation speed comparing to available CAD tools for electrothermal analysis. Moreover, the results reveal the importance of electrothermal characterization in the prediction of the temperature-aware PA dynamic operation.

Development of new electrical technological systems and complex in the production of hard-to-remove oil reserves

When developing hard-to-recover hydrocarbon reserves, enterprises use various complexes and systems to facilitate technological processes that contribute to the lifting of heavy and viscous oils to the surface, as well as the extraction of light oils from lowpermeability reservoirs. During the operation of fields, abnormal situations also arise, caused by the appearance of asphalt-resin-paraffin deposits (ARPD) and salt deposits on the walls of tubing pipes, Christmas trees, process pipelines and equipment at the bottom. The existing methods of combating and preventing the manifestations of ARPD and salt precipitation can be conditionally divided into mechanical, chemical, thermal. To prevent and combat ARPD, as well as to reduce the viscosity of produced oils, thermal methods are most preferred, among which electrothermal methods are considered effective. In the case of salt sediments, technologies based on electrical energy are also an effective means of prevention, in particular, exposure of the well emulsion to a magnetic field. Keywords: electrical technological systems and complexes; hard-to-remove oil reserves; asphalt-resin-paraffin deposits; induction heating systems.

Upgrading wave energy test sites by including overplanting: a techno‐economic analysis

Dynamic rating is an approach which implies to operate an electrical network closer to its thermal limits. This approach may be very beneficial for wave farms, as they are expected to present a highly fluctuating electrical current profile while benefiting from the large thermal inertia of the soil where their export cable will be buried. However, as the implementation of this approach is still in its infancy for offshore wind farms, it may be expected that the first wave farms, under the form of small-scale test sites, will be sized with respect to electrical current limits at a first stage. This sizing may be upgraded at a second stage when design methods will have included dynamic rating. However, this raises the question of the economic feasibility of this two-step approach, which is studied in this paper. Also, performing such a techno-economic analysis requires developing an electrothermal model of the export cable able to represent its transient response in a sufficiently precise manner while requiring also a reasonable computing time. In this perspective, a comparative analysis between several electrothermal modelling methods is also described in this paper.

Electric Propulsion Methods for Small Satellites: A Review

Over 2500 active satellites are in orbit as of October 2020, with an increase of ~1000 smallsats in the past two years. Since 2012, over 1700 smallsats have been launched into orbit. It is projected that by 2025, there will be 1000 smallsats launched per year. Currently, these satellites do not have sufficient delta v capabilities for missions beyond Earth orbit. They are confined to their pre-selected orbit and in most cases, they cannot avoid collisions. Propulsion systems on smallsats provide orbital manoeuvring, station keeping, collision avoidance and safer de-orbit strategies. In return, this enables longer duration, higher functionality missions beyond Earth orbit. This article has reviewed electrostatic, electrothermal and electromagnetic propulsion methods based on state of the art research and the current knowledge base. Performance metrics by which these space propulsion systems can be evaluated are presented. The article outlines some of the existing limitations and shortcomings of current electric propulsion thruster systems and technologies. Moreover, the discussion contributes to the discourse by identifying potential research avenues to improve and advance electric propulsion systems for smallsats. The article has placed emphasis on space propulsion systems that are electric and enable interplanetary missions, while alternative approaches to propulsion have also received attention in the text, including light sails and nuclear electric propulsion amongst others.

Development of methods of creation metal hydrogen permeation films

The application of electrothermal and magnetron sputtering methods for manufacturing thin films containing palladium and silver is investigated. In the process of electrothermal sputtering, indirect heating of the evaporated material was used in a tungsten and tantalum boat, through which a current has been conducted and a direct heating of a thin plate of palladium alloy has been entailed by current. A composite target for magnetron sputtering of alloys using silver and palladium plates with different ratios of their areas has been developed. The dependence of the film composition on the target composition is determined. As a result of sputtering for 40 min, a sample with a thickness of 1.1 microns and a silver content of 23.2±0.7% was obtained from a target with an area ratio S(Ag)/S(Pd) = 20.8/79.2.

Food preservation techniques and nanotechnology for increased shelf life of fruits, vegetables, beverages and spices: a review.

Food wastage is a major issue impacting public health, the environment and the economy in the context of rising population and decreasing natural resources. Wastage occurs at all stages from harvesting to the consumer, calling for advanced techniques of food preservation. Wastage is mainly due to presence of moisture and microbial organisms present in food. Microbes can be killed or deactivated, and cross-contamination by microbes such as the coronavirus disease 2019 (COVID-19) should be avoided. Moisture removal may not be feasible in all cases. Preservation methods include thermal, electrical, chemical and radiation techniques. Here, we review the advanced food preservation techniques, with focus on fruits, vegetables, beverages and spices. We emphasize electrothermal, freezing and pulse electric field methods because they allow both pathogen reduction and improvement of nutritional and physicochemical properties. Ultrasound technology and ozone treatment are suitable to preserve heat sensitive foods. Finally, nanotechnology in food preservation is discussed.

MOBILE FORMS OF METALS IN SOILS IN THE NADYM-PUR INTERFLUVE (WESTERN SIBERIA)

The total concentrations of metals (Fe, Mn, Cu, Ni, Cr, Sr) and their mobile forms extracted by an ammonium acetate buffer (pH = 4,8) were studied in soils samples collected from Nadym-Pur interfluve (West Siberia), near the northern limit of the taiga zone. The heavy metal content was determined in 55 background soil samples and in 25 pyrogenic ones. Gross content was determined on a spectrometer "SPECTROSCAN MAX-GV" using x-ray fluorescence analysis. Mobile forms of metals were determined on a ContrAA 700 atomic absorption spectrometer by flame and electrothermal methods. The statistics are calculated using the Excel software package. The study confirmed the weak accumulation of metals in the soils of the northern regions of Western Siberia. The total content below the soil world average for Fe is 5 times, Mn - 3 times, Sr - 2 times, Cr - 1,4 times. The content of mobile forms varies widely depending on the amount of organic matter. The percentage of mobile forms of metals from the total content was: Cr - 0.84%, Fe - 1,2%, Sr - 3,8%, Mn - 8,7%, Ni - 15%. In the profile of podzols, the distribution of mobile forms of metals has an eluvial-illuvial character. Mn and Sr accumulate intensively in the surface organogenic horizons, and the Fe content increases in the BF horizon. Minimum values are marked in horizon E. In pyrogenic soils, there is an increase in the content of mobile forms of metals due to the intake of ash. Metal content usually not exceeded the maximal permissible concentrations for soils.

A Review on Electrothermal Modeling of Supercapacitors for Energy Storage Applications

Supercapacitors (SCs) are drawing more and more attention in energy storage applications. This paper aims to discuss the state of the art of application-oriented electrothermal modeling methods for SCs and identify the limitations and future research opportunities. Electrothermal modeling is essential to model-based design, thermal management, and reliability analysis of SCs for energy storage applications. The review provides new perspectives with respect to the existing surveys, which focus mainly on materials, cell voltage balancing, electrical equivalent circuit models, and energy management systems. It covers the main aspects of electrothermal modeling of electric double-layer capacitors (EDLCs) and hybrid SCs, from heat generation mechanisms to different modeling and parameterization approaches. The outcome of the review is an archive of important research work in the topic area and an outlook on future efforts to be made.

КОНТРОЛЬ ПРОПИТКИ – ЭФФЕКТИВНЫЙ ФАКТОР ПОВЫШЕНИЯ НАДЕЖНОСТИ ЭЛЕКТРОДВИГАТЕЛЕЙ ГОРНОДОБЫВАЮЩЕЙ, СТРОИТЕЛЬНОЙ И ДРУГИХ ОТРАСЛЕЙ ПРОМЫШЛЕННОСТИ

Отказ электрической машины приводит к аварийным ситуациям, к простою оборудования и, как следствие, к высоким экономическим затратам на ликвидацию результатов отказа машины. Наибольший ущерб отечественной экономике наносит отказ электрических машин при разведке, добыче и транспортировке георесурсов в нефтедобывающей, горнорудной, угольной, химической и других отраслях промышленности, так как эти отрасли в настоящее время являются основой формирования бюджета страны. Надежность и безотказность работы этих машин в значительной степени определяется технологическими операциями пропитки и сушки обмоток, так как на этих операциях формируются важнейшие качественные характеристики обмоток: электроизоляционные, тепловые, влагостойкие и механические. Все эти свойства зависят от степени заполнения межвитковых и прикорпусных полостей обмотки пропиточным составом. В случае некачественной пропитки обмоток возможно появление дефектов в межвитковой изоляции в период хранения и транспортировки оборудования к месту эксплуатации, что неизбежно приводит к снижению надежности изоляции обмоток. Совершенствование указанных операций невозможно осуществлять без надлежащих способов неразрушающего контроля качества проведения этой операции. Поэтому разработка методов контроля качества пропитки обмоток является весьма злободневной проблемой. Цель: показать возможность контроля распределенности пропиточного состава по обмотке по результатам измерения теплоёмкости обмоток до пропитки и после неё. Методы: электротепловые и электромагнитные, связанные с измерением тепловых параметров обмотки и отдельных электрических величин при контроле качества пропитки. Результаты. Рассмотрен электротепловой способ контроля качества пропитки обмоток. Обоснованы физические принципы контроля качества пропитки, и приведен вывод основных критериев оценки качества указанной технологической операций. Приведена схема прибора контроля, и рассмотрен принцип его работы. Произведен анализ погрешностей предложенного способа контроля.

Thermal characterization of natural and synthetic spider silks by both the 3ω and transient electrothermal methods

Thermal conductivity, thermal diffusivity, and volumetric heat capacity of three spider silks are measured in this paper as a benchmark for further studies. These silks include the major and minor ampullate silks of the Nephila clavipes spider, and a synthetic spider silk fiber made from recombinant dragline silk proteins purified from transgenic goats' milk. Two complementary measurement techniques are employed in the thermal characterization of these microscale single fibers for self-verification. One is the transient electrothermal technique (TET) and the other is the 3ω method. Experimental measurements indicate that thermal properties of the dragline silk are very close to those of the minor ampullate silk, whereas the ones for the synthetic silk are much lower due in part to its low crystallinity. The directly measured thermal conductivity, thermal diffusivity, and volumetric heat capacity of the major and minor ampullate silks are 1.2–1.26Wm−1K−1, 5.7–6×10−7m2s−1, and 2–2.17 MJm−3K−1, respectively. The thermal conductivity and thermal diffusivity of the as-spun synthetic silk are 0.24Wm−1K−1 and 1.6×10−7m2s−1 respectively. As part of this study, a detailed comparison of the TET and 3ω methods is provided showing the complementary nature of the techniques and illustrating the strengths and weaknesses of each.

3C-Silicon Carbide Microresonators for Timing and Frequency Reference.

In the drive to miniaturise and integrate reference oscillator components, microelectromechanical systems (MEMS) resonators are excellent candidates to replace quartz crystals. Silicon is the most utilised resonator structural material due to its associated well-established fabrication processes. However, when operation in harsh environments is required, cubic silicon carbide (3C-SiC) is an excellent candidate for use as a structural material, due to its robustness, chemical inertness and high temperature stability. In order to actuate 3C-SiC resonators, electrostatic, electrothermal and piezoelectric methods have been explored. Both electrothermal and piezoelectric actuation can be accomplished with simpler fabrication and lower driving voltages, down to 0.5 V, compared to electrostatic actuation. The vibration amplitude at resonance can be maximised by optimising the design and location of the electrodes. Electrical read out of the resonator can be performed with electrostatic or piezoelectric transduction. Finally, a great deal of research has focused on tuning the resonant frequency of a 3C-SiC resonator by adjusting the DC bias applied to the electrodes, with a higher (up to 160-times) tuning range for electrothermal tuning compared to piezoelectric tuning. Electrothermal tuning lowers the frequency, while piezoelectric tuning can be used to raise the frequency.

Surface Characterization, Material Removal Mechanism and Material Migration Study of Micro EDM Process on Conductive SiC

SiC is an important industrial ceramic and also the fourth hardest ceramic after diamond, boron nitride and boron carbide. Due to very low fracture toughness, it is very difficult to machine SiC using conventional machining methods. EDM can machine such materials irrespective of their hardness. Micro electrical discharge machining (micro-EDM) is an adaptation of conventional EDM process that has similar electro-thermal methods of material removal for manufacturing miniature or micro parts. Micro EDM is used for obtaining burr-free micro dimensional apertures in difficult-to-cut materials. For improved understanding of the micro EDM process and achieve high quality machining on conductive SiC, it is necessary to characterize the machined surface and understand the material removal and material migration mechanism. In this work, micro depth holes were machined in SiC workpiece. The experimentation was planned using Taguchi's L9 theory. A combination of scanning electron microscopy (SEM), white light interferometry (WLI), energy dispersive x-ray spectroscopy (EDX), atomic force microscopy (AFM) and X-ray diffraction (XRD) was used to characterize the machined surface and study the material removal and material migration mechanism. It was found that improved characterization and understanding of μEDM can lead to better micro-machining of conductive SiC.

Reexamination of basal plane thermal conductivity of suspended graphene samples measured by electro-thermal micro-bridge methods

Thermal transport in suspended graphene samples has been measured in prior works and this work with the use of a suspended electro-thermal micro-bridge method. These measurement results are analyzed here to evaluate and eliminate the errors caused by the extrinsic thermal contact resistance. It is noted that the room-temperature thermal resistance measured in a recent work increases linearly with the suspended length of the single-layer graphene samples synthesized by chemical vapor deposition (CVD), and that such a feature does not reveal the failure of Fourier’s law despite the increase in the reported apparent thermal conductivity with length. The re-analyzed apparent thermal conductivity of a single-layer CVD graphene sample reaches about 1680 ± 180 W m−1 K−1 at room temperature, which is close to the highest value reported for highly oriented pyrolytic graphite. In comparison, the apparent thermal conductivity values measured for two suspended exfoliated bi-layer graphene samples are about 880 ± 60 and 730 ± 60 Wm−1K−1 at room temperature, and approach that of the natural graphite source above room temperature. However, the low-temperature thermal conductivities of these suspended graphene samples are still considerably lower than the graphite values, with the peak thermal conductivities shifted to much higher temperatures. Analysis of the thermal conductivity data reveals that the low temperature behavior is dominated by phonon scattering by polymer residue instead of by the lateral boundary.