Requirements on Carbon-Based Reducing Agents for Electrothermal Processes

Capillary discharge based pulsed plasma thrusters have great prospects of applications in in-orbit maneuvering of<bold/> micro-nano satellites. In this paper, the influence of different capillary cavity structure parameters on the thruster's energy deposition process, ablation characteristics, output thrust parameters and plasma plume parameters under an energy level of 5 J were studied. The experimental results indicate that the increase of the inner diameter of the capillary cavity will significantly reduce the discharge current density, which leads the deposition energy and equivalent power to decrease; the increase of the cavity length helps to improve the energy transfer efficiency. The influence of cavity structure on the ablation characteristics is reflected in the influence of deposition energy per unit area on the tube wall temperature. When the inner diameter of the capillary increases from 1 mm to 3 mm, the ablation mass decreases significantly, and then the equivalent ablation mass remains approximately unchanged as the inner diameter of the cavity increases further; the ablation mass continues to increase as the capillary length increases, while the ablation mass per unit area continues to decrease. The impulse bit depends on the ablation mass and plasma plume velocity, and the difference in ablation characteristic further affects the plasma in the cavity. The density and equivalent pressure determine the plasma electrothermal acceleration process. The continuous increase in the diameter and length of the capillary cavity will induce the acceleration process to lag behind the discharge and ablation process. And the decrease of the deposited energy impedes the electrothermal acceleration process, which results in the decrease of the impulse bit, specific impulse, and the overall efficiency. Furthermore, the overall efficiency transfer model analysis indicates the influence of the capillary inner diameter on thruster efficiency is mainly reflected in the energy transfer efficiency, and the capillary length change mainly affects the electrothermal acceleration efficiency. The overall efficiency optimization of the thruster needs to start from increasing both energy deposition efficiency and acceleration efficiency.

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.

A solar cell model that combines the photovoltaic and electro-thermal processes is proposed. The bond graph methodology is used as a reference frame, allowing the representation of the whole structure in a unified approach. The solar cell structure is modeled as a three-dimensional object allowing observation of a nonuniform solar radiation on the surface. Subsequently, the proposed model is used in the solar cell design.

Initially aluminum was very expensive to manufacture, but towards the end of the 19th century production on commercial scale became feasible. The production of aluminum increased rapidly in the 20th century, especially after the Second World War period. In the 1970s and early 1980s, approximately 15 million tons were produced per annum. Aluminum is produced from bauxite, a mineral containing aluminum oxide, ferrous oxide and silica. Bauxite is abundant in the earth’s crust in large areas of the world. Refining is carried out by means of a chemical process to leach out and sediment aluminum in the form of aluminum oxide. Pure aluminum is then produced using an electrothermal process, where electrolysis takes place in a carbon-lined steel reservoir containing molten cryolite (Na3Al6). Carbon anodes are dipped into the liquid molten cryolite. A direct current is passed through the cell resulting in formation and liberation of carbon dioxide at the anodes and production and collection of molten aluminum at the bottom of the cell, whose carbon lining serves as the cathode. The current used is about 100,000 A with a cell voltage of approximately 5 V. Enormous quantities of energy are necessary for the electrolytic reduction of aluminum, almost 16,500 kWh are utilized in the production of one metric ton of the metal. Due to this fact, aluminum plants are usually located close to relatively cheap power sources, e.g. in the vicinity of hydro-electricity plants.

Electrothermal-assisted all-weather solar steam generator based on hydrogel implantation strategy

The development of the power electronics industry has allowed the creation of highly efficient compact and powerful transistor voltage converters. Such voltage converters together with rectifiers and high frequency power transformers of increased frequency can be combined into increased frequency electrical power systems (IFEPS). Such IFEPS can be successfully used to realize the heat treatment of various composite materials using increased frequency currents. This publication describes the results of development and application IFEPS to organize a fundamentally new method of heat treatment of composite materials - electrothermal treatment with increased frequency currents. Methods of organizing power supply in enterprises using electrothermal processing are considered.

Electrothermal processes were studied in pyroresistive composites based on high-density polyethylene (HDPE) containing 8 vol.% carbon black (CB), 8 vol.% carbon fibers (CF), and their mixture 4 vol.% CB + 4 vol.% CF. It is shown that the kinetic heating curves of composites are well described by an exponential dependence with a certain heating rate constant k for each type of composite. After a short heating time, the equilibrium temperature Te is reached in the sample. When the applied voltage exceeds a certain value, the Te value decreases due to the presence of the positive temperature coefficient of resistance (PTC) effect. Due to the PTC effect, the composites exhibit a self-regulating effect relative to the Te. Relations between the applied voltage, electric power, and equilibrium temperature are found, the Te value depends on the applied voltage according to the quadratic law whereas there is a linear relationship between the Te and electric power. A possible application of such pyroresistive composites is resistance welding of plastics using a heating element (HE) made of a pyroresistive material. The use of HDPE-CB composite to create HE for resistance welding is demonstrated and the welded joint of HDPE parts obtained using HE is shown.

Electric discharge machining (EDM) is an electrothermal process where recast layer on the machined surface and heat-affected (HAZ) zone just below the machined surface are common phenomena. Thus, the assessment of surface integrity in EDM is a very important task. In this study, an attempt was made to modify the surface integrity of C-40 steel in EDM. WC-Cu powder metallurgy (P/M) green compact tools were used so that the tool material could be transferred to the work surface and thereby the surface characteristics could be altered. WC was used as tool material because of its ability to produce a hard layer over the work surface. A detailed experimental study was performed. The effect of various process parameters on the surface characteristics were presented with the support of analyses such as material transfer rate (MTR), tool wear rate (TWR), surface roughness, optical microscopy, scanning electron microscopy (SEM), energy dispersive x-ray (EDX), x-ray diffraction (XRD), microhardness testing, etc. It was established that the surface integrity of the workpiece changes with the desired deposition of a hard composite layer of WC and copper over the work surface.

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.

A comparative study on the performance of RESET based electro-thermal process in ring shaped confined Ge2Sb2Te5 and Ge1Cu2Te3 chalcogenide memory structures

Simulation of unsteady electro-thermal de-icing process of anisotropic composite skin

The water‐gas shift (WGS) reaction is often conducted at elevated temperature and requires energy‐intensive separation of hydrogen (H2) from methane (CH4), carbon dioxide (CO2), and residual carbon monoxide (CO). Designing processes to decouple CO oxidation and H2 production provides an alternative strategy to obtain high‐purity H2 streams. We report an electrothermal WGS process combining thermal oxidation of CO on a silicomolybdic acid (SMA)‐supported Pd single‐atom catalyst (Pd1/CsSMA) and electrocatalytic H2 evolution. The two half‐reactions are coupled through phosphomolybdic acid (PMA) as a redox mediator at a moderate anodic potential of 0.6 V (versus Ag/AgCl). Under optimized conditions, our catalyst exhibited a TOF of 1.2 s−1 with turnover numbers above 40 000 mol molPd−1 achieving stable H2 production with a purity consistently exceeding 99.99 %.

The condenser of 550kV RIP oil-gas bushings is in the solid structure of resin-epoxy impregnated paper(RIP), which has large difference with the oil-immersed one (OIP). Oil-gas bushings has compact configuration and heat conduction condition is harsh, while temperature distribution has direct relationship with bushings’ long-term stable operation performance, so it’s essential to carry out research in radial temperature within condenser during production of RIP oil-gas bushing prototype. In this paper, radial temperature distribution principle of bushing condenser under linear material conditions has been summarized by building electrothermal coupling theoretical model of bushing condenser. The model has been generalized by electro-thermal coupling finite element mode under nonlinear material conditions, and electrothermal coupling iterative computation process has also been proposed, then experimental measurement study in local temperature points of bushing condenser has been carried out. The study shows that plate model has advantages of high accuracy and simple form in calculating radial temperature distribution of bushing condenser; the hot-spot temperature of 550kV RIP oil-gas bushings is about 95°C which appears near the center conductor; radial temperature of bushings under nonlinear material conditions is lower than that under linear material conditions and the thermal breakdown voltage of condenser under rated current is 538kV which is higher than the maximum operation phase voltage. This paper provides theoretical foundation for radial temperature computation within RIP bushing condenser and has some reference value for the design of HVAC RIP bushings.

High electric field and temperatures can result in electrical property degradation of oil-paper insulation and accelerate its aging process. This paper describes the regulation of space charge in the process of electro-thermal aging. Electric field distortion and differences in characteristic parameters during electro-thermal aging are analyzed, along with the effects of electro-thermal aging on space charge from the perspective of trap energy. High temperature and an electric field are used to accelerate the aging of oil-paper, and space charge characteristics are measured using the pulsed electro-acoustic (PEA) method throughout the electro-thermal aging. Based on results obtained, it can be concluded that homo-charge injection occurs at the anode and the type of the charge injection at the cathode varies throughout the electro-thermal aging; the decrease of permittivity during aging allows for space charge injection to take place; growth of trap depth makes the space charge accumulate in the middle of the sample; and space charge accumulation after electro-thermal aging results in inner electric field distortion, which leads to large current and decreased breakdown in voltages.

An apparatus was developed for investigations of phase transformations and mechanical properties under programmed thermal and mechanical conditions, which makes it possible to study electrothermal treatment processes under any desired conditions, high-temperature thermomechanical treatment, lowtemperature thermomechanical treatment, machining, and treatment to obtain superplasticity.