Electromagnetic Heating Effects Research Articles

Preparation of carbon fiber conductive concrete and study on its mechanical and heating properties

Carbon fiber conductive concrete demonstrates great potential for effectively removing ice and snow from road surfaces. This study investigates the electrical conductivity and electromagnetic heating effects of carbon fiber conductive concrete, considering different carbon fiber dosages and temperatures. Experimental and numerical simulation methods were employed to assess the material's performance. The results show that as the carbon fiber content increases to 0.38 % and 1.5 %, the compressive strength decreases by 19 % and 55 %, respectively, which is related to the introduction of more bubbles and the agglomeration of carbon fiber when the carbon fiber is added, making it easier to produce stress concentration when the concrete is compressed. However, when the content of carbon fiber is small, the tensile properties of carbon fiber itself can improve the overall splitting tensile strength of concrete. With the increase of carbon fiber content, carbon fiber gradually forms a conductive network in the concrete, and the overall resistivity of the concrete decreases, but there is a certain threshold. Overall, 0.75 % fiber is the best solution. In addition, the heating process is accurately simulated by numerical simulation method. The simulation results are in good agreement with the experimental results, showing that the heating rate decreases with the increase of energizing time until reaching the heat equilibrium state. And the precise temperature distribution and change process that can be obtained through simulation provides valuable insights for engineering design.

Effects of microwave on the structural and emulsifying properties and interfacial properties of oxidized soybean protein aggregates.

This research explored microwave treatment impact on the structuro-functional aspects of oxidized soy protein aggregates (OSPI). Data showed that oxidative treatment promoted the formation of high molecular weight aggregates through hydrophobic interactions, thereby disrupting the structure of natural soy protein isolates (SPI). Microwave treatment for an appropriate time (≤30s) caused the molecular structure of OSPI to open up and reduction in molecular weight and disulfide bond content, while absolute zeta potential increased. These modifications increased emulsifying capacity of OSPI, as well as the interfacial adsorption of protein. Longer microwave treatment times (>30s) caused OSPI to exhibit a tendency to aggregate in TEM and CLSM images. It indicated the appropriate microwave electromagnetic field effect and microwave heating effect could coordinatively regulate soy protein functional properties by modifying their aggregation behavior. The results provided new ideas for reducing resource waste, and further expanding soy protein application in the food industry.

An ethyl cellulose-based supramolecular gel composite coating for metal corrosion protection and its self-healing property from electromagnetic heating effect

The barrier coating is the most important and effective method for corrosion protection. However, inevitable defects of various scales from micro to macro on coatings due to mechanical damage, aging, corrosive medium penetration, etc. will lead to coating failure. Usually, the damaged coating can only be removed and then recoated. At present, most of coatings are disposable coating and can not be recycled or healing repeatedly. In this paper, a supramolecular gel composite coating was prepared with ethyl cellulose, castor oil, mineral oil, and Fe3O4 nanoparticle, which are bonded together by hydrogen bonds and Van Der Waals forces. This coating could be multiple healed in situ by an alternating magnetic field based on the electromagnetic heating effect of Fe3O4 particles. The SEM/EDS results indicating that the best content of Fe3O4 in coating is 10% for good dispersion. Under an alternating magnetic field, the composite coating can be uniformly heated through hysteresis loss, and starts to heal when the temperature of the composite coating reaches 80 °C. After self-healing process, the mechanical properties and corrosion resistance of the composite coating have almost no difference with the original intact coating. Since the supramolecular gel is bonded by hydrogen bonding and Van Der Waals forces, these bonds are opened when heated and recombined after cooling without any change of properties. Therefore, the microstructure of supramolecular gel composite coating has no significant change and the corrosion protection performance has not decreased after 10 times of healing.

Study on safe distance between human body and wireless charging system of electric vehicles with different power and frequencies

In this paper, a wireless charging system and a human body model with various operating frequencies and output power are constructed to study the safe distance between the human body and the charging system when the electric vehicle is wirelessly charging. The models are simulated for electromagnetic fields and electromagnetic thermal effects. This paper mainly focuses on the induced electric field intensity of the human body and main organs during the static charging of electric vehicles under different operating conditions in a wireless charging system. The results are compared with the standards established by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) to derive the minimum safe distance for electric vehicles charged wirelessly. The results show that when the system works at a frequency of 85 kHz with output power of 3.7 kW, 7.7 kW, 22 kW, 33 kW, 66 kW, and 150 kW, the minimum safe distance between the human body and the system is 0.5 m, 0.6 m, 0.7 m, 1.0 m, 1.2 m, and 1.7 m; when the system works at an output power of 66 kW with frequency of 85 kHz, 300 kHz, 500 kHz, and 700 kHz, the corresponding minimum safe distance is 1.2 m,0.9 m, 0.8 m, and 0.6 m. Moreover, the induced electric field intensity distribution of human organs at different power is also calculated, and the results show that the induced electric field intensity of the liver and kidney is higher than that of other organs. When the human body is at the minimum safe distance, the temperature changes caused by the electromagnetic heating effect of various organs are within the normal adjustment range of the human body, indicating the rationality of the minimum safe distance when the electric vehicle wireless charging system works under parameters of this paper. It provides a theoretical basis for the setting of the safe distance of the electric vehicle wireless charging system.

Magnetic and Transient Temperature Field Simulation of Plate–Plate Magnetorheometer Using Finite-Element Method

This article presents a numerical simulation of a plate–plate magnetorheometer using the finite-element method. In this design of the rheometer, the electromagnetic coil generates a high and a constant magnetic-flux density (1.1 T at 3 A coil current) along the radius of the magnetorheological (MR) region. A uniform magnetic-flux density is distributed over the area of the MR region due to which there are no effects of magnetic-flux gradients on the MR properties. The other benefit of the proposed design is the reduction of electromagnetic heating effects on the MR sample. A uniform temperature generated in the MR region is 299 K due to the electromagnetic coil at 3 A current and 1.1 T magnetic-flux density after 30 min, while the maximum temperature caused due to electromagnetic coil heating is about 337 K around the coil. The temperature generated due to the slippage of MR fluid is 306 K at the same operating conditions. Thus, this design of the magnetorheometer minimizes the total temperature generated due to the electromagnetic coil and slippage in the MR region. Finite–element simulation involves magnetostatic, laminar fluid flow, and heat transfer analysis.

Electromagnetic Heating Effects in Power Distribution Cables under Different Operating Conditions

This paper presents a finite element simulation by COMSOL Multiphysics package to investigate the temperature distribution inside three-phase, three-core, 33 kV underground power cables (UGC) through a coupled electromagnetic-thermal modelling. The simulations are very controlled and fine realistic details can be added to the model such as the temperature conductivity dependence of any metallic layer and armour permeability. Distributions of magnetic field, current density, resistive losses and temperature inside UGC different layers are calculated at different operating conditions. The exponential increase in conductor temperature with increasing the conductor current limits the single-phasing operation of such cables. Therefore, they must be derated, otherwise their lifetime will be reduced exponentially. Finally, the effect of current harmonics on the temperature distribution inside the insulation material and hence its lifetime is calculated using MATLAB. It is found that higher steady-state conductor temperatures are expected for cables with larger conductor cross-sectional areas, using aluminium core rather than copper, or using 6-pulse rectifiers rather than a higher pulse types.

Electromagnetic Heating Effects in Power Distribution Cables under Different Operating Conditions

This paper presents a finite element simulation by COMSOL Multiphysics package to investigate the temperature distribution inside three-phase, three-core, 33 kV underground power cables (UGC) through a coupled electromagnetic-thermal modelling. The simulations are very controlled and fine realistic details can be added to the model such as the temperature conductivity dependence of any metallic layer and armour permeability. Distributions of magnetic field, current density, resistive losses and temperature inside UGC different layers are calculated at different operating conditions. The exponential increase in conductor temperature with increasing the conductor current limits the single-phasing operation of such cables. Therefore, they must be derated, otherwise their lifetime will be reduced exponentially. Finally, the effect of current harmonics on the temperature distribution inside the insulation material and hence its lifetime is calculated using MATLAB. It is found that higher steady-state conductor temperatures are expected for cables with larger conductor cross-sectional areas, using aluminium core rather than copper, or using 6-pulse rectifiers rather than a higher pulse types.

Experimental investigation of comparing electromagnetic and conventional heating effects on the unconventional oil (heavy oil) properties: Based on heating time and upgrading

This study examined the effects of microwave on Sarvak heavy crude oil sample from a reservoir in southwest Iran in a Fischer assay and heated by microwave for 2 min time steps until 14 min total heating time had elapsed. Unlike conventional heating, which caused light carbonic components to escape and raised C20+ components in oil samples, the value of light carbonic components increased under microwave heating. These materials cannot escape the oil sample in microwave heating because the cracked components approach a superheated state, and in this study a large portion of them remained. The sulfur content of heavy oil in microwave heating tends to decrease over time, approaching 16% at 14 min; in contrast, in conventional heating it remains constant. Sulfur is removed from the oil sample as H2S and SO2, predominantly in a gas state, but also as condensate, in increasing amounts over time. Sulfur removal from the heavy crude oil sample is highly important in the upgrading process because of having its high coefficient of microwave absorption. Saturation, Aromatic, Resin and Asphaltene (SARA) components analysis shows changes in the resin and asphaltene components. The amount of asphaltene components begins to decline starting early in the heating process, and approaches its lowest amount at 8 min (26% reduction). Reduction of resin components in microwave heating begins at 10 min and reaches 61% at 14 min. According to Fourier transform infrared (FTIR) spectra results, microwave irradiation caused cracking of large-chain molecules and drove light components from heavy crude sample. These two phenomena are a function of radiation time. The rate of cracking of heavy components was continuously greater than the rate of light components leaving the sample at early time intervals; ultimately, this resulted in an upgraded heavy oil.

Radiofrequency heating of nanomaterials for cancer treatment: Progress, controversies, and future development

In recent years, the application of nanomaterials to biological and biomedicine areas has attracted intensive interest. One of the hot topics is the nanomaterial mediated radiofrequency (RF) hyperthermia or ablation, i.e., using RF fields/waves to heat tumor tissues treated with nanomaterials to destroy cancerous cells while minimizing the side-heating effect. However, there are currently many contradictive results reported concerning the heating effect of nanomaterials under a RF field. This paper provided a comprehensive review to nanomaterial mediated RF ablation from both experimental and theoretical aspects. Three heating mechanisms were discussed, i.e., laser heating, magnetic field heating, and electric field heating in RF spectrum, with the focus on the last one. The results showed that while diluted pure metallic nanoparticles could be heated significantly by a laser through the surface plasmon resonance, they cannot be easily heated by a RF electric field. Further studies are proposed focusing on nanoparticle structure and morphology, electromagnetic frequency and localized heating effect to pave the way for future development.

Spatio-spectral analyses of electromagnetic wave energy absorption and heating effect

This study presents a theoretical analysis method to calculate electromagnetic (EM) wave power absorption spectrum of materials by using attenuation coefficients. The heating effect of EM waves is modeled to analyze spectral distribution of temperature rises inside material body as a result of EM wave power absorption. These analyses are very useful for the investigation of electromagnetic wave-material interaction on the bases of electro-physical material parameters (permittivity, permeability and conductivity). An illustrative analysis of spatio-spectral distribution of EM wave energy absorption and resulting heating effect were conducted for muscle tissues and the results are discussed.

Electromagnetic heating effect of aggregated gold nanoparticle colloids

Gold nanoparticles (GNPs) have been recently investigated intensively for potential hyperthermia treatment of malignant cancer cells in combination with radiofrequency (RF) electromagnetic (EM) fields/waves. However, many controversial results have been reported on whether GNPs can be heated by EM fields. It has been suggested that aggregated GNPs may be heated significantly by a RF field, which however has not been examined experimentally. This work proposes a novel electric treatment of mono-dispersed particles to create aggregated GNPs, and conducts an investigation of their bulk heating behavior under a 655 nm laser and a 13.56 MHz RF electric field. It is revealed that the heating rates of aggregated colloids are significantly higher than those of mono-dispersed GNPs for the 655 nm laser, whereas at 13.56 MHz, the heating effects are barely noticeable for both aggregated and mono-dispersed colloids. Various possible reasons are discussed and the negligible electric field enhancement is believed to be responsible at 13.56 MHz.

ROLE OF NÉEL AND BROWNIAN RELAXATION MECHANISMS FOR WATER-BASED Fe3O4 NANOPARTICLE FERROFLUIDS IN HYPERTHERMIA

Hydrophilic Fe3O4 nanoparticles with a mean diameter size of 15 nm were synthesized by means of the direct reduction of FeCl3 and FeCl2 in an aqueous solution. The heating properties of Fe3O4 nanoparticles under an alternating magnetic field were investigated in a frequency range of 50–500 kHz and a magnitude range of 3.1–5.0 kA/m. To distinguish the roles of Néel and Brownian relaxation mechanisms, polydimethylsiloxane (PDMS) and water were employed as a medium, in which PDMS plays a significant role of eliminating the effect of Brownian relaxation. It is experimentally and theoretically confirmed that, for the Fe3O4 /water system, high-specific absorption rates are due to a combination of both mechanisms, with an enhanced contribution due to Néel relaxation with increasing frequency and magnitude of the alternating electromagnetic field. The contribution efficiency of Néel relaxation increases from 36–56% by increasing the electromagnetic field frequency from 50–300 kHz, and then retains a saturated value of ~ 56% at 300–500 kHz. Moreover, a linear increase of the contribution efficiency of Néel relaxation at 300 kHz was observed from 55–65% by increasing the magnitude of electromagnetic field at 3.1–5.0 kA/m. The current research can be widely-expanded to explain the electromagnetic heating effect of other ferrofluid systems.

SAR versus Sinc: What is the appropriate RF exposure metric in the range 1–10 GHz? Part II: Using complex human body models

This is the second of the two articles that present modeling data and reasoned arguments for specifying the appropriate crossover frequency at which incident power flux density (S(inc)) replaces the peak 10 g averaged value of the specific energy absorption rate (SAR) as the designated basic restriction for protecting against radiofrequency electromagnetic heating effects in the 1-10 GHz range. In our first study, we compared the degree of correlation between these basic restrictions and the peak-induced tissue temperature rise (DeltaT) for a representative range of population/exposure scenarios using simple multi-planar models exposed to plane wave conditions. In this complementary study, complex heterogeneous head models for an adult and 12-year-old child were analyzed at 1, 3, 6, 8, and 10 GHz for a variety of exposure conditions. The complex models indicate that peak DeltaT is better correlated with peak 10 g SAR than S(inc) at 1 and 3 GHz and with S(inc) at 6-10 GHz, in contrast to the results from Part I. Considering the planar and complex body modeling results together, and given the equivocal indications of the two metrics in the 6-10 GHz range, we recommend that the breakpoint be set at 6 GHz. This choice is also based on other considerations such as ease of assessment. We also recommend that the limit level of S(inc) should be adjusted to provide a better match with 10 g SAR in the induced tissue temperature rise.

Transient heating effects in electromagnetic launchers with complex geometries: A 3D hybrid FE/BE analysis

A time-stepping finite-element (FE) and boundary-element (BE) coupling method was implemented to include 3D transient eddy current under electromagnetic heating effects in electromagnetic launchers. Lagrangian formulations were used to model electromagnetic and thermal diffusive processes with moving conductors. The finite-element formulation was employed for the general diffusion equation in a bounded conductor region including rail and armature; while, in the exterior region, the boundary element method was developed for Laplace's equation. The coupled boundary was employed directly on the surface of conductors and no special treatment on boundary was required. The electromagnetic and temperature fields were coupled through iterative calculations. This method results in considerable time saving in modeling as it eliminates the surrounding air region.

Global Modeling of Magnetized Capacitive Discharges

Capacitive reactors for semiconductor processing must simultaneously balance many physical phenomena with engineering constraints to achieve the desired processing properties. Important phenomena include electromagnetic RF propagation, gas ionization, plasma heating, plasma transport, and nonlinear sheath effects. Constraints are driven by process uniformity, radical production, thermal control, and reactor-component lifetime. These phenomena and constraints are often modeled in isolation; however, in a real system, they can interact in ways that are not easily foreseen. It is highly desirable to have global models that can provide relatively quick feedback for the proposed modifications to these systems. While an approach based on fundamental physics models is highly desirable whenever possible, the system can quickly become too complicated for quick design evaluations. In this paper, we explore the interaction between several processes by combining fundamental physics models when reasonable, with simplified, heuristic, or even empirical models for processes that are difficult to model from first principles. The goal is to understand the interaction between these processes in a global system without becoming overly encumbered by details in the individual components of the model. We study the effects of static magnetic field on plasma transport and electromagnetic effects arising at high RF frequency. We also change the RF-coupled power and ionization efficiency in a simplified 2-D model geometry to contrast the various effects. We find that discharges with very high frequency and high plasma density can exhibit localized nulls in the RF fields caused by electromagnetic-propagation effects in the sheath region. We find that relatively low static magnetic fields can modify the radial-plasma density profiles. Good agreement is found between the radial-plasma profiles given by the model and those measured in an experiment where the currents in two concentric coils near the plasma are the only variables.

Modeling of Electromagnetic Heating Effects During in vivo Testing of Prosthetic Heart Valves

In this paper, a numerical model is presented to investigate inductive heating during in vivo testing of prosthetic heart valves using electromagnetic acoustic transduction (EMAT) methods. The maximum temperature rise on the surface of the heart valve ring is calculated by solving the bioheat equation. The cooling effect of the blood flow is incorporated by imposing appropriate interface conditions. We show that the maximum temperature rise can be controlled to comply with applicable safety standards both by regulating the duty cycle of the tone-burst excitation signal and synchronizing the excitation with the cardiac cycle appropriately

Technique for producing crack arrest by electromagnetic heating

Crack arrest in current conducting materials by electromagnetic heating can be used effectively to extend the service life and improve the safety and reliability of structures and components. Theoretical analysis and experimental investigations have shown that due to heat concentration around the crack tip, small welded joints are formed by metal melting. Thus, the formation of the main crack source is prevented. From metallography, it has been found that a typical fine phase transformation microstructure can be obtained in the crack tip region as a result of rapid heating and cooling. The intensity, ductility, and wear capacity are promoted under the combined influence of superfine structure, thermal compressive stresses, and phase transformation compressive stresses. Microcracking and subsequent main crack propagation can both be prevented. The basic principles of the electromagnetic heating effect and the results of experimental work based on the theory are presented.

Numerical modelling of 3-D coupled electromagnetic and heating diffusion problems

In this paper a hybrid integral-finite difference approach for the analysis of the transient electromagnetic heating effects in three-dimensional conductor bodies, is presented. The electromagnetic analysis is carried out by the discretization of the conductive regions in suitable slabs, that allows the transformation of the Maxwell's equations to the equilibrium equation of an equivalent three-dimensional network. The thermal diffusion equation is solved by means of a finite difference approach in the time domain, using the same grid of the equivalent network above mentioned. The numerical solutions of the electrical and thermal equilibrium equations are performed separately and alternatively, and the values of the temperature dependent physical parameters are updated in time at each step. The method described in the paper has been tested with experimental data with regard to steady and transient state conditions of a bus-bars compartment of a low-voltage power center.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Integral equation approach for the analysis of three-dimensional transient electromagnetic heating effects

An integral approach for the analysis of three-dimensional transient electromagnetic heating effects is presented. The conductor bodies are decomposed in elementary parallelepipeds, and the centers of nearby parallelepipeds are connected in order to obtain a three-dimensional grid. The electrical and thermal equilibrium equations applied to this grid allow the evaluation of the current density and the temperature distribution inside the conductors of the system. The characteristics of the approach are shown through simulations of the tests provided in the experimental verifications of switchgear and control gear assemblies. >

Finite element analysis of transient electromagnetic heating effects in three dimensions

The high transient currents used by electromagnetic launch techniques produce a wide range of problems for modeling. The use of electromagnetic finite element (FE) analysis has allowed the electromagnetic effects to be modeled, and as a result the instantaneous heating effects. A technique for modeling the cumulative heating has been demonstrated for the 2-D case in Bath University's MEGA electromagnetic FE program, by an FE application of the thermal diffusion equation. The 2-D thermal model has been modified and extended to modeling the 3-D case, and to the coupling between electromagnetic and thermal material properties. >