International Journal of Applied Electromagnetics and Mechanics

In the paper, the dependence of the current characteristics of self-regulating heating cables on the environmental conditions is investigated. A method is proposed to determine the allowable length of a heating section depending on the environmental conditions and parameters of automatic circuit breaker used.

Considering the demand for low temperature bonding processes in packaging of micro-electro-mechanical systems (MEMS), such as accelerometers or micro mirrors, in this paper a method for selective and energy-efficient heating of metallic intermediate bonding layers by applying high-frequency electromagnetic fields with frequencies in the range of 1. 0 < f < 2.0 MHz is presented. Therefore, the induction heating process was modeled and analyzed by means of numerical simulation. Additionally, heating experiments were carried out by using IR thermography in order to verify the simulation results. The developed inductor shape allows almost homogeneous heating of all metallic layers with heating rates of more than ΔT∕Δt = 150 K∕s.

In this paper, a multi-stage numerical methodology for the description of the Dielectric Barrier Discharge physics in air is discussed. The behavior of the heavy species is computed using drift-diffusion equations. Electrons are taken into account by solving a non-linear formulation of electrostatics. The physical effects of the steamer discharges are modelled by means of a simplified 0D approach. The model also includes a semi-implicit 0D model for the assessment of the elementary chemical processes occurring in air. The developed methodology is employed for the simulation of a volumetric Dielectric Barrier Discharge reactor. The obtained species number density and surface charge deposition rates and are shown and discussed.

This paper deals with the numerical simulation and experimental investigation of magnetic flux concentrators (MFC) in particular with innovative additive manufactured MFC for induction heating applications. The novel type of magnetic flux concentrators presented in this paper is based on ferromagnetic particles embedded in ceramic matrix material guaranteeing high temperature mechanical stability and good magnetic performance. The additive manufacturing provides flexible, customized and complex geometry design of the MFC.

Nowadays, several applications of electroporation have been adopted in cancer therapy with promising results that have boosted research interest. To develop new treatment options, the development of electroporation models and measurement method in order to study the real distribution of the electric field potential are needed. Nowadays, current trends in electroporation techniques suggest the use of more powerful pulse generators that enables the treatment of larger tissue volumes. However, new challenges arise regarding the modeling of the electroporation process in large tissue volumes as well as the potential thermal effects when large amounts of energy are used. The aim of this paper is to propose a finite element analysis (FEA) based model using COMSOL of the irreversible electroporation process considering both electrical and thermal effects, and to validate it through in-vivo experimentation. Moreover, we propose a methodology for measuring the electrical potential in different points of a biological tissue during the application of a train of pulses to measure the distribution of the electric field inside the tissue. For this application, needle-based electrodes have been developed to achieve the least invasive measurement possible. These tools are aimed to improve the application of the electroporation treatment by reducing its side effects.

This paper presents detailed results of neutron imaging of argon bubble flows in a rectangular liquid gallium vessel with and without the application of external horizontal magnetic field. The developed image processing algorithm is presented and its capability to extract physical information from images of low signal-to-noise ratio is demonstrated. Bubble parameters, velocity components, trajectories and relevant statistics were computed and analyzed. A simpler version of the code was applied to the output of computational fluid dynamics simulations that reproduced the experiment. This work serves to further validate the neutron radiography as a suitable method for monitoring gas bubble flow in liquid metals, as well as to outline procedures that might help others to extract data from neutron radiography images with a low signal-to-noise ratio resulting from high frame rate acquisitions required to resolve rapid bubble motion.

Recent developments in domestic induction heating seek to increase the cooking surface flexibility while maintaining cost-effective implementations. In order to do so, the interconnection of classical topologies or the optimized design of new ones is being prospected. This approach usually leads to a higher complexity in the power control strategies. Thus, multiplexed load power control is used due to its versatility with the different topologies. Despite the advantages of this technique, power variations over the different pots generate a change in the forces between those and the inductors that might generate acoustic noise. This paper analyses multiplexed load power control and its restrictions and presents a modulation strategy based on switching frequency and duty cycle variation that allows a soft-transient load activation and deactivation, reducing the generated acoustic noise.

A new generation of Mg-based metallic alloys appears to be particularly promising in the field of biocompatible materials. These alloys have a controlled biodegradability in biological or living fluids. In this paper, nine Mg–Ca–Zn alloys with different chemical compositions were produced and analysed. The production of magnesium alloys by conventional technologies invariably introduces impurities from the refractory lining, which is not permitted in medical systems to be implanted into the human body. During levitation melting, the metal is maintained inside the inductor at a certain distance from the coil, avoiding the contact with any other material, by the action of induction currents. The induction currents cause the mixing of the chemical elements inside the melt, providing the homogeneity of the alloy. The alloys were produced in the levitation induction melting furnace under controlled atmosphere. By combining the effects generated by the magnetic field created in metallic parts, there was possible to hold, heat and melt solid material inside a specifically designed inductor fed by a medium frequency converter. The EDS analysis revealed the chemical compositions, and microhardness tests HV_0.1 and microstructural analysis were performed in order to establish the hardening effects and the homogenization degree of the solid solutions.

Application of air plasma jet was studied for the materials of light industry (rubber, wood, fabrics). Regulation of temperature of remote plasma was used to apply high energy treatment on thermo-sensitive materials like denim fabric. Air plasma jet with adjusted plasma temperature permitted to realize effective colour fading of denim without heat damaging of denim fabric.

A new type of EMBr, named Vertical-Combine Electromagnetic Brake (VC-EMBr) was introduced to investigate its applicability and adaptability. The characteristics of electromagnetic field and flow field inside a 1500 mm × 70 mm funnel shape mold with Ruler-EMBr and VC-EMBr have been compared. The simulation results indicate that in the funnel shape mold of thin slab continuous casting, the static magnetic field generated by Ruler-EMBr can cover the entire wide faces of the funnel shape mold, which can produce a breaking effect directly on the discharging jet flow. The static magnetic field generated by VC-EMBr can control both the funnel shape mold narrow faces and the impingement region of jet flow, which can effectively restrain the molten steel flow in the upper recirculation zone.

The paper aims to optimize niobium reactor electrical heating in deep vacuum conditions towards to original process of titanium production using vapour-phase reduction. The study aims to explore optimal electrical heating power of tungsten heater surrounded by molybdenum reflectors to reach temperature of niobium reactor up to 1200 [C] located in the vacuum chamber. Numerical modelling approach has been used to solve heat radiation problem using OpenFOAM solver coupled with Hemicube algorithm in a 3D, transient, parametric study varying electrical power and unknown emissivity coefficient of reflectors. The experiment in the same power range has been conducted obtaining temperature measurements of 8 thermocouples across the system. The paper provides a comparison and analysis of temperature distribution in the system obtained by numerical and experimental studies, which allowed to calibrate unknown emissivity coefficient of reflectors. The study also revealed necessity of systems geometry modification to achieve desired temperature profile.

Modern induction heating systems involve usually many non-linear systems with different constraints, making difficult implementing classical controllers. In this context, model predictive control arises as a powerful technique able to provide high performance controllers with advanced functionalities. This paper will discuss the benefits of this control technique for induction heating systems and will provide an example of application for domestic systems. As a conclusion, MPC will help powering future induction heating systems with improved control capabilities and performance.

Temperature is a key parameter in the industrial forging process. Induction heating is a fast, efficient and easily controllable system to have a uniform and controlled thermal profile before forging. The possibility to have a finer control over the temperature management leads to the improvement in process, a better product quality level, and lower maintenance cost. In this paper, the pyrometer noise and unstable signal is filtered and corrected using a Kalman filter based on a numerical electro-thermal model to obtain a reliable signal for the process management.

Flexible cooking surfaces, eg. fully active surfaces, have gained lately an increasing importance in the domestic induction heating. Multi-inverter structures are a cost-efficient solution to develop this technology. However, they add control restrictions that can be solved with a power factor corrector (PFC) stage as proposed in this work.

The proposed converter and modulation strategy work with zero voltage switching (ZVS), decreasing the switching losses, enabling a higher working frequency and, therefore, decreasing the magnetic devices size. The bus voltage is controllable and can be increased, easing the load power control and decreasing current through load and inverter and, so, the power losses. Besides, the switching frequency is constant in the mains cycle and can be modified to synchronize the load inverter and the PFC stage avoiding intermodulation noise. A 3.6 kW prototype has been implemented fulfilling the EMC requirements. The experimental waveforms and efficiency have been measured to prove the feasibility of this proposal.

The chemical, geometric and thermal properties of nanofluid obtained dispersing the same type of nanoparticles in water, octane and buffer solution after inclusion in polylactic and glycolic acid (PLGA) were investigated by means of an experimental set-up in adiabatic conditions. The Mn-ferrite nanoparticle were obtained by thermal decomposition. The aim is to obtain some very thermally performant nanoparticles suitable to treat cancer by Magnetic Fluid Hyperthermia (MFH). The heating properties of 1 ml suspension samples of the NPs were studied applying a time varying magnetic field of 27.1 kA/m at 245 kHz, a typical frequency for MFH, using a power generator and a cylindrical inductor.

The paper deals with the Consecutive Dual Frequency Induction Hardening of small gear wheels made of the special quality steel AISI 4340. Mathematical model of the process is elaborated. A special emphasis is put on a determination of hardness and microstructure calculated by the modified QT steel software. Exemplary computations are compared with measurements and reasonable accordance between them is achieved. An expected contour shape of the hardened zone is obtained. However for the analysed case the shape of the hardened zone is non-uniform. In order to achieve its uniform thickness along the working surface of tooth shorter heating times and higher power delivered to inductor-gear wheel system should be applied.

Many induction heating coils use soft magnetic composite materials (SMC) to improve induction heating system performance. In demanding induction heating applications, the core loss in the soft magnetic composite material is one of the critical factors in predicting the reliability of the induction coil using computer modelling. In this paper we have used calorimetry method for experimentally determining core losses in SMCs up to ≈1 T magnetic flux densities at a frequency near 150 kHz. This paper contains a discussion on the limitations of current methods for calculating core losses. To address these limitations, a new method for calculating core losses is presented. The results of the core loss measurement did not fit well with traditional core loss models over the full range of magnetic flux densities. A discussion on the different models and a hypothesis for the source of the variation from the models is presented.

Innovative non-conventional approaches, such as microwave sintering, are being developed as a method for sintering a variety of materials which shown advantages over conventional sintering procedures. This work involves an investigation of the microwave sintering of an ATZ composite with two different microwave applicators and frequency generators: 2.45 GHz and 5.8 GHz. Zirconia doped with ceria and toughened with alumina (10Ce-TZP/Al₂O₃) is the composite used in this study. The samples were sintered by microwave in air at 1200 and 1300 °C with 10 min of dwell time at 2.45 and 5.8 GHz in order to evaluate their effects on sintering, using an optimized experimental configuration. In addition, the mechanical properties of MW-sintered samples were compared with those obtained for the same composites sintered by the conventional method (1500 °C/120 min), such as relative density, hardness and fracture toughness.