Induction Heating System Research Articles

Experimental analysis of flow and convective heat transfer in the water-cooled packed pebble bed nuclear reactor core

A randomly packed pebble bed test facility is set up to study the flow and convective heat transfer in the water-cooled pebble-bed type nuclear reactor core. Water is used as the test fluid. The electrical induction heating system provides internal heat source for the packed pebble bed. The effects of input power, porosity, fluid velocity and inlet temperature are studied on the flow resistance and convective heat transfer coefficients. A new correlation is proposed to predict the pressure drop in the random packed pebble bed. The correlations given by Wakao et al. and KTA agree well with the experimental convective heat transfer coefficients in the high-velocity and low-velocity conditions respectively. A new correlation is presented based on the trend similarity between the Colburn j factor and friction factor, to predict the pebble bed convective heat transfer characteristics, with a discrepancy no more than 10%.

Envelope dynamics of resonant inverter driven electromagnetic levitation melting system with experimental verification

The paper presents a methodology for nonlinear envelope dynamics derivation of a levitation melting type induction heating system, fed by a resonant inverter, based on recently established work piece electro-mechanical model. The work piece under consideration is formed by an aluminum sphere, floated by conical-shaped copper coil. Resonant power converter is used to drive the induction heating system due to the fact that significant impedance of the work piece coil at high operation frequency (several tens of kilohertz) limits the power transferred to the load and therefore needs to be cancelled by corresponding capacitive impedance. Since the application requires levitation of the object being heated up, low-frequency (several hertz) dynamics appears, related to floating body movement. As a result, high-frequency electrical signals become modulated by low-frequency oscillations induced by mechanical side dynamics. It is known that power transfer in sinusoidal excited electrical system is governed by magnitudes and related phases of currents and voltages. Consequently, in order to assess both the low-frequency dynamics of levitated object mechanical motion and the amount of power transferred, information regarding envelope behavior of electrical-side signals is sufficient. Once established, envelope model of the electrical subsystem combined with typical model of the mechanical subsystem describe mechanical side parameters (position, speed and acceleration) exactly as if full electrical model would have been utilized. Moreover, envelope model significantly decreases simulation time and memory requirements of simulation platform. The proposed modeling approach is validated by comparing full and envelope model simulation results, accompanied by results obtained from experimental prototype.

Optimal design methods for the uniform heating of tube ends for stress relieving

Purpose An inductor for the uniform heating of the extremity of a ferromagnetic steel tube for stress relieving is considered. The main goal of the study is to investigate the possibility to achieve a reasonable design of the inductor when dealing with many design variables. Design/methodology/approach Genetic optimization algorithms are used for this purpose, demonstrating the applicability of these techniques to the design of induction heating inductors. Genetic algorithms provide to the designer several optimal solutions belonging to Pareto Front, and this way they allow choosing the solution that better fits the technological requirements. In any case, the designer has to adapt the chosen solution to fit in with the real possibilities in industrial application. Findings The study demonstrates that automatic optimization methods may help the designer of the induction heating system to solve complex problems with very conflicting technological requirements. Originality/value In the paper, a problem with a high number of design variables is solved. Moreover, the goals of the optimization process are strongly conflicting, and the proposed problem is a challenging one.

Cascade Equivalent A-H Circuit of an Induction Heating System with a Superconducting Inductor

Induction heating is used to heat metals before hot treatment. It provides a high quality of the process and is rather efficient in many cases. However, when heating nonmagnetic materials with low specific resistance, the efficiency of an induction heating setup becomes low. To increase the efficiency of induction heating systems, a heating method has been used in which a heated item is rotated in s transverse magnetic field created by superconducting coils. In this paper, an analytical method to calculate an electromagnetic field in a similar heating setup has been considered. The method is based on a cascade equivalent circuit obtained on the basis of the fundamentals of electromagnetic theory and the theory of electric circuits.

Design methodology of high performance domestic induction heating systems under worktop

This study presents design guidelines for planar induction systems whose winding is considerably farther from its load than in usual arrangements. Optimum efficiency design is paramount for larger distances due to the magnetic field dispersion. To this end, a parameterised finite element model is used to ascertain the system's parameters in this new configuration. This model is used to test variations in frequency, inductor-load distance and inductor diameter. From simulation results, efficiency, output power, power loss volumetric density and near field measurement predictions are obtained. Graphical representation of these results is used to determine the viability of each possible design, choosing one to develop a prototype. Moreover, a study was carried out with Pareto techniques to determine the effect of ferrite coverage and thickness, as well as its distance to the aluminium shielding on efficiency and near field predictions in order to develop a second prototype. The validity of the model is confirmed by experimental tests in small and operating signal regimes.

Continuous gradient ceramic/polymer composite for application in large temperature gradient connection by a polymer-derived ceramic route

The need for combined high-temperature insulation and load-bearing functions under large temperature gradient conditions imposes new demands on functionally graded composite materials. Herein, a ceramic-polymer continuous gradient composite was prepared by a polymer-derived ceramic route using a custom-designed induction heating system. The gradient composite was subjected to six impregnation-crosslinking-pyrolysis cycles to obtain a 55-mm-long gradient layer with varying density (1.76–1.43 g/cm3). The compositions of the gradient matrix varied from amorphous SiCN ceramics to silicon resin from top to bottom, satisfying the gradient change rule. The gradient material had good thermal insulation and reusability with a heat flux of 0.3 MW/m2 for 10 min. The resin layer has the minimum compressive strength of 68 MPa. This material could serve as a transition material for connecting a high-temperature zone (≥1000 °C) with a low-temperature one (≤350 °C).

Search optimal control of induction heating modes for a moving workpiece

Purpose This paper aims to create mathematical models and control algorithms allowing the authors to study and form effective modes of operation of multi-inductor system of electrical heating of moving hollow cylindrical blanks. Design/methodology/approach The developed mathematical models were based on the finite-difference method, the control volume method and their combination. The reliability of the results obtained was verified by comparing the calculated results with the experimental ones. The temperature control system was synthesized using methods of the object management theory with distributed parameters. Findings A set of mathematical instruments has been created that allow modelling the operation modes of installation for induction heating of moving hollow cylindrical blanks. Recommendations were given on the formation of an automatic control system that provides heating of a moving hollow cylindrical billet to the required temperature with simultaneous equalization of temperature along the length of the billet in case of highly uneven initial temperature along the length of the billet. Practical implications Part of the paper will be used by the industrial plant for the purpose of heat treatment of iron alloys workpiece. Particularly, a control system will be basically formed based on the models. Originality/value The scientific novelty of the paper is to create control algorithms and mathematical models for the induction heating system of tubular workpieces allowing to explore interrelated electromagnetic and thermal processes taking into account nonlinearities and design features of the system, as well as to form effective modes of its operation based on transfer functions and methods of the object management theory with distributed parameters.

Design and Analysis of Induction Heating System with Parallel Resonance Inverter

In comparison to the conventional heating systems, the induction heating systems have not only higher efficiency but also quite shorter processing time. Depending on their working conditions, they do not dissipate heat to the environment and cause pollution, and this makes them be environmentally friendly. The fact that the system does not allow any case such as explosion, combustion or injury reveals the reliability of this system.Because of the superiorities mentioned above, day by day it is more widely used in the modern industry treatments such as surface hardening, welding, tempering, rolling, heating, and melting. Whereas the induction heating systems with series resonance are designed as single-phase and low-powered in general, the induction heating systems with parallel resonance are used in high-powered and high-frequency three-phase industrial applications. In this study, an induction heating system which has 17 kW power enabling melting of brass material containing 58% copper, and has a frequency of 14,5 kHz, three-phase, voltage sourced, and full-bridged rectifier with parallel resonance inverter is designed.MATLAB simulation of the designed system is performed, and an analysis is carried out with the obtained results.An efficient system with the resonance inverter feature has been created by reducing the switching losses. In the operation of the system, a high current of 1132 A is provided on the load during the resonance. Thus,it is provided that the high value of short circuit current circulating in the brass material, which is considered as a load, produces heat in the part, and melts the metal part in a quite short time.

Analysis and Modeling of the Forces Exerted on the Cookware in Induction Heating Applications

We present a semianalytical model for calculating the forces exerted on cookware in domestic induction heating applications. The developed model is based on the Maxwell's stress tensor and is also based on the existing semianalytic expressions of the electromagnetic fields in planar induction heating systems, which are expressed in terms of Fourier-Bessel series. Taking advantage of the axial symmetry of usual domestic induction heating systems, the flux of the vertical component of the Maxwell's stress tensor is analytically integrated and the vertical force is obtained. The proposed model captures both eddy currents and magnetization that occurs in typical ferromagnetic cookware. The model is verified by means of two-dimensional Finite Element simulations and also is tested by means of measurements of the change of the weight experimented by cookware due to the forces during the heating process.

Temperature Control for Induction Heating of Thin Strips

In this work, a model-based temperature controller for an induction heating system for moving thin metal strips is developed. The most significant disturbance of the system is an uncertain air gap geometry caused by flatness defects of the metal strip. A computationally expensive calculation of the electromagnetic field is avoided by using an equivalent circuit model and the energy balance. A thermal model of the moving strip is derived in the form of a convection-reaction equation and simplified to a linear time-invariant model. A 2-degrees-of-freedom controller is designed based on the simplified model and tested using a finite-element simulation model of the induction heating system. The simulations demonstrate that the proposed controller clearly outperforms standard feedback control strategies.

Analysis of LGV usage for the improvement of a customized production

The paper describes an approach for analyzing the use of a Laser-Guided Vehicle (LGV) in the context of the small and medium-sized enterprise. The use of LGVs is an efficient solution to provide more flexibility in the context of Just-In-Time production; however, the investment cost can limit this application. A methodology has been proposed in this work to analyze the technical feasibility of using an LGV in the manufacturing industry of customized products. The test case focuses on the study of a laser-guided system to optimize the handling of molds for customized production. In this scenario, an LGV is proposed to substitute manual carts used for moving molds from the warehouse to the injection machines. The traditional path included an intermediate station for pre-heating the molds in hot-air ovens. The proposed solution includes the study of an induction heating system on the LGV to optimize time and energy consumption.

Intelligent Control Method of Power Supply for Tundish Electromagnetic Induction Heating System

An intelligent control method is proposed to improve the performance of power supply for tundish electromagnetic induction heating, which can adequately regulate the tundish temperature. The topology structure of power supply for tundish electromagnetic induction heating is presented, and its working principle is analyzed. The power supply consists of six power units, and each of them consists of a fore-stage three-phase rectifier and back-stage single-phase inverter. The feedforward control DC voltage is used by three-phase rectifier to obtain the stable DC voltage supplied to the inverter. The cloud controller based intelligent temperature control algorithm is combined with the power feed-forward algorithm to obtain accurate tracking of the output current and constant temperature control of the tundish steel in the back-stage inverter. The simulation and experiment are performed to verify the accuracy and effectiveness of the proposed method.

Cost analysis of T6 induction heat treatment for the aluminum-copper powder metal compacts

This work compares an energy cost and an energy consumption results of the 4 wt.% cupper mixed aluminum based powder metal (PM) compacts processing under induction or furnace heating. Total power and energy consumptions and total energy costs per kilogram and compact have been analyzed. T6 precipitation heat treatment applications have been applied with two different methods, one with 2.8 kW, 900 kHz ultra-high frequency induction heating system (UHFIHS), other with 2 kW chamber furnace. In the first method, Al-Cu PM compacts have been heated by induction at 580 ?C in one minute and then cooled down by water. Afterwards, the samples have been heated 170, 180, 190 and 200?C respectively for artificial ageing and cooled naturally. In the second treatment, unlike the first study, Al-Cu PM compacts are heated by chamber furnace at 540?C in 5 hours and cooled by water. Then PM compacts are artificially aged at 190?C in 10 hours with same furnace. During both processes, energy and power consumptions for each defined process have been measured. Optimum heat treatment of the induction is determined. The cheaper energy cost is obtained by the induction heat treatment.

Performance of 450 kW permanent magnet heater for aluminum billets

PurposeThe purpose of this paper is to present the main experimental results obtained on the first prototype of an innovative induction heating system. MAGNHEAT was a LIFE project, funded by EU Commission, proposed to demonstrate the possibility of industrial application of a new technology for the induction heating of aluminum billets before extrusion. This technology uses permanent magnet heaters (PMHs), which constitute a high efficiency solution for the heating of high conductive metals.Design/methodology/approachThe paper briefly describes the main steps of the project: the design of the PMH, the realization and installation of the demonstrator on an extrusion production line of Pandolfo Alluminio SpA and, mostly, the performance of the system.FindingsThe main results achieved during the preliminary tests on an industrial line have been summarized by evaluating some key performance indicators, as reported in the paper.Originality/valueThe new technology allows a significant reduction of the energy consumption and guarantees the same performance of a classical induction heater.

Investigation of heating and melting in ELTA programs

Purpose The purpose of this paper is obtaining the optimal parameters of induction heating and melting systems by use of the new programs ELectro-Thermal Analysis (ELTA) 8.0 and Induction Crucible Furnace (ICF) to improve a quality of final products. Design/methodology/approach Simulation of continuous through heating prior a drawing through the draw plate is realized by an optimization procedure. Additional application of ELTA 8.0 “Heating of Wire” reveals the relationship between power, time and thermal profile of load during heating. Rational variants of ICFs for melting processes are obtained using several step-by-step iterations. Findings ELTA 8.0 program permits to optimize the continuous heating of copper, steel, titanium and other wires. ICF ELTA program was used at the initial stage of the development of new technological processes and the ICFs. This program provides a preliminary evaluation of an induction melting process and system before the use of more sophisticated 2D or 3D programs. Results of optimization allowed to find a rational decision of an induction system, the required parameters of a refractory and a power supply. Non-conductive and graphite crucibles of the furnace were compared from electrical and economical points of view. Originality/value Fast calculation of ELTA programs allows the designer to provide the required temperature distribution in a cross section and along the part to control the real-time processes of heating and melting.

A study on de-icing for railway turnouts using 250kHz-200W-class induction heating system

In this paper, to complement the capability of the existing heating system using an electric-heating wire for melting snow and ice in railway turnouts, 250kHz-200W-class Induction Heating (IH) system was designed. The IH system consists of the resonant inverter and the IH device. In order to perform the electric circuit, the electromagnetic field, and the thermal analysis, the Multi-Physics analysis for IH system was derived. In addition, IH system was compared with the existing heating system.

A parallel multi-fidelity optimization approach in induction hardening

Purpose Reliable modeling of induction hardening requires a multi-physical approach, which makes it time-consuming. In designing an induction hardening system, combining such model with an optimization technique allows managing a high number of design variables. However, this could lead to a tremendous overall computational cost. This paper aims to reduce the computational time of an optimal design problem by making use of multi-fidelity modeling and parallel computing. Design/methodology/approach In the multi-fidelity framework, the “high-fidelity” model couples the electromagnetic, thermal and metallurgical fields. It predicts the phase transformations during both the heating and cooling stages. The “low-fidelity” model is instead limited to the heating step. Its inaccuracy is counterbalanced by its cheapness, which makes it suitable for exploring the design space in optimization. Then, the use of co-Kriging allows merging information from different fidelity models and predicting good design candidates. Field evaluations of both models occur in parallel. Findings In the design of an induction heating system, the synergy between the “high-fidelity” and “low-fidelity” model, together with use of surrogates and parallel computing could reduce up to one order of magnitude the overall computational cost. Practical implications On one hand, multi-physical modeling of induction hardening implies a better understanding of the process, resulting in further potential process improvements. On the other hand, the optimization technique could be applied to many other computationally intensive real-life problems. Originality/value This paper highlights how parallel multi-fidelity optimization could be used in designing an induction hardening system.

Solvothermal reflux synthesis of NiFe2O4 nanocrystals dielectric and magnetic hyperthermia properties

In this study, NiFe2O4 nanocrystals were prepared by solvothermal reflux method. The average crystallite size was found to be 9 nm by X-ray powder diffraction analysis. Selected area electron diffraction profile confirms the crystallinity behavior of the compound. Nanocrystals’ surface of the metal oxide and organic functional groups confirm the lattice vibrational studies. Temperature-dependent dielectric constant (e′) and dielectric loss (e″) analyses show small values at low temperature and high values at high temperature at different frequencies. Nyquist plot shows non-Debye type of relaxation up to 350 °C, and above 360 °C the plot reveals a Debye type of relaxation. The saturation magnetization of the obtained powder sample is 46.86 emu/g which is lower than that of bulk NiFe2O4. Specific absorption rates (SAR) of sample at two different concentrations were estimated using commercial induction heating system at a field of 235.2 A and frequency of 316 kHz.

A group work of semiconductor resonant inverters of magnetically coupled induction systems

The paper presents the advantages of modular induction heating systems in the problems of group heating with individual power supply stations. When they are close to each other, a magnetic bond may occur between them. The paper shows the non-operability of power sources of magnetically coupled inductors. General principles of construction of noise-resistant magnetically coupled induction heating systems with individual power supply stations are given. A comparison and analysis of the stability of the power sources based on the current inverter and the voltage inverter has been carried out.

Strain Rate and Temperature Dependent Plastic Response of AA7075 during Hot Forming

High strength 7xxx series aluminum alloys are being increasingly considered for automotive applications due to their superior specific strength compared to 6xxx series alloys. Complex structural components made from 7xxx series alloys need to be manufactured through warm forming or hot stamping due to their low ductility at room temperature. For hot stamping, the AA7075 blanks are heat treated to above 480°C, yielding a supersaturated solid solution, corresponding to a W temper state. The preheated blanks are then simultaneously formed and rapidly quenched using cooled dies. The entire forming process takes place in the W temper condition. The stamped parts are further subject to an artificial aging heat treatment to achieve the desired temper through precipitation hardening. Therefore, understanding the strain rate and temperature dependent plasticity behavior of AA7075-W is critical to establish optimum design parameters for the hot stamping process. The present work is concerned with the strain rate and temperature dependent plastic response of AA7075 in the W temper state. In particular, the results from a comprehensive experimental program on uniaxial tension specimens are presented. High temperature experiments are carried out at strain rates ranging from 0.001-2/s in a universal testing machine. An induction heating system with infrared high speed imaging is used to span the entire temperature range from 180°C to 480°C, over the full range of strain rates considered. Based on the experimental results, a candidate plasticity model with an empirical mixed Swift-Voce hardening law and a Johnson-Cook type strain rate and temperature dependence is calibrated.