Industrial heating using energy efficient induction technology

Abstract in UndeterminedThe demands for energy efficent heating solutions for the manufacturing industry can be met by a newinduction heating platform, presented in this article. A new concept and technology to design andmanufacture induction heating unit is presented, as well as a prototype induction heater, evaluated and testedin an industrial environment. Improvements compared to existing heating solutions can be clearly shown, e.g.higher heating efficiency, no requirement for advanced cooling, a higher geometrical flexibility and alsoenvironmental gains. The Greenheat platform is built on Litz wiring, SMC flux conductors, and a castingtechnology which is outlined in the article

Industrial Induction Heating - with a focus on multi coil solutions

Most types of materials and components use heating during the manufacturing process, with a large potential for cost and energy savings. Induction heating is the most energy efficient industrial heating technology for many applications, but so far technical limitations has delayed large scale introduction. The difficulties relate to heating of large flat and curved surfaces, and, perhaps most important of all, the difficulties in achieving a uniform heat distribution. The efficiency of existing industrial induction heating systems on the market is often low, with clear demands for improvement. The first part of this work aims to improve the efficiency and manufacturability of induction heaters. By combining a newly developed core material, a silicon-iron powder composite, with litz wire for high frequency applications, very high efficiency heaters can be manufactured. The powder composite can be molded into any size and shape which allows building large, complex structures with integrated cooling. The results from this work have been commercialized and an increasing number of companies can benefit of substantial economical and energy savings in the production. The second part of the work concerns investigating a type of induction heating based on several coils, in order to achieve uniform heating. The method is called travelling wave and characterized by a fast propagating electromagnetic field that moves along the workpiece. The challenges related to multi-coil solutions are many, because of the interaction between the currents in the coils. The work contains results of the system behavior based on analytical models, simulation results of the heating pattern, and above all, experimental validation of the models. The general accuracy of the analysis of travelling wave systems has been greatly improved. Solutions to the challenges limiting the practical use of travelling wave systems are presented. Combining the new materials and production methods developed for induction heaters, with the technology of multi-coil heating has the potential to greatly improve the output from industrial processes in terms of cycle time, energy efficiency and product quality. For thermal cycling operations, the thermal mass is a huge problem. Given a method to supply uniform heating of thin workpieces provides entirely new conditions for many industrial processes; considerably reduced energy consumption, an increased production rate and products with new and improved properties

A method for inductive measurement of equivalent electrical conductivity in thin non-consolidated multilayer carbon fibre fabrics

Carbon fibre fabrics are electrically conductive and therefore possess the prerequisites for being inductively heated. In-situ heating by induction could significantly reduce processing time and energy consumption during consolidation of carbon fibre composites, but to control the induction heating process properly the electrical conductivity of the fabric must be known. The work presented in this article puts forward and validates a method for inductively measuring the equivalent electrical conductivity in thin dry multilayer carbon fibre fabrics as a function of the fibre volume fraction by varying the applied pressure on the fabric. The method has been tested on twill weave fabric based on the PAN (polyacrylonitrile) fibre T700S from Toray and the results show good agreement with a simplified model for electrical conductivity in carbon fibre fabrics and existing models for the relation between fibre volume fraction and pressure

Numerical modelling of CFRP induction heating using temperature-dependent material properties

Induction heating of CFRP is an energy-efficient and fast method that may be used for example during consolidation of thermoset-based CFRP or welding of thermoplastic-based CFRP. This study investigates how induction heating of CFRP is affected by the temperature dependence of the thermal and electrical properties and presents a simple numerical model for computation of the temperature distribution during induction heating with a circular coil. Temperature-dependent electrical and thermal properties are measured on a macroscopic level and used in the numerical model. Thermographic recordings are made during induction heating to validate the results from the numerical model. The result shows the importance of using temperature-dependent thermal properties in the numerical model, while it might not be necessary to use temperature-dependent electrical conductivity because of the small impact on the computed heat generation and temperature

Analysis of Current Paths in Induction Heating of flat sheets using single sided Longitudinal Field Inductors

Longitudinal field inductors are frequently used in the industry for heating of flat objects. This paper aims to illustrate the current paths for the inductor design as a function of workpiece geometry using 3d FEA simulations. The results show how different parameters affect the heating pattern, creating guidelines for the optimal design depending on the requirements and applications. The simulation results are verified using experimental data

A numerical model to analyse the temperature distribution in cross-ply CFRP during induction heating

Heat generation in CFRP (carbon fibre reinforced plastic) with electromagnetic induction can result in several benefits to manufacturing and production. However, during induction heating of anisotropic materials such as CFRP, the temperature distribution depends on electrical and thermal conductivity in different directions. This article presents a numerical model for computing the temperature distribution and heating power distribution in cross-ply CFRP plates, based on unidirectional plies, during induction heating. The unidirectional layers are represented as homogeneous and anisotropic domains in which electrical and thermal conductivity are represented with tensors. The electrical and thermal properties were measured and used in the numerical model to compute the temperature distribution in a number of CFRP-plates with different fibre volume fractions and layer thicknesses, and then the numerical model was validated by recording the temperature distribution with a thermographic camera during induction heating of the CFRP-plates. The experiments showed good agreement with the results from the numerical model

A resistor network model for analysis of current and temperature distribution in carbon fibre reinforced polymers during induction heating

The interest in carbon fibre reinforced polymers (CFRP) is growing due to their high strength and stiffness compared to their weight, in industries such as automotive and aerospace. This creates a high demand for more effective production methods. Volumetric induction heating of the electrically conductive carbon fibres enable unmatched heat rates and can be used both during manufacturing and joining of parts, but also means technical challenges in terms of uniform temperature distribution. Understanding and prediction of the heating pattern is therefore an important step towards an industrial solution. This article presents a model for simulation of the current and temperature distribution in CFRP during induction heating in which the CFRP is modelled as a network of discrete resistors where the local currents are determined by Kirchhoff’s circuit laws and the temperature distribution is computed by the finite difference method. The model is a complement to traditional three-dimensional finite element simulations and allows for a better understanding of the current paths, and thereby the heating pattern, on a tow size level. Thermographic recordings during induction heating experiments validates the model

Analysis of the temperature distribution in weave-based CFRP during induction heating using a simplified numerical model with a cross-ply representation

Induction heating of carbon fibre reinforced plastics, CFRP, has a great potential within different application areas, such as induction welding and curing of thermosets, due to fast and energy efficient heating. Simulation models can obviously be valuable for example during optimization. This article shows how temperature distribution during induction heating of CFRP based on woven fabric can be simulated using a finite element model with a unidirectional layer representation, thus simplifying the geometry significantly. Electrical and thermal properties were measured and used in the numerical model. The simulated and measured temperature distributions show good agreement, where the prediction of peak temperature is within just a few percent for the plates with a fibre volume fraction above 50% while the same difference is just above 10% percent for the plate with a fibre volume fraction below 40%

A method for fast characterization of power efficiency in induction heating processes

A method for fast and precise measurement of effciency in induction heating processes is evaluated and tested. The method, based on thermal imaging is presented with advantages and drawbacks based on results from coupled transient simulations and from experimental results. The experiments are performed using two different induction heating platforms, equipped with high quality measurement equipment, including a thermal camera, capable of streaming 16 bits radiometric data for image recording on a computer. Post-processing of the recorded data, including compensation of camera position and integration of electrical and thermal properties is explained and the results presented with pictures of each step. Also some basic knowledge of radiometric measurement of temperature is described to better understand the possibilities and to avoid unnecessary pitfalls. Guidelines of how to choose the best equipment or setup forms the conclusion of the article, providing a method that can be used also for other applications