This study presents analytical formulation used for design of helical coil for induction heating of solid and hollow cylindrical non-magnetic workpiece (graphite crucible). This formulation is applied for estimation of the active power in graphite crucibles and reactive power drawn by the induction coil in presence of different wall thickness (30, 20, 10 and 5 mm) of graphite crucibles at different frequency (1-50 kHz). Magnetic field produced by induction coil is estimated by using empirical factors suggested by kNagaoka et al. Induction heating processes, i.e. electromagnetism and heat transfer physics are mathematically modelled by Maxwell and Fourier equations, respectively. Finite-element method is used to solve the electromagnetic field in frequency domain and heat transfer in transient domain. Numerical analysis is carried out by using two-dimensional axisymmetric geometry. Analytical results and numerical results are compared and are found to be in good agreement with each other. Experimentally obtained coil voltage and graphite crucible temperature were compared with numerical results and the authors found that they also match very well confirming the validity of their assumptions in analytical/numerical approach.
This study presents analytical and numerical modelling and experimental demonstration of a litz wire-based induction heating system suitable for high-temperature application such as melting. The use of litz wire in induction heating coil minimises the skin effect and proximity effect and in turn improves the system efficiency. This makes it superior compared with a solid wire and copper tube induction coil. However, the limitation of litz wire is temperature withstanding capacity of the strand insulation material as a result of which it is rarely used in high-temperature applications (>700°C). Numerical modelling of induction heating process was done by using magnetic vector potential formulation and Fourier equations. Temperature-dependent material properties were taken account to precisely model the induction heating process. Analytically estimated and measured equivalent impedances of litz coil were compared at different frequency (1-20 kHz) for initial validation of simulation. The number of turns and frequency were selected as per required litz coil efficiency and induced power in crucible. Finally during the experimental demonstration, crucible and litz coil temperatures were measured by 'K' type thermocouples and were compared with simulation results. The maximum temperature of ∼750°C could be attained in the design while limiting the litz coil temperature within 85°C. Fig. 10 Temperature profile in different part of induction heating setup (a) Simulation results, (b) Experimental results
Over the last few decades, E-waste has become a serious concern all over the world due to the large generation, improper policies of management, inefficient techniques of recycling, adverse safety hazards etc. Different methodologies have been used for recycling of E-waste, which further generates a large amount of secondary waste in the form of solid, liquid, and gases. Improper disposal of E-waste and secondary waste adversely affects the human health and environment. Pyrolysis process, which is considered the most suitable technique for recycling of various wastes such as bio waste, plastic waste, and E-waste has been discussed in detail. In this process, E-waste is required to be heated up to 1000°C for volume and weight reduction. In this study, resistance and induction heating techniques have been used for pyrolysis of E-waste. The study also focused on the mathematical modelling and validation of experimental data generated during the studies. Comparison evaluation of performance pertaining to both the heating techniques for pyrolysis of E-waste was carried out and the result shows that weight reduction of E-waste is relatively higher in case of induction heating and the same could be achieved at a faster rate and the technique was found to be more efficient as compared to resistance heating.
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