A sustainable waveguide-based design strategy for improving the energy efficiency of microwave hybrid heating systems: A combined theoretical and multi-physics simulation approach

The microwave hybrid heating (MHH) based processing has emerged as energy-efficient and productive manufacturing process. The efficiency of MHH depends upon the ability of waveguide system to transmit the electromagnetic radiation with minimal loss. Thus to improve the efficiency of MHH it is of paramount importance to understand the potential of waveguide systems. In the present work, the influence of different waveguide systems, their positioning, and different modes of operation on MHH efficiency were studied via theoretical and simulation investigations followed by experimental validation. Based on the study, the optimum waveguide system was identified as WR430. To assess the efficiency and effectiveness of the waveguide positioning on MHH, 12 different locations were considered, and the optimum location was identified as (+35, −35), with a maximum microwave utilization efficiency of 44.5 %. Subsequently, the simulation model (1049 °C) was validated using experimental data (1017 °C) with an error of less than 10 %. Also, MHH is sensitive to different waveguide operating modes, SiC susceptor positioning and microwave power. A microwave cavity operating with two waveguides on both sides is found to provide optimum results in terms of heating uniformity, electric field distribution, and microwave energy absorption. The SiC susceptor positioned at the centre of the alumina refractory yields maximum heat evolution of 1020 °C. In addition, as the microwave power grows, the temperature differential also increases, implying thermal heterogeneity inside the SiC susceptor. Thus, low microwave power is identified for improved thermal uniformity and energy efficiency, while high power is proven for rapid differential microwave heating.