Development of hotspot mapping technique in microwave cavity using resistive sheet

Abstract

Microwave ovens function through the emission of electromagnetic waves, which reflect off the walls of the cavities causing local fluctuations to the electromagnetic field. In multimode cavities, multiple hotspots are generated due to the presence of various nodes, causing the localized overheat. Understanding the location of the hotspots is important to improve the heating efficiency and homogeneity of the microwave. This work aimed to propose an innovative technique for mapping the hotspots inside the multimode cavities microwave, using a resistive sheet made of polypropylene and activated carbon in contents of 5, 10 and 20%. To validate the experimental mapping technique, numerical simulations were used to predict the electromagnetic fields inside the cavity, and the simulations were then compared to the experimental result. The numeric models were validated through the experimentally determined output power. The experimental mapping results showed it was possible to reproduce clear and easy identifiable hotspots in different heights inside cavities using resistive sheets with activated carbon contents of 10 and 20%. The numerical simulations showed results for the output power that were statistically equal to the experimental results, validating its application for the prediction of the electromagnetic and thermo fields. Comparing the experimental and numerical mapping of the hotspots, a consistent match was verified between the generated profiles. Thus, the developed mapping technique managed to predict adequately the hotspots inside microwave cavities, which is useful for applications such as scale-ups and the optimization of industrial cavities.