Optimizing microwave heating with slotted metal tubes for cylindrical loads

Cylindrical loads are commonly encountered in microwave heating and often suffer from uneven thermal distribution. Within certain radius and dielectric parameter ranges, cylindrical loads may exhibit central thermal focusing. This paper proposes a novel microwave heating method employing a slotted metal tube (SMT) to encase the cylindrical materials. The SMT alters the electric field distribution and enhances the coupling of microwave energy, thereby improving the heating uniformity and efficiency. We first developed a simulation model for microwave heating, analyzing how permittivity and dimensions affect the thermal focus of cylindrical materials. By optimizing the slot dimensions and positions, we overcome the thermal focusing phenomenon. Then, we conducted microwave heating experiments with mashed potatoes, showing that the use of SMT improved the temperature uniformity by 38 % and increased the microwave energy conversion efficiency by 48 %. Furthermore, we applied SMT to a more challenging scenario, involving the heating of cylindrical canned foods with metal lids, using a dual-source heating setup. The experimental results indicated that SMT remained effective in enhancing heating uniformity and efficiency. This method contributes to the development of microwave energy industrial applications, providing innovative solutions for cylindrical load heating.