Dimensionamento de cavidades micro-ondas de secadores pela simulação numérica de campos eletromagnéticos e térmicos

Abstract

The unitary drying operation is one of the most complex in existence, with an operating time that normally ranges. The long time involved in this operation can damage the final product, therefore, new techniques are being developed to solve this problem. The process called hybrid drying, which is defined as the application of microwaves coupled with convective drying, has been standing out. The objectives of this work are to apply the methodology of design of experiments, in numerical simulations, for design and determination of optimum dimensions of hexagonal microwave cavities used in hybrid dryers. The optimal width and length of the cavity were determined by the design of experiments seeking to obtain higher values of average temperature, electromagnetic field and output power. The influence of the volume of liquid on heating and the distribution of electromagnetic fields was verified, in addition to evaluating the preferred heating zones. The results showed that the length of the waveguide has no influence on the temperature profile during heating, however, the profile of the electromagnetic field suffers a lot of influence. It was observed that the width and length of the cavity have linear and quadratic behaviors, respectively, with respect to the output power results. In the optimum geometry, the average temperature, during heating, is little influenced by the volume of liquid. It was also found that, for the optimal cavity, the central region is recommended to arrange the material and the preferred zones of heating the liquid are positional perpendicular to the magnetron. It can be concluded that the techniques used were useful for the design of an optimal cavity and can also be applied in the scale-up of microwave dryers.