Model of Electromagnetic Interaction With Granular Product and Insects

Abstract

In a panorama of the electromagnetic field applications the range of radio frequencies (RF) met success in food processing, especially in grain cereal disinfection and drying. Electromagnetic RF energy penetrating a grain volume result in dielectric heating that causes its drying and pest (insects, microscopic fungi) mortality when the temperature is critical for them. This work proposes a new theoretical mathematical model of electromagnetic interaction with a small homogeneous dielectric ellipsoid of rotation which represents an individual kernel. Through the solution of the general problem of macroscopic electrodynamics and the boundary condition application for the system “air – kernel” the model permits to calculate precisely the energy expenses by absorption and dissipation in an individual kernel when electromagnetic energy converts into heat (dielectric heating). The calculation result depends on the characteristics of both the electromagnetic field (electric field intensity, frequency) and the dielectric individual objects (geometry, volume, dielectric parameters). Knowledge of dielectric parameters is considered to be a principal part of the model development. The dielectric properties depend on temperature, moisture content, the object volumetric density and field frequency that are proved with the experimental part of this work. The method of dielectric parameters measurement is proposed and experimentally tested that forms the base for the technology of the agricultural product disinfection and drying. The experiments on the dielectric parameters measurement were conducted for wheat grain Triticum aestivum L. and granary weevil Sitophilus granarius L. The grain processing is presented for two different types of chambers, the coaxial irradiation chamber and the irradiation chamber with plane capacitor. The experimental part was done for wheat grain Triticum aestivum L., granary weevil Sitophilus granarius L. and the species of microscopic fungi Aspergillus fumigatus, Cladosporium cladosporioides and Aspergillus candidus for the frequencies 47.5, 900 and 2,450 MHz at different processing regimes. The granary weevil (Sitophilus granarius L.) control achieved till 100% of insect mortality. The microscopic fungi control was about 21-97% that requires more investigation. Creation of the present mathematical model contributes not only to the development of food processing technology (particularly grain crops processing), but also forms the solid basis as a perspective to create models of electromagnetic interaction with much more complicated systems such as the human body cells for electric stimulation methods and consequent disease cure at the cellular level