17 - Radio-Frequency Processing

Abstract

Radio-frequency (RF) dielectric heating/drying has been used in various industrial applications for many years, especially in wood, textile, and some food industry processes. Since dielectric heating transfers energy directly to the product, applications of RF present obvious advantages over other conventional techniques (reduction in processing time and space and improvement in product quality). The success of an RF heating/drying setup lies in its design and in the impedance matching between the power generator and the applicator. The quality of the applicator's design is important for its efficiency. Attention must be given to the choice of materials (quality of the electric contacts or resistance to corrosion) and to the setup as a whole (durability, dielectric behavior of insulators, and proper grounding). In a radio-frequency heating system, the RF generator creates an alternating electric field between two electrodes. The material to be heated is placed between the electrodes where the alternating energy causes polarization and where the molecules in the material continuously reorient themselves to face opposite poles.