Shaojin Wang
College of Mechanical and Electronic Engineering, Northwest A&F University

Radio frequency (RF) technology has been identified as one advanced thermal treatment method for drying, disinfestation and pasteurization because it is relatively easy to apply and leaves no chemical residues. RF equipment is commercially available today, and is commonly used by the baking industry for final drying of crackers and by the other industries, such as for drying of yarn and paper. It involves the direct transfer of electromagnetic energy into bulk materials, resulting in rapid and volumetric heating. In RF systems, the product forms a “dielectric” mass between two metal capacitor plates, which are alternatively charged positively and negatively by a high-frequency alternating electric field. Rotation of polar molecules and movement of charged ions are the two main contributors of RF heat generation in the product. Thus, RF energy can directly interact with commodities to rapidly raise the temperature of the whole treated bed in an industrial system. This presentation introduces the RF heating principle and systems, explores the difference between free running oscillator and 50 W systems, presents three typical RF applicators, and finally demonstrates some recent developments of RF systems for drying, pasteurization and disinfestations of agricultural products. A major technical obstacle is to design appropriate RF applicators for providing uniform heating patterns in the treated products. With increasing computer speed and powerful simulation packages, computer simulation may greatly assist the design of effective RF heating systems and processes. This study would address critical challenges to the agricultural industry, enhance sustainability and competitiveness of agricultural products in international markets, and promote this novel and environmentally-friendly technology for commercial applications.