Ultrahigh-Frequency Hop Dryer with Tiered Resonators

Introduction. From the analysis of hop dryers of different systems and designs follows the prospect of hop drying by complex influence of the energy of the electromagnetic field of ultrahigh frequency and convective heat. Aim of the Article. The article aims at developing a small-sized microwave convective hop dryer with justified parameters for intensive drying technology of freshly harvested hops. Materials and Methods. Taking into account the justified criteria for the design of a hop dryer and the analysis of existing resonators, there was proposed a methodology for the development of a hop dryer with an energy supply in an electromagnetic field, including requirements for structural design, operational and economic indicators, and technology. The electrodynamic parameters of the resonator were investigated according to the CST Studio 2017 program. Results. The dielectric parameters of hops are theoretically investigated and functional dependences on humidity at a frequency of 2,450 MHz are obtained. The dynamics of hop heating is investigated when its dielectric loss factor changes during the action of an ultrahigh frequency electromagnetic field. There has been developed a design and technological scheme of a radio-hermetic microwave convective hop dryer of continuous flow action with tiered resonators for low-power agricultural enterprises. Resonators are arranged in tiers in the screening cylindrical housing: the first and third resonators are hemispherical, and the middle one is made in the form of an ellipsoid to ensure a high electric field strength. The transportation of raw materials takes place by rotating the discs in a gentle mode. Discussion and Conclusion. The expected specific energy costs of a hop dryer with a capacity of 12–13 kg/h at the microwave generator power of 4.0 kW for drying freshly harvested hops with a humidity of 76–82% to a humidity of 11–14% are 0.30–0.33 kWh/kg. The required electric field voltage of 2 kV/cm in all three resonators is provided, therefore, disinfection of raw materials occurs at a temperature of 65–70°C for 5–6 minutes of stay in three resonators. The intensity of moisture release from hop cones during endogenous convective heating increases 5–6 times compared to the convective drying method. The introduction of microwave drying technology using a convective method of evaporation and removal of moisture from the drying chamber reduces the duration of the process, saves valuable components of cones for brewing.