Substantiation of the parameters of the convective-ultrahigh-frequency hop dryer
Introduction. The article describes an endogenous-convective continuous-flow hop dryer with metal-dielectric resonators; the results of a study of the electrodynamic parameters (ED) of a toroidal resonator are presented; some aspects of moisture and heat exchange between the raw material surface and the environment are considered. Materials and methods. Using three-dimensional modeling in CST Microwave Studio programs, SolidWorks developed the design of the hop dryer; MS Office programs, including Excel, Mathcad 14, Statgrahics Plus Windows, were used for statistical processing of research results. Theoretical studies of moisture-heat exchange between the surface of hop cones and the environment were carried out taking into account the influence of forms of moisture bonding with raw materials on the drying kinetics. Results and discussion. The hop dryer contains toroidal resonators arranged in series in a vertical plane with alternating resonators in the form of astroids with truncated tops and ceramic biconvex perforated disks. The use of resonators in the form of astroids increases the radiative quality factor of the resonator, which depends on the ratio of the geometrical dimensions of the resonator, the dielectric constant of the biconvex disk, and the type of oscillations. The use of ceramic perforated biconvex discs makes it possible to maintain free electromagnetic oscillations of various types. When designing the resonators, it was taken into account that their dimensions ensured that the spectrum of the frequencies of the multimode electromagnetic field of standing waves excited in it coincide with the frequency spectrum of anomalous dispersions of free and bound moisture at various stages of their removal from hops. The results of the study of ED show that in the capacitor part of the toroidal resonator, it is possible to provide an electric field strength in the range of 1-3 kV/cm, which improves the microbiological parameters of hops at a sufficiently high drying rate. Conclusion. Preliminary results of the study of the process of drying freshly harvested hops by the endogenous-convective method show that in the metal-dielectric resonator, the heating of hop cones and the evaporation of moisture occur in a sparing mode.