THERMOGRAM ANALYSIS OF PULSE-TYPE IR DRYER
In the course of the study, the authorrs analysed the thermograms of plant raw materials that were dried in the pulse-type IR dryer at a constant surface temperature using a relay controller. Therefore, they identified the relationship between the changes in the frequency of the regulator functioning and the kinetics of moisture removal from raw materials. Thermograms, in the considered case, are arrays of numerical values of time points and temperature variations at those points of the dried raw materials where thermocouples are located. These thermograms were digitally filtered using the Fourier transform (FT) using the Cooley-Tukey algorithm. This analysis showed that the frequency of the regulator functioning during the drying process can be described as a dynamic model of a bi-capacity inertial link that characterizes the process of dehumidification as a general decrease in moisture content in the raw materials in the presence of a time-varying gradient of moisture content over the depth of the raw materials. The end of the drying process is characterized by a decrease in the frequency of the relay controller operation. The timely finishing of the drying process allows reducing the waste of energy for drying and saving a larger amount of biologically active substances in the dried products.