MATHEMATICAL MODEL OF THE PROCESS OF DRYING WALNUTS IN A CONVECTIVE-VIBRATION DRYER

Obtaining high-quality walnuts must necessarily involve drying them to a conditioned moisture content of 10%. To achieve this goal, dryers of various types and designs are used, but convective dryers with various upgrades to intensify the drying process are the most common. To implement the drying process with the highest possible efficiency, it is necessary to know the regularities of the course of events occurring inside the drying equipment, that is, according to what laws the interaction of the drying agent and the material occurs. Simply put, you need to get a mathematical model of the process of drying walnuts in a convective-vibration dryer. The analysis of recent studies and publications shows that despite the significant variety of measures and means for the implementation of the convective drying process, all of them have the development of a mathematical model of the process as one of the stages of the study. In most cases, the mathematical model describes the interaction between the drying agent and the material to be dried. Before starting work on the creation of a mathematical model of drying, some assumptions were made, including the constancy of thermophysical characteristics and the coefficient of heat transfer during the entire drying process. To adequately describe the change in the amount of moisture in the material, the concept of negative internal heat sources was applied, which is equivalent to the current moisture content of the material and depends on its initial humidity and the operating parameters of the process. The solution of the equation of non-stationary thermal conductivity was carried out analytically by the operational method. The solution of the equation of the non-stationary process of thermal conductivity, taking into account the potential change in the intensity of negative internal heat sources in time, made it possible to obtain an equation by which it is possible to determine the temperature of the material at an arbitrary point of the nut volume depending on the drying exposure. The obtained equation makes it possible to adequately simulate the process of drying walnuts in a convective-vibration dryer and control the change in the temperature of the material to ensure the high quality of the final product.