Energy costs for grain drying are about 30% of the total energy consumption for grain produc-tion. Reducing the energy consumption of drying is possible due to the use of a microwave field. In this case, it is necessary to develop a design of a convection drying zone with a microwave field which will provide uniform drying of the grain throughout the volume. For this purpose, it is advis-able to carry out the simulation of the process. The developed computer model of heat and moisture exchange in the grain layer allows to model one under varying parameters of the grain layer and the drying agent. A computer model implements a stepwise calculation method. According to this method, the grain layer is represented as a series of computer models of the elementary layer. The grain layer is divided into three sections. The specific power of the microwave field is set to con-stant throughout each part. In addition, the model takes into account the features of changing in the specific power of the microwave field in the drying zone from the moisture content of the grain and the distance from the magnetron. The air flow in the microwave convection zone can has an im-portant value for the energy intensity of the process. The paper presents the results of modeling grain drying with two variants of air distribution in the microwave convection zone. Graphs of changes in grain moisture in each of the sections of the layer are given. It is shown that when the air moves from the magnetron, the time and the non-uniformity of drying decrease.

Keywords: drying of grain, grain layer, microwave field, microwave - convection drying, heat and - moisture exchange, computer model, modeling

The action of the microwave field is used for drying, pretreatment and disinfection of grain. In all these processes, it is very important to control the change in the parameters of the grain layer. The use of sensors for direct measurement of temperature and humidity of grain and air is difficult. The microwave field leads to errors in the measurements, and therefore the possibility of an indirect control of these quantities is considered. For the indirect measurement of these quantities, a computer model has been developed. To develop a computer model, a system of equations was used that describes the exchange of heat and moisture in the grain layer under the action of the microwave field and convection. Some equations in the mathematical model are partial differential equations. To develop a computer model, these equations were presented in an operator form. The article shows how this procedure was used to transform the equation showing the relationship between the grain temperature and the microwave field, air temperature and moisture content of the grain. This approach allowed the use of computer software for analysis and syn-thesis of control systems. In this case the Simulink software package was used. Simulink - a model for the exchange of heat and moisture in a thick layer of grain, when exposed to microwave and air, was created using elementary dynamic elements of automation. When developing a computer model, a step-by-step method is implemented. The essence of the method is that the grain layer is divided into elementary layers. The output parameters of one grain layer become input parameters for the next layer. A complete model for the exchange of heat and moisture in a layer of grain consists of models of elementary layers. The results of modeling the change in the temperature of grain heating confirmed the adequacy of the model. The use of this model in the control systems of drying and processing of grain will increase the accuracy of control and regulation.

Keywords: drying grain, grain layer, grain moisture, grain temperature, drying agent, microwave action, heat and moisture exchange, modeling