JUSTIFICATION OF HEAT AND ENERGY PARAMETERS OF CONTACT DRYING PROCESS OF GRAIN

Abstract

The purpose of the research is to identify factors that directly affect the thermophysical characteristics of the developed means for grain contact drying. In case of system analysis, this goal is achieved by widespread usage of modeling, which allows to substantiate not only the parameters of the appropriate process mode, but also to choose the most suitable way to control the drying process under production conditions. The conditions for heat transfer from the heating surface to the grain depend on the heat given off by the heating surface of the drying chamber, W; heat transfer coefficient W/(m2 ºС), temperature of the heating surface and the grain at the outlet from the drying chamber, °С; heating surface area, m2. In addition, in case of contact heat transfer, the problem of grain heating is linear (tgr2 = f(z, )), where z is the distance from the grain to the heating surface, m;  - time from the drying process start, s. It was found that the heating temperature limit of the surface of the drying chamber (made in the form of a cylinder, with a screw transporting working body) should not exceed 61С to ensure the grain temperature at the chamber outlet of 39С. In case of using a belt conveyor in the drying chamber and if it is in the form of a rectangular parallelepiped, the temperature limit of the chamber surface heating is 69 С. When the drying chamber is made in the form of a stepped surface enclosed in a box with vibration induction of grain movement, the heating temperature of this surface can be increased to 129 С without harm to the dried grain quality. It also allows to increase the throughput of the device compared to the first version of the drying chamber: from 0.2 t/h to 0.4 t/h.