Mathematical modeling of thermal processes of a double-stone press-extruder with induction heater

Abstract

The thermophysical phenomena that occur during the rape seed pressing process can be represented as follows. The heat energy generated by the heating devices is spent on heating the press body (increasing its heat content), partially transferred to the material moving in the body of the press, conductive heat transfer and thermal convention is transferred to the environment (external air). From the moving material, the heat is transferred to the surface of the screw and spent on its heating. The complexity of the process is that the intensity of the heating process of the plant mass changes both in time and coordinates in the direction of movement of the material.

To obtain a mathematical description of the dynamics of the process of heating the plant mass in a screw press, we assume the following assumptions:

- the gradient of temperature in the radial direction is absent, taking into account the fact that the case is heated due to induction heating;

- the thermophysical characteristics of the material and the structural elements of the processes do not change in time according to the coordinate x and do not depend on temperature;

- neglect heating the mass at the expense of heat equivalent mechanical energy, which is spent on pressing and moving material; the coefficients of heat transfer and heat transfer do not depend on temperature and in time do not change;

- do not take into account the temperature gradient for heat transfer by the thermal conductivity in the radial and axial directions in the body and the material flow;

- we will also accept a one-dimensional distribution of heat in the direction of material movement (axis x).

By comparing the received dependences of temperature distributions in the body of a twin-screw extruder, one can see that the oil-bearing material in the middle of the case is given by a given technological process at a distance of 1 m from the beginning of the body of the press at a constant value of the transferred power and at a distance of 0.6 m from the beginning of the press body in differentiated mode of transfer of power to the heater

As a result of mathematical modeling, the possibilities of increasing the efficiency of the press extruder through the use of differentiated heating modes of the case, the graphical characteristic of the temperature distribution in the working zone of the press and the target theoretical graphical dependence, which will ensure more efficient use of energy, have been identified. According to a preliminary study, an increase in the width of the press body zone with a temperature of 115 ºС leads to a 16% reduction in the extruder engine power consumption by changing the physical characteristics of the oil material when the temperature rises.