Математичне моделювання і розрахунок динамічних режимів повітроохолоджувача для охолодження зерна за зберігання

Анотація

Mathematical modeling and calculation of air coolers dynamic mode COOLING GRAIN STORAGE

V. Gryschenko, B. Kotov

In connection with the application of high-performance combine harvesters, advanced methods of storing and delivering the grain to the place of processing and storage, during the mass flow of freshly grain significantly reduced. This causes additional difficulties associated with ensuring the preservation of a large mass of wet grain in a short time. To prevent damage to high moisture grain aeration grain mass used in temporary shelters and fixed atmospheric artificially cooled air [1, 2]. However, the possibility of cooling the grain outside air during cleaning not always strike [3] can at 18-26 °C. Therefore, in recent years increasingly used to cool the grain in storage artificial cooling refrigeration machines [4]. Application artificially cooled air to reduce the self-warming grain allows slow intensity of physiological, biochemical, microbiological processes and vitality of pests of grain stocks. To cool the grain using stationary and mobile refrigeration.

It is known [5] chillers rely on fixed parameters input streams, but they function with variable parameter input values. Effective use of refrigeration units can be achieved by automating the process of control that necessary to determine dynamic properties of refrigeration equipment, such as inertial object - air, steam and compressor unit.

The purpose of research – creating mathematical description of the dynamic properties steam and compressor air cooler unit and determining transients in object modeling.

Materials and methods of research. The presence of a significant variety embodiment of the air coolers leads to analytical research methods that allow design features characterize only by the exchange surfaces, heat and mass transfer coefficients (defined hydraulic conditions) and energy costs.

The methodology is a mathematical description of the analysis of heat and material balance, which is written in the form of differential equations with generally accepted for such facilities simplification [6]. The adequacy of the models determined by comparison of the theoretical and experimental data.

Results. Air evaporator refrigeration unit - pipe-finned design which moves coolant through tubes in gas-liquid phase in the process of moving completely evaporates. The heat is spent on bringing coolant to boil and removed from the evaporation which cools the air. Because the evaporator can be represented as a heat exchanger through which refrigerant (Freon) and air. Considering it as an object with three concentrated volume, changing the temperature of refrigerant and air at the outlet of the cooling system can provide heat balance equation.

When isobaric cooling air to the surface temperature of the evaporator, which is below the dew point temperature is a partial condensation of water vapor is in the humid air. Moist air is saturated and condenses on the surface wet. Complemented equation of material balance in the volume of air cooler based condensation.

The resulting system of equations nonlinear equations contain as works of variables. For linearization of nonlinear equations variables recorded growth in their value in steady state and used the Laplace transform with zero initial. system of equations in operator form, the solution of which receive as transfer functions to regulate parameters relative to regulatory impacts and disturbances. Developed block diagram of the linear model of the dynamics of air cooler and built a transient air cooler (temperature and moisture content of the air).