Подільський державний аграрно-технічний університет В. О. Грищенко, кандидат технічних наук Національний університет біоресурсів і природокористування України Ю. І. Панцир, кандидат технічних наук, доцент І.Д. Герасимчук, кандидат технічних наук, доцент Подільський державний аграрно-технічний університет

The article considers the issue of increasing the efficiency of coolers of the material heated during drying by using a heat pump unit to produce artificial cold. The scheme of use of a thermal pump in a complex with the drying installation and the portable cooler of material is offered. A mathematical description of the stationary modes of operation of the drying unit, material cooler and heat pump elements on the basis of a steam compressor refrigeration unit is formulated. At creation of physical and mathematical models of heat and mass transfer in the course of drying and cooling of material (grain) the following conditions are accepted simplifying the mathematical description, but without changing real process: moisture from the material is removed according to Dalton's evaporation law, while the moisture in the material evaporates and is removed simultaneously; moisture content and temperature in the volume of the material are evenly distributed, heat and mass transfer occurs only between the surface of the material and the drying agent; the effects of radiation and contact heat transfer are taken into account by heat transfer coefficients; stationary fields of temperature and moisture content are assumed to be one-dimensional, which vary according to the coordinate calculated in the direction of movement of the material; when cooling the moisture removal material is not taken into account for low residual moisture; the size of the surface of the material in the process of drying and cooling does not change; the heat exchange equipment of the heat pump is an object with concentrated parameters. Using the obtained mathematical dependences, graphical dependences of changes in grain and air temperature are constructed, which allow to evaluate the expediency of using a heat pump. The formulated mathematical model of stationary modes of the heat pump drying unit with artificial cooling of the dried material can be used to evaluate the feasibility and energy efficiency of the used refrigeration machines for grain cooling, especially after high-temperature processing. The obtained analytical dependences in the form of a closed system of equations can be used to optimize the parameters of the heat pump drying unit by the criterion of minimizing energy consumption.

No abstract

The article determines the relevance of research options for the use of heat exchange equipment for the utilization of the heat of the exhaust air of livestock building. It has been analyzed that for the efficient functioning of heat-utilizers, it is necessary not only to choose optimal design parameters, but also to implement rational energy-efficient modes. It was determined that for the synthesis of the system of automatic control of the thermo-humidity mode in the room, it is necessary to determine the dynamic characteristics of the control object based on the mathematical model of dynamic modes. The analysis of the existing heat utilization systems is presented and it is stated that they have only analytical dependencies for their description, which describe the stationary regimes of heat utilization systems that determine the statics of heat and mass exchange (moisture condensation on the surface) processes. In the considered works, the combined functioning of the heat recovery unit and the livestock building in non-stationary mode is not considered. On the basis of the analysis of the heat-moisture regime of the livestock building, the ventilation system of which is equipped with a recuperative type heat recovery unit, a mathematical description in the form of differential equations of the heat and material balance of the livestock building with the heat utilization ventilation system was compiled. Mathematical models of the heat and material balance for the livestock building have been developed in the form of a system of three differential equations, which contain two interrelated parameters: temperature and air humidity. But since the parameters of the air in the room with the waste ventilation air heat utilizer depend on the parameters and mode of operation of the heat exchanger, the equation of the thermal regime of the room was developed with the equations that determine the non-stationary thermal regime of the heat utilizer. The formulated mathematical model describes the non-stationary process of heat exchange in the microclimate creation system and can be used to justify the design and operating parameters of the heat exchanger regardless of design features. The mathematical model defines the transition process in the "room-heat-utilizer" system and can be used to create a system for automatic temperature-humidity control.

Подільський державний аграрно-технічний університет В. О. Грищенко, кандидат технічних наук Національний університет біоресурсів і природокористування України Ю. І. Панцир, кандидат технічних наук, доцент І. Д. Герасимчук, кандидат технічних наук, доцент Подільський державний аграрно-технічний університет Р. А. Калініченко, кандидат технічних наук, доцент ВП НУБіП України «Ніжинський агротехнічний інститут»