The mass transfer (diffusion) properties of a colloidal capillary-porous material (pears cut into plates 5 mm thick for convective drying) as a function of the moisture content of the material at different temperatures of the drying agent (air) were studied experimentally. Since the pear sample shrinks significantly during drying, the change in sample thickness during the process was taken into account when calculating the mass conductivity coefficient. At the same time, the linear shrinkage of the specified material was studied. The dependences of the mass conductivity coefficient on the moisture content of the material k = f(u) were obtained from drying curves based on the zonal method at a constant temperature of the drying agent tdr. They represent dependences concave to the abscissa axis that increase with moisture content, which is typical of dried materials. The minimum values of the mass conductivity coefficient on the graphs k = f(u) vary from 0.3∙10–10 m2/s at 30°C to 2.2∙10–10 m2/s at 60°C. With a change in the moisture content of the material, the mass conductivity coefficient changes multiply. The shrinkage data for engineering calculations was described by equation. The possibility of describing the temperature dependence of the mass conductivity coefficient (moisture diffusion) by Arrhenius equation is shown. The values of the Arrhenius equation parameters are obtained.

The kinetics of drying dense wool fabric in different regimes has been studied experimentally. The mass-conducting (diffusion) properties of the fabric are determined depending on the content of moisture in it and its temperature. For the convenience of engineering calculations, the obtained data on the mass conductivity of the fabric are approximated by its dependences on moisture content and temperature. It has been established that the kinetics of convective drying of a dense wool fabric is adequately described by A. V. Luikov’s model of heat and moisture transfer subject to the dependence of the mass conductivity of the fabric on its moisture content and the temperature of the drying agent. The proposed approach to the calculation of the kinetics of drying a dense wool fabric, its moisture content, and its temperature can be used in the design of the processes of drying various fabrics.

В статье представлены структурно-функциональная схема виртуального осциллографа, описание макетной платы, описание блока «COM-порт». Представлены режимы работы аналого-цифрового преобразователя и UART в микроконтроллере STM32. Из представленных режимов работы выбраны оптимальные для работы блока виртуального осциллографа. Цель исследования: разработать виртуальный осциллограф на основе микроконтроллера STM32, предложив его структурно-функциональную схему. Материалы и методы. Для разработки структуры виртуального осциллографа необходимо спроектировать схему его взаимодействия с лабораторной установкой, выбрать оптимальный метод для снятия напряжений с точек макетной платы и способ их передачи на компьютер. Также необходимо реализовать блок COM-порта и его взаимодействие с блоком виртуального осциллографа в среде моделирования. Результаты. Разработана структурно-функциональная схема программно-аппаратной реализации работы виртуального осциллографа. Описаны режимы работы аналого-цифрового преобразователя микроконтроллера STM32. Описаны режимы передачи данных по UART в STM32. Представлен формат передаваемых по UART кадров. Также реализован блок COM-порта и его взаимодействие с блоком виртуального осциллографа в среде моделирования МАРС. Заключение. В результате рассмотрения методов работы с внутренним аналого-цифровым преобразователем микроконтроллера STM32 и методов работы с UART был сделан вывод, что оптимальным режимом работы является работа с использованием технологии прямого доступа к памяти. Использование виртуального осциллографа позволяет сделать более удобным отображение аналоговых сигналов за счёт использования большого монитора компьютера. Также реализация на компьютере позволяет реализовать функционал для сравнения и хранения информации с множества каналов и сделать удобным масштабирование графика отображаемого сигнала. Использование внутренних аналого-цифровых преобразователей микроконтроллера позволяет значительно сэкономить на покупке реального осциллографа.

Based on the zonal method, the temperature and concentration dependences of the moisture diffusion coefficient in materials subject to shrinkage in the process of drying (plates cut from apple, carrot, and beet) were found experimentally. The concentration dependences of the moisture diffusion coefficient in these materials were determined from drying curves obtained in the absence of external diffusion resistance. Shrinkage of materials was determined experimentally, the temperature dependences of the obtained diffusion coefficients were described on the basis of the theory of activated molecular diffusion of moisture in the material. It is shown that the temperature dependence of the moisture diffusion coefficient in the indicated materials is described satisfactorily by the Arrhenius equation, on the basis of which, for these materials, formulas were obtained that express the dependence of the coefficient of moisture diffusion in them on their moisture content and temperature and that can be used in engineering calculations. The obtained data on the moisture diffusion coefficient in the studied materials are compared with similar data obtained for other materials. It is shown that the concentration dependences of the moisture diffusion coefficients of materials subject to shrinkage during drying have the same nature and order of magnitude as similar dependences for materials without shrinkage. The drying curves calculated using the obtained formulas were compared with the experimental drying curves, which showed their satisfactory similarity.

A mathematical model of the processes of heat and mass transfer during the convective drying of a colloidal capillary-porous material, taking into account the phenomenon of shrinkage, is presented. This model is formulated in an area with a movable boundary. The mass conductivity equation includes a convective term to describe the additional internal mass transfer of the material by the matrix. The formulated nonlinear problem of heat and mass transfer is solved numerically using the data obtained in this work on the coefficient of mass conductivity and the known literature data on other thermophysical characteristics. The verification of the one-dimensional model was carried out on the basis of experimental drying curves for apple disks cut from a whole fruit. It is shown that the deformation of the sample during its dehydration significantly affects the kinetics of the drying process of the colloidal capillary-porous material.

Experimentally obtained and analyzed the mass transfer properties during drying of kernels and shells of sunflower seeds.

The mass-conduction (diffusion) properties of sunflower seeds of the "MAS 95 OL" variety were experimentally investigated. From the experimental drying curves obtained in the intradiffusion kinetic mode at two temperatures of the drying agent (air), the coefficients of mass conductivity (moisture diffusion) were calculated by the zonal method, which are presented as dependences on the moisture content of the core and shell, respectively. It is shown that the coefficients of mass conductivity of nuclei and shells depend on the moisture content of the material and differ significantly both in magnitude and in the nature of the concentration dependences. The coefficient of mass conductivity of nuclei in different areas of moisture content is 15-25 times higher than that of shells, this is explained by differences in the structure of these materials. In the area of moisture content less than 0.5 kg / (kg of dry materiall), both dependences have the same character of concave functions increasing with moisture content, this is a consequence of the same mechanism of mass transfer dominating in this area of moisture content, which is osmotic mass transfer. In seed kernels, the area of moisture content of more than 0.5 kg / (kg of dry material) is absent, but in seed shells it is present and vapor diffusion dominates in it. The data on the coefficient of mass conductivity for seed shells were compared with the coefficient of mass conductivity of another capillary-porous colloidal material with a similar structure - wood. The nature of the concentration dependences for both materials is the same, which is explained by the similarity of the morphological structure of wood and seed shells, which have a tree-like structure. The coefficient of mass conductivity of the seed kernel was compared with the coefficients of mass conductivity of other capillary-porous colloidal materials of plant and animal origin. Comparison showed that they have the same order of mass conductivity coefficient: 10-9 m2/s. This is explained by the identical structure of these materials, which have a cellular structure, and, probably, by the same mechanisms of mass transfer at the corresponding moisture content. The obtained data on the coefficients of mass conductivity of the kernel and shell of sunflower seed can be used for the kinetic calculation of the process of convective drying of this material based on the solution of the differential equations of internal heat and mass transfer A.V. Lykov with the representation of the seed as a two-layer body.

The widespread use of polymer composite materials makes it necessary to study their physical properties. Particular attention is given to polymers reacted with water and other low molecular weight compounds in their preparation as well as during operation. Most studies have been devoted in the diffusion properties of materials in the form of films, while operating materials often have a different shape, for example pellets. Well at small sizes of granules is impossible to use stationary methods. In this paper, the diffusion coefficient is determined by the zonal method based on the integration of the diffusion equation. A significant increase in the effective diffusion coefficient with an increase in the diffusant concentration associated with the plasticizing action of water was detected. Temperature-humidity dependence of diffusion effective coefficient is approximated by the refined formula which helps to calculate mass transfer process kinetics and carry out theoretical analysis of water diffuse properties in polymer matrix. With the movement of individual particles of polymer materials in real dryers, it is expedient to break the kinetic problem of mass transfer into external and internal one. The validity of the two-level consideration of the kinetic problem of granular polymer materials deep drying and the applicability of the data obtained for their diffusion properties are shown. The microkinetics of a single particle drying is considered, it is the determining condition for the accuracy of the kinetic calculation.

В данной статье рассматривается проблема планирования процесса снегоуборки, недоработки которой приводят к увеличению «пробок» на дорогах, числа дорожно-транспортных происшествий. Для осуществления планирования процесса снегоуборки в статье предлагается использовать имитационное моделирование, позволяющее «проиграть» планируемые процессы на моделях, определить «узкие места», недоработки, погрешности системы и т. д. Предлагаемая концептуальная модель планирования процесса снегоуборки позволит сформировать информационную модель процессов; разработать имитационную модель, включающую в себя физическую, дискретно-событийную и экономическую модель объекта и на завершающем этапе, на основе полученных варьируемых параметров модели сформировать управленческое решение в виде плана снегоуборочных работ.

Mass conducting (diffusional) properties of capillary-porous colloidal materials have been studied experimentally in the process of their convective drying depending on the moisture content and temperature of the material using as an example maize grains of three varieties. The physical mechanisms that influence the dependence of the mass conductivity coefficient of such a material on its moisture content are considered. It is shown that provided there is invariance of the dependence of the local temperature of the material on its local moisture content, the mass conductivity coefficient of the material can be determined depending on the moisture content of the latter and on the drying agent temperature, which simplifies the calculation of the drying kinetics substantially.

The possibility of using a heat pump as a part of on-farm drying plant is considered taking drying of corn grain as an example. The methodology for kinetic calculations of a drying plant with a batch fluidized bed for granular materials is developed. These calculations are based on the use of an analytical solution for the problem of mass conductivity and taking into account the time-related changes in drying agent parameters over the layer height. To determine the concentration dependence of the mass-conductivity coefficient, a zonal method has been used. Keywords: heat pump; dryer; kinetic calculation.

Data on the mass conductivity coefficient have been obtained during drying the onion seeds in a thick layer of 5 mm thick ventilated on the surface, which were calculated by the zonal method on the basis of experimental curves of drying and heating. These data are described by the dependence of the mass conductivity coefficient on temperature and moisture content of the material. The comparison of the mass conductivity coefficient values for a layer and for single seeds is given, which shows that: 1) the mass conductivity coefficient in the layer changes significantly during drying, therefore, this change must be taken into account; 2) the change in the mass conductivity coefficient is due to its dependence on both moisture content and temperature, but the influence of temperature prevails over the influence of moisture content, therefore, themass conductivity coefficient increases during drying, 3) the mass conductivity coefficient in the layer is two orders of magnitude higher than for single seeds. The curve of seeds drying in a layer of 5 mm thick have been calculated using the obtained data on the mass conductivity coefficient for the process of oscillating infrared seeds drying carried out at a material temperature fluctuation in the range from tmin = 34 °C to tmax = 40 °C, which showed satisfactory agreement of the results of calculation and experiment. Experimental and calculated curves of oscillating infrared seeds drying in a layer of 5 mm thick are compared with analogous curves of drying the seeds in a monolayer, which showed that, despite the fact that the mass conductivity coefficient of seeds in a layer of 5 mm thick is two orders of magnitude greater than in a monolayer, the drying of seeds in the first case is slower because of the greater thickness of the layer. To calculate the kinetics of the process of oscillating infrared seeds drying in a dense layer, when its surface temperature oscillates in the range from tmin = 34 °C to tmax = 40 °C, the zonal method is recommended using the obtained data on the mass conductivity coefficient, taking into account the change in the mass conductivity during the process.Forcitation:Rudobashta S.P., Zueva G.A., Dmitriev V.M. Study of mass conductivity properties of seedslayer. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 7. P. 72-77.