MASS CONDUCTIVITY FOR DRYING NUCLEI AND SEED SUNFLOWER SHELLS

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.

MATHEMATICAL MODELING OF CONCRETE STRUCTURE CORROSION IN BIOLOGICALLY AGGRESSIVE ENVIRONMENTS

In the aquatic environment, biocorrosion is an important factor affecting the reliability and durability of concrete structures. The destruction of cement concretes during biological corrosion is determined by the processes of mass transfer. The article presents the development of a calculated mathematical model of liquid corrosion in cement concrete, taking into account the biogenic factor. For the first time, a model of mass transfer in an unbounded two-layer plate is considered in the form of differential equations of parabolic type in partial derivatives with boundary conditions of the second kind at the interface between concrete and liquid and of the fourth kind at the interface between concrete and biofilm. The results of a numerical experiment are presented to study the influence of the coefficients of mass conductivity and mass transfer on the kinetics and dynamics of the process.

The Experimental Study of the Kinetics of the Cyclic Adsorption Process of Air Enrichment with Oxygen

For mass transfer cyclic processes in the “adsorptive - porous adsorbent” system when air is enriched with oxygen by the method of short-cycle heatless adsorption, a new method has been implemented for determining the coefficients of mass transfer and mass conductivity of processes in systems with a solid phase from kinetic curves. It has been experimentally proved that during the adsorption separation of atmospheric air, the rate of cyclic “adsorption - desorption” processes can be limited by both internal and external diffusion resistance. The mass conductivity coefficients are determined depending on the mass content of the distributed adsorptive (O2, N2) by a method that does not require the implementation of the intradiffusion kinetic regime. The analysis of the kinetics of the process of air enrichment with oxygen is carried out; the coefficients of mass transfer and mass conductivity, which can be used in kinetic calculations and numerical study of the properties and modes of the cyclic adsorption process of atmospheric air separation and oxygen concentration, are determined.

Drying the corn in a farm heat pump dryer with fluidized bed

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.

INFLUENCE OF THERMAL DIFFUSION ON KINETICS OF OSCILLATING IR DRYING

The relative thermal diffusion coefficient δt was calculated from the obtained moisture sorption isotherm for the seeds of onions. It allowed estimating the contribution of thermal diffusion with respect to the flow of mass conductivity in the considered version of the oscillating IR drying, and it turned out to be 5%. Hence, the thermal diffusion can be ignored for engineering calculations of the kinetics of the oscillating IR drying.

STUDY OF MASS CONDUCTIVITY PROPERTIES OF SEEDS LAYER

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.