Mass Conductivity for Drying Nuclei and Seed Sunflower Shells

Abstract

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.