Distribution of temperature and moisture content fields in a rectangular beet pulp particle during convection drying

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The mathematical model describing distribution of fields of temperatures and moisture contents in a particle of a squared beet press at convective drying is given. As the initial equations the differential equations of material and thermal balances in which transfer of warmth and weight is caused by phase transformations have been accepted. The algorithm of the numerical solution of a non-stationary regional problem of heat conductivity with variable heat and mass transfer coefficients of the dried-up product, boundary and entry conditions and also phase transition with mobile limit of the section of phases is developed for the solution of mathematical model. At the same time the initial system of the equations is given to a dimensionless look. For the solution of a problem of non-stationary heat conductivity the zone method of calculation of temperature fields when drying a beet press is used. Process of drying broke into some time intervals. Within each interval geometrical form of a particle, its density, heatphysical and mass-exchanged characteristics; initial distribution of temperature and moisture content on particle volume and also density of a mass and thermal stream with the evaporated moisture are constant. The zone method of the solution of a problem of the non-stationary three-dimensional equation of heat conductivity for a parallelepiped taking into account internal sources of warmth has been checked on experimental data of stationary drying of a beet press with use of basic data. For realization of a zone method dependences of change of the linear size of a particle of a beet press on spatial coordinate x and its moisture content in the course of drying are received. At constant values of moisture content and the sizes of the party of the dried-up particle on each step the method of a machine experiment has found the current values of coefficient of phase transformation on condition of the maximum rapprochement of settlement and experimental data. The offered method of calculation of distribution of temperature fields and fields moisture containing at convective drying of a beet press in the variable modes with use of the three-dimensional equation of heat conductivity has shown compliance of settlement and experimental data with a margin error of modeling 8–10%. The received results have been used when developing a two-level way of drying of a beet press. The offered method of calculation of two-level drying of a beet press has allowed to provide the maximum kinetic compliance at implementation of temperature conditions in the field of admissible technological properties of the dried-up product.

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Mathematical model, drying, beet pulp, zone method, way of drying, temperature, humidity

Короткий адрес: https://readera.ru/140229944

IDR: 140229944   |   DOI: 10.20914/2310-1202-2018-1-11-19

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