Методичні основи визначення коефіцієнтів перенесення теплоти та вологи у дисперсних матеріалах

Abstract

The investigation of moisture and heat transfer coefficients in various materials is an important stage in the study of drying processes. Data on these coefficients are necessary for conducting calculations based on analytical relationships describing moisture content and temperature distributions, as well as moisture and heat fluxes in the material. Numerous studies demonstrate that accurate knowledge of mass transfer coefficients in dispersed systems is crucial for successful design and for improving the energy efficiency of industrial equipment. Data on heat and mass transfer coefficients for a range of materials are presented, along with a comparison of various analytical equations used to determine the effective diffusion coefficient. It is noted that analytical relationships for calculating mass transfer coefficients do not capture the full spectrum of factors influencing moisture transport within a material, as they typically consider idealized structures that account for only some of the existing transport mechanisms. Therefore, in most cases, these analytical dependencies are used not for the direct calculation of transfer coefficients, but rather for a qualitative assessment of their dependence on temperature, pressure, and component properties. Hence, experimental methods of determining these coefficients acquire primary importance. This work describes a methodology for obtaining data on effective transfer coefficients for dense layers of dispersed materials. The theoretical basis of this methodology is a system of differential equations for coupled moisture and heat transfer in capillary-porous bodies during drying processes, as formulated by A.V. Lykov. A dense layer of dispersed material is treated as a quasi-homogeneous medium with effective transfer coefficients. An experimental setup and an algorithm for processing the obtained experimental data are presented. The resulting moisture content and temperature distributions in a dense layer of zeolite are reported for the conductive drying process