Kinetics of Drying of Wood Profile Blanks

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UDС

674.047

DOI:

10.17238/issn0536-1036.2016.2.114

Abstract

The drying process of profile blanks of solid wood has a number of features. First of all it is a variable cross-section along the length of a blank, which poses a number of challenges to form the staples or packages, to select the modes, technologies and drying equipment. The beechwood is selected as an experimental material, which is often used for firewood. The
drying process is a complex process of heat and mass transfer which includes the heat exchange between the wood surface and the medium, thermal conductivity and moisture conduction inside the material, evaporation of moisture on its surface. To study the heat and mass transfer it is necessary to know the distribution of moisture in the cross section of material. Basically, the nature of moisture distribution inside the material is considered for the research in the form of a parabolic or cosine dependence. The cosine dependence is described by the drying rate law in the form of moisture balance. Moisture evaporates from the material surface. The resulting physical and mathematical model is the starting position for the methodology of the kinetics experimental studies of drying process. The moisture content of the central and surface layers of wood, change in the average moisture content at the drying process, linear dimensions of blanks, operational parameters of the drying process (the environmental temperature and the equilibrium moisture content of wood) are determined experimentally. The paper presents formulas, determining the coefficients of drying, moisture conduction, moisture-yielding ability, mass exchange Nusselt and Fourier numbers.
According to the experimental data the drying curves reflecting the change in the moisture content during the drying process and the drying rate curves, which help to determine the kinetic characteristics of the process, should be constructed. The drying rate during the test is reduced by more than six times. The obtained values of drying and moisture coefficients can be used in the theoretical equations to determine the duration of the drying process. Kinetics general characteristics of drying process are dimensionless Nusselt and Fourier
numbers.

Authors

P.V. Biley, Doctor of Engineering Sciences, Professor R.A. Rokun', Postgraduate Student

Affiliation

National Institute of Forestry of Ukraine, General Chuprynka str., 103, Lviv, 79057,
Ukraine; e-mail: p.biley@ukr.net, R525@ukr.net

Keywords

wood, moisture content, drying coefficient, moisture conduction, moisture- yielding ability, criteria, kinetics.

References

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Received on February 08, 2015