Modelling of process of high-frequency heating of wet timber in the vacuum dielectric drying chamber

In the study questions of high-frequency dielec-tric heating when drying wood in vacuum and die-lectric drying chambers were considered. As the amount of loading was usually commensurable with the length of an electromagnetic wave, electromag-netic field distribution gained wave character. Het-erogeneity of a field was the reason of unevenness of temperature on the loading length. As a result of uneven heating and drying the defects reducing quality of dried-up timber and increasing flaw of production were formed. As a result specific costs of the electric power of drying which were so high for this type of chambers increased. An ultimate goal of research was the increase of energy effi-ciency of vacuum and dielectric chambers requiring deeper studying of processes of high-frequency heating and drying. Two-dimensional mathematical model considering the specified wave phenomena and dependence of heat and physical and dielectric properties of material on temperature and moisture content was developed for theoretical studying of wood heating in vacuum and dielectric chamber. At numerical modeling it was accepted that current distributors were connected to electrodes in the middle therefore calculation was made only for one symmetric part. In the study the results of the solu-tion of the developed model were illustrated by final elements method at different moisture content of material and different frequency of the field. Distri-butions of internal sources of warmth and tempera-ture were carried out for various time points of heat-ing in the range from 0 to 30 min. The analysis of the results showed that the most uniform heating can be carried out at the frequency of 1.73 MHz, but low intensity of process was technologically undesirable. High intensity was reached at the fre-quency of 13.56 MHz, but was followed by uneven-ness of heating.