The use of microwave radiation for technological wood and lumber drying

Abstract

The article considers the different methods of drying wood. Are compared the induction, infrared and microwave heating. Induction heating is considered as a heat conductive material through which the excitation of electrical currents in an alternating electromagnetic field, and infrared heating as heating of materials with electromagnetic radiation with a wave length of 2 mm - 760 nm. Microwave heating is considered as the optimal method of drying wood. It is based on the penetration of electromagnetic energy into the material and converting it into heat. The purpose of the article is to determine the optimal parameters of electromagnetic radiation for drying wood. With microwave heating temperature distribution of the heated material is such that temperature gradients, pressure and moisture concentration directed to one side from the center to the periphery, which accelerates the drying of the wood. The equations for calculating the fluid flow rate through the capillary of timber are considered. The dependence of the heat generated in the wood under the influence of electromagnetic field, the field frequency, field strength and dielectric parameters of the of timber is shown. The microwave radiation parameters for optimizing the drying process of wood-based panels and lumber clarified. Drying quality is improved owing to the fact that the heating of the dried areas is automatically terminated. Heating is continued only there where it is still kept humid. Takes into account electrophysical parameters of drying wood in a fairly wide range of frequencies. Dielectric properties of wood are considered through the dielectric constant and dielectric loss tangent. Frequencies of microwave radiation for different values of the parameters of the wood pile are recommended. It is not possible to change randomly the frequency to optimize the wood drying process, so developers can vary the process parameters and the parameters of camera settings for drying wood. It is possible to draw with high speed and highlight in a unit volume of timber the capacity which is not available to any of the traditional ways of energy supply. The application of non-contact selective heating is shown. The ways of increasing the efficiency of drying wood in the electromagnetic field of ultrahigh frequency are considered.