The high frequency technology is used in the many different areas.
HF energy (high-frequency energy) is in an electric field. By means of «dielectric» or «inductive» heating this energy is converted into heat energy.
Inductive heating is applicable only for metallic materials (highly electrically conductive materials). The dielectric heating is only applicable for poor electrical conducting materials. Iner alia is this method for drying and preheating of resin powder, used for the welding of plastic films.
In the wood industry it finds applications e.g. for drying of wood but especially for heating of adhesives. The key advantage of the dielectric heating in relation to conventional heating modes, such as contact, convection and radiation heat, is that they are not depending on the temperature conductivity of the material. Therefore, materials with any volume and cross-sectional dimensions can be heated in a very short time. Is there a body of various components, a selective heating of certain materials (parts) is possible. This advantage has significantly contributed to establishing the dielectric heating in the timber industry. This allows to heat up the adhesive joint and the adhesive is cured without substantially increasing of the temperature of the surrounding layers of wood. The setting time can be reduced to less than 30 seconds.
Following features of the dielectric heating should especially be mentioned:
Immediate heating of the treated materials after switching on the high frequency power - no heat losses
Constant increasing the temperature in nearly homogeneous material. It's not possible to overheat local areas
Various heating of different materials (eg, wood and glue), so selective heating of certain substances are posssible
Due to the special arrangement of the electrodes, individual parts of a body can be preferably heatedwith high frequency