To heat that material which can not conduct electrical current, in this process heat is produced in non conducting materials internally. This type of heating require the frequencies above 1 MHz to 50 MHz, the current cannot flow through these materials, high voltage is applied across the materials by placing it between several parallel conducting plates(electrodes). When the output leads of the high power oscillator are connected to the feeders of these electrodes, the work material is stressed by the high voltage , alternating field, the very rapid reversal of this high field destroy the molecular structure, due to which the molecular fraction is more which produce heat inside the material uniformly throughout the material.
The thick layer of the material is heated in minutes instead of hours, even through those materials which are poor to thermal conduction. The figure shows the high frequency di-electric heating of non-conducting material, this arrangement is similar to the capacitor. The material between the high voltage plates (electrodes) of the capacitor. di-electric heating depends on the square of voltage applied across the electrodes. Voltage of the heater is from 2000V to 5000V is applied to produce the desired amount of heat.
Application of de-electric heating
The di-electric heating has large number of application in the industries some of which are given below,
- Heating of plastic in industries,
- In textile industry di-electric heating is used for drying purpose,