Dielectric heating - QuickField simulation example
Simulation of the wood drying process* in a high frequency heater. The heater creates an alternating electric field between capacitor plates. Heating occurs due to the dielectric loss in the wood placed inside the capacitor.
How to find dielectric heating in capacitive drying systems?
Answer Typical applications Geometry
Given
Task
Solution
When temperature hits maximim limit the high frequency source is switched off. After temperature falls to the min limit the high frequency source is switched on.
Results
References:
Engineering question
Set up a plane-parallel QuickField Multiphysics problem for a dielectric heating system and evaluate heating distribution from computed field results.
capacitive drying systems, HF wood drying kilns, dielectric heating installations
Download
Simulation problem
Problem Type
Plane-parallel multiphysics problem of AC conduction and transient heat transfer.
Lz = 3 m.
Relative permittivity of wood ε = 2, loss tangent tan(δ) = 0.1
Voltage U~ = 1 kV (r.m.s.), frequency f = 6.87 MHz.
Initial wood temperature is +20°C. Maximum heating temperature is +70°C.
Calculate temperature rise in the wood.
Electrical conductivity of materials should be set in AC conduction problems. We can take into account dielectric losses by specifying the apparent value of conductivity**:
g = 2πf·εε0·tan(δ) = 2·3.142·68700000·2·(8.854·10-12)·0.1 = 76.4 uS/m.
The conductivity of wood may change during the drying process. It may be needed to simulate several problems with different conductivity of the wood. In this example we consider the conductivity to be independent of time.
Distribution of power losses in wood and temperature rise after 2 hours of heating.
*High frequency vacuum wood dryer
**Dielectric loss
Video
Related examples