dielectricheating

Dielectric heating is the heating of dielectric or insulating materials by exposure to a high-frequency alternating electric field. The mechanism relies on the polarization of molecules and dipoles within the material; as the field alternates, these dipoles continuously lag behind the field and release part of the absorbed energy as heat. In non-conductive materials this dielectric loss is the primary source of heating; metals heat mainly by conduction and eddy currents and are not typically heated by dielectric methods.

The electrical response of a material to an alternating field is described by a complex permittivity ε*(ω) = ε'(ω) − jε''(ω). Here ε' is the dielectric constant and ε'' is the loss factor. The time-averaged power converted to heat per unit volume is P = 1/2 ω ε0 ε'' E^2. The ratio ε''/ε' (the loss tangent tan δ) indicates heating efficiency and typically depends on frequency and temperature.

Dielectric heating occurs mainly at radio- and microwave frequencies. Common applications include microwave cooking and industrial drying, curing, and polymer processing, as well as certain medical therapies that use controlled heating. The effectiveness depends on the dielectric properties of the material and the penetration depth of the field, which influences heating uniformity.

Practical considerations include non-uniform heating in heterogeneous materials, temperature-dependent dielectric properties, and the need for proper equipment design (waveguides, cavities, or applicators) and safety measures for exposure to high-frequency fields.