Two uncommon heating methods of electric heaters

Electric heaters heat by connecting power to the alloy heating wire to generate high temperature. The more common heating methods are resistance heating, induction heating, arc heating, electron beam heating, infrared heating and dielectric heating, but there are two heating methods that are rare, as follows:

1. Infrared heating

Electric heaters use infrared radiation to radiate objects. After absorbing infrared light, the object converts the radiation energy into heat energy for heating.

Infrared heating is actually a special form of resistance heating, which uses materials such as tungsten, iron-nickel or nickel-chromium alloy as radiation sources. After power is turned on, heat radiation is generated due to resistance heating. Common types of infrared radiation sources are spherical, tubular and flat. An infrared bulb uses tungsten filament as the radiator, which is sealed in a glass shell filled with inert gas, similar to a general lighting bulb. After the radiator is started, the annealing furnace heats up and then generates a lot of infrared light with a wavelength of 1.2 microns. If the reflective layer is applied to the inner wall of the glass shell, the infrared rays can be concentrated and radiated in one direction, so the lamp-type infrared radiation source is also called a reflective infrared radiator.

Infrared rays have strong penetrating ability and are easily absorbed by objects. Once absorbed by objects, they will be immediately converted into heat energy; infrared radiation heating has small energy loss before and after, is easy to control, has good heating quality, and has broad application prospects.

2. Dielectric heating.

Use high-frequency electric fields to heat insulating materials. The main heating object of electric heaters is electrical dielectrics. In an alternating electric field, the electric heater medium will be repeatedly polarized, and then the electrical energy in the electric field will be converted into thermal energy.

Use high-frequency dielectric heating. In the medium-short wave and ultra-short wave bands, the frequency is between tens and 300MHz, which is called high-frequency dielectric heating, and above 300MHz is called microwave dielectric heating. Usually, high-frequency dielectric heating is carried out under the effect of the electric field between the north and south poles; while microwave dielectric heating is carried out under the radiation field of waveguides, resonators or microwave antennas. Dielectric heating generates heat inside the dielectric (heated object), so compared with other external heating, it has a fast heating speed, high thermal efficiency, and uniform heating.

Dielectric heating can be used in industry to add thermal gel, dry grains, paper, wood, and other fiber materials; it can also preheat plastics before molding, vulcanize rubber, and bond wood and plastics.