Main Classification of Heaters
Classification of Electric Heaters
Electric heaters are appliances that use electrical energy to achieve heating effects. According to the type of heating method, they can be roughly divided into three categories:
1. Electromagnetic heating
Electromagnetic heating generates an alternating magnetic field through electronic circuit board components. When a ferrous container is placed on it, the container surface cuts the alternating magnetic field lines, producing alternating current (i.e., eddy current) in the metal part at the bottom of the container. The eddy current causes the iron atoms at the bottom to move rapidly and irregularly, and the atoms collide and rub against each other to generate heat energy, thus achieving the effect of heating objects [1] . Because the iron container itself generates heat, the thermal conversion rate is particularly high, up to 95%. Induction cookers and induction stoves all use electromagnetic heating technology.
2. Infrared heating
The heat transfer form of infrared is radiation heat transfer, which transmits energy through electromagnetic waves. When far-infrared rays irradiate the object to be heated, part of the rays are reflected back, and part penetrate through. When the wavelength of the emitted far-infrared matches the absorption wavelength of the heated object, the object absorbs the far-infrared, causing the molecules and atoms inside the object to undergo “resonance”——generating strong vibration and rotation, which raises the temperature of the object, achieving the purpose of heating [2] .
3. Resistance heating
A heating method that uses electric current passing through a heating element to release heat to heat the workpiece. Common resistance wire heating, ceramic heaters, resistance coil heating, and quartz tube heating all belong to resistance heating in principle.
Comparison
1. Resistance heating is the most primitive, so its thermal efficiency is the worst, usually only about 70%, with a large amount of heat energy dissipated into the air.
2. Infrared heating is better than resistance heating, but still a large amount of heat is dissipated into the air, though not by the infrared itself, but by the heated object radiating heat into the air.
3. For example, when an electromagnetic heater works, there is an insulation layer wrapping the heated object, and the magnetic field directly heats the object itself through the insulation layer, so the thermal efficiency is the highest, with almost no heat loss, exceeding 95%. Moreover, because the electromagnetic heater heats the object itself, there is no heat transfer loss, and overall energy saving is about 30%-70% compared to resistance heating under the same conditions. Infrared heaters cannot be compared in detail with electromagnetic heating due to their heating characteristics, but based on the temperature emitted, under the same conditions, electromagnetic heating should save more than 20% energy compared to infrared heating.
