Ceramic infrared heater
Ceramic infrared emitters are devices with a ceramic surface that emit electromagnetic radiation in the infrared spectral range ( heat radiation ) that is invisible to humans . Such devices are technical radiation sources; in contrast to natural IR radiation sources such as the sun or fire . The article in question deals with the use of infrared radiation in heating technology . For other applications see infrared radiation.
construction
The ceramic infrared heater consists of an electrical resistance heating conductor that is completely embedded in a suitable ceramic material and has a ceramic surface. The embedding transfers the energy generated by the heating conductor to the surrounding material. This protects the heating conductor from overheating and enables its service life to be extended . The material that is used to embed the heating conductor is electrically non-conductive and should have good emission properties in the desired IR wavelength range. Taking these criteria into account, ceramic IR emitters can be manufactured in different geometries.
Ceramic infrared emitters are therefore bodies in which part of the surface is made of ceramic and is therefore used particularly well as a radiation surface. With ceramic IR emitters there is also the option of positioning a thermocouple in the immediate vicinity of the heating conductor.
In a special design, the heating conductor is embedded directly in the ceramic, which is also the surface. The inventor of this ceramic infrared heater is the Elstein factory. The patent for the basic model of the ceramic screw-in heater was granted on March 24, 1949 (still sometimes called Elstein heater today). At the same time, flat ceramic IR radiators were developed, which made it possible to build large IR heating surfaces. The patent for flat ceramic IR emitters was granted to the Elstein factory on March 8, 1950. In other methods, the heating conductors are embedded in such a way that the heat conduction to the rear is as low as possible.
Applications as a heating element
The IR emitters dealt with here are technical components or devices that, due to their design, are designed to convert as large a proportion of the energy fed into them as possible (electrical current, gas) into heat, and these are predominantly in the form of IR heat radiation via a radiation surface submit; this is in contrast to convection heaters, in which the air flowing past is heated, which then transports the heat into the environment.
Regardless of the design of the IR radiator, the aim is always to supply the heat radiation emitted by the IR radiator and which propagates in waves, independently of a transport medium, to the material to be heated with as little loss as possible. It should be noted that the IR emitter - depending on its technical design - emits its radiation in a certain wavelength range (spectral range). The emitted spectral range is described by Planck's law of radiation . This always has a wavelength with the radiation maximum which, according to Wien's displacement law, is indirectly proportional to the temperature. When used as IR heating in living areas, the surface temperature is 40 to 80 ° C, in heated cabins and in industrial areas a few hundred degrees Celsius. Depending on this, the radiation power maximum results from 2 to 9 µm.
Effects on the illuminated body
Because of the different atomic structure of goods to be heated, they differ in terms of the spectral range within which they can best absorb the emitted radiation. Radiation components that they cannot absorb due to the material are passed through the material or reflected from it.
The absorption of the IR radiation by the material to be heated is called absorption. The absorption process on the material to be heated is therefore always (partly) a process that is accompanied by reflection and transmission of the IR radiation.
Humans as warming goods perceive radiant warmth as extremely pleasant, especially when it comes from the front, from the side or diagonally from above. For use in infrared cabins, high temperatures over a small area and visible radiation are desirable.
In private apartments, heating panels can be larger, but must be inconspicuous. The surface temperature must be so low that touching it does not cause any burns. Compared to wall heating, ceramic infrared heaters have the advantages of lower losses in the walls and the elimination of installation work. The heating panels are also heated up more quickly and are therefore particularly suitable when the heating effect is not constantly required, for example in bathrooms. Due to the higher proportion of radiation compared to heating based on air convection, less heating energy is required for the same well-being. Compared to tiled stoves with comparable living comfort, the purchase is much cheaper and no operation is required, but the long service life is comparable.
literature
- Heinz M. Hiersig (Hrsg.): VDI-Lexikon Energietechnik . Springer-Verlag Berlin-Heidelberg GmbH, Berlin 1994, ISBN 3-642-95749-8 .
- Carl Kramer (Hrsg.): Practical manual thermoprocess technology . Volume 1, Basics - Process, Vulkan Verlag, Essen 2002, ISBN 3-8027-2922-6 .
- Herbert Pfeifer (Hrsg.): Pocket book industrial heat technology . Basics - Calculations - Methods, 4th edition, Vulkan Verlag, Essen 2007, ISBN 978-3-8027-2937-9 .