Infrared heater
The main applications were in the metal finishing fields, particularly in the curing and drying of paints and lacquers on military equipment.
After World War II the adoption of infrared heating techniques continued but on a much slower basis.
[1][2][3] The most common filament material used for electrical infrared heaters is tungsten wire, which is coiled to provide more surface area.
Low temperature alternatives for tungsten are carbon, or alloys of iron, chromium, and aluminum (trademark and brand name Kanthal).
Containing 8 meters (26 ft) of coiled alloy resistance wire, they emit a uniform heat across the entire surface of the heater and the ceramic is 90% absorbent of the radiation.
As absorption and emission are based on the same physical causes in each body, ceramic is ideally suited as a material for infrared heaters.
Many heat lamps include a red filter to minimize the amount of visible light emitted.
[8] These heaters emit long wave infrared radiation using low watt density ceramic emitters based on carbon fibre technology.
[9] Because the heating elements are at a relatively low temperature, far-infrared heaters do not give emissions and smell from dust, dirt, formaldehyde, toxic fumes from paint-coating, etc.
[10] This has made this type of space heating very popular among people with severe allergies and multiple chemical sensitivity in Europe.
Quartz infrared lamps are used in highly polished reflectors to direct radiation in a uniform and concentrated pattern.
During development of space re-entry vehicles, banks of quartz infrared lamps were used to test heat shield materials at power densities as high as 28 kW/sq ft (300 kW/m2).
[16] In 2000, General Electric launched the first quartz waterproof lamp alongside British infrared heating manufacturer Tansun.
[citation needed] Quartz glass heating elements were originally designed for lighting applications, but when a lamp is at full power less than 5% of the emitted energy is in the visible spectrum.
This form of heating maintains warmth even when a large volume of cold air is suddenly introduced, such as in maintenance garages.
While there will always be some amount of convective heat generated through the process, any introduction of air motion across the heater will reduce its infrared conversion efficiency.
In addition to the dangers of touching the hot bulb or element, high-intensity short-wave infrared radiation may cause indirect thermal burns when the skin is exposed for too long or the heater is positioned too close to the subject.
Individuals exposed to large amounts of infrared radiation (like glass blowers and arc welders) over an extended period of time may develop depigmentation of the iris and opacity of the aqueous humor, so exposure should be moderated.
[20] Nearly all the electrical energy input is converted into infrared radiant heat in the filament and directed onto the target by reflectors.
For practical applications, the efficiency of the infrared heater depends on matching the emitted wavelength and the absorption spectrum of the material to be heated.
On the other hand, some metals absorb only in the short-wave range and show a strong reflectivity in the medium and far infrared.
This makes a careful selection of the right infrared heater type important for energy efficiency in the heating process.
Most plastics and many other materials absorb infrared best in this range, which makes the ceramic heater most suited for this task.
