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Quartz glass infrared emitters frequently prove superior to conventional heating sources such as warm air, steam, ceramic, gas or metal emitters, because they transfer large amounts of energy very quickly and can be precisely matched to the product and the manufacturing step –
the ideal heating process.
n Infrared radiation requires neither contact nor intermediate transfer medium
n Quartz glass infrared emitters are precisely matched to the materials to be heated
n Fast response times allow controllable heat
n Heat is applied precisely where and only for so long as
it is required
Compared for example to warm air heating, this often means less energy consumption, higher line speed, a smaller footprint and better heating results.
To achieve successful process heating, it is important that the infrared emitter is carefully matched to the properties of the product to be heated in terms of its wavelength,
its shape and its power output. Radiation which precisely matches the absorption characteristics of the product is quickly converted into heat in the product, without unnecessary heat being transferred to the surroundings. It also saves time and money if products can be transferred quickly for further processing after the heating stage.
The correct wavelength
Depending on the temperature of the heating element, an infrared emitter delivers distinctly different radiation at various wavelengths.
It is important to select the correct emitter for the product, as the wavelength has a signiicant inluence on the heating process. Short wave radiation can penetrate deep into some solid materials and ensure a uniform through heating. Medium wave radiation is absorbed mostly in the outer surface and predominantly heats the surface. Medium wave radiation is particularly well absorbed by many plastics, glass and especially water and is converted directly into heat.
Proportion of heat
600 °C
900 °C 1200 °C 1600 °C 2200 °C 2700 °C 3000 °C
< 2μm
2,2% 13,0 % 26,1 % 43,2 % 62,5 % 73,3 % 77,9 %
2–4μm
37,2 % 46,4 % 46,9 % 40,1 % 28,7 % 21,0 % 17,6 %
> 4μm
60,6 % 40,6 % 27,0 % 16,7 %
8,8 % 5,7 % 4,5 %
Typical emitter
Ceramic/Metal Sheathed Standard Medium Wave Carbon
Fast Response Medium Wave Short Wave
Halogen/NIR
High Powered Halogen/NIR
Correct selection of heaters
If the temperature of the heating element of a short wave emitter is greatly reduced, medium wave infrared radiation can be emitted. However, the emitter power output then drops so much that economical heating is no longer possible. Consequently,
for applications in the medium wave range, only medium wave emitters should be used, as these offer ive times the power out put at the same temperature.
Radiation power (relative units)
250 200 150 100 50
UV
short wave
Halogen/NIR
2600 °C
0 1 2 3
wavelength (μm)
short wave
2200 °C
fast response medium
Spectral radiation curves for different infrared emitters, normalised to the same power.
medium w
1600 °C
carbon
1200 °C
ave
wave
long wave
medium wave
900 °C
Absorption (%)
100 50
short wave
0 1 2 3 wavelength (μm)
Plastics such as polyethylene and polyvinylchloride are particularly good absorbers of infrared radiation in the medium wave region.
medium wave
900 °C
Polyethylen 0,1 mm
PVC 0,02
2200 °C
short wave
medium wa
900 °C
Water evaporates more quickly with medium wave infrared emitters as water absorbs radiation particularly well in this region.
ve
mm
Absorption (%)
100 50
2200 °C
0 1 2 3 wavelength (μm)
water
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Visible light