IN OUTDOOR HEATING
INFRARED RADIATION AND RADIANT HEATING
For internalising the system, which is formed by these two concepts together, it will be fruitful to refer shortly to the nature; in a word the most impressive example in our daily life is the sun.
Sun, spreads all of the ULTRAVIOLE (UV),VISIBLE LIGHT (VL) and INFRARED (IR) radiations that exists in radiation spectrum. We will examine only IR radiation due to our topic.
The IR radiation that is emited by the sun, passes through the atmosphere, which surrounds the earth, and at that moment that it hits the earth surface, it is absorbed and leads to the increase of temperature. Meanwhile, the atmosphere, which IR radiation passed through in, remains cold. Because IR radiations' wave length is out of the wave length, which air will absorb; so air can not absorb infrared radiations and will not cause to the increase of temperature.
This reality, builds up the reason of this statement: "RADIANT HEATING, IT HEATS PEOPLE WITHOUT HEATING THE AIR". In other words, in winter or in spring, the sun, which hides and comes back from the behind of cloud transiently, explains the instant feeling of temperature difference. Or, it can explain the temperature difference between two automobiles; one is under the sun and the other is under the shadow on the same day and at the same area.
As a conclusion, radiant heating brings into use more than 50 % of the useful heat with the technique of infrared radiation. Therefore the key property is; heat goes from the source directly to the point that will be warmed on linear direction without being absorbed by the air. There is no loss of heat.
INFRARED RADIATION CLASSIFICATION
Let's look at the radiation classification according to their wave length and spectrums.
As it shows above, radiation spectrum based on to electromagnetics wave length is classified according to DIN 5031 T.7 as given below:
100-380 nm ULTRAVIOLE
380-780 nm LIGHT, VISIBLE
780-1.000.000 nm INFRARED
As seen on our topic optic spectrum, infrared radiation splits up to three main category. These are:
780-1400 nm Short Infrared/IR-A
1400-3000 nm Medium Infrared/IR-B
3000-1.000.000 nm Long Infrared/IR-C
In infrared radiations, as the wave length goes shorter, it will stay out of the wave length in which the air will absorb. So, radiation intensity, sensible temperature and therefore the percentage of radiant / radiation at source will be much more as that ratio.