In the 19th century, the Anglo-German astronomer HERSCHEL demonstrated the existence and the calorific properties of the infrared radiation. In the spectrum of light, the infrared radiation (IR = Infrared = superior) is an electromagnetic radiation with a wavelength superior to that of visible light, hence invisible. He demonstrated that sunlight can transport energy (heat), without contact, across the universe. It is only in contact with the surface of the earth that this energy is transmitted. In scientific language, photons that compose light are said to carry their energy to objects that are exposed to radiation (causing their atoms to agitate).
Everyone can experience this natural phenomenon. Hypothesis: in winter (in the mountains, for example), it is -15° C outside. The sun’s rays reach your face. You feel a sense of well-being and the “felt” temperature is pleasant (20-22° C). A cloud passes by and you no longer benefit from the sun, you are immediately cold. Your face has “used” infrared rays as a source of heat.
The heating by infrared radiation is based entirely on this principle while adapting its use to the field of thermal comfort.
Using a specific heat emitter (carbon, copper or aluminium alloy, quartz, etc.), the electricity is transformed into a thermal infrared radiation identical to that of the sun (not to be confused with the harmful UV rays). This radiation is transmitted in all directions (at 180° angle) in the room and does not heat the ambient air (at least not directly)!
This is essential: it is no longer necessary to heat directly the whole volume of a room to feel the heat.
Conventional heaters heat the cold air on the floor which then ends up on the ceiling once it is heated. Therefore, the heat accumulates gradually on the ceiling and is therefore not homogeneous from the floor to the ceiling, provoking a feeling of discomfort. Moreover, the walls remain cold and accumulate very little energy in contact with the air in perpetual motion.
Diagram illustrating the difference between convection and radiation:
Infrared radiant heaters (far infrared or long infrared) work on an opposite principle. Their radiance (in all directions) is absorbed by the walls, floor, ceiling, furniture, humans, etc… These rays undergo an absorption, a transmission and a reflection (which means they are sent back towards the rest of the room) that varies according to the nature of the materials. The structure of the building, having accumulated this energy, restores it in a homogeneous and slow way throughout the room. The walls are no longer cold, which is essential for a good thermal comfort. In addition, the floor-ceiling temperature gradient is almost eliminated. You do not heat the ceiling unnecessarily anymore.
This simple principle is at the origin of the development and the increasing awareness of electric infrared radiators. The technical advances made in recent years have made it possible to make a very efficient conversion of electricity into radiation. Do not confuse the conventional low-end radiant heaters which radiation level is around 30% (or less depending on the case), with high-end far infrared heaters which awareness is growing.
There are 3 main families of infrared emitters: IR (infrared) of short or close infrared type (IR-A), medium infrared (IR-B), and far infrared (IR-C). The wavelength of the thermal infrared radiation (between 1 μm and 100 μm) will directly determine the application (heating, drying, science, etc.) that it will be use for.
- The close infrared (0.7 to 2-3 μm) are not used for heating (detection).
- The medium infrared (3 to 25 μm) are not used for heating (scientific measures).
- The long or far infrared (20 to 100 μm) are used:
- for the heating of conventional dwellings or commercial premises. The most performant have a range of 4 to 5 meters. We are talking about high power radiation emittance and luminance. The time required to heat a room by radiation is substantially shorter than with conventional heating. See the family of interior radiators DEGXEL.
- for heating at distances of 2 to 3 meters (terraces, verandas, winter gardens, places of worship, libraries, warehouses, yoga room, etc.). Here, only the targeted area – delimited – where we are (= comfort zone) is heated, without contact, on the same principle as the sun. Heating the whole volume of air would be a nonsense from the energy point of view (= impossible to heat the whole volume of a church!). The heating time is minimal, one immediately feels the heat. See the family of covered outdoor radiators DEGXEL.
Infrared have been used for decades in very large applications from domestic to industrial applications: from thermography, through welding, to drying, to infrared vision, scientific analysis, your remote control…, and the heating of course!