Discovery of infrared radiation
Types of heat exchange
Physical properties
Range of IR waves favorable for humans
The English researcher Herschel W. in 1800, in the process of studying sunlight, established that in the sun's rays, when they are decomposed into separate spectra using a prism beyond the red visible spectrum, the thermometer readings increase. The thermometer placed in this area showed a higher temperature than the reference thermometer. Later it was established that the properties of these rays are amenable to the laws of optics, and it turns out that they have the same nature as light radiation. Thus, infrared radiation was discovered.
Let's clarify how hot objects give off heat to the objects around them:
heat transfer(heat exchange between bodies upon contact or through a separator),
convection(heat transfer by coolant, liquid or gas from a heat source to colder objects)
thermal radiation(a flow of electromagnetic radiation in a specific wavelength range emitted by a substance based on its internal excess energy).
All objects of the material world around us are sources and at the same time absorbers of thermal radiation.
Thermal radiation, which is based on infrared rays, is a stream of electromagnetic rays that satisfy the laws of optics and have the same nature as light radiation. The IR beam is located between the red light perceived by humans (0.7 µm) and short-wave radio emission (1 - 2 mm). In addition, the IR region of the spectrum is divided into short-wave (0.7 - 2 µm), medium-wave (from 2 to 5.1 µm), long wave(5.1 - 200 µm). Infrared rays are emitted by all substances liquid and solid, while The emitted wavelength depends on the temperature of the substance. At higher temperatures, the wavelength emitted by the substance is shorter, but the radiation intensity is greater.
In the range of long-wave radiation (from 9 to 11 microns) there is the most favorable thermal radiation for humans. Long-wave emitters have a lower radiation surface temperature and are characterized as dark - at low surface temperatures they do not glow (up to 300°C). Medium-wave emitters with a higher surface temperature are characterized as gray; those with maximum body temperature emit short waves, they are called white or light.
Confirmation by Soviet scientists
Physical properties of infrared radiation
For infrared rays there are a number of differences from the optical properties of visible light. (transparency, reflectance, refractive index) For example, IR radiation having a wavelength of more than 1 micron, absorbed by water in a layer of 1-2 cm, so water is in some cases used as a heat-protective barrier. The silicon sheet is opaque in the visible region, but transparent in the infrared. A number of metals have reflex qualities which are higher for infrared radiation than for light perceived by humans, in addition, their properties significantly improve with increasing radiation wavelength. Namely, The reflection index of Al, Au, Ag at a wavelength of about 10 microns approaches 98%. Considering these properties of materials, they are used in the production of infrared equipment. Materials that are transparent to infrared rays - as emitters of infrared radiation (quartz, ceramics), materials with a high ability to reflect rays - as reflectors that allow you to focus IR radiation in the desired direction (mainly aluminum).
It is also important to know about the absorption and scattering properties of infrared radiation. Infrared rays travel through the air almost unhindered. Namely, nitrogen and oxygen molecules themselves do not absorb infrared rays, but only slightly scatter, reducing the intensity. Water vapor, ozone, carbon dioxide, as well as other impurities in the air, absorb infrared radiation: water vapor - in almost the entire infrared region of the spectrum, carbon dioxide - in the middle part of the infrared region. The presence of small particles in the air - dust, smoke, small drops of liquids - leads to a weakening of the strength of infrared radiation as a result of its scattering on these particles.
About infrared radiation
From the history of the study of infrared radiation
Infrared radiation or thermal radiation is not a discovery of the 20th or 21st century. Infrared radiation was discovered in 1800 by an English astronomer W. Herschel. He discovered that the "maximum heat" lies beyond the red color of visible radiation. This study marked the beginning of the study of infrared radiation. Many famous scientists have put their heads into the study of this area. These are names such as: German physicist Wilhelm Wien(Wien's law), German physicist Max Planck(Planck's formula and constant), Scottish scientist John Leslie(thermal radiation measuring device - Leslie cube), German physicist Gustav Kirchhoff(Kirchhoff's radiation law), Austrian physicist and mathematician Josef Stefan and Austrian physicist Stefan Ludwig Boltzmann(Stefan-Boltzmann law).
The use and application of knowledge of thermal radiation in modern heating devices only came to the fore in the 1950s. In the USSR, the theory of radiant heating was developed in the works of G. L. Polyak, S. N. Shorin, M. I. Kissin, A. A. Sander. Since 1956, many technical books on this topic have been written or translated into Russian in the USSR ( bibliography). Due to changes in the cost of energy resources and in the struggle for energy efficiency and energy conservation, modern infrared heaters are widely used in heating domestic and industrial buildings.
Solar radiation - natural infrared radiation
The most famous and significant natural infrared heater is the Sun. Essentially, it is nature's most advanced heating method known to mankind. Within the Solar System, the Sun is the most powerful source of thermal radiation that determines life on Earth. At a solar surface temperature of about 6000K the maximum radiation occurs at 0.47 µm(corresponds to yellowish-white). The sun is located at a distance of many millions of kilometers from us, however, this does not prevent it from transmitting energy through this entire vast space, practically without consuming it (energy), without heating it (space). The reason is that solar infrared rays travel a long way in space and have virtually no energy loss. When any surface is encountered on the path of the rays, their energy, being absorbed, turns into heat. The Earth, which is hit by the sun's rays, and other objects that are also hit by the sun's rays are heated directly. And the earth and other objects heated by the Sun, in turn, give off heat to the air around us, thereby heating it.
Both the power of solar radiation at the earth's surface and its spectral composition most significantly depend on the height of the Sun above the horizon. Different components of the solar spectrum pass through the earth's atmosphere differently. 
At the Earth's surface, the spectrum of solar radiation has a more complex shape, which is associated with absorption in the atmosphere. In particular, it does not contain the high-frequency part of ultraviolet radiation, which is harmful to living organisms. At the outer boundary of the earth's atmosphere, the flux of radiant energy from the Sun is 1370 W/m²; (solar constant), and the maximum radiation occurs at λ=470 nm(blue). The flux reaching the earth's surface is significantly less due to absorption in the atmosphere. Under the most favorable conditions (the sun at its zenith) it does not exceed 1120 W/m²; (in Moscow, at the moment of the summer solstice - 930 W/m²), and the maximum radiation occurs at λ=555 nm(green-yellow), which corresponds to the best sensitivity of the eyes and only a quarter of this radiation occurs in the long-wave region of radiation, including secondary radiation.
However, the nature of solar radiant energy is quite different from the radiant energy given off by infrared heaters used for space heating. The energy of solar radiation consists of electromagnetic waves, the physical and biological properties of which differ significantly from the properties of electromagnetic waves emanating from conventional infrared heaters, in particular, the bactericidal and healing (heliotherapy) properties of solar radiation are completely absent from radiation sources with low temperatures. And yet infrared heaters provide the same thermal effect, as the Sun, being the most comfortable and economical of all possible heat sources.
The nature of infrared rays
Outstanding German physicist Max Planck, while studying thermal radiation (infrared radiation), discovered its atomic nature. Thermal radiation- this is electromagnetic radiation emitted by bodies or substances and arising due to its internal energy, due to the fact that the atoms of a body or substance move faster under the influence of heat, and in the case of a solid material they vibrate faster compared to the equilibrium state. During this movement, atoms collide, and when they collide, they are excited by shock, followed by the emission of electromagnetic waves. 
All objects continuously emit and absorb electromagnetic energy. This radiation is a consequence of the continuous movement of elementary charged particles inside matter. One of the basic laws of classical electromagnetic theory states that a charged particle moving with acceleration emits energy. Electromagnetic radiation (electromagnetic waves) is a disturbance of the electromagnetic field propagating in space, that is, a time-varying periodic electromagnetic signal in space consisting of electric and magnetic fields. This is thermal radiation. Thermal radiation contains electromagnetic fields of different wavelengths. Since atoms move at any temperature, all bodies are at any temperature greater than the temperature of absolute zero (-273°С), emit heat. The energy of electromagnetic waves of thermal radiation, that is, the strength of the radiation, depends on the temperature of the body, its atomic and molecular structure, as well as on the state of the surface of the body. Thermal radiation occurs at all wavelengths - from the shortest to the longest, but only that thermal radiation of practical importance that occurs in the wavelength range is taken into account: λ = 0.38 – 1000 µm(in the visible and infrared parts of the electromagnetic spectrum). However, not all light has the characteristics of thermal radiation (for example, luminescence), therefore, only the infrared spectrum can be taken as the main range of thermal radiation (λ = 0.78 – 1000 µm). You can also make an addition: a section with a wavelength λ = 100 – 1000 µm, from a heating point of view - not interesting.
Thus, thermal radiation is one of the forms of electromagnetic radiation that arises due to the internal energy of the body and has a continuous spectrum, that is, it is part of electromagnetic radiation, the energy of which, when absorbed, causes a thermal effect. Thermal radiation is inherent in all bodies.
All bodies that have a temperature greater than absolute zero (-273°C), even if they do not glow with visible light, are a source of infrared rays and emit a continuous infrared spectrum. This means that the radiation contains waves with all frequencies without exception, and it is completely pointless to talk about radiation at any particular wave.
The main conventional areas of infrared radiation
Today there is no unified classification for dividing infrared radiation into its component areas (areas). In the target technical literature there are more than a dozen schemes for dividing the infrared radiation region into component areas, and they all differ from each other. Since all types of thermal electromagnetic radiation are of the same nature, the classification of radiation by wavelength depending on the effect they produce is only conditional and is determined mainly by differences in detection technology (type of radiation source, type of meter, its sensitivity, etc. .) and in the technique of measuring radiation. Mathematically, using formulas (Planck, Wien, Lambert, etc.), it is also impossible to determine the exact boundaries of the regions. To determine the wavelength (maximum radiation), there are two different formulas (temperature and frequency) that give different results, with a difference of approximately 1,8
times (this is the so-called Wien's displacement law) and plus, all calculations are made for an ABSOLUTELY BLACK BODY (idealized object), which does not exist in reality. Real bodies found in nature do not obey these laws and, to one degree or another, deviate from them. Information was taken by ESSO Company from the technical literature of Russian and foreign scientists" data-lightbox="image26" href="images/26.jpg" title="Expand areas of infrared radiation">!} 
The radiation of real bodies depends on a number of specific characteristics of the body (surface condition, microstructure, layer thickness, etc.). This is also the reason why different sources indicate completely different values for the boundaries of the radiation regions. All this suggests that temperature must be used to describe electromagnetic radiation with great care and with an order of magnitude accuracy. I emphasize once again that the division is very arbitrary!!!
Let us give examples of conditional division of the infrared region (λ = 0.78 – 1000 µm) to individual areas (information taken only from the technical literature of Russian and foreign scientists). The above figure shows how diverse this division is, so you should not get attached to any of them. You just need to know that the spectrum of infrared radiation can be divided into several sections, from 2 to 5. The region that is closer in the visible spectrum is usually called: near, close, short-wave, etc. The region that is closer to microwave radiation is far, far, long-wave, etc. According to Wikipedia, the usual division scheme looks like So: Near area(Near-infrared, NIR), Shortwave region(Short-wavelength infrared, SWIR), Medium wave region(Mid-wavelength infrared, MWIR), Long wavelength region(Long-wavelength infrared, LWIR), Far area(Far-infrared, FIR).
Properties of infrared rays
Infrared rays- This is electromagnetic radiation, which has the same nature as visible light, therefore it is also subject to the laws of optics. Therefore, in order to better imagine the process of thermal radiation, we should draw an analogy with light radiation, which we all know and can observe. However, we must not forget that the optical properties of substances (absorption, reflection, transparency, refraction, etc.) in the infrared region of the spectrum differ significantly from the optical properties in the visible part of the spectrum. A characteristic feature of infrared radiation is that, unlike other main types of heat transfer, there is no need for a transmitting intermediate substance. Air, and especially vacuum, is considered transparent to infrared radiation, although this is not entirely true with air. When infrared radiation passes through the atmosphere (air), some attenuation of thermal radiation is observed. This is due to the fact that dry and clean air is almost transparent to heat rays, but if it contains moisture in the form of steam, water molecules (H 2 O), carbon dioxide (CO 2), ozone (O 3) and other solid or liquid suspended particles that reflect and absorb infrared rays, it becomes a not entirely transparent medium and, as a result, the flow of infrared radiation is scattered in different directions and weakens. Typically, scattering in the infrared region of the spectrum is less than in the visible. However, when the losses caused by scattering in the visible region of the spectrum are large, they are also significant in the infrared region. The intensity of the scattered radiation varies in inverse proportion to the fourth power of the wavelength. It is significant only in the short-wave infrared region and decreases rapidly in the longer wavelength part of the spectrum.
Nitrogen and oxygen molecules in the air do not absorb infrared radiation, but attenuate it only as a result of scattering. Suspended dust particles also lead to scattering of infrared radiation, and the amount of scattering depends on the ratio of particle sizes and wavelength of infrared radiation; the larger the particles, the greater the scattering.
Water vapor, carbon dioxide, ozone and other impurities present in the atmosphere selectively absorb infrared radiation. For example, water vapor very strongly absorbs infrared radiation throughout the entire infrared region of the spectrum, and carbon dioxide absorbs infrared radiation in the mid-infrared region.
As for liquids, they can be either transparent or opaque to infrared radiation. For example, a layer of water several centimeters thick is transparent to visible radiation and opaque to infrared radiation with a wavelength of more than 1 micron.
Solids(bodies), in turn, in most cases not transparent to thermal radiation, but there are exceptions. For example, silicon wafers, opaque in the visible region, are transparent in the infrared region, and quartz, on the contrary, is transparent to light radiation, but opaque to thermal rays with a wavelength of more than 4 microns. It is for this reason that quartz glass is not used in infrared heaters. Ordinary glass, unlike quartz glass, is partially transparent to infrared rays; it can also absorb a significant part of infrared radiation in certain spectral ranges, but does not transmit ultraviolet radiation. Rock salt is also transparent to thermal radiation. Metals, for the most part, have a reflectivity for infrared radiation that is much greater than for visible light, which increases with increasing wavelength of infrared radiation. For example, the reflectance of aluminum, gold, silver and copper at a wavelength of about 10 µm reaches 98% , which is significantly higher than for the visible spectrum, this property is widely used in the design of infrared heaters.
It is enough to give here as an example the glazed frames of greenhouses: glass practically transmits most of the solar radiation, and on the other hand, the heated earth emits waves of long length (about 10 µm), in relation to which glass behaves like an opaque body. Thanks to this, the temperature inside the greenhouses is maintained for a long time, much higher than the temperature of the outside air, even after solar radiation stops.
Radiant heat transfer plays an important role in human life. A person transfers to the environment the heat generated during the physiological process, mainly through radiant heat exchange and convection. With radiant (infrared) heating, the radiant component of heat exchange of the human body is reduced due to the higher temperature that occurs both on the surface of the heating device and on the surface of some internal enclosing structures, therefore, while providing the same warm sensation, convective heat loss may be greater, those. The room temperature may be lower. Thus, radiant heat exchange plays a decisive role in the formation of a person’s feeling of thermal comfort.
When a person is in the range of an infrared heater, IR rays penetrate the human body through the skin, and different layers of the skin reflect and absorb these rays in different ways.
With infrared long wave radiation the penetration of rays is significantly less compared to shortwave radiation. The absorption capacity of moisture contained in skin tissue is very high, and the skin absorbs more than 90% of the radiation reaching the surface of the body. The nerve receptors that sense heat are located in the outermost layer of the skin. The absorbed infrared rays excite these receptors, which causes a feeling of warmth in a person.
Infrared rays have both local and general effects. Shortwave infrared radiation, unlike long-wave infrared radiation, can cause redness of the skin at the site of irradiation, which reflexively spreads 2-3 cm around the irradiated area. The reason for this is that the capillary vessels dilate and blood circulation increases. A blister may soon appear at the radiation site, which later turns into a scab. Also when hit shortwave infrared rays to the organs of vision, cataracts may occur.
The possible consequences of exposure listed above shortwave IR heater, should not be confused with impact long-wave IR heater. As already mentioned, long-wave infrared rays are absorbed at the very top of the skin layer and cause only a simple thermal effect.
The use of radiant heating should not endanger people or create an uncomfortable microclimate in the room.
Radiant heating can provide comfortable conditions at lower temperatures. When using radiant heating, the indoor air is cleaner because the air flow speed is lower, which reduces dust pollution. Also, with this heating, dust decomposition does not occur, since the temperature of the radiating plate of a long-wave heater never reaches the temperature necessary for dust decomposition.
The colder the heat emitter, the more harmless it is for the human body, the longer a person can stay in the heater’s area of effect.
Prolonged stay of a person near a HIGH TEMPERATURE heat source (more than 300°C) is harmful to human health.
Impact of infrared radiation on human health.
How the human body emits infrared rays, and absorbs them. IR rays penetrate the human body through the skin, and different layers of the skin reflect and absorb these rays differently. Long-wave radiation penetrates the human body significantly less compared to shortwave radiation. Moisture in the skin tissue absorbs more than 90% of the radiation reaching the surface of the body. The nerve receptors that sense heat are located in the outermost layer of the skin. The absorbed infrared rays excite these receptors, which causes a feeling of warmth in a person. Short-wave infrared radiation penetrates the body most deeply, causing its maximum heating. As a result of this effect, the potential energy of the body's cells increases, and unbound water will leave them, the activity of specific cellular structures increases, the level of immunoglobulins increases, the activity of enzymes and estrogens increases, and other biochemical reactions occur. This applies to all types of body cells and blood. However Long-term exposure to short-wave infrared radiation on the human body is undesirable. It is on this property that it is based heat treatment effect, widely used in physiotherapy rooms in our and foreign clinics, and note that the duration of procedures is limited. However, the data restrictions do not apply to long-wave infrared heaters. Important characteristic infrared radiation– wavelength (frequency) of radiation. Modern research in the field of biotechnology has shown that it is long-wave infrared radiation is of exceptional importance in the development of all forms of life on Earth. For this reason it is also called biogenetic rays or life rays. Our body radiates itself long infrared waves, but it itself also needs constant feeding long wave heat. If this radiation begins to decrease or there is no constant replenishment of the human body with it, then the body is attacked by various diseases, the person quickly ages against the background of a general deterioration in well-being. Further infrared radiation normalizes the metabolic process and eliminates the cause of the disease, and not just its symptoms.
With such heating, you will not have a headache from the stuffiness caused by overheated air under the ceiling, as when working convective heating, - when you constantly want to open the window and let fresh air in (while letting out heated air).
When exposed to infrared radiation with an intensity of 70-100 W/m2, the activity of biochemical processes in the body increases, which leads to an improvement in the general condition of a person. However, there are standards and they should be followed. There are standards for safe heating of domestic and industrial premises, for the duration of medical and cosmetic procedures, for working in HOT workshops, etc. Don't forget about this. When infrared heaters are used correctly, there is COMPLETELY NO negative impact on the body.
Infrared radiation, infrared rays, properties of infrared rays, radiation spectrum of infrared heaters
INFRARED RADIATION, INFRARED RAYS, PROPERTIES OF INFRARED RAYS, RADIATION SPECTRUM OF INFRARED HEATERS Kaliningrad
HEATERS PROPERTIES RADIATION SPECTRUM OF HEATERS WAVELENGTH LONG WAVE MEDIUM WAVE SHORT WAVE LIGHT DARK GRAY HARM HEALTH IMPACT ON HUMAN Kaliningrad
Infrared (IR) radiation is a type of electromagnetic radiation that occupies the spectral range between visible red light (INFRAred: BELOW red) and shortwave radio waves. These rays create heat and are scientifically known as thermal waves. These rays create heat and are scientifically known as thermal waves.
All heated bodies emit infrared radiation, including the human body and the Sun, which in this way warms our planet, giving life to all life on it. The warmth that we feel from a fire near a fire or fireplace, a heater or warm asphalt is all a consequence of infrared rays.
The entire spectrum of infrared radiation is usually divided into three main ranges, differing in wavelength:
- Short wavelength, with wavelength λ = 0.74-2.5 µm;
- Medium wave, with wavelength λ = 2.5-50 µm;
- Long wavelength, with wavelength λ = 50-2000 µm.
Near or short-wave infrared rays are not hot at all; in fact, we don’t even feel them. These waves are used, for example, in TV remote controls, automation systems, security systems, etc. Their frequency is higher, and accordingly their energy is higher than that of far (long) infrared rays. But not at such a level as to harm the body. Heat begins to be created at mid-infrared wavelengths, and we already feel their energy. Infrared radiation is also called “thermal” radiation, because radiation from heated objects is perceived by the human skin as a sensation of heat. In this case, the wavelengths emitted by the body depend on the heating temperature: the higher the temperature, the shorter the wavelength and the higher the radiation intensity. For example, a source with a wavelength of 1.1 microns corresponds to molten metal, and a source with a wavelength of 3.4 microns corresponds to metal at the end of rolling or forging.
Of interest to us is the spectrum with a wavelength of 5-20 microns, since it is in this range that more than 90% of the radiation produced by infrared heating systems occurs, with a radiation peak of 10 microns. It is very important that it is at this frequency that the human body itself emits infrared waves of 9.4 microns. Thus, any radiation at a given frequency is perceived by the human body as related and has a beneficial and, even moreover, healing effect on it.
With such exposure to infrared radiation on the body, the effect of “resonance absorption” occurs, which is characterized by the body’s active absorption of external energy. As a result, one can observe an increase in a person’s hemoglobin level, an increase in the activity of enzymes and estrogens, and, in general, a stimulation of a person’s vital activity.
The effect of infrared radiation on the surface of the human body, as we have already said, is useful and, on top of that, pleasant. Remember the first sunny days at the beginning of spring, when after a long and cloudy winter the sun finally came out! You feel how it pleasantly envelops the illuminated area of your skin, face, palms. I no longer want to wear gloves and a hat, despite the temperature being quite low compared to the “comfortable” one. But as soon as a small cloud appears, we immediately experience noticeable discomfort from the interruption of such a pleasant sensation. This is the very radiation that we so lacked throughout the winter, when the Sun was absent for a long time, and we, willy-nilly, carried out our “infrared post”.
As a result of exposure to infrared radiation, you can observe:
- Acceleration of metabolism in the body;
- Restoration of skin tissue;
- Slowing down the aging process;
- Removing excess fat from the body;
- Release of human motor energy;
- Increasing the body's antimicrobial resistance;
- Activation of plant growth
and much much more. Moreover, infrared irradiation is used in physiotherapy to treat many diseases, including cancer, as it promotes the expansion of capillaries, stimulates blood flow in the vessels, improves immunity and produces a general therapeutic effect.
And this is not at all surprising, because this radiation is given to us by nature as a way of transmitting heat and life to all living things that need this warmth and comfort, bypassing empty space and air as intermediaries.
In order to understand the principle of operation of infrared emitters, it is necessary to imagine the essence of such a physical phenomenon as infrared radiation.
Infrared range and wavelength
Infrared radiation is a type of electromagnetic radiation that occupies the range from 0.77 to 340 microns in the spectrum of electromagnetic waves. In this case, the range from 0.77 to 15 microns is considered short-wave, from 15 to 100 microns - medium wave, and from 100 to 340 - long-wave.
The short-wave part of the spectrum is adjacent to visible light, and the long-wave part merges with the region of ultrashort radio waves. Therefore, infrared radiation has both the properties of visible light (it propagates in a straight line, is reflected, refracted like visible light) and the properties of radio waves (it can pass through some materials that are opaque to visible radiation).
Infrared emitters with a surface temperature from 700 C to 2500 C have a wavelength of 1.55-2.55 microns and are called “light” - in wavelength they are closer to visible light, emitters with a lower surface temperature have a longer wavelength and are called "dark".
Infrared radiation sources
Generally speaking, any body heated to a certain temperature emits thermal energy in the infrared range of the electromagnetic wave spectrum and can transfer this energy through radiant heat exchange to other bodies. Energy transfer occurs from a body with a higher temperature to a body with a lower temperature, while different bodies have different emissive and absorptive abilities, which depend on the nature of the two bodies, the state of their surface, etc.
Electromagnetic radiation has a quantum-photonic character. When interacting with matter, a photon is absorbed by the atoms of the substance, transferring its energy to them. At the same time, the energy of thermal vibrations of atoms in the molecules of the substance increases, i.e. radiation energy turns into heat.
The essence of radiant heating is that the burner, being a source of radiation, generates, forms in space and directs thermal radiation into the heating zone. It falls on enclosing structures (floors, walls), technological equipment, people in the irradiation zone, is absorbed by them and heats them up. The radiation flux, absorbed by surfaces, clothing and human skin, creates thermal comfort without increasing the ambient temperature. The air in heated rooms, while remaining almost transparent to infrared radiation, is heated due to “secondary heat”, i.e. convection from structures and objects heated by radiation.
Properties and applications of infrared radiation
It has been established that exposure to infrared radiation heating has a beneficial effect on humans. If thermal radiation with a wavelength greater than 2 microns is perceived mainly by the skin with the resulting thermal energy being conducted inside, then radiation with a wavelength of up to 1.5 microns penetrates the surface of the skin, partially heats it, reaches the network of blood vessels and directly increases the temperature of the blood. At a certain intensity of heat flow, its impact causes a pleasant thermal sensation. In radiant heating, the human body releases most of its excess heat by convection to the surrounding air, which has a lower temperature. This form of heat transfer has a refreshing effect and has a beneficial effect on well-being.
In our country, the study of infrared heating technology has been carried out since the 30s, both in relation to agriculture and industry.
Conducted medical and biological studies have made it possible to establish that infrared heating systems more fully meet the specifics of livestock buildings than convective central or air heating systems. First of all, due to the fact that with infrared heating the temperature of the internal surfaces of the fences, especially the floor, exceeds the air temperature in the room. This factor has a beneficial effect on the thermal balance of animals, eliminating intense heat loss.
Infrared systems, working in conjunction with natural ventilation systems, ensure a reduction in relative air humidity to standard values (on pig farms and calf barns to 70-75% and below).
As a result of the operation of these systems, the temperature and humidity conditions in the premises reach favorable parameters.
The use of radiant heating systems for agricultural buildings allows not only to create the necessary microclimate conditions, but also to intensify production. In many farms in Bashkiria (collective farm named after Lenin, collective farm named after Nurimanov), the production of offspring significantly increased after the introduction of infrared heating (increasing farrowing in winter by 4 times), and the safety of young animals increased (from 72.8% to 97.6%).
Currently, the infrared heating system has been installed and has worked for one season at the Chuvash Broiler enterprise in the suburbs of Cheboksary. According to reviews from farm managers, during the period of minimum winter temperatures -34-36 C, the system worked uninterruptedly and provided the required heat for raising poultry for meat (floor housing) for a period of 48 days. They are currently considering the issue of equipping the remaining poultry houses with infrared systems.
In 1800, scientist William Herschel announced his discovery at a meeting of the Royal Society of London. He measured temperatures outside the spectrum and discovered invisible rays with great heating power. He carried out the experiment using telescope filters. He noticed that they absorb light and heat from the sun's rays to varying degrees.
After 30 years, the existence of invisible rays located beyond the red part of the visible solar spectrum was indisputably proven. The French Becquerel called this radiation infrared.
Properties of IR radiation
The spectrum of infrared radiation consists of individual lines and bands. But it can also be continuous. It all depends on the source of the IR rays. In other words, what matters is the kinetic energy or temperature of an atom or molecule. Any element of the periodic table has different characteristics at different temperatures.
For example, the infrared spectra of excited atoms, due to the relative state of rest of the nucleus bundle, will have strictly line IR spectra. And excited molecules are striped and randomly located. Everything depends not only on the mechanism of superposition of the own linear spectra of each atom. But also from the interaction of these atoms with each other.
As the temperature rises, the spectral characteristics of the body change. Thus, heated solids and liquids emit a continuous infrared spectrum. At temperatures below 300°C, the radiation of a heated solid is entirely in the infrared region. Both the study of IR waves and the application of their most important properties depend on the temperature range.
The main properties of IR rays are absorption and further heating of bodies. The principle of heat transfer by infrared heaters differs from the principles of convection or conduction. Being in a flow of hot gases, an object loses some amount of heat as long as its temperature is lower than the temperature of the heated gas.
And vice versa: if infrared emitters irradiate an object, this does not mean that its surface absorbs this radiation. It can also reflect, absorb or transmit rays without loss. Almost always, the irradiated object absorbs part of this radiation, reflects part and transmits part.
Not all luminous objects or heated bodies emit infrared waves. For example, fluorescent lamps or the flame of a gas stove do not have such radiation. The operating principle of fluorescent lamps is based on glow (photoluminescence). Its spectrum is closest to the spectrum of daylight, white light. Therefore, there is almost no IR radiation in it. And the highest intensity of radiation from a gas stove flame occurs at the blue wavelength. The IR radiation of the listed heated bodies is very weak.
There are also substances that are transparent to visible light, but are not capable of transmitting infrared rays. For example, a layer of water several centimeters thick will not transmit infrared radiation with a wavelength greater than 1 micron. In this case, a person can distinguish objects located at the bottom with the naked eye.
