An infrared heater or heat lamp is a body with a higher temperature that transfers energy to the body with lower temperatures through electromagnetic radiation. Depending on radiating body temperature, the infrared radiation peak wavelength ranges from 780 nm to 1 mm. No contact or media between the two bodies is required for energy transfer. The infrared heater can be operated in a vacuum or atmosphere.
One classification of infrared heaters is by infrared wavelength infrared band.
- Shortwave or near infrared for the range from 780Ã, nm to 1400Ã, nm , this transmitter is also named bright because there is still visible light emitted;
- Infrared medium for range between 1400Ã, nm and 3000Ã, nm ;
- Remote or dark infrared transmitter for everything above 3000Ã, nm .
Video Infrared heater
Histori
German-British astronomer Sir William Herschel is credited with the invention of the infrared in 1800. He devised a device called a spectrometer to measure the magnitude of the radiation forces at different wavelengths. This tool is made of three parts. The first is a prism to capture the sunlight and direct and spread the color to the table, the second is a small cardboard panel with a gap that is wide enough for just one color to pass through and ultimately, three mercury-in-glass thermometers. Through his experiment Herschel found that red light had the highest temperature change rate in the light spectrum, however, infrared heating was not commonly used until World War II. During World War II infrared heating became more widely used and recognized. The main applications are in the field of metal finishing, especially in drying and drying paints and lacquers on military equipment. Bank lamp lamps used very successfully but according to current standards, power intensity is very low. This technique offers a much faster drying time than the convection fuel oven at the time. Production bottlenecks are reduced and military supplies to the armed forces are maintained. After World War II, the application of the infrared heating technique continued but much slower. In the mid-1950s the motor vehicle industry began to show interest in infrared capability for cat curing and a number of infrared tunnel production lines began to be used.
Maps Infrared heater
Element
The most common filamentary material used for electric infrared heaters is the tungsten wire, which is rolled to provide more surface area. The low temperature alternatives to tungsten are carbon, or iron, chromium, and aluminum alloys (trademarks and brand names Kanthal ). While carbon filaments are more volatile to produce, they heat faster than comparable wave heats based on FeCrAl filaments.
When light is unwanted or not needed in a heater, infrared ceramic radiation heaters are the preferred choice. Contains 8 meters of circular alloy wire resistance, they radiate uniform heat across the heating surface and the ceramic is 90% absorbent of radiation. Because absorption and emissions are based on the same physical cause in every body, ceramics are particularly suitable as materials for infrared heaters.
Industrial infrared heaters sometimes use a golden layer on a quartz tube that reflects infrared radiation and directs it toward the product to be heated. As a result, the infrared radiation that affects this product is almost twice that. Gold is used because of the high oxidation resistance and infrared reflectivity around 95%.
Type
Infrared heaters are typically used in infrared modules (or transmitter banks) that combine multiple heaters to reach a larger heat area.
The infrared heater is usually classified by the wavelength it emits:
Near infrared (NIR) or short-wave infrared heaters operate at high filament temperatures above 1800Ã, Â ° C and when arranged in the field reaches high power densities of several hundreds of kW/m 2 . Its peak wavelength is well below the absorption spectrum for water, making it unsuitable for many drying applications. They are particularly suitable for silica heating where deep penetration is required.
The medium-wave and carbon infrared heater (CIR) operates at a filament temperature of approximately 1000Ã, Â ° C . They achieve maximum power density up to 60 kW/m 2 (medium wave) and 150 kW/m 2 ( CIR).
Remote infrared transmitters (FIRs) are commonly used in so-called low temperature far infrared saunas. This is just a higher and more expensive range of the infrared sauna market. Instead of using carbon, quartz or high wattage ceramic producers, which emit near and medium infrared radiation, heat and light, the far infrared transmitter uses low wattage ceramic plates that remain cool, while still emitting far infrared radiation.
The relationship between temperature and peak wavelength is expressed by the law of Wien displacement.
Metal wire elements
The metal wire heating element first appeared in the 1920s. These elements consist of wires made of chromel. Chromel is made of nickel and chrome and is also known as nikrom. This wire is then rolled into a spiral and wrapped around a ceramic body. When heated to high temperatures, this forms a protective layer of chromium-oxide that protects the wire from combustion and corrosion, this also causes the element to shine.
Hot light
The heat lamp is an incandescent bulb used for the main purpose of creating heat. The black body radiation spectrum emitted by the lamp is shifted to produce more infrared light. Many hot lights include red filters to minimize the amount of emitted visible light. The heat lamp often includes an internal reflector.
Heat lamps are usually used in bathrooms and showers for warm showers and in the food preparation area of ​​the restaurant to keep the food warm before serving. They are also commonly used for farms. The lights used for poultry are often called reflective lights. In addition to young birds, other types of animals that can utilize heat lamps include reptiles, amphibians, insects, arachnids, and young from some mammals.
Sockets used for heat lamps are usually ceramic because plastic sockets can melt or burn when exposed to a large amount of waste heat generated by the lamp, especially when operated in a "basing" position. Shrouds or lamp shades are generally made of metal. There may be a wire shield on the front of the shroud, to prevent touching the surface of a hot bulb.
Common white household incandescent lamps can also be used as heat lamps, but red and blue lights are sold for use in headlamps and reptile lamps. 250 Watt heat lamps are generally packed in "R40" (5 "reflector lights) form factor with intermediate screw base.
The heat lamp can be used as a medical treatment to provide dry heat when other treatments are ineffective or impractical.
Ceramic infrared heat system
Ceramic infrared heating elements are used in a variety of industrial processes where long-wave infrared radiation is required. Reachable wavelength is 2-10 Âμm. They are often used in the field of animal/pet health as well. Ceramic infrared heater (emitter) is manufactured with three basic emitter faces: trough (concave), flat, and bulb or Edison screw element for normal installation through E27 ceramic lamp holder.
Far-infrared
This heating technology is used in some expensive infrared saunas. It was also found in the space heater. These heaters use low-density wattage emitters (usually large panels) that emit long-wave infrared radiation. Since heating elements are at relatively low temperatures, far infrared heaters do not emit and smell from dust, dirt, formaldehyde, toxic fumes from paint coating, etc. This has made this type of heating room very popular among people with severe allergies and some chemical sensitivities in Europe. Because far infrared technology does not heat the room air directly, it is important to maximize the exposure of the available surfaces which then re-radiate warmth to provide even ambient warmth.
Quartz heat lamp
Halogen lamps are incandescent lamps filled with high pressure inert gas. This gas is combined with a small amount of halogen gas (bromine or iodine) which causes the tungsten atoms to regenerate by reducing filament evaporation. This leads to halogen lamp life longer than the incandescent bulb. Due to the high pressure and halogen temperature temperatures it produces, they are relatively small and made of quartz glass because it has a higher melting point than standard glass. Common use for halogen lamps is table heaters.
The quartz infrared heater element emits medium wave infrared energy and is highly effective in systems where rapid heating responses are required. The tubular infrared lamps in quartz lamps produce infrared radiation in the 1.5-8 Âμm wavelength. Closed filaments operate around 2500Ã, K , producing radiation with shorter wavelengths than open-coil wire sources. Developed in 1950 at General Electric, these lamps produce about 100 W/in ( 4Ã, W/mm ) and can be combined to transmit 500 watts per square foot ( 5400 W/m 2 ). To achieve a higher power density, a halogen lamp is used. Quartz infrared lamps are used in very fine reflectors for direct radiation in a uniform and concentrated pattern.
Quartz heat lamps are used in food processing, chemical processing, paint drying, and liquefaction of frozen materials. They can also be used for convenient heating in cold areas, in incubators, and other applications for heating, drying, and burning. During the development of re-entry space vehicles, the quartz infrared light bank was used to test the heat shield material at a power density as high as 28 kilowatts/square foot (300 kW/m 2 ).
The most common design consists of a milky quartz white or quartz glass tube with an electrically resistant element, usually a tungsten wire, or a thin coil of iron-chromium-aluminum alloy. The atmospheric air is removed and filled with inert gas such as nitrogen and argon then sealed. In a quartz halogen lamp, a small amount of halogen gas is added to extend the operating life of the heater.
Most of the infrared energy and visible energy released are caused by direct heating of the quartz material, 97% of the near infrared is absorbed by the silica quartz glass tube causing the tube wall temperature to rise, this causes the silicon-oxygen bond. to emit far infrared rays. Quartz glass heating elements are initially designed for lighting applications, but when full-power lights are less than 5% of the emitted energy is in the visible spectrum.
Tungsten quartz
The quartz tungsten infrared heater emits medium wave energy reaching operating temperature up to 1500 Â ° C (medium wave) and 2600 Â ° C (shortwave). They reach the operating temperature in seconds. Peak wavelength emissions are about 1.6 Âμm (infrared medium wave) and 1 Âμm (infrared shortwave).
Carbon Heaters
Carbon heaters use carbon fiber heating elements capable of generating long, medium and short far infrared heat waves. They need to be accurately determined for the space to be heated.
Gas-fired
There are two basic types of infrared radiation heating.
- Luminous or high intensity
- The radiant tube heater
Radiant tubes of gas-fired heaters are used for space heaters and commercial buildings that burn natural gas or propane to heat the steel emitter tubes. The gas that passes through the control valve flows through the cup burner or venturi. The gas combustion product heats the emitter tube. As the tube heats up, radiation energy from the tube strikes the floor and other objects in the area, warming it up. This warming form maintains warmth even when large volumes of cold air suddenly appear, as in the maintenance garage. However, they can not fight the cold draft.
The efficiency of infrared heaters is a rating of the total energy consumed by the heater compared to the amount of infrared energy produced. Although there will always be some convective heat generated through the process, any introduction of air movement in the heater will reduce the efficiency of infrared conversion. With the new non-stained reflector, the luminous tube has a downward emission efficiency of about 60%. (The other 40% consists of irreversible radiant and convective losses, and stack losses.)
Health effects
In addition to the danger of touching the ball or heat element, short-wave infrared high intensity radiation can 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 (such as glass blowers and arc welders) over a long period of time can develop iris depression and aqueous humor opacity, so exposure should be moderated.
Efficiency
Electrically heated infrared heaters emit up to 86% of their inputs as radiant energy. Almost all the electrical energy inputs are converted into infrared radiation heat in the filament and directed to the target by the reflector. Some heat energy is removed from the heating element by conduction or convection, which may be no loss at all for some designs where all electrical energy is desired in the heat chamber, or can be considered a disadvantage, in situations where only desired heat transfer radiation is desired or productive.
For practical applications, the efficiency of infrared heaters depends on matching the wavelength emitted and the absorption spectrum of the material to be heated. For example, the absorption spectrum for water has a peak around 3000Ã, nm . This means that emissions from infrared microwave or infrared heating medium are much better absorbed by water and water-based coatings than NIR or shortwave infrared radiation. The same goes for many plastics like PVC or polyethylene. Their peak absorption is about 3500Ã, nm . On the other hand, some metals only absorb in the shortwave range and exhibit strong reflectivity in the medium and far infrared. This makes choosing the right type of infrared heater very important for energy efficiency in the heating process.
The ceramic elements operate at temperatures of 300 to 700 ° C (570 to 1,290 ° F) resulting in infrared wavelengths in the range 2000 to 10 000 Ã, nm . Most plastics and many other materials absorb the best infrared in this range, which makes ceramic heaters best suited for this task.
Apps
IR heaters can meet various heating requirements, including:
- The temperature is very high, largely limited by the emitter's maximum temperature
- Quick response time, in sequence of 1-2 seconds
- Temperature gradient, especially on material nets with high heat input
- The hot areas are focused relative to convective and convective heating methods
- Non-contact, so as not to interfere with the product as a conductive or convective heating method do
Thus, IR heating is applied for many purposes including:
- Heating system
- Healing layers
- Plastic shrink
- Plastic heating before form
- Plastic welding
- Glass & amp; hot metal cure
- Cooking
- Heating of mammals or captive animals at zoos or animal clinics
References
Further reading
- Deshmukh, Yeshvant V.: Industrial Heaters, Principles, Techniques, Materials, Applications, and Design . Taylor and Francis, Boca Raton, Fl.: 2005.
- Siegel, Robert and Howell, John R.: Heat Transfer Thermal Radiation . Ed 3rd. Taylor and Francis, Philadelphia.
Source of the article : Wikipedia
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