Infrared heater: Difference between revisions

An '''infrared heater''' or '''heat lamp''' is a bodyheating withappliance containing a higher high-temperature whichemitter that transfers energy to a bodycooler with a lower temperatureobject through electromagnetic radiation. Depending on the temperature of the emitting bodyemitter, the wavelength of the peak of the [[infrared radiation]] ranges from {{val|780750|uul=nm}} to 1 mm. No contact or medium between the twoemitter and cool bodiesobject is needed for the energy transfer. Infrared heaters can be operated in [[vacuum]] or atmosphere.

One classification of infrared heaters is by the [[wavelength]] bands of infrared emission.

* Short wave or near infrared for the range from {{val|780750|uul=nm}} to {{val|1.4|uul=μm}},; these emitters are also named "bright" because still some visible light is emitted;

The most common filament material used for electrical infrared heaters is [[tungsten]] wire, which is coiled to provide more surface area. Low temperature alternatives for tungsten are [[carbon]], or alloys of [[iron]], [[chromium]], and [[aluminum]] ([[trademark]] and brand name ''[[Kanthal (alloy)|Kanthal]]''). While carbon filaments are more fickle to produce, they heat up much more quickly than a comparable medium-wave heater based on a FeCrAl filament.

When light is undesirable or not necessary in a heater, ceramic infrared radiant heaters are the preferred choice. Containing {{Convert|8 meters|m|ft|abbr=out|sp=us}} of coiled alloy resistance wire, they emit a uniform heat across the entire surface of the heater and the ceramic is 90% absorbent of the radiation. As absorption and emission are based on the same physical causes in each body, ceramic is ideally suited as a material for infrared heaters.

Industrial infrared heaters sometimes use a [[gold]] coating on the [[quartz]] tube that reflects the infrared radiation and directs it towards the product to be heated. Consequently, the infrared radiation impinging on the product is virtually doubled. Gold is used because of its oxidation resistance and very high infrared reflectivity of approximately 95%.<ref>[http://www.tvu.com/PNextGenTFWeb.html Next Generation Transparent Furnace], Dr. Stephen C. Bates</ref>

Near infrared (NIR) or short-wave infrared heaters operate at high filament temperatures above {{valconvert|1800|u°C|lk=on|abbr=degCon}} and when arranged in a field reach high power densities of some hundreds of kW/m{{sup|2}}. Their peak wavelength is well below the absorption spectrum for water, making them unsuitable for many drying applications. They are well suited for heating of silica where a deep penetration is needed.

Medium-wave (MWIR) and carbon (CIR) infrared heaters operate at filament temperatures of around {{valconvert|1000|u°C|abbr=degCon}}. They reach maximum power densities of up to {{valConvert|60|u=kW/m{{supm2|2}}kW/ft2|lk=on|abbr=on}} (medium-wave) and {{valConvert|150|u=kW/m{{supm2|2}}kW/ft2|abbr=on}} (CIRcarbon).

[[Far infrared]] emitters (FIR)<ref>[https://yandiya.com.au/pages/what-is-far-infrared-heating WHAT IS FAR INFRARED HEATING (FIR)]</ref> are typically used in the so-called low-temperature far [[infrared sauna]]s. These constitute only the higher and more expensive range of the market of infrared sauna. Instead of using carbon, quartz or high watt ceramic emitters, which emit near and medium infrared radiation, heat and light, far infrared emitters use low watt ceramic plates that remain cold, while still emitting far infrared radiation.

Metal wire [[heating element]]s first appeared in the 1920s. These elements consist of wire made from chromel. [[Chromel]] is made from [[nickel]] and [[chromium|chrome]] and it is also known as [[nichrome]]. This wire was then coiled into a spiral and wrapped around a ceramic body. When heated to high temperatures it forms a protective layer of [[chromium- oxide]] which protects the wire from burning and corrosion, this alsoand causes the element to glow.<ref>Primer of Lamps and Lightning; Willard Allphin, P.E.; Addison-Wesley Publishing Company, third edition 1973; {{ISBN|0-201-00170-5}}</ref>

Ordinary household white incandescent bulbs can also be [[Heatball|used as heat lamps]], but red and blue bulbs are sold for use in brood lamps and reptile lamps. 250- [[watt]] heat lamps are commonly packaged in the "R40" (5" reflector lamp) form factor with an intermediate screw base.

This heating technology is used in some expensive infrared saunas. It is also found in energy efficient space heaters. They are usually fairly big flat panels that are placed on walls, ceilings<ref>{{Cite web |last=Williams |first=Dawn |date=2017-11-02 |title=Where Should I Place My Infrared Heater? |url=https://www.infraredheatersdirect.co.uk/news/where-should-i-place-my-infrared-heater/ |access-date=2022-09-18 |website=Advice Centre |language=en-GB |archive-date=2020-10-31 |archive-url=https://web.archive.org/web/20201031044229/https://www.infraredheatersdirect.co.uk/news/where-should-i-place-my-infrared-heater/ |url-status=dead }}</ref> or integrated in floors.<ref>{{Cite web |title=Infrared Underfloor Heating |url=https://www.eco-world-northeast.com/product-range/infrared-underfloor-heating/ |access-date=2022-09-18 |website=Eco World Northeast Limited |language=en-GB}}</ref> These heaters useemit long wave infrared radiation using low watt density ceramic emitters (usuallybased fairlyon bigcarbon panels)fibre whichtechnology. emitMore longefficient wavedesigns infrareduse radiationcarbon crystals, a combination of carbon fibre, integrated with nanotechnology, transforming carbon into nanometer form.<ref>{{Cite web |title=Infrared Panels NZ |url=https://infraredpanels.co.nz/the-green-technology-behind-far-infrared-heating |access-date=2022-09-18 |website=Infrared Panels NZ |language=en}}</ref> Because the heating elements are at a relatively low temperature, far-infrared heaters do not give emissions and smell from dust, dirt, formaldehyde, toxic fumes from paint-coating, etc.<ref>{{Cite web |title=Advantages of Infrared Heat Panels |url=https://www.tansun.com/gb_en/blog/advantages-of-infrared-heat-panels.html |access-date=2024-05-08 |website=www.tansun.com}}</ref> This has made this type of space heating very popular among people with severe allergies and [[multiple chemical sensitivity]] in Europe.<ref>{{Cite book |last=Shah |first=Yatish T. |url=https://books.google.com/books?id=QdArDwAAQBAJ&dq=far+infrared+heating+allergies&pg=PT818 |title=Thermal Energy: Sources, Recovery, and Applications |date=2018-01-12 |publisher=CRC Press |isbn=978-1-315-30593-6 |language=en}}</ref> Because far infrared technology does not heat the air of the room directly, it is important to maximize the exposure of available surfaces which then re-emit the warmth to provide an even all round ambient warmth. This is known as radiant heating.<ref>{{Cite webjournal |last1=Wilson |first1=Cathal |last2=McGranaghan |first2=Gerard |date=2014-03-01 |title=Infrared heating comes of age |url=https://yandiyawww.comsciencedirect.aucom/blogsscience/infrared-heatersarticle/best-way-to-heat-our-home-this-winterpii/S0034361714701092 |titlejournal=BestReinforced Way To HeatPlastics Your Home This Winter|lastvolume=58 |firstissue=2 |datepages=|website=Yandiya43–47 Australia|languagedoi=en|archive10.1016/S0034-url=|archive3617(14)70109-date=2 |access-dateissn=2019-050034-163617}}</ref>

Halogen lamps are [[incandescent lamps]] filled with highly pressurized [[inert gas]] combined with a small amount of [[halogen]] gas ([[bromine]] or [[iodine]]); this lengthens the life of the filament (see {{crossrefcrossreference|[[Halogen_lampHalogen lamp#Halogen_cycleHalogen cycle]]}}). This leads to a much longer life of halogen lamps than other incandescent lamps. Due to the high pressure and temperature halogen lamps produce, they are relatively small and made out of [[quartz glass]] because it has a higher melting point than standard glass. Common uses for halogen lamps are table top heaters.<ref>Heat-dissipating Light Fixture for Use with Tungsten-halogen Lamps. Allen R. Groh, assignee. Patent 4780799. 25 Oct. 1988. Print.</ref><ref>Schmidt, F. "Modelling of Infrared Heating of Thermoplastic Sheet Used in Thermoforming Process." Journal of Materials Processing Technology 143-144 (2003): 225-31. Print.</ref>

Quartz infrared heating elements<ref>{{Cite web |title=Quartz Heating and How it Works {{!}} Tansun |url=https://www.tansun.com/gb_en/technical/how-quartz-heating-works.html |access-date=2024-05-08 |website=www.tansun.com}}</ref> emit medium wave infrared energy and are particularly effective in systems where rapid heater response is required. Tubular infrared lamps in quartz bulbs produce infrared radiation in wavelengths of 1.5–8&nbsp;μm. The enclosed filament operates at around {{valConvert|2500|u=K|°C °F}}, producing more shorter-wavelength radiation than open wire-coil sources. Developed in the 1950s at [[General Electric]], these lamps produce about {{valConvert|100|u=W/in}} ({{val|4|u=W/mm|0|abbr=out}}) and can be combined to radiate 500 watts per square foot ({{valConvert|5400500|W/ft2|u=W/m2|abbr=out}}).{{Citation needed|date=September 2021}} To achieve even higher power densities, [[halogen lamp]]s were used. Quartz infrared lamps are used in highly polished reflectors to direct radiation in a uniform and concentrated pattern.

Quartz heat lamps are used in food processing, chemical processing, paint drying, and thawing of frozen materials. They can also be used for comfort heating in cold areas, in incubators, and in other applications for heating, drying, and baking. During development of space re-entry vehicles, banks of quartz infrared lamps were used to test heat shield materials at power densities as high as {{Convert|28&nbsp;kilowatts|kW/square foot (300&nbsp;ft2|kW/m²)m2|abbr=on}}.<ref>Raymond Kane, Heinz Sell ''Revolution in lamps: a chronicle of 50 years of progress (2nd ed.)'', The Fairmont Press, Inc. 2001 {{ISBN|0-88173-378-4}} chapter 3</ref> In 2000, General Electric launched the first quartz waterproof lamp alongside British infrared heating manufacturer Tansun.<ref>{{Cite web |title=History of Tansun {{!}} Infrared Space Heater Manufacturer |url=https://www.tansun.com/gb_en/about-us/about-history.html |access-date=2024-05-08 |website=www.tansun.com}}</ref>

The majority of the [[radiant energy]] released at operational temperatures is transmitted through the thin quartz tube but some of that energy is absorbed by the silica quartz glass tube causing the temperature of the tube wall to increase, this causes the [[silicon-oxygen bond]] to radiate far infrared rays.{{citation needed|date=March 2015}} Quartz glass heating elements were originally designed for lighting applications, but when a lamp is at full power less than 5% of the emitted energy is in the visible spectrum.<ref>[http://www.fsec.ucf.edu/en/research/solarthermal/solar_cooker/documents/reflectivematerialsreport.pdf Investigation of Reflective Materials for the Solar Cooker]</ref>

Quartz tungsten infrared heaters emit medium wave energy reaching [[operating temperature]]s of up to {{valconvert|1500|u°C|abbr=degCon}} (medium wave) and {{valconvert|2600|u°C|abbr=degCon}} (short wave). They reach operating temperature within seconds. Peak wavelength emissions of approximately 1.6&nbsp;μm (medium wave infrared) and 1&nbsp;μm (short wave infrared).

Radiant tube gas-fired heaters used for industrial and commercial building space heating burn [[natural gas]] or [[propane]] to heat a steel emitter tube. Gas passing through a control [[valve]] flows through a [[cup burner]] or a [[Venturi tube|venturi]]. The combustion product gases heat the emitter tube. As the tube heats, radiant energy from the tube strikes floors and other objects in the area, warming them. This form of heating maintains warmth even when a large volume of cold air is suddenly introduced, such as in maintenance [[Automobile repair shop|garages]]. They cannot however, combat a cold draught.

In addition to the dangers of touching the hot bulb or element, high-intensity short-wave infrared radiation may 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 (like glass blowers and arc welders) over an extended period of time may develop depigmentation of the [[Iris (anatomy)|iris]] and opacity of the [[aqueous humor]], so exposure should be moderated.<ref>{{cite web |url=http://www.goaskalice.columbia.edu/0753.html |title=Infrared heat lamps |website=www.goaskalice.columbia.edu |access-date=11 January 2022 |archive-url=https://web.archive.org/web/20060220181822/http://www.goaskalice.columbia.edu/0753.html |archive-date=20 February 2006 |url-status=dead|date =22 December 1995}}</ref>

Electrically- heated infrared heaters radiate up to 86% of their input as radiant energy.<ref>''2008 ASHRAE Handbook – Heating, Ventilating, and Air-Conditioning Systems and Equipment (I-P Edition)'', American Society of. Heating, Refrigerating and Air-Conditioning Engineers, Inc., 2008, Electronic {{ISBN|978-1-60119-795-5}}, table 2 page 15.3</ref> Nearly all the electrical energy input is converted into infrared [[radiative heat transfer|radiant heat]] in the filament and directed onto the target by reflectors. Some heat energy is removed from the heating element by [[Conduction (heat)|conduction]] or [[ConvectiveConvection (heat transfer)|convection]], which may be no loss at all for some designs where all of the electrical energy is desired in the heated space, or may be considered a loss, in situations where only the radiative heat transfer is desired or productive.

For practical applications, the efficiency of the infrared heater depends on matching the emitted wavelength and the absorption spectrum of the material to be heated. For example, the absorption spectrum for water has its peak at around {{val|3|u=μm}}. This means that emission from medium-wave or carbon infrared heaters is much better absorbed by water and water-based coatings than NIR or short-wave infrared radiation. The same is true for many [[plastics]] like PVC or polyethylene. Their peak absorption is around {{val|3.5|u=μm}}. On the other hand, some metals absorb only in the short-wave range and show a strong reflectivity in the medium and far infrared. This makes a careful selection of the right infrared heater type important for [[energy conversion efficiency|energy efficiency]] in the heating process.<ref>{{citationCite web |title=What is Infared Heating? Types, Comparisons, and Advantages {{!}} Tansun |url=https://www.tansun.com/gb_en/blog/what-is-infrared-heating-and-why-is-it-making-waves.html needed|access-date=March2024-05-08 2015|website=www.tansun.com |language=en}}</ref>

Ceramic elements operate in the temperature of {{convert|300|to|700|°C|°F|-1}} producing infrared wavelengths in the 2 to {{val|10|u=μm}} range. Most plastics and many other materials absorb infrared best in this range, which makes the ceramic heater most suited for this task.<ref>{{Cite web|date=2017-06-25|title=36 Mind Blowing Facts about Infrared Radiation (IR Rays)|url=https://www.infrared-light-therapy.com/infrared-radiation/|access-date=2021-01-24|website=InfraRed Light Therapy|language=en}}</ref>{{citation needed|date=April 2011}}