Difference between revisions of "Heating element"
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==Composition== | ==Composition== | ||
| − | Heating elements are made from a conductive (though resistive) | + | Heating elements are made from a conductive (though resistive) material—although other materials may be usable, metal is generally preferred. They are usually made from alloys containing primarily either iron or nickel. One of the most common compositions uses [[nichrome]], an alloy of about 80 percent nickel and 20 percent chromium. Nichrome is a resistant conductor, does not oxidize regardless of temperature, has a very high melting temperature (about 2550 °F), and expands very little when heated. For these reasons it is a very good material for heating elements. All other alloys used also must satisfy these basic requirements as well. However, there are many other specific requirements, and resistance must be carefully calibrated.<ref name="explainthatstuff.com"/> |
==Types== | ==Types== | ||
Most heating elements are used for convection heating. In this case, air or fluid is heated directly, at which point it becomes lighter than the surrounding substance and rises, drawing colder atoms/molecules in to take its place by the element. Electric stoves, toasters, coffee makers, heaters, and many other appliances usually use convection. Some devices use a fan or pump to more the heat more quickly. This process is called forced air convection.<ref name="ehow.com">http://www.ehow.com/how-does_4966716_heating-elements-work.html</ref><br /> | Most heating elements are used for convection heating. In this case, air or fluid is heated directly, at which point it becomes lighter than the surrounding substance and rises, drawing colder atoms/molecules in to take its place by the element. Electric stoves, toasters, coffee makers, heaters, and many other appliances usually use convection. Some devices use a fan or pump to more the heat more quickly. This process is called forced air convection.<ref name="ehow.com">http://www.ehow.com/how-does_4966716_heating-elements-work.html</ref><br /> | ||
| − | A less common but often more efficient method uses infrared to heat objects directly, but not air. A specialized heating element is encased in quartz, which seals in the heat it produces. However, it allows infrared radiation to escape. This radiation passes through air with no effect. However, this radiation is converted to heat when it reaches most kinds of solid material. People, furniture, food, and many other objects exposed to it are heated with relatively minimal waste.<ref name="ehow.com" | + | A less common but often more efficient method uses infrared to heat objects directly, but not air. A specialized heating element is encased in quartz, which seals in the heat it produces. However, it allows infrared radiation to escape. This radiation passes through air with no effect. However, this radiation is converted to heat when it reaches most kinds of solid material. People, furniture, food, and many other objects exposed to it are heated with relatively minimal waste.<ref name="ehow.com"/> |
==References== | ==References== | ||
Latest revision as of 22:51, December 8, 2018
A heating element is a device which converts electricity into heat energy using the method of joule (or "resistance") heating. Electricity is run through a specially developed connection, which allows the electric flow, but resists it enough that a significant amount of it is converted to heat.[1]
Heating elements are generally long, curving and often coiled strips. This kind of design allows for enough length to make efficient use of electricity, and enough surface area to release the heat into its environment.
Contents
Uses
Heating elements are used by almost every electronic device which is designed to produce heat. This includes room heaters, electric stoves and ovens, toasters, coffee makers, hot pots, hot plates, and many other such appliances. Even some electronic printers use heating elements. In some rare cases, incandescent lights are used by appliances instead, usually for keeping food warm. In this cases, the filaments are used as heating elements, which in a sense they are. Depending on their purpose, heating elements must be designed differently.
Composition
Heating elements are made from a conductive (though resistive) material—although other materials may be usable, metal is generally preferred. They are usually made from alloys containing primarily either iron or nickel. One of the most common compositions uses nichrome, an alloy of about 80 percent nickel and 20 percent chromium. Nichrome is a resistant conductor, does not oxidize regardless of temperature, has a very high melting temperature (about 2550 °F), and expands very little when heated. For these reasons it is a very good material for heating elements. All other alloys used also must satisfy these basic requirements as well. However, there are many other specific requirements, and resistance must be carefully calibrated.[1]
Types
Most heating elements are used for convection heating. In this case, air or fluid is heated directly, at which point it becomes lighter than the surrounding substance and rises, drawing colder atoms/molecules in to take its place by the element. Electric stoves, toasters, coffee makers, heaters, and many other appliances usually use convection. Some devices use a fan or pump to more the heat more quickly. This process is called forced air convection.[2]
A less common but often more efficient method uses infrared to heat objects directly, but not air. A specialized heating element is encased in quartz, which seals in the heat it produces. However, it allows infrared radiation to escape. This radiation passes through air with no effect. However, this radiation is converted to heat when it reaches most kinds of solid material. People, furniture, food, and many other objects exposed to it are heated with relatively minimal waste.[2]
