resistance heating


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Related to resistance heating: Electrical resistance heating

resistance heating

[ri′zis·təns ‚hēd·iŋ]
(electricity)
The generation of heat by electric conductors carrying current; degree of heating is proportional to the electrical resistance of the conductor; used in electrical home appliances, home or space heating, and heating ovens and furnaces.

Resistance heating

The generation of heat by electric conductors carrying current. The degree of heating for a given current is proportional to the electrical resistance of the conductor. If the resistance is high, a large amount of heat is generated, and the material is used as a resistor rather than as a conductor.

In addition to having high resistivity, heating elements must be able to withstand high temperatures without deteriorating or sagging. Other desirable characteristics are low temperature coefficient of resistance, low cost, formability, and availability of materials. Most commercial resistance alloys contain chromium or aluminum or both, since a protective coating of chrome oxide or aluminum oxide forms on the surface upon heating and inhibits or retards further oxidation.

Since heat is transmitted by radiation, convection, or conduction or combinations of these, the form of element is designed for the major mode of transmission. The simplest form is the helix, using a round wire resistor, with the pitch of the helix approximately three wire diameters. This form is adapted to radiation and convection and is generally used for room or air heating. It is also used in industrial furnaces, utilizing forced convection up to about 1200°F (650°C). Such helixes are stretched over grooved high-alumina refractory insulators and are otherwise open and unrestricted.

The electrical resistance of molten salts between immersed electrodes can be used to generate heat. Limiting temperatures are dependent on decomposition or evaporization temperatures of the salt, Parts to be heated are immersed in the salt. Heating is rapid and, since there is no exposure to air, oxidation is largely prevented. Disadvantages are the personnel hazards and discomfort of working close to molten salts.

A major application of resistance heating is in electric home appliances, including electric ranges, clothes dryers, water heaters, coffee percolators, portable radiant heaters, and hair dryers. Resistance heating also has application in home or space heating.

If the resistor is located in a thermally insulated chamber, most of the heat generated is conserved and can be applied to a wide variety of heating processes. Such insulated chambers are called ovens or furnaces, depending on the temperature range and use. The term oven is generally applied to units which operate up to approximately 800°F (430°C). Typical uses are for baking or roasting foods, drying paints and organic enamels, baking foundry cores, and low-temperature treatments of metals. The term furnace generally applies to units operating above 1200°F (650°C). Typical uses of furnaces are for heat treatment or melting of metals, for vitrification and glazing of ceramic wares, for annealing of glass, and for roasting and calcining of ores. See Electric heating

References in periodicals archive ?
The system uses resistance heating to precisely melt metal wire for an additive process that foregoes the use of metal powders.
HH-8 digital resistance heating furnace is produced by Zheng Kai Precision Instrument Co., Ltd., in the city of Dongguan in China.
In July, LATA Kentucky completed installation of an electrical resistance heating system to remove the degreaser trichloroethene (TCE) from the ground near the C-400 Cleaning Building in the center of the Paducah site.
Some specific topics include thermal deformation of quart flat mirror surfaces under non-uniform heating, a hot-forming process using direct resistance heating, boronizing of the whetstone forming die, and a calculation model of punch force during tube extension.
All energy loads in the house during the winter contributed to heating the house with an effective COP of 1.0 (that is, electric resistance heating).
The transportable electric ladle is a shell-contained refractory crucible comprised of modular baffle or side pocket panels in which high-intensity electric resistance heating elements are embedded (Figs.
The semiproduct was heated using high-frequency resistance heating (Masek et al., 2010) directly in the die cavity.
According to the Northwest Energy Efficiency Alliance, nearly one million homes in the Northwest still rely on electric resistance heating as a primary heat source.
In general, the cost of operating electrical resistance heating remains approximately twice as much as natural gas source heating, depending on the location.
means such as gears or by a chain." The back surfaces of the moldboard and landside were provided with electrical resistance heating units connected to the generator by a heavy cable.
The heaters generate electrical eddy currents in the barrel wall, which cause resistance heating without expending energy to heat the mass of a heater band.