Heating element

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The heating element converts energy into heat through resistive heating or Joule. The electric current passing through the element encounters resistance, resulting in heating of the element. In contrast to the Peltier effect, this process does not depend on the direction of current flow.

Video Heating element

Metal heating element

• Nichrome: Most heating elements use 80/20 nichrome wire (80% nickel, 20% chromium), ribbon, or strip. Nichrome 80/20 is an ideal material, because it has a relatively high resistance and forms an adherent layer of chromium oxide when heated for the first time. The material under this layer will not oxidize, preventing the wire from breaking or burning.

• Resistant wire: The metal-resistant heating element can be either wire or ribbon, straight or rolled. They are used in common heating devices such as toasters and hair dryers, industrial heating furnaces, floor heating, roof heating, warming lanes for melting snow, dryers, etc. The most commonly used material classes include:
  • Kanthal Cable (FeCrAl)
  • 80/20 Nichrome Wire and strip
  • Cupronickel (CuNi) alloy for low temperature heating
• Foil Scratched: The engraved foil elements are generally made of the same alloy as a resistance wire element, but are produced by sub-infrared photo processing which begins with continuous metal foil sheets and ends with a complex pattern of resistance. These elements are usually found in precision heating applications such as medical diagnostics and aerospace.

Maps Heating element

Ceramic heater element

• Disilicide Molybdenum (MoSi ₂ ) The intermetallic compound, the molybdenum silicide, is a refractory ceramic mainly used in heating elements. It has a moderate density, a melting point of 2030 Â ° C, (3,686 degrees F) and an electric conductive. At high temperatures it forms a passive layer of silicon dioxide, protecting it from further oxidation. Application areas include glass industry, sintering ceramics, heat treatment furnaces and semiconductor diffusion furnaces.
• PTC ceramic elements: PTC ceramic materials are named for their positive thermal resistance coefficients (ie, resistance increases during heating). While most ceramics have negative coefficients, these materials (often barium titanate and lead titate composites) have a very nonlinear thermal response, so that above their thermostat-dependent threshold temperature their resistance increases rapidly. This behavior causes the material to act as its own thermostat, because the current runs when cold, and not when it is hot. Thin films of this material are used in automotive rear window defrost heater, and honeycomb-shaped elements are used in more expensive hair dryers and room heaters.

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PTC Polymer heating element

Resistive heaters can be made from performing PTC rubber materials where resistivity increases exponentially with increasing temperature. Such a heater will produce high power when it cools, and rapidly heats itself to a constant temperature. Due to the exponentially rising resistivity, the heater can not heat itself warmer than this temperature. Above this temperature, the rubber acts as an electrical insulator. Temperature can be selected during rubber production. Typical temperatures are between 0 and 80 ° C (32 and 176 ° F).

It is a self-regulating point-wise heater and self limiting heater. Self-regulation means that each heating point independently maintains a constant temperature without the need to regulate electronics. Self-limitation means that the heater can never exceed a certain temperature at any point and does not require overheating protection.

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Composite heating element

• Tubular elements (sheathed) usually consist of a fine coil of nickel alloy heating wire (NiCr), located inside a metal tube (of stainless steel alloys, such as Incoloy, or copper) and isolated by magnesium oxide powder. To keep moisture from the hygroscopic insulator, the tip is provided with insulating material beads such as ceramic or silicone rubber, or a combination of both. The tube is pulled through the dice to compress the powder and maximize heat transmission. This can be a straight rod (as in a toaster oven) or bent into shape to reach the area to be heated (such as in an electric stove, oven, and coffee maker).
• Ceramic-metal footprints printed on paper deposited on ceramic insulated metal plates (generally steel) have found widespread applications as elements in kettles and other household appliances since the mid-1990s.
• Radiation heating elements (heat lamps): High-energy incandescent lamps typically operate at less than maximum power to transmit most infrared rather than visible light. These are commonly found in radiant room heaters and food warmers, either taking the shape, tubular length or R40 reflector-shape lights. Reflector light styles are often colored red to minimize visible light produced; Tubular shapes come in different formats:
  • Gold coated - Made famous for patented Phillips Helen lamps. A dichroic gold film is stored on the inside that reduces visible light and allows most of the short and medium wave infrared waves. Especially for heating people. A number of manufacturers are now producing these lamps and they are improving constantly.
  • Ruby Layer - The same function as a gold-plated lamp, but with a cost fraction. The look looks much taller than the gold variant.
  • Clear - There is no coating and is mainly used in the production process.
• Ceramic core elements that can be removed using threaded circular wire heating wires are threaded through one or more cylindrical ceramic segments to create the required lengths (associated with output), with or without a central rod. Inserted into a metal shell or tube sealed at one end, this type of element allows replacement or repair without damaging the process involved, usually heating the liquid under pressure.

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Combination heating element system

• Thick film technology: Heating elements for high-temperature furnaces are often made from exotic materials, including platinum, molybdenum disilicide, molybdenum (vacuum furnace) and silicon carbide. Silicon carbide igniters common in gas ovens. Laser heaters are also used to achieve high temperatures in thick film technology.
• Electric stove: Early electric furnaces use tubular heating elements for all functions, but some use other technologies for surface burners to produce smoother ranges that are easier to clean.

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See also

• Hot hose
• Heater coat
• Positive temperature coefficient
• Thermoelectric effect

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References

Source of the article : Wikipedia