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A folded tubular heating element from an espresso machine
Symbol of a heater-coil or heating element
Some other symbols used for heater-coils or heating elements

A heating element converts electrical energy into heat through the process of Joule heating. Electric current through the element encounters resistance, resulting in heating of the element. Unlike the Peltier effect, this process is independent of the direction of current.

Heating elements types

Tubular electric heater.
  1. Resistance heating element
  2. Electrical insulator
  3. Metal casing
A coiled heating element from an electric toaster


Resistance wire: Metallic resistance heating elements may be wire or ribbon, straight or coiled. They are used in common heating devices like toasters and hair dryers, furnaces for industrial heating, floor heating, roof heating, pathway heating to melt snow, dryers, etc. The most common classes of materials used include:

Ceramic and semiconductor

Thick film heaters

A thick film heater printed on a mica sheet.
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Thick film heaters are a type of resistive heater that can be printed on a thin substrate. Thick film heaters exhibit various advantages over the conventional metal-sheathed resistance elements. In general, thick film elements are characterized by their low profile form factor, improved temperature uniformity, quick thermal response due to low thermal mass, low energy consumption, high watt density and wide range of voltage compatibility. Typically, thick film heaters are printed on flat substrates, as well as on tubes in different heater patterns. These heaters can attain watt densities of as high as 100 W/cm2 depending on the heat transfer conditions.[5] The thick film heater patterns are highly customizable based on the sheet resistance of the printed resistor paste.

These heaters can be printed on a variety of substrates including metal, ceramic, glass, polymer using metal/alloy-loaded thick film pastes.[5] The most common substrates used to print thick film heaters are aluminum 6061-T6, stainless steel and muscovite or phlogopite mica sheets. The applications and operational characteristics of these heaters vary widely based on the chosen substrate materials. This is primarily attributed to the thermal characteristics of the heater substrate.

There are several conventional applications of thick film heaters. They can be used in griddles, waffle irons, stove-top electric heating, humidifiers, tea kettles, heat sealing devices, water heaters, clothes irons and steamers, hair straighteners, boilers, 3D printer heated beds, thermal print heads, glue guns, laboratory heating equipment, clothes dryers, baseboard heaters, warming trays, heat exchangers, deicing/defogging devices for car windshields, side mirrors, refrigerator defrosting, etc.[6]

For most applications, the thermal performance and temperature distribution are the two key design parameters. In order to avoid any hotspots and to maintain a uniform temperature distribution across a substrate, the circuit design can be optimized by changing the localized power density of the resistor circuit. An optimized heater design helps to control the heater output and modulate the local temperatures across the heater substrate. In cases where there is a requirement of 2 or more heating zones with different output power over a relatively small area, a thick film heater can be designed to achieve a zonal heating pattern on a single substrate.

Thick film heaters can largely be characterized under two subcategories—negative temperature coefficient (NTC) or positive temperature coefficient (PTC)—based on the effect of temperature increase on the element's resistance. The NTC type heaters are characterized by a decrease in resistance as the heater temperature increases and thus have a higher output power at higher temperatures for a given input voltage. The PTC heaters behave in an opposite manner with an increase of resistance and decreasing heater power at elevated temperatures. This characteristic of the PTC heaters make them self regulating too, as their output power saturates at a fixed temperature. On the other hand, NTC type heaters generally require a thermostat or a thermocouple in order to control the heater runaway. These heaters are used in applications which require a quick ramp-up of heater temperature to a predetermined set-point as they are usually faster acting than the PTC type heaters.

Thick film heater printed on a metal substrate

Polymer PTC heating elements

A flexible PTC heater made of conductive rubber

Resistive heaters can be made of conducting PTC rubber materials where the resistivity increases exponentially with increasing temperature.[7] Such a heater will produce high power when it is cold, and rapidly heat up itself to a constant temperature. Due to the exponentially increasing resistivity, the heater can never heat itself to warmer than this temperature. Above this temperature, the rubber acts as an electrical insulator. The temperature can be chosen during the production of the rubber. Typical temperatures are between 0 and 80 °C (32 and 176 °F).

It is a point-wise self-regulating heater and self-limiting heater. Self-regulating means that every point of the heater independently keeps a constant temperature without the need of regulating electronics. Self-limiting means that the heater can never exceed a certain temperature in any point and requires no overheat protection.


An electrode boiler uses electricity flowing through streams of water to create steam[citation needed].

Composite heating elements

Tubular Heating Element
Tubular Oven Heating Element

Combination heating element systems

See also


  1. ^ Sorrell, Chris (2001-02-06). "Silicon Nitride (Si₃N₄) Properties and Applications". AZo Journal of Materials. ISSN 1833-122X. OCLC 939116350.
  2. ^ How to Specify a PTC Heater for an Oven or Similar Appliance2. Process Heating. 26 May 2005. ISSN 1077-5870.
  3. ^ Fang, Shu; Wang, Rui; Ni, Haisu; Liu, Hao; Liu, Li (2022). "A review of flexible electric heating element and electric heating garments" (PDF). Journal of Industrial Textiles. 51 (15): 1015–136S. doi:10.1177/1528083720968278. S2CID 228936246.
  4. ^ Jang, Joohee; Parmar, Narendra S.; Choi, Won-Kook; Choi, Ji-Won (2020). "Rapid Defrost Transparent Thin-Film Heater with Flexibility and Chemical Stability". ACS Applied Materials & Interfaces. 12 (34): 38406–38414. doi:10.1021/acsami.0c10852. PMID 32698575. S2CID 220717357.
  5. ^ a b Prudenziati, Maria; Hormadaly, Jacob (2012). Printed films: materials science and applications in sensors, electronics and photonics. Cambridge, UK: Woodhead Publishing. ISBN 978-0857096210. OCLC 823040859. Preview at Google Books
  6. ^ Radosavljević, Goran; Smetana, Walter (2012). "Printed heater elements". In Prudenziati, Maria; Hormadaly, Jacob (eds.). Printed Films: Materials Science and Applications in Sensors, Electronics and Photonics. Oxford: Woodhead Publishing. pp. 429–468. doi:10.1533/9780857096210.2.429. ISBN 978-1-84569-988-8.
  7. ^ US patent 6,734,250 
  8. ^ Rashidian Vaziri, M R; et al. (2012). "New raster-scanned CO2 laser heater for pulsed laser deposition applications: design and modeling for homogenous substrate heating". Optical Engineering. 51 (4): 044301–044301–9. Bibcode:2012OptEn..51d4301R. doi:10.1117/1.OE.51.4.044301. Archived from the original on 2016-10-10.