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Heating Elements: Types and Properties

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Introduction

This article presents a comprehensive guide about heating elements. Read further to learn more about:

  • What is a heating element and how does it work?
  • Heating element properties
  • Different heating element materials
  • Types of heating elements
  • And Much More...
Heating Elements

Chapter 1: What is a Heating Element?

A heating element is a component or material designed to transform electrical energy into heat through a phenomenon known as Joule heating. This process happens when an electric current travels through a conductor, with electrons or charge carriers interacting with the atoms or ions within the conductor. These interactions create friction on an atomic scale, which manifests as heat. The heat produced is quantified by Joule's first law (or the Joule-Lenz law), which states:

P = IV or P = I²R

These formulas indicate that the heat generated is influenced by the current, voltage, and the conductor's resistance. The resistance of the conductor is a key consideration in the design of heating elements.

Immersion Heater

Joule heating happens across all conductive materials, with the exception of superconductors, albeit to varying extents. Materials with lower electrical resistance emit less heat as charge carriers pass through them with ease, whereas materials with higher resistance generate greater heat. Superconductors are unique in that they allow current to pass without producing heat. Generally, the heat generated in conductors is seen as energy loss. For instance, when powering equipment, some electrical energy results in unwanted heating, known as copper loss, which is not beneficial for practical work.

Heated Storage Tank

Electrical heating elements are close to 100% efficient in converting electrical energy into thermal energy since nearly all the energy supplied is turned into heat. These elements might also emit energy as light and radiation. However, this level of efficiency is particularly true for resistors. Minor losses occur due to the intrinsic capacitance and inductance of materials, transforming electrical energy into electric and magnetic fields, respectively. Moreover, the overall efficiency can decrease due to heat escaping into the surroundings from the heater or the process fluid. Therefore, to ensure optimal use of generated heat, the heating system should be insulated effectively.

Chapter 2: What are the properties of heating elements?

Nearly all conductors generate heat when an electric current passes through them, but not all are optimal for use as heating elements. To ensure efficient performance and long-term durability, the preferred heating element materials must have a precise balance of electrical, thermal, mechanical, and chemical properties. These make them suitable for a variety of industrial heating applications such as furnaces, electric ovens, kilns, and water heaters. Below are the key properties critical to effective heating element design and selection:

  • Resistivity: Effective heat production relies on the electrical resistance of the material. The heating efficiency of an element is determined by its ability to convert electrical energy into heat. The right resistivity ensures consistent performance and manageable energy consumption. Electrical resistance is equal to the resistivity multiplied by the length of the conductor divided by the conductor cross-section. For a given cross-section, to have a shorter conductor, a material with high resistivity is used. Choosing the correct resistivity is essential for the safe and efficient operation of industrial heaters, wire heating elements, nichrome wires, and cartridge heaters.
    Resistance as a Function of Resistivity, Length, and Cross Sectional Area

  • Oxidation Resistance: Intense heat accelerates oxidation in both metals and ceramics, which can degrade heating coils and heating rods over time. Resistance to oxidation, or oxidation stability, is essential for maintaining heating element lifespan and performance. For metal heating elements, alloying with elements like chromium and aluminum forms protective oxide layers that shield against further oxidation (a key property in nichrome and kanthal wires). Ceramic heating elements such as silicon carbide and molybdenum disilicide develop naturally protective oxide scales like SiO2 or Al2O3. Some element types unsuitable for oxidizing atmospheres (e.g., graphite) are primarily used in vacuum furnaces or those with protective atmospheres (H2, N2, Ar, He) to prevent rapid degradation.
  • Temperature Coefficient of Resistance (TCR): Resistivity in most conductive materials changes with temperature. A lower temperature coefficient of resistance is desirable in heating element applications to ensure stable and predictable heating output, whereas high TCR materials are preferred for thermal sensors and temperature control devices like thermistors. In advanced systems, feedback and automation technologies are often integrated to compensate for resistance variations, maintaining consistent and safe operation in electric heaters or precision heating elements.
    An Example of a Temperature-Resistance Curve

  • Mechanical Properties: Heating elements must retain their shape and strength at elevated temperatures—a property known as creep resistance or thermal stability. Good ductility and tensile strength are necessary for wire elements and tubular heating elements, allowing for easy fabrication into coils, mats, or custom shapes without failure. Mechanical durability ensures reliable long-term use in both residential and high-demand industrial electric heating systems.
  • Melting Point: The maximum operating temperature of a heating element is limited by its melting point as well as its oxidation resistance. Materials such as ceramics and specialty alloys (e.g., nichrome, kanthal) are chosen for their ability to function safely at high temperatures, supporting applications like high-temperature furnaces, toasters, industrial ovens, and water heating systems.

When evaluating and purchasing heating elements, industrial buyers and engineers often consider additional factors such as cost-effectiveness, energy efficiency, compatibility with specific voltage and wattage requirements, and ease of integration with existing heating systems. Custom heating elements—whether cartridge heaters, band heaters, or infrared heating elements—can be designed to address unique environmental conditions and process specifications, making them suitable for industries including manufacturing, food processing, and laboratory equipment. Understanding these properties allows buyers to choose between electric heating element types (e.g., metallic vs. ceramic) and ensures compliance with safety certifications and industry standards.

In summary, the right choice of heating element material and configuration directly impacts overall system performance, safety, and operational lifetime. For expert guidance or specific product recommendations, contacting leading heating element manufacturers and suppliers is highly recommended.

Leading Manufacturers and Suppliers

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    Chapter 3: What Materials Are Used for Heating Elements?

    The selection of materials for heating elements is determined by thermal stability, electrical resistivity, oxidation resistance, and operating environment. The most commonly utilized heating element materials in industrial and commercial applications include nickel-chromium (nichrome) alloy, iron-chromium-aluminum (FeCrAl) alloy, molybdenum disilicide, and silicon carbide. These materials are ideal for electric heating elements because they withstand high temperatures, offer reliable performance under electrical load, and resist oxidation, making them suitable for open-air and industrial furnace environments.

    Another category of heating element materials includes graphite, molybdenum, tungsten, and tantalum—refractory elements that excel in ultra-high-temperature conditions. However, because these advanced materials are prone to oxidation at elevated temperatures, they are predominately used in vacuum furnaces or controlled-atmosphere applications where oxygen is absent or minimized. This critical property is essential in applications such as metallurgy, crystal growth, and specialty material processing.

    Nickel-Chromium (Ni-Cr) Alloy

    Nickel-chromium alloys, often referred to as nichrome wire, are among the leading electrical heating element materials due to their outstanding combination of ductility, high resistivity, corrosion resistance, and superior oxidation resistance at elevated temperatures. Standard compositions, such as 80% nickel and 20% chromium, provide a balance of high electrical resistance and mechanical flexibility, allowing these alloys to be easily shaped into coils and wires. Applications include home appliances (toasters, hair dryers, space heaters), laboratory heating, and industrial kiln heating elements. Nichrome wires can reach maximum operating temperatures of approximately 1,100 to 1,200°C, making them suitable for medium- to high-temperature heating solutions with long service life.

    Ni-Cr Wire

    Iron-Chromium-Aluminum (Fe-Cr-Al) Alloy

    Iron-chromium-aluminum alloys, widely recognized under the Kanthal brand, represent a major advancement in heating technology for industrial furnaces, tubular heating elements, and electric ovens. Typical Fe-Cr-Al compositions consist of 20–24% chromium, 4–6% aluminum, with iron as the base metal. These alloys offer higher operating temperatures—up to 1,300 to 1,400°C—compared to nickel-chromium counterparts and feature excellent resistance to oxidation and sulfur attack. Fe-Cr-Al heating elements are commonly used in glass kilns, ceramic manufacturing, and process heating, as well as high-temperature dryers and heat treat furnaces. Economically, they are favored for their lower cost due to iron's price stability.

    Advanced Fe-Cr-Al alloys can be manufactured via powder metallurgy processes, which finely grind the alloy into powder, compress it into a die, and then sinter or hot-press it in a controlled atmosphere. The incorporation of oxide dispersoids during this process enhances high-temperature strength, creep resistance, and mechanical durability, extending the lifespan in harsh operating environments.

    Molybdenum Disilicide (MoSi2)

    Molybdenum disilicide (MoSi₂) is a premium refractory cermet material recognized for its exceptional oxidation resistance, high melting point (over 2,000°C), and electrical conductivity. MoSi₂ heating elements are indispensable in laboratory and industrial high-temperature furnaces, glass processing, and sintering of advanced ceramics. Common fabrication methods include mechanical alloying, combustion synthesis, shock synthesis, and advanced hot isostatic pressing to achieve optimal density and material purity. MoSi₂ elements are capable of reaching continuous operating temperatures up to 1,900°C, making them ideal for demanding high-temperature electric heating solutions.

    Despite their extraordinary temperature capabilities, MoSi₂ elements are relatively brittle at ambient temperature and susceptible to thermal shock. Their strength and toughness increase dramatically above 1,000°C, at the material's brittle–ductile transition point. The most widely used MoSi₂ element design is the U-shaped (2-shank) hairpin form, suspended in both vertical and horizontal furnace arrangements to maximize thermal efficiency and process uniformity. To further optimize performance, these elements are often paired with ceramic insulation which helps to minimize heat loss and improve energy efficiency in high-temperature processing environments.

    Molybdenum Disilicide Heating Element

    Silicon Carbide (SiC)

    Silicon carbide heating elements, fabricated from high-purity SiC grains by recrystallizing or reaction bonding above 2,100°C, are widely used for electric furnaces operating at temperatures up to 1,600–1,700°C. As a robust ceramic, silicon carbide exhibits excellent thermal conductivity, corrosion resistance, and mechanical strength. SiC heaters are inherently porous, enabling interaction with furnace atmospheres, which can influence element aging and resistance changes over time—a factor mitigated by adjustable power supplies that maintain constant heating performance throughout the element's service life. Silicon carbide's ability to sublimate at 2,700°C, combined with its low thermal expansion and resistance to chemical attack, make it especially valuable for heat treatment, metallurgy, laboratory muffle furnaces, and semiconductors manufacturing.

    SiC heating rods do not sag under their own weight at elevated temperatures, eliminating the need for internal supports, even in large-scale furnace designs. This, along with their excellent thermal shock resistance and longevity, contributes to their popularity in high-temperature industrial process heating and thermal oxidation environments.

    Graphite

    Graphite heating elements, composed of high-purity carbon, are essential for applications requiring operation above 2,000°C, including vacuum heat treatment, high-temperature sintering, and crystal growth. The unique crystalline structure of graphite provides high thermal and electrical conductivity, minimal thermal expansion, and exceptional resistance to thermal shock. However, graphite is prone to oxidation at temperatures above 500°C, limiting its use in atmospheres where oxygen or moisture is present. As a result, it is the material of choice for vacuum and inert-gas furnace systems, where it achieves extended service life and maintains dimensional stability without degradation or embrittlement.

    Vacuum Furnace with Graphite Heating Elements

    Molybdenum, Tungsten, and Tantalum

    Refractory metals—molybdenum, tungsten, and tantalum—are renowned for their exceptional melting points, high thermal and electrical conductivity, and chemical stability in oxygen-free environments. Tungsten heating elements, found in vacuum furnaces and electron-beam systems, can operate at temperatures exceeding 2,500°C, making them indispensable for advanced material processing and high-temperature heat treatment. Molybdenum and tantalum are valuable for similar applications, offering optimal performance in vacuum or reducing atmospheres due to their reactivity with oxygen, nitrogen, and hydrogen at moderate temperatures (300 to 500°C). Cost and material availability often drive the selection among these refractory metals, as tungsten tends to be the most expensive, while molybdenum strikes a balance between performance and affordability.

    These metals are typically specified for sensitive thermal processing, semiconductor manufacturing, and specialty glass production, where precision, consistency, and extreme temperature capability are paramount.

    Positive Thermal Coefficient (PTC) Materials

    Positive Temperature Coefficient (PTC) materials represent a class of self-regulating heating elements widely used in safety-critical or low-wattage applications. Standard PTC materials include conductive rubbers and ceramics, such as barium titanate or PDMS infused with carbon nanoparticles. PTC heaters deliver rapid warm-up due to their low initial resistance and inherently limit power draw as their resistance rises with increasing temperature, stabilizing output and preventing overheating. This makes them ideal for wearable heating, automotive seat warmers, underfloor heating systems, and medical device heating solutions.

    The technology behind PTC heating elements reduces the need for external thermal controls, as the material itself ensures precise and automatic temperature regulation. This feature enhances safety and simplifies design in consumer appliances and industrial systems where temperature uniformity, efficiency, and protection from thermal runaway are essential considerations.

    PTC Heating Element

    Choosing the right heating element material depends on the specific industrial application, required temperature range, environmental conditions (such as exposure to air, vacuum, or process gases), and cost considerations. For further technical data or assistance in selecting optimal heating element materials for your industrial furnace, electric heating system, or custom thermal processing application, consult with experienced manufacturers or refer to comprehensive industry resources.

    Chapter 4: What are the different types of heating elements?

    A heating system includes more than just the heating element. It also comprises terminations, leads, insulation, packing, sheath, and seals. Heaters come in various forms and configurations to meet specific application needs. Below are some of the most common types of heaters and their applications.

    • Air Process Heaters: As the name suggests, this type of heater is used to heat up flowing air. Air process heaters are basically a heated tube or pipe wherein one end is for introducing cold air while the other end is the hot air exit. Along the walls of the pipe are coils of heating elements insulated by ceramics and non-conducting gaskets. These are typically used in high-flow, low-pressure applications. Applications for air process heaters are heat shrinking, laminating, adhesive activation or curing, drying, baking, etc.
      Air Process Heaters

    • Cartridge Heaters: In this type of heater, the resistance wire is coiled around a ceramic core, typically made of compacted magnesium oxide. Rectangular configurations are also available where the resistance wire coils pass three to five times along the length of the cartridge. The resistance wire or the heating element is situated near the walls of the sheathing material for maximum heat transfer. To protect the internals, the sheath is usually made of corrosion resistant materials like stainless steel. The leads are usually flexible with both of their terminations located on one end of the cartridge. Cartridge heaters are used in die or mold heating, fluid heating (immersion heaters), and surface heating.
      Cartridge Heaters

    • Tubular Heaters: Tubular heaters‘ internals is the same as that of cartridge heaters. Its main difference from cartridge heaters is that the lead terminals are on the opposite ends of the tube. The whole tubular construction can be bent into different forms to suit the heat distribution required by the space or surface to be heated. Also, these heaters can feature fins that are mechanically bonded onto the sheath surface to aid in an effective heat transfer. Tubular heaters are as versatile as cartridge heaters and are used in similar applications.
      Tubular Heating Elements

    • Band Heaters: These heaters are designed to wrap around cylindrical metal surfaces or containers such as pipes, barrels, drums, extruders, and so forth. They feature bolted locking tabs to securely clamp onto the surface of the container. Inside the band, the heater is a thin resistance wire or ribbon typically insulated by a mica layer. The sheathing is made of stainless steel or brass. Another advantage of using band heaters is that it indirectly heats the fluid inside the vessel. This means the heater is not subjected to any chemical attack from the process fluid. Possible ignition is also prevented when used for oil and lubricant service.
      Band Heaters

    • Strip Heaters: This type of heater is flat and rectangular in form and is bolted on to the surface to be heated. Its internals are similar to a band heater. However, the insulating material, aside from mica, can be ceramics such as magnesium oxide and fiberglass. The typical use of strip heaters is surface heating of dies, molds, platens, tanks, ducts, etc. Aside from surface heating, they can also be used for air or fluid heating by having finned surfaces. Finned strip heaters are seen in ovens and space heaters.
      Miniature Strip Heater

    • Etched Foil Heaters: Etched foil heaters can also be referred to as thin-film heaters. In this type, the resistive heating material is etched and bonded onto a foil usually made of aluminum. If more flexibility and tear resistance is required, the substrate can also be made of heat-resisting synthetic rubber or thermoplastic polyurethane (TPU). In addition to its flexibility, another advantage is the tight spacing of the heating elements. This is the inherent advantage of photochemical etching. Even heat distribution with a larger heat density can be achieved in such small forms. Its applications are more specialized in comparison with the conventional wire heaters. Etched foil heaters are usually seen in medical devices, electronics and instrumentation, aerospace, and clothing. One side can be lined with an adhesive layer for easy mounting.
      Etched Foil Heater

    • Ceramic Heaters: These heaters use ceramics with a high melting point, high thermal stability, high-temperature strength, high relative chemical inertness, and small heat capacity. Note that these are different from ceramics used as an insulating material. Due to its good thermal conducting properties, it is used to conduct and distribute heat from the heating element. Notable ceramic heaters are silicon nitride and aluminum nitride. These are commonly used for rapid heating as seen on glow plugs and igniters. However, when subjected to quick high-temperature heating and cooling cycles, the material is prone to cracking due to fatigue caused by thermal stresses. A special type of ceramic heaters is a PTC ceramic. This type can self-regulate its power consumption which then prevents it from becoming red hot.
      Ceramic Heaters

    • Ceramic Fiber Heaters: In this type of heater, the ceramic fiber is used as an insulator to concentrate the heat into the surface to be heated to prevent system losses. Ceramic fiber pads have a resistance wire wound on one-side. This side is bonded on the surface to be heated which can reach up to 1,200°C.
      Ceramic Fiber Heater

    Chapter 5: What factors should be considered when selecting a heater?

    While heating elements generally operate on the same principle, their performance and service life are influenced by several factors. Key specifications for heaters include power or wattage, maximum operating temperature, type of process fluid, sheath material, and power supply (voltage and frequency). Additionally, factors such as fluid flow and temperature control must also be considered to optimize performance.

    • Watt Density: Watt density is the heat delivered of a heating element per unit area. The right watt density must be used for a specific application to fully utilize the service life of the heater. Note that for a given wattage, both high and low-density heaters will deliver the same amount of heat but at different temperatures. High-density elements can reach much higher temperatures which leads to premature burning or failure of the element. In selecting a heating element, check the manufacturer's recommended watt densities for a particular application.
      Comparison of High- and Low-watt Density Heaters

    • Temperature: The target operating temperature directly affects the watt density. There must be a balance between these two factors. In designing a process heater, the temperature is determined first which is usually a process parameter required by the system.
    • Power Supply: The heating element must be able to operate with the available power supply. Check the voltage rating which is typically 120V or 240V. In selecting a target wattage, verify the amperage produced. Be careful not to exceed the power supply circuit breaker tripping point or the ratings of the power cables.
    • Fluid Flow: From intuition, stagnant fluids are easier to heat with a controlled temperature than flowing fluids. Air or other gases do not generally absorb heat quickly because of their low density. A solution would be to slow down the flow, but most of the time, this is not an option. Thus, heaters with large surface areas are required. Finned surfaces and long wire coils (low-density heating elements) are the usual features of air heaters.
      Finned Tubular Heaters

    • Temperature Sensor Location: Conventional heaters come with a temperature sensor and a controller. In most applications, the sensing device only measures the temperature of the process fluid. Note that this does not usually represent the actual heating element temperature. Before installing the heater and the temperature sensing device, check if its location is appropriate for the heater unit. If the sensor is too far, the temperature reflected may be much lower due to heat dissipation and low heat transfer rate. This can lead to very high temperatures that can burn the heating element.
      Thermostats

    • Corrosion: Corrosion can be from the process fluid or the external environment. The sheathing material protects the heating element, leads, and insulators from chemical attack. Thus, the sheath must be able to maintain its strength in high temperatures while being resistant to corrosion. Widely used sheathing materials are stainless steel, brass, copper, and other special alloys such as Monel and Incoloy. Moreover, the integrity of the sheath and terminal sealing must be sufficient for the application. For demanding applications, hermetic sealing is the best option in providing complete protection from the process fluid.
      Stainless Steel Sheathed Heater

    Conclusion

    • A heating element is a material or device that directly converts electrical energy into heat or thermal energy through a principle known as Joule heating.
    • The most important heating element characteristics are sufficient resistivity, high oxidation resistance, low-temperature coefficient of resistance, high toughness, and high melting point.
    • Widely used heating elements are nickel-chromium alloy, iron-chromium-aluminum alloy, molybdenum disilicide, and silicon carbide. These are followed by graphite and other refractory metals which generally have higher oxidation rates.
    • Aside from the heating element, a heater consists of the terminations, leads, insulation, packing, sheath, and seals. These heaters have various forms and configurations to suit a particular application.
    • Typical heater ordering specifications are the power or wattage, maximum operating temperature, type of process fluid, sheath material, and power supply (voltage and frequency).

    Leading Manufacturers and Suppliers

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      Table of Contents

      What is a Heating Element?

      Heating Element Properties

      Heating Element Materials

      Types of Heating Elements

      Factors to Consider in Selecting a Heater

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