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Introduction

This article presents all the information you need to know about infrared heating.

Read further and learn more about:

  • What is Infrared Heating?
  • Operating Principles Behind Infrared Heaters
  • Types of Infrared Heaters
  • Advantages of Infrared Heaters
  • And much more…
Infrared Tube Heater

Chapter 1: What is Infrared Heating?

Infrared heating is a method for heating materials that uses electromagnetic waves to transfer energy from the infrared source to the product without heating the air in between. The emitted infrared energy is between 0.7 microns (µ) and 6 µ. At peak efficiency, wavelengths are selected for the product to be heated to minimize energy usage.

Thermal energy is transferred directly to a material at a lower temperature. The surrounding air is not heated and is uninvolved in the transfer of heat, making infrared heaters energy efficient, convenient, and healthy. Power is supplied by electricity, natural gas, or propane to create heat efficiently and economically.

The electromagnetic waves in the infrared spectrum have a wide range of wavelengths, from 780 nm up to 10 microns for industrial processes. The shorter wavelengths in the infrared spectrum have higher frequencies and associated energies. Heat produced by infrared waves ranges from hundreds of degrees Celsius up to 6,512 °F (3,600 °C).

In recent years, developments have been made to harness energy based on these scientific principles. Today, infrared heaters are available with different features and designs to flexibly accommodate industrial, commercial and residential needs. They heat surfaces in living spaces, offices, workplaces, garages, and warehouses. Industries benefit from infrared heaters as they can perform several processes such as drying, curing, printing, and thermoforming. In medicine, infrared heaters are used in physiotherapy to improve rehabilitation.

Industrial Infrared Heater

History of Infrared Heating

The infrared region was discovered by Sir William Herschel, a British-German astronomer, during the first Industrial Revolution (1760-1840). Infrared heating was not widely used, however, until World War II, where it was recognized by the military and used for drying the paints and lacquers applied to military equipment. This exceptionally-efficient heating process replaced fuel-consuming convection ovens that were far more expensive and depleted precious fuel reserves.

Infrared heaters during the war were frequently seen in workshops and factories. Their popularity radically declined after World War II as more people started to venture into central heating systems.

With the drive for greener technologies, the development of infrared heaters resumed between the late 20th century and early 21st century. The range of infrared heating has expanded to more uses during this period. Design flexibility and new configurations have been studied such that infrared heaters could be installed in multiple locations including homes and offices, or be used in industrial facilities for manufacturing. Rapid technological advancements and improvements in control systems have led to the continued growth and development of infrared heating use.

Chapter 2: Operating Principles Behind Infrared Heaters

Infrared heat is the most basic form of heating and is the direct transfer of heat from a heater to an object or material without heating the air. The type of heat produced by an infrared heater is the same as environmental heat from the sun.

In an infrared heater, panels are heated until they get hot enough to emit infrared radiation that continually travels until it meets a solid object or workpiece. It is a direct heat transfer process that is similar to the transfer of heat between metals, coils, and materials using radiant waves.

With traditional heating, the air in an environment is heated before any objects will feel the increase in temperature. Infrared heaters are designed to project heat to warm objects directly and not change the temperature in a space. Aside from their ability to rapidly raise the temperature of objects or materials, infrared heaters complete the heating process using a minimal amount of energy at lower cost.

Electromagnetic Waves

Electromagnetic waves are composed of waves that oscillate perpendicular to each other. One of the waves is an electric field, while the other is a magnetic field.

Electromagnetic waves are described by wavelength and frequency, with wavelengths being the distance between adjacent crests in the cycle of a wave. In the electromagnetic spectrum, wavelengths are usually expressed in nanometers or angstroms. Frequency is the number of wave cycles per second, which is expressed in Hertz (Hz), which is used to classify electromagnetic waves.

Electromagnetic Wave

Wavelength and frequency are inversely related to each other. The energy of a wave is directly proportional to the frequency but inversely proportional to the wavelength. Waves with higher frequencies and shorter wavelengths carry higher energy and are more transmissive. Waves with lower frequencies and longer wavelengths carry less energy.

Unlike mechanical waves, electromagnetic waves do not require a medium to generate. Sound waves or mechanical waves move through the air and do not need surrounding molecules to move through the air, objects, or even a vacuum. It is the reason it is possible to feel the warmth of the sun, though it is thousands of miles away from the earth, as well as the surrounding cold air, when we stay under the sun. This principle is also applied in the operation of infrared heaters, which are comparable to the sun.

Economic Tube Heaters

Infrared Waves

The infrared region is between the visible and the microwave regions of the electromagnetic spectrum. Infrared waves have a wavelength ranging from 700 nm (430 THz) – 1 mm (300 GHz).

Infrared Waves

The infrared region is broad, as is its associated energy and temperature range, with its waves classified into:

Classification of Infrared Waves

Radiative heating is one of the many applications of infrared waves. They are also useful in spectroscopy, imaging, and communications.

Radiative Heat Transfer

Radiation is the mechanism of heat transfer caused by the emission, absorption, and reflection of electromagnetic waves of bodies. All bodies above the absolute temperature (-459.4 °F or -273 °C) emit thermal radiation. The release of thermal radiation is caused by random movements, vibrations, and collisions of atoms and molecules and their constituting protons and electrons.

Various types of materials, items, and objects radiate heat based on their temperature. As they get hotter, these objects radiate thermal energy that is transferred by radiation but does not affect the surrounding molecules. Thermal energy easily travels through the air, objects, and even a vacuum and is independent of the amount of radiation emitted by a receiving material. Other factors affecting radiation are the nature of the surface and the angle of incident radiation.

Conduction and convection are other mechanisms of heat transfer that can happen simultaneously with radiation. In conduction, heat is transmitted through collisions and vibrations between neighboring atoms or molecules that readily occur in solids. The direction of heat transfer in conduction is from a region of higher kinetic energy to a region of lower kinetic energy.

In convection, thermal energy is transferred through the displacement of molecules in a bulk fluid. When a portion of the fluid is heated, the molecules closest to the primary heat source expand and travel away from it. Thermal energy is carried along with the molecules’ movement and is transferred to a cooler portion of the fluid mass.

Conduction, Convection, and Radiation

How do infrared heaters work?

Infrared heaters are composed of a heating system and a reflector. The heating system converts electrical energy or chemical energy from fuel sources into thermal energy. The reflector then directs the thermal energy produced by the heating system as radiant heat to the objects in its surroundings.

Reflectors greatly determine the efficiency of an infrared heater. They must have high reflectivity and must absorb minimal radiation from the heating system in order to store less heat. Their shapes and contours are designed to bend the infrared waves to space and prevent them from bouncing back. Other desirable properties of reflectors are high resistance to corrosion and moisture, ability to withstand high temperatures during their service life, and ability to be easily cleaned.

Reflective materials that are commonly used are aluminum, stainless steel, ceramics, and quartz. Some reflectors are plated with gold or ruby to increase their reflectivity and focus more heat on the surrounding objects.

Reflectors

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Chapter 3: Industrial Uses for Infrared Heaters

Several industrial applications require the use of flameless heating as part of drying processes, preparing a surface for different applications, and enhancing workflow. In each of the applications, precision and controlled heating are required to ensure the quality of products. Modern technological manufacturing depends on heat and heating methods that are efficient, economical, and accurate while still supplying the necessary levels of heat.

Infrared heating systems can be engineered and designed to heat a surface rapidly, evenly, and homogeneously. When activated, heat is immediately available and ready to be applied for preparing a workpiece for stamping, pressing, or welding – all of which are performed at a lower cost due to the energy savings provided by infrared heaters.

Drying with Infrared Heating

There are any number of industrial processes that involve the application of coatings (which can be powders or liquids that are sprayed or brushed on), paints, varnishes, or other forms of surface protection. Regardless of the type of application, a central part of the successful adherence of a coating is the method used to dry it.

In the case of liquid coatings, infrared heaters are used to dry a coating quickly to produce a smooth, even surface finish. Powder coatings are not dried but need gelling or curing. Infrared heaters are used to speed up the gelling and curing processes to reduce production times.

Welding with Infrared Heating

Infrared welding is mainly used on plastics to seal and connect fan components. It is also used on plastic containers and pipes that need to withstand pressure. In the sealing of pressure vessels, infrared welding connects parts without leaving particles or debris in plastic containers and tubes.

In some plastic manufacturing processes, infrared heating is combined with vibration welding, a process that uses both vibration and pressure to connect components. Infrared radiation prepares the surface of a plastic for vibration welding and minimizes particle formation.

Embossing and Laminating with Infrared Heating

When the surface of a plastic is going to be embossed or laminated, it has to be heated evenly to avoid the loss of the applied materials, especially along the borders. The ability of infrared heaters to be engineered and configured to precisely heat and prepare surfaces makes them ideal for embossing and laminating processes.

In the auto industry, infrared laminating ovens create fusion between layers of material which results in superior protection and enhanced durability. Car doors, consoles, and dashboards have plastic parts that are covered in foil. Infrared heaters heat the foil quickly to secure it to the surfaces of these parts. The quick and efficient work of infrared heaters reduces cycle times and saves on energy.

Types of Industrial Infrared Heaters

The three types of industrial infrared heaters are quartz, ceramic, and metal-sheathed. They are electromagnetic infrared radiation heaters that, depending on the material employed, rapidly reach temperatures between 1300 °F and 1600 °F (704 °C to 871 °C) for enhanced efficiency and productivity. Quartz infrared heaters can reach the highest temperatures, while ceramic infrared heaters are the most economical.

  • Quartz Infrared Heaters: Quartz infrared heaters produce short wavelengths to provide the hottest type of infrared heat. They are ideal for high heat applications but are not suitable for heating open spaces.
  • Ceramic Infrared Heaters: Ceramic infrared heaters are inexpensive and used to heat work areas.
  • Metal-Sheathed Infrared Heaters: Metal-sheathed infrared heaters are the most durable and can reach temperatures over 2000 °F (1093 °C). They can be used for submersible heating applications.

Chapter 4: Types of Infrared Heaters

  • Electric Infrared Heaters – Electric infrared heaters utilize electricity to deliver heat to their surroundings. The heating system produces heat using the principle of Joule heating or resistive heating. Joule heating is the conversion of electrical energy to heat by passing an electric current to an element with high electrical resistance. The resistance of the heating element must not be as high as the resistance of insulators. The common heating element materials employed with this process are tungsten, nichrome (80% nickel, 20% chromium), Kanthal® (FeCrAl), cupronickel (CuNi), and carbon fibers.
    Electric Foil Heaters

  • Radiant Gas Heaters – Radiant gas heaters, also known as gas-fired infrared heaters, depend on chemical energy stored in natural gas, propane, or petroleum for the heat source. They also use a heating element that converts the heat energy from the gas flames into infrared electromagnetic radiation. The heating elements and the combustion chambers are contained in a metal, ceramic, or glass encasing. Some types of radiant gas heaters are:
    • Radiant Tube Infrared Heaters – In radiant tube infrared heaters, the gas-air mixture is combusted in a long steel tube, which heats up to between 800-1,472 °F (500-800 °C) and subsequently emits infrared radiation to its surroundings. It is one of the most popular decentralized heating devices since heating takes place in the exact location it is required.
    • Luminous Infrared Heaters – In luminous infrared heaters, the gas-air mixture is directly fired through a porous matrix of refractory material that ignites and heats the surface above 1350 °F (732 °C). Large amounts of radiant heat are released to the surroundings and can be directed where heat is desired. Luminous infrared heaters are unvented when operating; thus, proper ventilation is necessary.
      Gas Fired Infrared Heater

Infrared heaters can also be classified based on the wavelength of the infrared waves they emit:

  • Near-Infrared (NIR) or Short-Wave Infrared Heaters – NIR heaters produce infrared waves of around 0.78-1.5 microns in wavelength and operate at high temperatures ranging between 2,600-4,712 °F (1,300-2,600 °C). Since these wavelengths have higher frequencies, they tend to be more transmissive and reflective but less absorptive to the surfaces they strike. Thus, they are less efficient and are not suitable for drying applications. They can produce harsh heat which can be felt 2-3 meters from the source but cannot provide consistent heat throughout specific areas.

    NIR heaters instantaneously warm the environment and are typically used in outdoor heating applications.

    Near-Infrared Heater

  • Medium-Wave Infrared Heaters – MWIR heaters produce infrared waves of around 1.5-3 microns and operate at 1,300-2,372 °F (500-1,300 °C). These wavelengths have lower frequencies, which are better absorbed by objects, but they are still not suitable for comfort heating. They are used in industrial applications such as the drying and curing of paints, lacquers, and solvents as well as in the economic processing of plastic foils and sheets.
    Medium-Wave Infrared Heater

  • Far Infrared (FIR) or Long-Wave Infrared Heaters – FIR heaters produce infrared waves of around 3-1000 microns in wavelength and operate at lower temperatures. Since these wavelengths have lower frequencies, they are better absorbed by the surface they strike. Water begins to absorb the infrared heat in this spectrum.
    • FIR heaters produce comfortable heat that is optimally absorbed by our skin and further led into our tissues, blood, and the rest of our bodies. They take a longer time (around 5 minutes) to warm surrounding areas. They are used in saunas, incubators, heating cabins, and other indoor heating applications.
      Far Infrared Heaters

Some infrared heaters can be distinguished by the material used in their construction. A few of such infrared heaters are listed here:

  • Quartz Heat Lamps – Quartz heat lamps were developed by General Electric™ in the 1950s. They produce intense heat with a temperature above 2,732 °F (1,500 °C) and emit medium- to short-infrared waves. They heat surrounding bodies quickly. Quartz is used as the enclosing material protecting the tungsten heating element since it can withstand higher temperatures than glass. It is filled with highly-pressurized inert gas containing halogens, gaseous bromine, or iodine that regenerates tungsten atoms in the filament and prolongs the service life of the heating element.
    • Quartz heat lamps are used as outdoor patio heaters and in several industrial processes for the drying, curing, and the thawing of frozen products.
      Quartz Heat Lamps

  • Carbon Infrared Heaters – Carbon infrared heaters have heating elements made from woven carbon fibers which are housed in quartz. They are also filled with halogen gas like quartz heaters. They operate at around 2,912 °F (1,200 °C) and emit medium infrared waves. The carbon fibers produce gentler heat, and their light is less intense than tungsten. They also have long service lives.
    • Carbon infrared heaters are used in heating spaces with large, drafty, and hard-to-heat interiors including public halls, café terraces, and covered outdoor spaces.
      Carbon Infrared Heater

  • Ceramic Heaters – Ceramic heaters have a heating element that is directly cast into a ceramic material. They operate at 300-700 °F (149 to 371 °C) and emit medium to long infrared waves with 2-10 microns in wavelength. The ceramic casting comes in different shapes: a flat-shaped cast spreads the infrared heat over a wider area, while the concave-shaped cast focuses the infrared heat into one spot. The surface is glazed to prevent corrosion.
    • Ceramic heaters are used in comfort heating and industrial processes such as paint drying, curing, printing, annealing, thermoforming, and packaging. Food processing industries and medical facilities employ the use of ceramic heaters.
      Ceramic Infrared Heater

The following are a few types of infrared heaters categorized by their application:

  • Construction Heaters – Construction heaters are portable infrared heaters used in outdoor or indoor construction areas, and they can be installed over a tank top. They are used in spot heating. Construction heaters use infrared energy to radiate heat to their surroundings through a ceramic or steel surface.
    Construction Heaters

  • Over-Door Heaters – Over-door heaters are positioned in building entrances and frequently-opened doors where the inside air is noticeably hotter. These heaters use axial fans to generate a high-velocity air stream to rapidly heat the cold entering air; this avoids heat losses and saves energy.
    • Over-door heaters are also known as air curtains. They can work in the opposite manner during summer to reduce air conditioning costs.
      Over-Door Heaters

  • Garage Heaters – Garage heaters are used in large spaces that are not meant for insulation like garages and workshops. They emit high-frequency radiation for the heat to penetrate large areas and warm the personnel working in those spaces as well.
    Garage Heaters

  • Warehouse Heaters – Warehouse heaters are used to heat large spaces such as warehouses where complete insulation and forced air convection heating are impractical.
    Warehouse Heaters

Chapter 5: Advantages of Infrared Heating

Infrared heaters are versatile, easy to install and maintain, and are available in different designs to suit various needs. The benefits of infrared heating are as follows:

  • Infrared heaters are energy-efficient. Infrared heaters warm surrounding objects directly. Heat loss is avoided because these heaters don’t waste energy by heating the surrounding medium. This feature consequently reduces energy costs.
  • Infrared heaters work instantly. Since the heat produced by radiant heaters is directed to the surrounding bodies, they don’t spend time heating the air and then transferring it to the objects like traditional convection heaters. This feature is helpful in drying applications.
  • Infrared heaters give off comfortable and more-natural heat. The heat given off by infrared heaters is comparable to the radiant heat from the sun (excluding the ultraviolet waves). Their heat doesn’t increase the humidity level and reduce the oxygen content in their environment and infrared heaters do not evaporate moisture in the air. With infrared heaters, we feel warm and refreshed at the same time.
  • Infrared heaters reduce the growth of molds and mildew. Infrared heaters inhibit the growth of these microbes since the mobility of moisture is limited. This feature reduces cases of stuffy noses, wheezing, and itchy eyes and skin. This is also beneficial for places where food and medicines are handled, stored, and consumed.
  • Infrared heaters operate silently. Unlike convection heaters, most infrared heaters don’t rely on fans and blowers to circulate the heated air. Those other devices generate noises that are undesirable for bedrooms and office areas.
  • Electric infrared heaters are environmentally-friendly. Electric infrared heaters don’t generate gaseous products, toxic fumes, or fine particulates that have adverse effects on the environment. Additionally, they do not agitate the surrounding air, which carries dust and allergens. The energy efficiency of infrared heaters also helps to green the environment.
  • Infrared heaters have amazing health benefits. The use of infrared heaters improves living by providing numerous health benefits to our bodies. Infrared heaters promote overall health because:
    • They do not dry out skin or sinuses.
    • They promote blood circulation.
    • They promote good respiratory health.
    • They reduce muscle and joint pain and inflammation.
    • They boost the immune system.
    • They promote good sleep.

Despite all this, infrared heaters can be a safety hazard. The hot core material of an infrared heater must be maintained to radiate heat to its surroundings. This may cause serious burns when touched or when one is exposed for a long period at too close a distance. Looking directly at the glow of high-intensity infrared heaters may cause impairment to the vision. Injuries and harm can be prevented by placing engineering controls and practicing vigilance when around an infrared heater. These few negative considerations, however, will never outweigh the benefits that an infrared heater can bring.

Conclusion

  • Infrared heating is used to heat surrounding bodies using infrared radiation.
  • Developments have been made to harness thermal energy through infrared electromagnetic radiation for the benefit of mankind.
  • In infrared heating, thermal energy is carried by infrared waves. The waves in the infrared region have a wide range of wavelengths. The shorter wavelengths have higher frequencies and higher heating temperatures.
  • Radiation is the heat-transfer mechanism involved in infrared heaters. It directly warms the surfaces of the objects within sight without heating the surrounding air, making infrared heaters unique and advantageous.
  • Infrared heaters are composed of a heating element and a reflective surface. The reflector greatly influences the efficiency.
  • Infrared heaters can be classified based on the source of energy. Electric infrared heaters convert electricity to heat by resistive heating. Radiant gas heaters utilize the energy stored in fuels.
  • Infrared heaters can be classified based on the wavelengths of the infrared waves they emit. There are near-infrared heaters, medium-wave infrared heaters, and far-infrared heaters. Each type of infrared heater has different characteristics of the heat they produce and operates within different temperature ranges.
  • Infrared heaters are made from different materials and are useful for a variety of applications.
  • Infrared heaters are advantageous. They are energy-efficient, work instantly, and are environmentally-friendly. They promote the overall health of users and produce heat safely, economically, and efficiently.
  • Extra precaution must be taken when working around infrared heaters. However, the benefits provided through infrared heaters far outweigh the few negatives associated with these devices.

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Table of Contents

Chapter 1: What is Infrared Heating?

Chapter 2: Operating Principles Behind Infrared Heaters

Chapter 3: Industrial Uses for Infrared Heaters

Chapter 4: Types of Infrared Heaters

Chapter 5: Advantages of Infrared Heating

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