FAQ

Q&A About Infrared Heating

  • What is infrared (IR) energy?
    IR energy is a form of electromagnetic wave with a longer wavelength than visible light that is sometimes referred to as “heat radiation”. It is the main form of energy that the Sun uses to heat the Earth.

  • What are the differences between short and medium wavelength IR?
    Definitions of the short and medium wavelength ranges differ from source to source, but for our purposes we typically operate short wavelength heaters in the 1 to 2.5-micron range and medium wavelength heaters in the 2.5 to 6-micron range. Shortwave heaters typically operate at higher watt densities (over 100 W/in2) and their energy is less able to penetrate into a product. Thus, they are used for drying thin coatings or for surface heating applications. Medium wavelength heaters operate at lower watt densities (10-60 W/in2) and are better able to heat through a product.

  • What type of IR heater is suitable for a given process?
    Every application is unique and needs to be evaluated on a case-by-case basis. Factors such as material thickness, production rate, and even the facility environmental conditions all need to be considered. Casso-Solar has dealt with a wide variety of processes over our 60-year history and by utilizing our extensive knowledgebase we can determine the proper heater for a given process. For new and unique processes we perform lab testing on our in-house equipment to obtain the information needed to select an appropriate heater.

  • How do you determine the proper wavelength of IR to use for a given process?
    Every material has what is called a “spectral absorption curve” which determines what wavelengths of IR will be absorbed. Most IR heaters operate between 1 and 6 micron wavelengths. A material’s absorption curve is evaluated, and a heater is chosen that can produce energy at a wavelength that matches the material’s peak absorption point. For example, in the chart below we can see that water absorbs best between 2.6 and 3.0 microns, so an appropriate heater will be specified to match that output. More information on this methodology can be found here.


  • What thickness of material can IR energy penetrate and heat?
    It depends on the material and the wavelength of IR energy used. In the chart below the spectral absorption curve for polypropylene in 2 different thicknesses (1 mil and 10 mil) is shown. You can see that the curves are similar, but the thicker material absorbs more of the energy passing through at a given wavelength. For example, energy at a wavelength of 3.5 microns will be almost entirely absorbed by the first 1 mil of thickness, whereas at 4 microns the first 10 mils of material thickness will only absorb about 40% of the energy and the rest will penetrate through the material further. Casso-Solar evaluates every application using these curves to determine the proper heater type and wavelength to maximize efficiency.


  • What are the benefits of an IR system as compared to a gas-fired convection system?
    • Lower up-front capital investment
    • Less floor space required for equivalent system
    • No hazardous combustion by-products
    • Considerably less maintenance required
    • Fewer components = fewer points of failure
    • More flexibility with heat zoning possible
    • Simpler to install
    • Faster heat-up and response times
    • Does an electric infrared oven cost more to operate than a gas-fired convection oven?
    • In most places, gas is available for a lower cost than electricity per BTU or kW. However, because IR energy can be used to heat products directly and not waste energy heating the air inside the oven, it is much more efficient and ends up being cost competitive with gas-fired systems.

  • Is an IR always the most effective way to heat a product?
    Not always. IR works best when dealing with heating that needs to occur near the surface of a product. For most materials IR energy can only penetrate a short distance before being fully absorbed. For some applications it will be necessary to utilize a combination of infrared and convection heating to achieve the best results. Casso-Solar FHT and Furnace Tube heaters combine these technologies to take advantage of both types of heating.

  • Why is quartz frequently used in the construction of infrared heaters?
    The benefits of quartz in heater construction are numerous. Firstly, quartz is extremely resistant to thermal shocks so it can be rapidly heated and cooled without breaking. It also is nearly transparent to IR energy thus allowing almost all of the heat to pass through it to the product being heated. Lastly, quartz is an electric insulator so it will not short out heating elements.

  • Can IR heaters be added to an existing convection oven to increase its effectiveness?
    Certainly! IR “booster” sections can be added prior to the entrance of a convection oven or sometimes even within the oven itself. In many cases, a small IR section can greatly increase the overall effectiveness of a typical convection system for relatively little cost. Casso-Solar custom designs all of our systems, so we can work directly with our customers’ drawings and engineers to incorporate IR installations into existing equipment.