In powder coating, this direct transfer of energy creates an immediate reaction in the polymer, and curing called crosslinking begins quickly once the surface is exposed to the emitter. In IR curing ovens, heat is very rapidly transferred by radiation directly to the coating. Infrared ovens can cure a coating much faster than convection ovens, since they directly heat the part surface that is coated and do not waste BTUs to heat the entire substrate or the surrounding air. Subsequent heat conduction may sometimes cure even areas of the part that are not completely exposed to direct IR heat; however, differences in part structure and mass will affect the uniformity of this cure unless the intensity of the infrared heat is adjusted for these differences.
Infrared light is located on the electromagnetic spectrum between visible light and microwaves, and is measured in microns. Temperature determines the wavelength of the source IR emitter, so its peak wavelength can be controlled by changing its temperature. However, although all emitters can be adjusted for wavelength in this way, not all heaters are designed to emit the complete spectrum of long, medium and short wavelengths.
It is measured on a scale of 0 to 1, with an ideal blackbody having an emissivity of 1. Emissivity and absorptivity are closely related, so materials with a high emissivity value also readily absorb radiant energy. Highly reflective surfaces e. Another important spectral characteristic that plays a role in the ability of the coating to absorb or reflect IR energy is color sensitivity. This is of particular concern with highly reflective colors such as chrome or silver.
Color sensitivity is more pronounced with short-wavelength IR that is produced by higher-temperature emitters. Previous Next. Three Methods of Heat Transfer: Convection, Conduction, and Radiation Heat transfer is the physical act of thermal energy being exchanged between two systems by dissipating heat.
Conduction Occurring through contact, conduction is the transfer of energy from an area with greater kinetic energy to an area with lower kinetic energy. Convection When a fluid, such as air or a liquid, is heated and then travels away from the source, it carries the thermal energy. Radiation The final type of heat transfer is thermal radiation.
How Infrared Process Heating Works Whether used for preheating, heating, finishing, or postheating infrared heating can be used for a wide variety of applications. New to Air Pollution Control Technology? Not Sure Where to Begin? Leave A Comment. Connect With Us:. This field is for validation purposes and should be left unchanged.
However, as a precaution, one should avoid prolonged viewing of high intensity infrared emitters at distances less than 15'. Reflectors and shields used to improve the efficiency of the oven also make them safer. Often costs for infrared ovens are comparable to convection ovens, and they can be less expensive. In general, the overall size of the infrared oven will be smaller than a comparable convection oven, resulting in savings in materials and fabrication costs.
Individual components of an infrared oven may be more expensive than those of a convection oven. For example, electric infrared emitters may cost more than a gas burner. Another factor to consider is the ability to control infrared, which results in more efficient use of electric or gas. Infrared ovens are more efficient than convection ovens in delivering energy to the product. Actual costs will be determined by the cost of gas vs. Some infrared ovens' emitters provide a nearly instant response with virtually no warmup time required.
These ovens can be turned on shortly before the process begins and off during production stoppages, which may reduce operating costs.
Both infrared and convection ovens require regular preventative maintenance. Maintenance of infrared ovens includes examination of emitters and replacement of any that have failed. In addition, regular cleaning of reflectors in electric infrared ovens will help maintain efficiency.
Every object with a temperature above absolute zero emits infrared energy. This is because there exists in every object a measured amount of heat, so each object has the ability to radiate heat from itself. The object that radiates heat is called the emitting source, and the object to which it radiates heat, having a lesser amount of heat content, is called the target.
There are several physical laws that explain the properties of infrared radiation. The Stefan-Boltzman law of radiation states that as the temperature of a heat source is increased, the radiant output increases to the fourth power of its temperature.
The conduction and convection components increase only in direct proportion with the temperature change. In other words, as the temperature of a heat source is increased, a much greater percentage of the total energy output is converted into radiant energy. For the purpose of this handbook, we will address only those sources of infrared heat used in industrial heating applications. This generally means looking at emitting source temperatures in a range from degrees Fahrenheit to 4, degrees Fahrenheit.
These temperatures are not to be confused with oven set point temperatures or any other temperature requirements related to your product or process. As the emitting source temperature moves from degrees to 4, degrees, the radiant output increases with a corresponding increase in peak wavelength.
At each temperature point, there is a unique set of wavelength characteristics and peak wavelengths. An additional set of physical laws helps us to understand this relationship. Infrared heating is the transfer of thermal energy in the form of electromagnetic waves.
It is related to visible light and other forms of electromagnetic energy shown in the electromagnetic spectrum below. The infrared portion of this spectrum has been expanded to show that we can further divide infrared into long wave, medium wave and short wave.
The electromagnetic spectrum describes the various types of electromagnetic energy based on wavelength. By describing an infrared emitter as long wave, medium wave, or short wave, one can quickly determine the approximate temperature range an emitter is operating, as well as an approximate wavelength range measured in microns.
Since the temperature of a source determines the wavelength characteristics of that source, the peak wavelength of a given emitter can be controlled only by changing the temperature of the emitter.
All emitters can be adjusted for wavelength simply by adjusting their temperatures.
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