The application of infrared (IR) energy in process heat ovens has provided industry with an established method for saving energy in selected operations, when compared with traditional convection oven systems.
Infrared ovens are especially prevalent in finishing, thermoforming and other thermal processing operations where drying, preheating or dehydrating is needed. The energy saving benefits of infrared over convection, or in combination with convection heat, can be realized by first knowing some of the characteristics of infrared and convection heat, and how these differences can affect the process.
Infrared is not dependent on air movement to deliver heat to the product in the oven. Because infrared is a direct heat, it utilizes a fraction of the energy since convection heat must raise the volume of air in the oven to a set temperature. For this reason, along with other benefits mentioned below, the required energy may only be 25% of the energy load needed in a convection oven.
If the cost of gas (convection) is 1/3 the cost of electric for example, you will achieve a direct energy savings, since the electric percentage consumed vs. gas is less than the cost-difference percentage.
Another reason why infrared saves energy is the ability to zone-control the heat output to the product. Convection air cannot be nearly as precisely controlled as infrared energy. Since infrared waves can be focused and directed, the ovens are almost always divided into zones to deliver just the right amount of energy to the product. Intensity may be varied according to the type and thickness of the product, the placement of the parts in the oven (distance from the emitter, etc.), or the shape of the parts.
IR has a relatively fast response time in comparison to convection heat. Therefore, startups and shutdowns can occur without much loss of energy from the emitters, and parts already in the oven are not overheated if a line stoppage occurs. Energy is essentially used only when the system calls for heat to be directed to the product.
Faster emitter response also means that zoning, mentioned above, can be even more accurately controlled. In all, this means product can be brought to desired temperatures in a shorter period of time and processed through the oven more quickly, normally translating into energy savings.
Fitting Infrared to the Process Heating Application
Not all applications are suited for infrared due to properties of the product or how the parts are presented in the oven. Infrared can, however, be combined with convection heat to marry the best properties of convection heat and infrared heat.
Using an infrared "booster" oven should result in energy savings. Infrared can preheat or ramp up the heat much faster, and ultimately allow for the eventual turndown of the convection oven.
All manufacturers of infrared oven systems testing, normally free of charge. They can quickly identify the right system for a specific process heating application and can readily advise the energy savings that could be expected.
This article was provided by the Infrared Equipment Division of the Industrial Heating Equipment Association. For further information, contact IHEA at www.ihea.org.