Infrared Heating

Infrared Heating: Much More than Temperature

Infrared (IR) heating technology can be a rare real-user knowledge throughout the world.  An article written by By Adrian Lunney and C. Wilson for industrialheating.com addresses the myths about IR,  along with how it may be applicable to different industries.

Infrared Myths

  • IR energy can be harmful. Wrong. IR energy is naturally occurring from the sun, travels to Earth in wavelengths and is absorbed by all objects. Every object emits and absorbs IR naturally without harmful effects.
  • IR radiation is heat. Wrong. It is electromagnetic energy that can be used to generate heat.
  • An IR system is only concerned with heating. Wrong. There are three considerations when dealing with IR: absorption, reflection and transmission. IR systems emit electromagnetic energy. An emitter produces wavelengths with mechanical properties that have to be absorbed, transmitted or reflected. An effective system will deal with these three issues as efficiently as possible.
  • To control temperature is to adequately control an IR emitter. Wrong. Radiation is generated by source temperature. Adjustment of temperature changes the IR wavelength, hence the reason systems operate within a waveband output and not a wavelength output.
  • IR absorption of a target material is dictated by a single spectral analysis at ambient (e.g., 70°F). Wrong. The spectral analysis and spectral absorption characteristics change as the target material temperature changes. It is therefore important to consider the use of waveband rather than wavelength to ensure the output from an emitter or system is capable of meeting the spectral absorption characteristics of the material.
  • Emitters can be set at full values without thermocouple watch control. Wrong. There is a significant difference between starting the emitters (heaters) at an ambient temperature (e.g., 70°F) and starting emitters in an ambient temperature of 760°F. Turning on the heater at higher ambient values could result in burnout of the emitter.
  • Temperature control systems can typically set the performance of IR systems. Wrong. This method of operation is a poor way to control radiation because temperature and % control are not developed with radiation in mind. Since this usually presents as the typical control choices available, however, it should be used with care.
  • IR emitters can be used like furnace elements. Wrong. The materials used to build effective infrared emitters do not lend themselves to being used in a furnace-like environment. Transmission, absorption, reflection and the resulting directional qualities imparted are not being adequately dealt with, which will lead to heat-up and burnout of the emitters if used in a furnace-like capacity.
  • Radiation can be treated in a similar fashion to conduction and convection. Wrong. Under no circumstances are conduction and convection comparable to radiation. These are three separate methods of heat transfer that do not relate to one another.
  • Environmental conditions such as weather have no impact on the use of IR. Wrong. These have a huge impact. The conditions of the surroundings (e.g., humidity) will have a big effect on the transfer of infrared radiation.

Infrared Heating

Thermoforming

Plastic sheet material is simply heated and then impressed or vacuum formed, and commodity polymers such as polypropylene, polystyrene and various kinds of polyethylene are dominant. Plastic thermoformed products vary hugely in size, shape and technical parameters.

Much of the world’s small-container food and beverage packaging is made from fast-cycling, multi-impression tools quickly punching out product from plastic sheet, which has been heated to a temperature range between 400°F and 800°F.

Thermoformed plastic products can also comprise some of the largest mass manufacturing that plastics has to offer, including many large moldings for the automotive markets (e.g., door liners; body liners; fridge and freezer door liners).

The IR heating issues here are of a different kind. The dwell time for each product cycle is normally much longer and the plastics much thicker. Given the increasing product sophistication, the heat control system perhaps needs to apply radiation to the mold in a particular pattern for a set length of time (Fig. 2).

Despite the lack of know-how, plastics manufacturing generally solves its own IR issues. The fixed nature of the high-value capital plant in thermoforming generally means that the owners are incentivised to understand their IR heating and to resolve problems.

Infrared Heating

Other IR Heating Applications

Other manufacturing sectors, such as construction, metal fabrications or process/chemicals, present different challenges. The same lack of understanding of IR as a heating technology can lead to the misuse of effort and equipment.

Whatever the job, the essence of IR heating involves three factors: absorption, transmission and reflection. The heating has to generate a source temperature to generate an IR wavelength. It must then have the ability to transfer that energy to a target material while ensuring that the electrical input is transferred to IR output in a very efficient, controllable and comprehensive manner.

Infrared Heating

Emissions Treatment

IR heating, for example, might be used in an emissions treatment plant. The process might require a certain intensity of IR radiation to bring the temperature up to 1472°F to destroy dioxins. By contrast, evaporating a substance – for instance, to reduce humidity in a plant location – more typically requires a source temperature of 2730-4352°F.

Industrial Opportunity

German heating-expert partner, Friedr Freek, in providing manufacturer BM Anlagenbau with some cutting-edge production processes in order to make its innovative range of plastic-coated concrete and stone products (Fig. 3).

These specially treated concrete and stone products resist wear and tear, hold their aesthetic through the product lifetime and are graffiti and vandal proof.

IR heating technology is increasing in popularity since it creates weather resistance and other aspects of aging and thus extends product life and service life; reduces efflorescence; and guards against tire abrasions, food, oil and chemical contamination.

To read more on the article, please click here.

AccuTherm can help you learn more about infrared heating, contact one of our experts today at 573-735-1060 or visit us at www.accutherm.com.

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