Whether the customer is blue-chip and international or small and local, it seems to make no difference: Real user know-how about infrared (IR) heating technology is generally rare and limited in manufacturing across all international markets.
Our company, Ceramicx, based in southwest Ireland, supplies IR heating technology to over 62 countries around the globe, and – with the possible exception of the Far-East markets – the lack of know-how is something that we often have to overcome from the start of a project.
Despite being in the marketplace for about 50 years, the misconceptions about IR are many and longstanding. So much so that Ceramicx has invested in communications work to put the record straight. IR myths include the following. Perhaps you may have even guessed one or two wrong.
- 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.
|Fig. 1. Infrared-heating test rig used to characterize the process heat performance for plastic sheet and film materials|
IR Heating of Plastics
At the world’s largest plastics exhibition, K 2010 in Dusseldorf, many, if not all, of the aforementioned misconceptions were recently on view.
Our IR test rig for heating plastics (Fig. 1) got plenty of use in order to help many plastics manufacturers see the differences between three different kinds of typical IR heating for their industry and their effects on various kinds of plastics – old and new.
|Fig. 2. Thermoformers require sophisticated heating patterns|
ThermoformingThe bulk of Ceramicx IR heating work in plastics is for the oldest part of the plastics processing industry – the thermoforming process. 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.
|Fig. 3. Infrared furnace for bonding polymer to concrete|
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.
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.
But if in the case of dioxins we started using a source temperature of 4532°F to create the watt density needed, the effective radiation would probably not hit the atomic structure of the gas that you are trying to destroy. With IR processes, we need to match the wavelength to the molecular bonds.
One area where industrial opportunity has been grasped is via our 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 contaminations.
In production, most of the BM Anlagenbau product range is typically treated with polymer paints and then needs to dry before being packaged and shipped. IR heating has a key role to play by preparing the concrete and stone surfaces before the polymer paints are applied. As with plastic thermoforming, IR preheating improves the surface readiness and also the penetration of the coating material into the concrete. This makes for better adhesion and for better long-term protection of the concrete product. Pre- and post-spray infrared heating also eliminates the tendency for a developing film surface to “bubble” and crack the surface of the coating. With two heat applications, the material initially evaporates from the substrate and then from the top.
The overall effect of the plastic film is a silk-like finish to the concrete and stone. This is often referred to as the “wet effect” and increases the depth of color in the case of concrete, making the product much more visually appealing.
We learned a great deal from being part of this project, from designing the right array of elements and infrared emissions to engineering the infrared reflectors to provide exactly the right kind of heating for the concrete, which gives the whole system the right price/performance ratio. The high-speed infrared heating also allowed the client to adjust the overall heating systems in a modular manner – minimizing space, helping changeovers, reducing production costs and improving competitiveness.
The Science of IR
Ceramicx is also happy to report that we are advancing the science of IR within leading universities, helping one leading U.K. institute to investigate the distortion of complex pressure-vessel systems under varying thermal-boundary conditions.
The project brief requires that the vessel be heated to temperatures in excess of 760°F and that a variety of heat-flux distributions be considered. The university undertook a program of thermally induced distortion of the vessel, which was measured using laser triangulation sensors that could be traversed circumferentially and axially along the part. These measurements were made under a variety of heating conditions.
The university devised an approach using IR heating as a means of creating the relevant heat loads and approached Ceramicx as a supplier of a heater assembly.
We designed a 65-kW, 56-element radiant heater system for application on the inner surface of 900-mm conical vessels, giving the capability to vary the output power from each IR element individually.
The expertise we offered in terms of heater-element specification, reflector properties and overall build standard has proven essential to the successful outcome of the project.
The Future of IR
Future pursuits by Ceramicx will include better definition of the IR toolbox and its abilities. Ceramicx is currently working with leading universities worldwide to better define the use and understanding of IR and develop education modules for both customers and third-level institutions alike. Armed with an understanding of the science and art of infrared, Ceramicx now intends to find methods to educate engineers, companies and educational institutions worldwide as to how to identify opportunities for infrared through understanding of the topic. IH
For more information: Contact Cáthál Wilson, projects manager, Ceramicx, Gortnagrough, Ballydehob, Co. Cork, Ireland; tel: +353 28 37510; fax: +353 28 37509; e-mail: firstname.lastname@example.org; web: www.ceramicx.com or the U.S. distributor, Brett Wehner, president, Weco International, 841 Tacoma Court, P.O. Box 189, Clio, Mich., 48420; tel: 810-686-7221; fax: 810-686-7564; e-mail: email@example.com; web: www.wecointernational.com
Additional related information may be found by searching for these (and other) key words/terms via BNP Media SEARCH at www.industrialheating.com: infrared heating, IR, wavelength, electromagnetic energy, absorption, relection, transmission, thermoforming, heat flux