Infrared Application of the Month #1:
Preheating of Plastic Pipes for Welding
A manufacturer of plastic (polymeric) pipes had been using a hot plate preheating system in process prior to end welding; they sought a more effective means of preheating. The solution was a series of shortwave heaters from Heraeus. The new system provides more than four times the power yet uses less energy because the cycletime has been reduced 90%.
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Infrared Application of the Month #2:
Curing of Powder Coating on Steel Cylinders
A manufacturing process made use of a gas-heated air oven for powdercoating of steel cylinders. The manufacturer upgraded to a Heraeus infrared system. The new system offers rapid heat-up time; more even curing of the powder; low maintenance costs and a reduction in oven size from 30m long to only 6m.
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Tech Center Spotlight:
Carbon Mediumwave Heaters
High heating efficiency and rapid cool down make the mediumwave carbon heater from Heraeus the only medium-wave heater to offer you shortwave response times. Suitable for all medium-wave applications, this heater also offers the capability to match temperatures to the optimum absorption wavelength for each application. Together, these features eliminate overheating and contamination of sensitive substrates.
A particular large portion of medium wave radiation is absorbed in water, solvents and plastics and converted into heat. This allows significant benefits: carbon heaters dry printing inks, with less stress for the paper because the radiation acts more intensively on the ink. The high power heater increases print drying speed and reduces drying time. It also heats plastics in a targeted manner, with less heating of the surrounding environment.
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Special Designs:
Slot Heater
Infrared heater with a slot in one of the tubes, working like a drying channel for fibers or ropes. Twin tube made of quartz glass, gold coating around the whole heater. Fast response medium wave heater. The special slot design makes drying very intensive and efficient.
A wide assortment of special design heaters is available from Heraeus. Click HERE to for details.
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Technical Learning: Introduction to IR Technology, Part 1
There are two basic means of heating a product electrically, by direct and indirect methods. With direct heating, heat is generated within the mass of the material (e.g. by microwave and radio frequency energy in the case of dielectric materials or by induction or resistance heating in the case of electrically conducting materials). With indirect heating, heat is transferred to an article by any of the three familiar methods of conduction, convection, and radiation.
Conductive heating is achieved by placing an article into touch contact with a heat source. The rate of heat transfer is determined by several factors, not just the thermal properties and temperatures of the two bodies.
The surface conditions over the contact area, the pressure of contact and the nature of any gas, liquid or solid films at the interface all play a part in the conductive process. Radiation can also contribute to heat transfer across the interface.
Convective heating relies on the movement of a hot fluid or gas, such as air, which acts as a carrier of heat from one body to another. Natural convection occurs when different zones of the gas or liquid have different temperatures and densities. Industrial process heating commonly makes use of forced (air) convection, whereby the air is directed towards the substrate by a fan.
The rate of heat transfer depends on many factors including the temperature differential between the heating air and the substrate, and the density and rate of movement of the air.
In the context of heat transfer, radiation refers to the thermal variety (non-ionizing radiation), and should not be confused with radiation produced at wavelengths shorter than the visible spectrum (e.g. X-rays).
Thermal radiation takes place without the need for an intermediary agent such as air because energy is transmitted as electromagnetic rays emitted from a heated body. The rate of heat transfer depends on such factors as the temperatures of the heater and the receiver, the ability of each to emit and absorb radiant heat, their geometrical shape, their active areas, and relative positions or proximity.
The human eye differentiates between light-producing or glowing sources and invisible emissions. Infrared radiation occupies a waveband immediately adjacent to the red end of the visible spectrum. “Black heat” is a term sometimes used to describe the infrared band.
Heaters of visible radiation produce thermal radiation within the IR band as well as the visible band. Even at the very intense light producing temperatures in the order of 5000°C, a heater produces more energy in the infrared than in the visible band. Heaters that produce some light energy are also classified as infrared, although in scientific terms the description is not absolutely accurate.
Coming in the next issue: Intro to IR Technology, Part 2.
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That's it for this month's issue of Application Notes for IR Heating. Feel free to encourage your colleagues to subscribe. Just click HERE to send them an invitation to subscribe. It's quick, easy, FREE, and no-obligation.
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