An infrared heater is a body with a higher temperature which transfers energy to a body with a lower temperature through electromagnetic radiation. Depending on the temperature of the emitting body, the wavelength of the infrared radiation ranges from 780 nm to 1 mm. The relationship between temperature and wavelength is expressed by the Stefan-Boltzmann Law. No contact or medium between the two bodies is needed for the energy transfer.A rough classification of infrared heaters is connected to wavelength bands of major emission of the energy: short wave or near infrared for the range from 780 nm to 1400 nm, these emitters are also named bright because still some visible light with glare is emitted; medium infrared for the range between 1400 nm and 3000 nm; far infrared or dark emitters for everything above 3000 nm.
For practical purposes, most infrared heaters are constructed by either using the emission of a flame (usually soot or a heated matrix) or an electrically heated filament as the emitting body. If an electrically operated infrared heater (infrared lamp) is used, the filament is usually protected by a heat-resistant quartz glass tube. Depending on the filament temperature, a filling of the quartz tube with inert gas (e.g. halogen) may be required to prevent filament degradation. These emitters use the same materials and principle as a light bulb.
Infrared heaters are commonly used in infrared modules (or emitter banks) combining several heaters to achieve larger heated areas.
Theoretically, the efficiency of an infrared heater is 100% as it converts nearly all electrical energy into heat in the filament. The filament then emits its heat by infrared radiation that is directly or via a reflector impinging on the product to be heated. Some energy is lost due to conduction or convection.
IR heaters are used in industrial manufacturing processes including curing of coatings; heating of plastic prior to forming; plastic welding; processing glass; cooking and browning food. They are used when high temperatures are required, fast responses or temperature gradients are needed or products need to be heated in certain areas in a targeted way. Their application is difficult for objects with undercuts.
Deshmukh, Yeshvant V. : Industrial Heating, Principles, Techniques, Materials, Applications, and Design. Taylor and Francis, Boca Raton, Fl: 2005.
Spectral Analysis for a range of Infrared Heater Types
