![]() Infrared heaters are commonly used in infrared modules (or emitter banks) combining several heaters to achieve larger heated areas. Gold is used because of its oxidation resistance and very high infrared reflectivity of approximately 95%. Consequently, the infrared radiation impinging on the product is virtually doubled. Industrial infrared heaters sometimes use a gold coating on the quartz tube that reflects the infrared radiation and directs it towards the product to be heated. As absorption and emission are based on the same physical causes in each body, ceramic is ideally suited as a material for infrared heaters. Containing 8 meters (26 ft) of coiled alloy resistance wire, they emit a uniform heat across the entire surface of the heater and the ceramic is 90% absorbent of the radiation. When light is undesirable or not necessary in a heater, ceramic infrared radiant heaters are the preferred choice. While carbon filaments are more fickle to produce, they heat up much more quickly than a comparable medium-wave heater based on a FeCrAl filament. Low temperature alternatives for tungsten are carbon, or alloys of iron, chromium, and aluminum ( trademark and brand name Kanthal). The most common filament material used for electrical infrared heaters is tungsten wire, which is coiled to provide more surface area. In the mid 1950s the motor vehicle industry began to show interest in the capabilities of infrared for paint curing and a number of production line infrared tunnels came into use. After World War II the adoption of infrared heating techniques continued but on a much slower basis. Banks of lamp bulbs were used very successfully though by today's standards the power intensities were very low, the technique offered much faster drying times than the fuel convection ovens of the time. The main applications were in the metal finishing fields, particularly in the curing and drying of paints and lacquers on military equipment. During World War II infrared heating became more widely used and recognized. Through his experiment Herschel found that red light had the highest degree of temperature change in the light spectrum, however, infrared heating was not commonly used until World War II. The first was a prism to catch the sunlight and direct and disperse the colors down onto a table, the second was a small panel of cardboard with a slit wide enough for only a single color to pass through it and finally, three mercury-in-glass thermometers. ![]() This instrument was made from three pieces. He made an instrument called a spectrometer to measure the magnitude of radiant power at different wavelengths. German-British astronomer Sir William Herschel is credited with the discovery of infrared in 1800.
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