Radiant heaters (also known as infrared heaters, quartz heaters, electric infrared heaters or quartz infrared heaters) transmit energy as infrared waves. A number of factors must be considered when thinking about radiant heat: energy transfer is only “line of sight”; different materials absorb different wavelengths and amount of infrared energy; different emitters will generate different wavelengths; and operating environment and control are environmental factors to consider.
Electric radiant heaters can be ceramic, quartz, T3 (tungsten), or tubular in construction. T3 lamps generate the shortest wavelength and are the “hottest” of the group. Quartz (either quartz tubular or panel) heaters are considered to generate a medium wavelength. Ceramic and metal sheathed tubular emitters generate long wavelengths. The wavelength emitted by the heater is directly proportional to the watt density of the heater. Unlike convection or contact heating, the wattage of an infrared heater is not necessarily an indicator of the amount of energy being absorbed by the target.
T3 lamps are tungsten element, inert gas filled bulbs. Of the infrared heaters, T3 lamps respond the fastest. The tungsten filament causes an inrush current when these are turned on. T3 bulbs tend to be expensive and fragile, relative to other forms of infrared emitters.
Quartz heaters can be made of tubular quartz or in panel form. Because the element can be exposed to open air, quartz heaters do not have to be sealed, and thus are less expensive than T3 lamps. Sizes and shapes of quartz elements are limited only by structural support of the element. In addition, coatings can be placed on the tubular quartz to provide additional focus and reflectivity.
Quartz infrared panels are used extensively in drying, textile, thermoforming and curing processes. The variations of sizes of a quartz infrared panel allow many applications and ease of wiring.
Ceramic emitters are made by encasing a resistance element in ceramic. Characteristics of the ceramic limit individual the size of individual heaters. Often these heaters are often placed in grids to make a larger panel. These heaters excel at tasks such as heating heat shrink tubing, warming and curing, thermoforming, and softening plastics.
Thermocouples can be added into both the ceramic infrared and the quartz panel heaters, giving a benchmark for repeatability and baseline information for testing purposes.