How Does Quartz Heating Work
The principle of radiant heating is a well-known one and has been in use for some years. However, there are important differences between long wave emitters such as the metal sheath and medium or short wave emitter quartz lamps. For example, the radiant efficiency of a short wave infrared heater is up to 96% and that of a medium wave heater is around 40%.
Electric infrared energy travels in straight lines from the heat source. This energy is directed into specific patterns by optically designed reflectors. Infrared, like light, travels outward from the heat source and diffuses over a distance. Therefore for successful comfort heating, there must be reasonably even levels of heat throughout the area to be heated. Proper mounting heights of the individual heaters, accurate heater spacing, reflector beam patterns, and heat wattage must all be specified to generate the proper heating levels at the task area. The amount of heat delivered can also be adjusted by controllers which can provide On-Off or variable outputs.
Short wave high intensity radiants work like sunshine and give warmth you can feel the instant the heaters are switched on. Short wave heaters warm people and objects within the beam rather than the air; resulting in a pleasantly fresh rather than stuffy environment. Long and medium wave heat has comparatively poor heating characteristics, especially when used outdoors as it relies on heating the air and does not penetrate the skin to warm up the person. The heat is not directional and is susceptible to air movement. The wavelength is inversely proportional to temperature. As the temperature goes up, the wavelength goes down. A medium wave filament only heats up to around 900º Celsius, making it suitable for curing and drying processes rather than outside heating. Long wave heaters are ideal for heating inside, where a low level of heat is required and pre-heat time is acceptable. Ceramic plaque heaters fall between medium and long wave heating up to around 500º Celsius, but again are of no use whatsoever for alfresco heating as they warm the air rather than penetrating through it and warming the person.
Short Wave Lamp
Short wave halogen heat lamps consist of a tungsten filament heated by the passage of an electric current to a temperature of some 2200º Celsius. At this temperature most of the emission is in the short wave infrared band (1.2 microns). However, as with all tungsten filament lamps, the tungsten will evaporate in time and deposit itself on the wall of the lamp. To prevent this undesirable effect, a small amount of halogen gas is added to the envelope of the lamp and hence a process of re-composition takes place. As the tungsten evaporates it will combine with the halogen gas to form a tungsten halide and so prevent the tungsten being deposited in the wall of the lamp. The tungsten halide will re-combine with the filament releasing the halogen and re-depositing the tungsten on the filament. This process is a continuous one and is known as the halogen cycle.
For heating applications, a ruby sleeve or gold dichroic coating encloses the halogen heat lamp to filter out the intense white light and provide a pleasant warm glow.