Why are Quartz Lamp Heaters Better Than Quartz Tube Heaters or Metal Sheathed Tubular Heaters, for Radiant Efficiency, in a Windy Outdoor Environment?
Why are Quartz Lamp Heaters Better Than Quartz Tube Heaters or Metal Sheathed Tubular Heaters, for Radiant Efficiency, in a Windy Outdoor Environment?
Outdoor Radiant Comfort Heating
Outdoor heating (such as patio heating) has unique considerations. The main aspects are wind level, radiant efficiency, infrared wavelength, response time and durability.
The presence of wind, however, can be the deciding factor. Any heating element will have convective heat losses that are greater in the wind than with no wind. Basically, some of the heat that is contained in the thermal mass of the element gets lost quicker in windy conditions due to convection and gets blown away before it has a chance to get emitted as infrared waves. The element loses heat quicker to convection because the wind is constantly blowing away any heated air near the element. The greater the temperature differential between the element and the air, the greater the heat loss is to convection from the heater.
Quartz Lamps
For these reasons, when choosing heaters to use outdoors, the weight and density of the element is considered. Quartz lamps (also known as Tungsten, Short-wave, T3 or Quartz Halogen) are the most effective choice from a heating standpoint because they have the lowest mass and they emit short-wave infrared radiation from their tungsten element surrounded by halogen gas, which quickly heats up and emits to people and objects with less heat loss due to wind.
Metal Tubular Heaters and Flat Panel Emitters
On the other end of the performance in wind range (due to weight and efficiency issues) is metal sheathed tubular heaters with long-wave infrared. They emit much more convective heat (heating the air). Flat-Faced Panel Emitters and Black Body Heaters are similar.
Quartz lamps radiant efficiency is 80-90% and Metal tubulars radiant efficiency is 40-60%. This is mainly due to the much higher temperature of quartz lamps which produces a short wavelength of infrared.
Quartz Tube Heaters
Quartz tubes are in the middle of the two at 60-75% radiant efficiency and Medium-wave infrared. They have less wind-resistant than quartz lamps due to their higher mass and lower wavelength of infrared from their nichrome element in air. Quartz tubes, along with quartz lamps are also a popular choice since they still provide efficient medium-wave infrared that is absorbed well by people and materials, and they are much less fragile and longer life than quartz lamps.
Conclusion
When selecting an outdoor radiant heater, wind should be a primary consideration.
Quartz lamp heaters (short-wave IR) offer the highest radiant efficiency, fast response, and minimal wind sensitivity. They can deliver superior comfort, energy efficiency and high performance. However they offer the shortest life, with 5,000 hour or less average life expectancy being common.
Quartz tube heaters (medium-wave IR) provide a balance between durability and moderate efficiency, with greater than 10,000 hour average life expectancy being common.
Metal sheathed tubular heaters (long-wave IR) are highly durable with the longest life but least efficient with much higher heat lost to convection. Average life expectancy is very long and can even be greater than 20,000 hours of operation.