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Air Heaters Sheathed Elements Open Coil Heaters Osram Sylvania Air Heaters
Air heaters, or Convection Heaters, heat a gas
which transfers heat to the target material. Common uses The application determines the air heater required. Variables are: exit and inlet air temperature; air pressure; air flow or volume; space for installation; process requirements for temperature response and ability to control temperature range; quality (cleanliness) of air; and installation or plumbing connections. Electric air heater elements can be sheathed heaters, or bare resistance wire (open coil heaters). Each has advantages and disadvantages. Sheathed Elements
are durable, are electrically insulated from gas being heated, and Upper limit exit air temperatures approach 1000 Deg F for sheathed heaters. When looking at high temperature applications, great care must be taken to evaluate watt densities on the element. Sheathed elements are ideal for duct heaters; for applications where heat response is not important; where space is not a consideration; or where contaminated inlet air is a problem. Sheathed elements can be tubular heaters, finned heaters, or cartridge heaters. Open
Coil Heaters use bare resistance wire to heat air. Because the
resistance wire operates at greater watt Because of low element mass, open coil heaters respond much faster to changes in power levels. The fast response allows precise temperature control, even in a variable process. Open coil heaters require much less space than sheathed elements. Process connections and plumbing requirements are also simplified. Because of the compact size, open coil heaters are easily deployed Higher watt densities cause open coil heaters to be more susceptible to catastrophic failure when heat cannot be transferred to the gas. Control improvements have helped to reduce or eliminate the potential for failure due to rapid changes in air flow. Open coil heaters are more sensitive to contaminated air. Temperatures of 1400 Deg F are possible with air, and up to 1600 Deg F possible with heaters in series. Top of Page |
for air
heaters include drying, laminating, sealing, shrinking, softening, annealing, bonding,
activating, melting and welding.
can be more durable than open coil. Sheathed elements also require much
larger installation space and are slower to respond to process change. 
densities than sheathed elements,
greater heat transfer can occur in a smaller space, resulting in higher exit air temperatures
and or smaller physical heater size.