Open coil heating elements are coiled resistance wire (usually Ni-Chrome or Kanthal, but also others) fixed onto a supporting element.
Selection of correct wire gauge, wire type and coil diameter requires experience in industrial heating. Standard air heating elements are available on the market, but quit often they need to be custom built. Open coil air heaters work best below air velocities of 80 FPM. Higher air velocities could cause the coils to contact each other and short out. For higher velocities, select a tubular air heater or strip heater.
We recommend the use of a flow switch in the airstream to avoid any potential overheating of the resistance wire. Because of the low mass and fast response time of air heaters, we recommend the use of solid state relays or a zero-cross SCR or phase fires SCR.
DeltaT has the capability of repairing your open coil elements.
The big advantage of open coil heating elements is the very quick response time.
There are standard open coil heating elements available on the market and we carry some in stock. Most of these elements need a constant airflow over the resistance wire, but if watt densities are low enough they may not burn out in still air.