An air heater is any device designed to heat air prior to another process. It is used for a variety of applications such as baking, synthetic or vinyl fabric sewing, adhesive curing, ink or wafer of PC board drying, shrink fitting, laminating, lead frames soldering, metal-working, sealing, packaging, preheating process gases, and plastic welding.

There are many types of air heaters: the tubular type, the regenerative air heater, and the regenerator.

The tubular type and the regenerative air heater are used in thermal power stations’ steam generators. The regenerator is used for glass or iron manufacturing.

The tubular type is built into the boiler flue gas ducting. It is made up of tube bundles that pass through the boiler.

The regenerative air pre-heaters are made of two types—the rotating-plate regenerative air pre-heaters (RAPH) and the stationary-plate regenerative air pre-heaters (Rothemuhle).

The regenerator is made of brick checkerwork that enables hot gas exhaust to flow through and heat the bricks. The airflow is then reversed, with the hot bricks heating up the combusting air and fuel.

An air heater uses any of the following heat forces: forced convection, radiant heat, or resistive heating elements to heat air.

•    Forced convection
Forced convection is the transfer of heat by the flow of air or water driven by fans, blowers, or pumps.

Forced convection devices include slow combustion wood heating, heat torches, flued and unflued gas heaters, and fixed electric fan heaters.

•    Radiant heat
Radiant heaters make use of electromagnetic heat, which raises the temperature of any substance or material that can absorb radiation. They use reflective shield to divert radiant heat to heated surfaces.

•    Resistive heating elements
Resistance air heaters are sheaths surrounding a resistive heating element.

Another type of air heater is a duct heater, which is mounted in air delivery ducts. It supplies heat to delivered air. An enclosure heater offers humidity control, and freeze and equipment protection. A strip heater is a flat device that can be attached to solid surfaces, and is likewise used for freeze protection and humidity control.

An air heater can utilize various power sources such as electricity, propane, fuel oil, natural gas, diesel, kerosene, and gasoline. Some heaters are also solar-powered while others burn wood products. Other heaters with fins improve dissipation of heat.

Air heaters are now manufactured to be portable, resistant to corrosion, finned, explosion-proof, controlled by microprocessors, or Underwriters Laboratories (UL)-approved. UL or other agencies rate air heaters. Other products encase their coil or grounding wire, and some have independent timing controls.

Portable air heaters are light and easy to move. Heaters that are to be placed in hazardous locations are designed for usage in such environments.

Air heater restrictions include heating capacity, maximum air temperature, and maximum air flow. Heating capacity is the wattage that the heater can deliver. It is also the measurement of the capability of the unit to add heat to the enclosed space. Maximum air temperature and maximum air flow are the highest temperature and flow of air produced by the heater, respectively.