Air Heaters

In an air heater, industrial heat radiates into flowing air or fluid. Dirt, grease, and water in unfiltered air can shorten the life of heaters, especially open coil air heaters. Even after the heater is switched off, a time delay relay will maintain air flowing over the air heating element for some time. An over-temperature sensor can be placed next to the air heater itself if the temperature sensor is far down from the air heating element. Compared to tubular heaters, wire wound heating elements constructed of resistance wire have minimal pressure drop across the heating components.

Salient Features of Air Heaters

• For extended life and corrosion resistance, sheathed heating elements are employed. It's also possible to employ stainless steel-clad heating elements.
• Insulation integrity is guaranteed as recompacted element bends eliminate voids.
• Air heaters for high temperatures can provide up to a 20 W/in² rating and a max outlet temperature of 1200 °F (650 °C).
• Stainless steel element spacers and supports are used to ensure the spacing and avoid drooping.
• High-temperature air heaters have 5 to 300 kW ratings up to 480V.
• The terminal enclosure is thermally insulated, which keeps the wire cool and decreases heat loss.
• Procedure and over-temperature monitoring are possible with integrated sensors.
• C-UL-approved systems are made up to 600VAC, ensuring safe and dependable operation.
• For cool wiring temperatures, air heaters feature an insulated stand-off housing structure.

Material used for Air Heaters

Heating elements with rectangular fins are materials that guarantee maximum heat exchange with a minimal gradient.

All the resistors of an air heater have standardized production with the following characteristics:

• Aluminized steel is used to make rectangular fins.
• A high-quality AISI 321 steel tube acts as a rectangular fins mount.
• Industrial heaters are available in both options, with or without an onboard thermocouple.
• The resistors are assembled with a connection using a zinc-plated steel fitting and terminal blueprints.

Types of Air Heaters

Air heater is a broad phrase that can refer to various heaters.

1. Duct Heaters

   Duct heaters work to heat gas streams in continuous movement as the gas passes through the heater.

   

2. Forced Air Heaters

   These heaters use forced convection to pass air through a heat source with a fan or blower.

3. Radiators

   Radiators consist of coils that contain circulated and heated media such as hot water, oil, or steam.

   

4. Tubular Heaters

   These are typically used in custom heating applications because the element is bendable into custom shapes.

   

5. Enclosure Heaters

   Enclosure heaters provide humidity control, protection, and freeze control. They are commonly designed to be used in enclosures.

   

6. Room Heaters

   Safe from emitting noxious fumes or hazardous pollutants, these are used in confined spaces and are generally portable.

   

7. Heat Torches

   These devices generate a focused flame or stream of abnormally hot air or gas.

   

Energy Sources of Air Heaters

Electricity, combustible fluids & solids, solar energy, or thermal fluids are the most common energy sources for air heaters.

• Electrically Powered: Electric heaters either use single-phase or three-phase power. They differ in watt density and commonly use AC instead of DC.
• Combustible Fluids and Solids: The fluids used to power air heaters include hydrocarbons. They can be classified as either liquid (diesel, fuel, oil) or gaseous (propane, natural gas). The solids acting as a power source can be wood or wood pallets.
• Solar Energy: Solar energy is a renewable energy source used to power air heaters by applying a solar collector and a thermal mass transfer system.
• Thermal Fluids: These are used to carry thermal energy in air heaters. Steam and hot water are the two most common fluids used in industrial applications.

Applications

Air heaters can be used in various residential, commercial, and industrial situations. HVAC systems and room or space heating are the primary applications for residential and commercial air heaters. Industrial applications include:

• Calcination is a high-temperature heat treatment method for metals, ores, and minerals. The procedure removes hydrates and other impurities from solid materials to change their physical and chemical characteristics.
• Air heaters can be used for preheating processes to prepare unfinished goods and materials for further processing.
• Drying includes evaporation to remove water or other solvents. Inks, raw materials, coatings, and other goods may be dried with air heaters.
• In addition, air heaters are utilized in a wide range of industries, including automotive, rubber, textiles, plastics, electronics, and packaging.
• Air heaters are used in the semiconductor industry for drying wafers and PC boards, preheating process gases, heat shrinking wire insulation, and soldering lead frames.