- I. Application Scenarios
Industrial duct heaters are commonly used in the regeneration systems of adsorption-type compressed air dryers and can also be applied to hot air-type material drying equipment.
1. Adsorption dryer regeneration heating (most mainstream)
After the molecular sieve and activated alumina in the adsorption tower become saturated with moisture, they require regeneration through high-temperature hot air. The air heater heats the regeneration air, and the warmed hot air is then directed into the adsorption tower to strip the moisture from the adsorbent, completing the regeneration process. Once regeneration is finished, the temperature is reduced, restoring the adsorption tower's water-absorbing capacity and ensuring stable, low dew point in the compressed air.
2. Preheat treatment
When the ambient temperature is low or the incoming air humidity is high, use a duct heater to preheat the air entering the dryer, reducing the relative humidity of the air, alleviating the adsorption load on the dryer, and preventing condensation and icing in the pipelines.
3. Hot air supply for material drying
In process material drying equipment, the air duct heater directly heats the circulating air to enhance its moisture-carrying capacity. The heated air continuously flows over the material surface, removing moisture, and is commonly used in continuous hot air drying production lines.
- II. Equipment Structure and Working Principle
The entire air duct heater consists of a housing, electric heating elements, guide plates, temperature sensors, and an electrical control system.
The air flows through the interior of the duct housing, where the deflector plate forcibly directs the airflow to thoroughly scrub the surface of the heating elements, enhancing the air temperature via forced convection heat transfer. The accompanying temperature control system continuously monitors the outlet temperature, automatically adjusting the output power via PID regulation to maintain a stable hot air temperature.
Safety Configuration: Fan interlock (no heating without airflow), overtemperature protection, and thermal fuse protection to prevent dry burning damage to equipment.
• Clean Air Operation: Select finned electric heating tubes with large heat exchange area and high thermal efficiency
• For dust and moisture-laden conditions: Opt for smooth heating elements to prevent dust accumulation and facilitate maintenance and cleaning
III. Key Considerations for Selection
1. Determine the basic parameters: air volume, inlet and outlet air temperatures, working pressure, calculate the heating power, and reserve a 15%-20% power margin.
2. Shell Material: Cold-rolled steel plate with powder coating for normal working conditions; stainless steel shell made of 304 is selected for humid and slightly corrosive environments.
3. Wind speed design: The air velocity within the duct should be controlled between 3 to 8 m/s. If the wind speed is too low, the heating tube will accumulate heat and be prone to damage; if the wind speed is too high, the air resistance will increase, leading to higher fan load.
4. Safety Configuration: The fan interlock protection must be configured to cut off the heating power supply when the fan is not operating or the airflow is insufficient; dual overtemperature protection is available and can be linked with the dryer's main control PLC.
5. Explosion-proof requirements: For flammable and explosive working conditions such as chemical and oil & gas industries, select explosion-proof air duct heaters.
- IV. Installation Key Points
Installation sequence: Fan → Air duct heater → Drying tower / Drying chamber. The fan is positioned in front to ensure continuous airflow through the heater.
2. Install the unit as close to the dryer as possible to minimize heat loss from the hot air duct; ensure proper insulation on the outer layer of the hot air duct.
3. The temperature sensor is installed in the straight pipe section at the heater outlet, avoiding the vortex area to ensure accurate temperature measurement.
4. Ensure proper vibration damping in the piping to minimize the transmission of fan vibrations to the heater and prevent fatigue fractures in the heating tubes.
- V. Advantages
1. Fast heating response, wide temperature adjustment range, stable temperature control, and precise regulation of regeneration hot air temperature.
2. The heat source is electric heating, with no open flame, producing clean hot air that does not contaminate compressed air or process materials.
3. The structure is modular, facilitating easy disassembly and maintenance, and compatible with various specifications of drying equipment.
4. It can be equipped with an automatic control system to achieve fully automated operation of the dryer's regeneration process.
- VI. Common Issues
1. Heating tube burnout: Fan malfunction, insufficient airflow leading to dry burning; excessively low wind speed, resulting in excessive surface load on the heating tube.
2. Temperature instability: Incorrect sensor installation position, significant airflow fluctuations, and improper temperature control parameter tuning.
3. Excessive air resistance: Unreasonable design of internal flow deflectors and undersized air duct cross-sections increase fan energy consumption.
4. High surface temperature of the casing: lack of pipeline insulation leads to heat loss and increased energy consumption.
- VII. Air Duct Heater vs. Pipe-type Heater (Drying Machine Scenario)1. Air duct heater: Low pressure, high flow rate, relatively high air resistance, commonly used for constant-pressure hot air circulation and high-flow regeneration; the casing is typically a square air duct.2. Pipe heater: Pressure-bearing type, cylindrical tube structure, suitable for high-pressure compressed air circuits and small-flow high-pressure regenerated gas scenarios.
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Post time: Oct-08-2026
