U-Shaped Air Tubular Heater
Industrial Heaters

U-Shaped Air Tubular Heater

The U-shaped double-ended air heating element consists of a nickel-chromium resistance wire, compacted high-purity magnesium oxide, and a metal sheath, with both terminals located on the same mounting side. The element can be arranged in ovens, air ducts, drying equipment, and circulating hot air systems to heat air via natural convection or forced airflow. The power density must be determined according to the inlet air velocity, outlet temperature, allowable sheath temperature, and airflow uniformity; forced-air equipment should interlock the fan status with the heating power and provide operational temperature control and independent over-temperature protection.

Basic Structure
Nickel-chromium resistance wire + compacted high-purity magnesium oxide + metal tube sheath
Structural Form
U-shaped double-ended air heating tube, two terminals located on the same installation side
Common Voltage
220 V / 380 V AC; the air duct system can be designed up to 480 V
Power Supply Method
Single-phase or three-phase, three-phase circuits are configured balanced according to the number of components and total power
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Product highlights

  • The U-shaped double-ended design concentrates both terminals on the same mounting side, facilitating panel mounting, wiring, and maintenance.
  • Sheaths made of steel, 304/316L stainless steel, and Incoloy 800 are suitable for dry air, moist airflow, and high-temperature oxidizing environments.
  • The duct design is based on a minimum airflow of 61 m/min, a maximum surface load of 6.2 W/cm², and a maximum sheath temperature of 760°C.
  • Stationary air and forced airflow should be selected according to the corresponding load tables, and the air must flow evenly across the entire heating section.
  • Fan interlock, operational temperature control, manual reset over-temperature limit, and reliable grounding collectively prevent burning without airflow and overheating.

Technical specifications

Basic Structure
Nickel-chromium resistance wire + compacted high-purity magnesium oxide + metal tube sheath
Structural Form
U-shaped double-ended air heating tube, two terminals located on the same installation side
Common Voltage
220 V / 380 V AC; the air duct system can be designed up to 480 V
Power Supply Method
Single-phase or three-phase, three-phase circuits are configured balanced according to the number of components and total power
Common Pipe Diameters
6.25 / 6.6 / 8 / 9.5 / 10.9 / 12.7 mm
Sheath Material
Carbon steel, AISI 304 / 316L stainless steel, Incoloy 800
Sheath Temperature Limit
Carbon Steel 399°C; Stainless Steel 649°C; Incoloy 871°C
Duct Design Limit
Minimum Air Velocity 61 m/min, Maximum Surface Load 6.2 W/cm², Maximum Sheath Temperature 760°C
Still Air Load
Incoloy Sheath: 371°C at 4.65 W/cm²; 538°C at 3.10; 649°C at 1.55; 816°C at 0.31
2.74 m/s air flow load
Incoloy sheath: 260°C at 6.20 W/cm ²; 427°C at 4.96; 538°C at 3.88; 649°C at 2.33; 816°C at 0.31
Power calculation
P = air volume (m³/h) × air density (kg/m³) × specific heat at constant pressure (J/kg·K) × temperature rise (K) ÷ 3600
Dimension configuration
Total length, heating length, cold end, U-shape spacing, bending radius, terminal length, and mounting parts are produced according to the drawing
Installation Direction
Airflow passes uniformly laterally through the heating section; terminals are placed outside the insulation layer, avoiding convection hot air and radiant heat
Horizontal Support
When installed horizontally at high temperature, provide support every 305–457 mm to prevent the component from sagging due to heat
Thermal Expansion Allowance
Reserve about 3.2 mm for thermal expansion in the length direction every 305 mm, do not rigidly lock the heating section
Terminals and Sealing
M4 / M6 studs, tabs, round pins, or welded leads; keep the wiring area clean, dry, and secure
Temperature Control
Install a working temperature sensor at the outlet; place an independent over-temperature limiter near the heating tube for faster response
Fan Interlock
The airflow switch or air pressure switch confirms airflow before allowing heating; cut off the heating power immediately when the fan stops
Electrical Protection
The metal sheath and frame are reliably grounded, and overcurrent and short-circuit protection suitable for the rated current is provided.
Typical Applications
Ovens, air ducts, circulating hot air furnaces, drying and curing equipment, dehumidifiers, and air reheating
Selection Parameters
Provide inlet/outlet temperature, minimum/maximum airflow and air velocity, air composition, working pressure, voltage, number of phases, power, installation diagram, and continuous/intermittent operation conditions
Industrial Heaters

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