KL-Type (Knurled L-Footed) Stainless Steel Finned Tube for Heat Exchangers

Material

A KL-type finned tube (Knurled L-Foot fin tube) is a heat-exchanger tube made by helically wrapping a metal fin strip around a stainless-steel base tube. Before wrapping, the tube surface is knurled, and the L-shaped fin foot is mechanically embedded into this knurled surface. This creates a tight metallurgical/mechanical bond, producing enhanced heat-transfer efficiency, strong fin adhesion, and robust durability.

Specifications

Typical ranges from industrial KL-type fin tube manufacturing:

• Base tube material: Stainless steel (e.g., 304, 304L, 316, 316L, 321)

• Tube OD: 12.7 mm (1/2″) to 50.8 mm (2″)

• Tube wall thickness: ≥ 1.24 mm (0.049″), depending on size

• Fin material: Aluminum or copper strip

• Fin thickness: 0.30–0.50 mm

• Fin height: 6.35 mm (1/4″) to 25.4 mm (1″)

• Fin pitch: 5–12 fins per inch

Main Characteristics

• High thermal efficiency – Strong fin-to-tube bonding increases heat conduction and reduces thermal resistance.

• Strong mechanical engagement – Knurled bonding prevents fin loosening under vibration and temperature cycling.

• Corrosion-resistant performance – Stainless steel base tube provides long service life, especially in corrosive or humid atmospheres.

• Durable and stable – Suitable for high-stress industrial environments.

• Flexible material combinations – Stainless-steel tubes with aluminum, copper, or stainless fins.

• Customizable geometry – OD, wall thickness, fin height, fin pitch, and materials can be tailored to application needs.

Our Advantages

After researching typical buyer concerns for fin-tube heat exchangers, the following advantages address the most common requirements:

• Optimized thermal performance: Customers often worry about insufficient heat-transfer efficiency.
  KL-type knurled bonding provides superior thermal contact, resulting in higher heat-exchange performance than standard L or LL fin tubes.

• Reliable long-term bonding: Many clients ask about fin loosening over time.
  The mechanical embedding of the L-foot into the knurled tube ensures stable bonding even under severe cycling.

• Corrosion protection: Users working with corrosive air, moisture, or industrial gases require corrosion-resistant tubes.
  Stainless steel base tubes ensure long-term resistance to corrosion, extending the service life of the exchanger.

• Design flexibility for custom systems: Engineers frequently need tailored dimensions to match coil or exchanger design.
  We support full customization of tube OD, wall thickness, fin type, fin pitch, and length.

• Optional surface treatments:
  We can provide copper plating, zinc plating, or color-zinc plating on the base tube surface where additional corrosion resistance or thermal requirements are needed.

Chemical Composition

Mechanical Properties

Applicable Standards

KL-type finning is a manufacturing method, so the standards apply mainly to the base tube materials:

• ASTM A213 – Seamless ferritic and austenitic heat-exchanger tubes

• ASTM A269 – Austenitic stainless-steel seamless/welded tubing

• ASTM A312 – Seamless/welded stainless-steel pipes and tubes

• EN 10216 / EN 10217 – European seamless/welded stainless-steel tubes

• JIS G3463 – Stainless steel boiler and heat-exchanger tubes

• GB/T 13296 – Chinese seamless stainless-steel boiler and heat-exchanger tubes

Application Fields

KL-type stainless-steel fin tubes are widely used in:

• Industrial heat exchangers

• Air-coolers and condensers

• Petrochemical processing

• Power plant heat-recovery systems

• HVAC coils, evaporators, and condensers

• Boiler economizers and flue-gas coolers

Typical Use Inside These Fields

• Air Cooling Units: Exchange heat between process fluids and ambient air

• Condensers: Improve condensation efficiency of steam or refrigerants

• Heat-Recovery Systems: Recover waste heat from flue gases

• Chemical Processing: Resist corrosion in aggressive environments

• HVAC Industry: Provide compact, high-efficiency coil construction