L/LL/KL Finned Tube

Aluminum L-Foot Finned Tubes consist of thin aluminum fin strip tightly wound helically around the tube circumference.

Aluminum L foot Fin Tube
Aluminum L foot Fin Tube

L finned tubes, LL (Doulbe L) finned tubes, KL finned tubes (knurled fin tubes) (with aluminum fins)The aluminum fin strip or the copper fin strip is folded into an L shape and spirally wound tightly under the action of tension on the outer surface of the base tube. Tension in the fin strip is wrapped around the tube serves to make the fin foot forcefully on the tube, thus hold the fin firmly in place.

Aluminum Fin KL Type Knurled Fin Tubes

This type of fin has a knurled L shape base and is fixed by pressure on the tube.

  • Fin Materials: Aluminum, Copper
  • Tube Materials: No limits
  • Fin Thickness: Min: 300 µ Max: 800µ

“KL” finned tube relies on maximum surface contact between fin and tube which is ensured by tension forming fin strip helically around the pre knurled tube offering an improved bond and heat transfer.

Wrapped L Foot Tension Tube
Wrapped L Foot Tension Tube
Helically Tension KL Fin Tube
Helically Tension KL Fin Tube

L Finned Tube is combined with two different materials

Core Tube: Carbon steel, stainless steel, copper

Fins: Aluminum, copper, steel


  1. Adopting winding process, high production efficiency
  2. Uniform fin pitch, good heat transfer performance
  3. Core tube is protected from air corrosion by base of fin

Maximum Working Temperature: 230°C


  1. Air cooler in petrochemical, power plant, paper-making, tobacco and building heating.
  2. Air heater in food processing equipment
  3. Air heater in plant protein and starch spay drying system

Uncovered Tube Area between the fins

Fin foot is pre-formed into an LL shape (overlapped LL) and applied to base tube under tension. However, foot is pre-shaped to give overlap of one foot onto another, thereby improving base tube protection and thermal contact area Fin materials: Aluminum Base tube materials: Any metallic material. The smooth flat fins perpendicular to the tube surface give rise to very low resistance to air /gas flow and ensure that fouling is kept to a minimum. The foot of the fin is in contact with base tube and provides a complete sheathing over the finned length.

The Overlapped "L" fin design has interlocking fins that are wound together to prevent movement and separation. The fin protects the entire tubes, so the designation works well for the applications where corrosion is a factor.This type of finned tube is often used as an alternative to the more expensive extruded type fin in corrosive environments.