Application of KL-Type Wound Fin Tubes SA179 + AL1060 in Industrial Waste Heat Recovery Systems

1. Overview

In the flue gas waste heat recovery systems of boilers, process heaters and industrial kilns, the low heat transfer coefficient on the flue gas side, the high dust content of the medium and the limited equipment installation space have long constituted the major technical bottlenecks restricting the improvement of heat recovery efficiency. How to achieve efficient heat transfer within a limited volume while ensuring long-term stable operation of the system in a dusty environment has become a key issue in the design of waste heat recovery units.

To address the above challenges, this solution recommends the KL type knurled embedded fin tube as the core heat transfer element. The base tube is an ASME SA179 carbon steel seamless tube (25.4mm outer diameter, 2.77mm wall thickness), and the external fins are made of AL 1060 pure aluminum (15.88mm fin height, 10 FPI density). A pre-knurling embedding process achieves a tight mechanical bond between the fins and the base tube. Through three core advantages – high-density fins greatly extending the secondary heat transfer area, the knurling process effectively reducing contact thermal resistance, and the serrated fin structure optimizing anti-fouling performance – this combination delivers a coordinated improvement of both thermal efficiency and operational reliability in waste heat recovery systems.

2. Product Structure Features

2.1 KL Type Process Principle

The core process feature of the KL type fin tube lies in the pre-knurling treatment of the base tube: before fin winding, the base tube surface is first knurled to form a fine surface pattern, and the aluminum fin is then helically wound onto the base tube under mechanical tension. This process embeds the fin root into the surface pattern of the base tube, forming a mechanically interlocked structure whose contact area is approximately 50% larger than that of a standard L type fin tube.

2.2 Structural Advantages

• Low contact thermal resistance: the knurling process keeps the fins in tight contact with the base tube, reducing contact thermal resistance by more than 30% compared with a standard L type fin tube.
• High bonding strength: the peel strength of the fins is 1.5 times that of conventional products, effectively withstanding high-velocity flue gas erosion and thermal cycling impact.
• Applicable temperature range: the maximum continuous operating temperature of the aluminum fins is approximately 250°C (peak 280°C).

3. Application Advantages in Waste Heat Recovery Systems

3.1 Highly Extended Heat Transfer Area

With a fin height of 15.88mm and a density of 10 FPI, this product belongs to the medium-high fin configuration. Compared with bare tubes, finned tubes multiply the effective heat transfer area several times over. Studies show that finned-tube waste heat boilers are more compact and use less material than bare-tube structures, while achieving significantly higher thermal efficiency. Within a limited flue duct space, this compact structure enables a higher heat recovery rate.

3.2 Adaptation to Dusty Flue Gas Environments

The flue gas handled by waste heat recovery systems often contains dust particles. Thanks to its serrated fin edge design, the KL type fin tube disrupts the fluid boundary layer while intensifying heat transfer, which helps reduce dust deposition. This characteristic makes it particularly suitable for waste heat recovery in high-dust conditions such as coal-fired power plants, sinter machine flue ducts and industrial kilns.

3.3 Economy of the Material Combination

This product combines an ASME SA179 carbon steel base tube with AL 1060 aluminum fins – a mature solution balancing performance and cost:

• The carbon steel base tube provides sufficient pressure-bearing strength and structural rigidity.
• The aluminum fins offer a thermal conductivity of approximately 200 W/m·K, delivering excellent heat conduction together with good oxidation resistance in atmospheric environments.
• Compared with all-stainless-steel materials, this combination significantly reduces equipment manufacturing cost.

3.4 Typical Application Scenarios

Based on the above advantages, this product can be widely applied in:

4. Performance Parameters and Limitations

4.1 Service Applicability

• Working temperature: long-term operating temperature is recommended not to exceed 250°C.
• Working pressure: with a base tube wall thickness of 2.77mm, it is suitable for low-to-medium pressure service.
• Suitable media: suitable for gas-side heat exchange of flue gas, air and similar media; the tube-side medium shall be free of strongly corrosive fluids.

4.2 Precautions

• Aluminum fins may corrode in strong acid or strong alkali environments, so the corrosivity of the flue gas should be evaluated.
• If the flue gas temperature continuously exceeds 280°C, an all-metal welded fin tube or a stainless steel material solution is recommended.
• Avoid mechanical damage to the fins during installation to prevent any negative effect on heat transfer efficiency.

5. Summary

This KL type fin tube (ASME SA179 carbon steel base tube / AL 1060 aluminum fins / 25.4mm OD × 2.77mm wall thickness / 15.88mm fin height / 10 FPI) is a preferred solution in waste heat recovery systems that balances heat transfer efficiency, structural reliability and economic cost. Its pre-knurling embedding process ensures fin bonding strength, the serrated fin design supports stable operation under dusty conditions, and the material combination controls equipment investment while guaranteeing performance. For medium- and low-temperature (≤250°C) flue gas waste heat recovery projects, this product can significantly improve heat recovery efficiency and reduce energy consumption, making it an ideal choice for engineering design.