Aluminum Flat Tube with Serpentine Fins

In the field of power plant air-cooling technology, heat dissipation efficiency directly determines the operational economy and safety of generating units. Among various technical approaches, the aluminum flat tube with serpentine fins has become the core component of modern direct air-cooling systems. Its design philosophy and manufacturing process represent decades of evolution and fundamental breakthroughs in air-cooling technology.

I. From Multi-Row Tube Bundles to Single-Row Flat Tubes

The development of power plant air-cooling technology is a history of tackling challenges centered on "improving efficiency, reducing energy consumption, and mitigating fouling." Before the aluminum flat tube with serpentine fins became mainstream, the systems primarily went through two typical phases:

Phase One: Multi-Row Round Tubes with Spiral Aluminum Fins

This was the prevalent early design. L-shaped or LL-shaped aluminum fins were wound around round tubes, typically arranged in bundles of 3 to 6 rows. Its limitations were significant: high form resistance as air flowed through multiple rows of round tubes, leading to high fan energy consumption; severe efficiency degradation for rear-row fins sitting in the shadow of the front rows wake; and a complex structure prone to dust accumulation and difficult to clean.

Phase Two: Multi-Row Elliptical Finned Tubes

To reduce air resistance, elliptical tubes replaced round tubes, often with rectangular steel fins threaded onto them. The elliptical tube offered a better aerodynamic profile and a more compact structure. However, the fundamental issues of multi-row arrangement—high flow resistance, severe fouling, and low heat transfer efficiency in rear rows—remained unresolved.

The advent of the aluminum flat tube with serpentine fins brought a revolutionary change. Its core concept was to compress multi-row bundles into a single row, thoroughly eliminating rear-row efficiency decay; to use flat tubes instead of round/elliptical ones, drastically cutting air resistance; and to achieve seamless integration of tubes and fins via integral brazing, enhancing heat transfer. This shift represents a systematic redesign based on aerothermodynamics and heat transfer principles.

 

II. Materials, Process, and Design

3. The Key Process: Integral Brazing Technology

Brazing is the process that gives the entire tube bundle its soul. In a vacuum or controlled atmosphere furnace, precisely controlled heating melts the brazing filler metal, which then uniformly penetrates every microscopic gap at the tube-fin interface via capillary action, forming a solid integral structure upon cooling.

• Performance Leap: Brazing completely eliminates the "contact thermal resistance" inherent in mechanical joints, potentially improving heat transfer efficiency by over 15%.
• Structural Reliability: The resulting monolithic structure has high mechanical strength, effectively resisting vibration fatigue caused by fans and natural wind, ensuring decades of operational life.

III. Advantages of Single-Row Design

Advantage	Mechanism & Impact	Result
Reduces Fan Power Consumption	Air passes through only a single row, reducing flow resistance by 40%-50%.	Substantial electricity savings from lower fan energy consumption.
Mitigates Fouling Problems	Unobstructed channel minimizes dust accumulation and facilitates online cleaning.	Much lower performance degradation rate compared to multi-row structures.
Uniform & Efficient Heat Transfer	Every fin faces undisturbed cool air, eliminating thermal shadowing.	100% utilization of the heat exchange surfaces efficiency.
Excellent Anti-Freeze Safety	Flexible steam flow layout allows precise control of fan speed and steam intake in winter.	More effective prevention of freezing, offering higher operational safety.

IV. Manufacturing Quality, Selection, and Operation