In modern industrial production, efficient heat exchange technology is crucial for optimizing energy utilization and enhancing equipment performance. Fin tubes, as widely used heat transfer elements, significantly improve heat exchange efficiency by increasing the external surface area through the addition of fins on the heat exchange tube surface. However, the welding process employed for fin tubes has a non-negligible impact on their ultimate heat transfer performance.

The fundamental principle of fin tubes is to enhance heat transfer between fluids inside and outside the tube by utilizing the increased surface area provided by the fins. When a hot fluid flows inside the tube or a cold fluid passes over the external surface, heat is transferred through the tube wall to the fins, which then dissipate it into the surrounding environment. In power plant boilers, fin tubes can recover heat from high-temperature flue gas to preheat air or water, thereby improving combustion efficiency. In the chemical industry, they are used for heat exchange and transfer in various chemical reaction processes. In refrigeration and air conditioning systems, they facilitate heat exchange between the refrigerant and air or water to regulate temperature.

High-frequency welding is based on the skin effect and proximity effect of high-frequency electric current. During welding, the high-frequency current rapidly heats the steel strip and the outer surface of the base tube to a plastic or molten state, completing the weld under the pressure of the wound steel strip. This method produces high-quality welds, with a fin weld bonding ratio potentially reaching 95%. Because heat is concentrated on the surface during welding, the heat-affected zone is small, minimizing the impact on the base material properties. HF welding is fast, offers high production efficiency and low energy consumption, and is suitable for mass production of fin tubes using similar materials such as steel tube with steel fins or copper tube with copper fins. It is widely used in industrial radiators, boilers, and other fields.

Laser welding utilizes a high-energy-density laser beam to join the fins to the base tube. Laser welding produces extremely high-quality welds with minimal thermal resistance at the joint, allowing heat to transfer smoothly from the base tube to the fins. By precisely controlling laser parameters, it enables accurate design and manufacturing of fin shape and arrangement, optimizing fluid flow outside the tube and enhancing the convective heat transfer coefficient. Laser-welded fin tubes excel in increasing the heat transfer area and can improve heat transfer efficiency by 10%-20% compared to traditional welding methods. Their good corrosion resistance and high-temperature performance make them suitable for complex operating conditions such as those in power plant boilers and the chemical industry.

Gas shielded welding uses gases such as argon or carbon dioxide as a protective medium to shield the weld area from atmospheric air, preventing oxidation and nitridation of the weld metal. Among these methods, Tungsten Inert Gas (TIG) welding offers high weld quality, aesthetically pleasing weld appearance, and a small heat-affected zone, making it suitable for welding materials like stainless steel, aluminum, and aluminum alloys. However, its welding speed is relatively slow, and costs are higher. Metal Inert Gas (MIG) and Metal Active Gas (MAG) welding offer faster welding speeds, high production efficiency, and high deposition rates, and can be used for welding various metal materials. However, they require higher operator skill, and defects such as porosity can occur if gas shielding is ineffective. Gas shielded welding is widely used in applications demanding high quality and large batch production, such as automotive radiators and air conditioning heat exchangers.

Brazing uses a filler metal with a melting point lower than that of the base materials. The assembly and filler metal are heated to a temperature above the filler metal's melting point but below the melting point of the base materials, allowing the liquid filler metal to wet the base materials, fill the joint gap, and diffuse to form a connection. Soft soldering uses filler metals with melting points below 450°C, involves low welding temperatures, and has minimal impact on base material properties, but results in lower joint strength. It is suitable for applications with low loads and moderate operating temperatures. Hard brazing (or silver brazing/braze welding) uses filler metals with melting points above 450°C, producing higher strength joints suitable for fin tube welding subjected to higher loads and temperatures. Brazing is commonly used for aluminum and copper fin tubes and is widely applied in industries such as refrigeration and air conditioning.

The welding process directly determines the quality of the connection between the fin and the base tube, thereby influencing the contact thermal resistance. Methods like HF welding and laser welding create tight connections with low contact thermal resistance, allowing heat to transfer efficiently from the base tube to the fin, establishing a solid foundation for the subsequent heat dissipation process. In contrast, manual arc welding quality can vary significantly depending on the welder's skill level, potentially leading to higher contact thermal resistance and impeding heat transfer.

High-quality welds ensure the integrity of the connection between the fin and the base tube, avoiding gaps or defects that could cause heat leakage or obstruction during transfer. For instance, HF welds are typically virtually gap-free, significantly reducing leakage risks, ensuring safe and stable operation of the equipment during heat exchange, and contributing to higher heat transfer efficiency. Conversely, if gas shielded welding suffers from inadequate gas protection leading to defects like porosity, the continuity and strength of the weld can be compromised, subsequently reducing heat transfer efficiency.

The welding process significantly impacts the structural integrity of the fins. Laser welding allows precise control over the process, preserving the intended fin shape and arrangement, optimizing fluid flow, and enhancing the convective heat transfer coefficient. During brazing, if temperature and holding time are not properly controlled, issues like filler metal erosion or base material overheating can occur, affecting the structural integrity of the fins and reducing heat transfer efficiency.

Different fin tube welding processes significantly impact heat transfer efficiency through factors such as weld quality, contact thermal resistance, and fin structural integrity. High-frequency welding demonstrates strong heat transfer performance in industrial applications due to its high weld bonding ratio, low contact thermal resistance, and high production speed. Laser welding excels in complex operating conditions and applications demanding extremely high heat transfer efficiency, leveraging its advantages of high precision, low thermal resistance, and optimized fluid flow. Gas shielded welding and brazing play important roles in their respective suitable materials and application scenarios. In practical applications, the appropriate welding process should be selected comprehensively based on factors such as the fin tube's operating environment, material requirements, and cost considerations. This ensures that the fin tube achieves optimal heat transfer efficiency, providing robust support for the efficient operation of industrial processes.