Longitudinal finned tubes are efficient heat exchange elements manufactured by welding, rolling, or wrapping metal fins axially along the outer surface of a base tube. This design significantly increases the outer surface area of the tube, thereby greatly enhancing the heat transfer process between the fluid outside the tube and the fluid inside the tube. Its core structure consists of two parts: the base tube and the fins. The base tube serves as the pressure-bearing main body, and its material is usually selected based on the pressure, corrosiveness, and temperature of the fluid; the fins, as the core part of the extended surface, are mostly made of aluminum, copper, or carbon steel, with their height, thickness, and spacing being key design parameters.

 

The manufacturing processes of longitudinal finned tubes mainly include high-frequency welding, fin collaring/brazing, and roll forming. High-frequency welding is currently the most widely used and best-performing process. It uses high-frequency current to heat and melt the contact edges between the fins and the base tube for welding, resulting in high connection strength and low contact thermal resistance. The fin collaring/brazing process is applicable to any brazable metal combination but has relatively high contact thermal resistance. The roll forming process is mainly used for aluminum tubes, where the base tube and fins are integrally formed with no contact thermal resistance, but the material is limited.

 

The advantages of longitudinal finned tubes lie in high heat transfer efficiency, compact structure, energy saving, and high-temperature resistance. They are particularly suitable for situations where the convective heat transfer coefficient outside the tube is much lower than that inside the tube, such as when the outside is gas and the inside is liquid. However, their limitations include high manufacturing cost, easy dust accumulation and blockage, poor corrosion resistance, and limited pressure-bearing capacity.

 

In terms of application fields, due to their excellent gas-liquid heat exchange capacity, longitudinal finned tubes are widely used in the power industry (e.g., gas turbine inlet coolers and air-cooled islands), petrochemical industry (e.g., air coolers and economizers), heating, ventilation, air conditioning and refrigeration industry (e.g., condensers and industrial air conditioning units), and other industrial fields (e.g., compressor coolers and engine radiators).

 

Compared with transverse finned tubes, longitudinal finned tubes have the advantages of low flow resistance, low pressure drop, and less dust accumulation, making them more suitable for forced convection scenarios. Overall, longitudinal finned tubes are a key technology for efficiently solving heat exchange problems between gas and liquid, with outstanding advantages in energy saving, water saving, and equipment compactness.