The core heat transfer principle of a fin tube is based on the engineering optimization of the heat exchange process. In gas-liquid heat exchange scenarios, the convective thermal resistance on the air side is significantly higher than on the internal fluid side, creating the bottleneck that limits the total heat transfer rate. According to the fundamental heat transfer equation (Q=U⋅A⋅ΔT. )

The solution provided by the finned tube is to dramatically increase the heat exchange area (A) by attaching metal fins, at the cost of an inevitable reduction in the effective temperature difference (as temperature decreases along the fin height). Simultaneously, the fins help improve the heat transfer coefficient on the air side by disturbing the airflow. The essence lies in reducing the proportion of the air-side thermal resistance within the total thermal resistance, thereby significantly increasing the overall heat transfer coefficient (U) and the heat transfer rate (Q).

1. Internal Convective Heat Transfer: The high-temperature working fluid (water, refrigerant, etc.) flows inside the tube, transferring heat to the inner wall of the base tube with a relatively high convective heat transfer coefficient.
2. Radial Conduction through the Tube Wall: Heat is conducted efficiently through the metal wall of the base tube from the inner surface to the outer surface.
3. Lateral Heat Diffusion: Heat from the outer tube wall propagates in two key directions: firstly, directly heating the surrounding air, and secondly, conducting longitudinally along the fin starting from its root (where it is in tight contact with the tube). This transforms the entire fin into an extended heat dissipation surface.
4. Convective Heat Transfer from Fin Surface to Air: As air flows across the fin array, forced convective heat exchange occurs with the vast fin surface area, carrying the heat away. The complex shapes of the fins (corrugated, louvered, etc.) help break the air boundary layer, enhance turbulence, and improve the efficiency of this stage.

In summary, the finned tube employs the core mechanism of "surface area extension" to transform the high-resistance gas-side heat transfer into a synergistic process combining efficient metal conduction and large-area convective heat transfer. This enables highly efficient heat exchange between gases and liquids within an economical and compact space, which is precisely why it is so widely used in applications such as air conditioners, radiators, and air-cooled heat exchangers.