Basic heat transfer element-- fin of the fin tube

The fin of fin tube is the basic heat transfer element, the function is to expand the heat exchange area and improve the efficiency of heat transfer. The fins can be regarded as the extension and expansion of the pipe; secondly, the different forms of fins make the air form strong turbulence in the pipe, and make the flow boundary layer and the heat boundary layer break and recombine, so as to strengthen the heat exchange; then, the fins can also improve the overall strength of the radiator and effectively expand its application range. The commonly used fin structures are flat fin, louver fin, serrated fin, porous fin and corrugated fin.

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Increasing the fin height will increase the surface area, but this parameter is limited by the following factors. The fin height affects the basic parameter of mass flow, which affects heat transfer and pressure drop; the manufacturing limit of integral fin is much more than that of serrated fin tube; the fin efficiency is reduced, similarly, the overall fin is more serious than serrated fin; for the fin whose height is less than 12mm, laser welding composite fin tube is recommended. If the other.

parameters remain unchanged and only the fin height is increased, the cost of heat exchanger will first decrease, then remain unchanged, and then start to increase. This is because the increase of heat exchange area is offset by the larger tube spacing effect, lower gas flow rate, lower fin efficiency and lower fluid permeability. Smaller fin thickness can bring higher fin density, but it also reduces fin efficiency and structural stiffness.