What is a finned tube heat exchanger?

Le finned tube heat exchanger is one of the earliest and most successful discoveries in improving tubular heat exchange. This method remains the most widely used of all methods for enhancing heat transfer on tubular heat exchange surfaces. It is not only applicable to single-finned tube heat exchangers, but is also widely used in power, chemical, petrochemical, air conditioning, and refrigeration engineering.

Types of Finned Tubes

The basic heat transfer element of a finned tube heat exchanger is a finned tube, which is composed of a base tube and fins. The base tube is typically a round tube, but elliptical and flat tubes are also available.

The surface structures of the fins include flat fins, interrupted fins, corrugated fins, and perforated fins. The latter two are highly efficient heat transfer fin types.

Structure of finned tubes

1. Classification of finned tubes by structural type

From the structural type, finned tubes can be divided into two basic types: longitudinal and radial. Other types are the development and deformation of these two types. For example, large helical angle finned tubes are close to longitudinal, and small helical angle finned tubes are close to radial. The shapes of fins are circular, rectangular and needle-shaped. In addition, fins can be set outside the tube, called external finned tubes; or set inside the tube, called internal finned tubes or both internal and external finned tubes.

2. Classification of finned tubes by manufacturing process

According to the manufacturing process, finned tubes can be classified into integral finned tubes, welded finned tubes, high-frequency welded finned tubes and mechanically connected finned tubes.

(1) Integral finned tubes are made by casting, machining or rolling, and the fins and tubes are integrated.

(2) Welded finned tubes are manufactured using processes such as brazing or inert gas shielded welding. Modern welding technology can connect fins of different materials together and can make fin tubes simple and economical to manufacture. They have good heat transfer and mechanical properties and have been widely used. Since the residue in the weld is not conducive to heat transfer and may even cause breakage, the welding process quality must be guaranteed when producing this type of fin tube.

(3) High-frequency welding of fin tubes uses high-frequency induction generated by a high-frequency generator to generate high temperature at the contact point between the tube surface and the fin, melting the two within a depth range of about 10μm, and then pressurizing to connect the fin and tube into one. There is no flux or solder, and the manufacturing is simple, the productivity is high, and the heat transfer and mechanical properties are excellent. This is the most ideal type of fin tube and is being recognized and adopted by the majority of users.

(4) Mechanically connected fin tubes usually have three types: winding type, inlaid type, sleeve type or string type. Wound-finned tubes are simple to manufacture. A metal strip is mechanically or welded around one end of the tube. The strip is then tightly wound around the tube’s outer wall using the tube’s rotational torque. The other end is then fixed to form a wound-finned tube. The strip can be made of copper, steel, or aluminum.