How to increase the use efficiency of finned tube

What is a finned tube

To improve the heat exchange efficiency, fins are usually added on the surface of the heat exchange tube to increase the outer surface area (or inner surface area) of the heat exchange tube, to achieve the purpose of improving the heat exchange efficiency. Such a heat exchange tube is called a fin tube.

Fin tube types

The finned tube is divided into square finned tube, spiral finned tube, longitudinal finned tube, spiral serrated finned tube, and inner finned tube according to shape and structure;

The finned tube is divided according to the material: single metal finned tube, bimetallic composite finned tube;

According to different processing techniques, finned tubes are divided into: rolled finned tubes, welded and formed finned tubes, roll-formed finned tubes, and set-shaped finned tubes.

Fin tube advantages

1. Strong heat transfer ability: Compared with the light pipe, the heat transfer area can be increased by 2-30 times, and the heat transfer coefficient can be increased by 1-2 times.

2. Compact structure: due to the increased heat transfer area per unit volume, the heat transfer capacity is enhanced. Compared with the smooth tube under the same thermal load, the finned tube heat exchanger has fewer tubes, and the diameter or height of the barrel can be reduced because of the compact structure and easy layout .

3. The materials can be used more effectively and reasonably: not only because of the compact structure and the reduced amount of materials, but also the possibility to flexibly select materials for heat transfer and process requirements, such as inlays or welded finned tubes made of different materials;

4. When the medium is heated, compared with the light pipe, the temperature of the finned tube wall under the same thermal load has been reduced, which is beneficial to reduce the high-temperature corrosion and overtemperature damage of the metal surface.

Regardless of whether the medium is heated or cooled, the heat transfer temperature difference is smaller than that of the smooth tube, which is beneficial to reduce the scaling of the outer surface of the tube. Another important reason for reducing fouling is that finned tubes do not form along the circumference or the axis like light tubes

The uniform overall scale layer, the scale piece formed along the surface of the fin and the tube will break at the root of the fin under the action of expansion and contraction, which will cause the scale to fall off by itself.

5. For phase transformation heat, the heat transfer coefficient or critical heat flux density can be used. The main disadvantages of finned tubes are high cost and large flow resistance. Due to the complicated process, the finned tube of the air cooler can cost 50-60% of the equipment cost; the large resistance leads to large power consumption. However, if properly shaped, it can reduce power consumption, which is cost-effective compared to the benefits of enhanced heat transfer.

Finned tube boiler application

As well-known boilers use finned tubes. The finned tubes of the boiler are mainly used for heat transfer. So whether the more finned tubes for the boiler is better, the answer is no.   

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