Longitudinal finned tubes vs welded helical finned tubes

What are longitudinal finned tubes?

Longitudinal finned tubes are used to give a great performance in any heat transfer application, especially in petrochemical area. They are the heart of heat exchangers that use their effective characteristics.

Longitudinal finned tube is particularly efficient as the channels are welded on the external surface of the tube by means of resistance weld technique. Every channel is the result of a fin strip shaped into a U form (made by us), such that each leg of the U will form a fin. The number of fins will be always a multiple of four with a maximum number depending on the outside diameter of the tube and on the thermodynamic calculations promoted for a specific job.

This continuous resistance weld gives the channels a very high adhesion to the external surface of the tubes. This adhesion has been measured in more than 30 kg by means of a fin pull test. This characteristic grants a great heat transfer efficiency, so that thermodynamic calculations can although design heat exchangers equipments at the best way .

We can also supply Longitudinal finned tubes with perforated fins ( e.g. for use with heaters B5 type ) and cut and twist configuration.

For possible combinations of materials and dimensions you can find below some information about the most used configurations. We are always available to try new technical solutions on Clients requests:

Longitudinal finned tubes technical product sheet:

For a given pipe or tube size, the desired heat transfer surface area per unit length of tube can be obtained by specifying the appropriate fin height and number of fins. The maximum number of fins is dependent upon the tube outside diameter — larger OD tube can accommodate a greater number of fins. See Design Information for extensive tables of surface areas and fin weights.

Some customers specify that the longitudinal finned tubes be “Cut and Twisted.” This operation consists of cutting through the fin channels circumferentially at specified intervals along the tube length. The fins are then bent (or “twisted”) on one side of each cut, creating a discontinuity that promotes turbulent fluid flow, thereby enhancing heat transfer efficiency.

Longitudinal finned tubes VS welded helical finned tubes

Longitudinal welded configuration can be used for practically any heat transfer application, and is particularly suited to high temperature, high pressure applications with high fin-side temperatures. The choice of longitudinal finned tubes versus helical finned tubes seems to be governed mainly by geometric considerations. For example, some heater configurations consist of finned tubes inserted inside other tubes — longitudinal finned tubes are the obvious choice for such applications. In other cases, users prefer longitudinal finned tubes for installations where the tube will be oriented in a vertical direction — the fin orientation facilitates fluid drainage on the fin side of the tube.

1. Finned Surface Area:

   - Longitudinal finned tubes have fins that run parallel to the length of the tube, providing increased surface area for heat transfer compared to plain tubes.

   - Welded helical finned tubes have fins that spiral around the tube, offering a continuous finned surface with potentially even greater surface area compared to longitudinal fins.

2. Heat Transfer Efficiency:

   - Both types of finned tubes significantly enhance heat transfer efficiency compared to plain tubes.

   - Welded helical finned tubes may offer slightly higher efficiency due to their continuous spiral fins, which maximize the surface area in contact with the surrounding medium.

3. Resistance to Fouling:

   - Longitudinal finned tubes may be more prone to fouling due to the presence of longitudinal channels between the fins, which can accumulate debris or deposits.

   - Welded helical finned tubes, with their continuous spiral fins, may have better resistance to fouling as there are no longitudinal channels for debris to accumulate.

4. Strength and Durability:

   - Longitudinal finned tubes typically have fins attached along the length of the tube with methods like welding or mechanical bonding, providing good strength and durability.

   - Welded helical finned tubes have fins that are welded directly to the tube surface in a helical pattern, which can provide excellent strength and durability, especially in high-pressure or high-temperature applications.

5. Flow Characteristics:

   - Longitudinal finned tubes are suitable for applications where straight airflow is preferred, such as in some boilers or HVAC systems.

   - Welded helical finned tubes may offer better performance in applications with turbulent airflow, such as air-cooled heat exchangers for refrigeration systems.

6. Cost and Manufacturing Complexity:

   - Longitudinal finned tubes may be simpler and more cost-effective to manufacture compared to welded helical finned tubes, especially for smaller-scale production.

   - Welded helical finned tubes may involve more complex manufacturing processes due to the spiral welding of fins, potentially leading to higher production costs.

Both longitudinal finned tubes and welded helical finned tubes offer enhanced heat transfer efficiency compared to plain tubes, but they differ in aspects such as surface area, resistance to fouling, suitability for different flow characteristics, and manufacturing complexity, making each type more suitable for specific applications based on the requirements and operating conditions.

Longitudinal finned tubes