Carbon Steel Spiral Finned Tube as Heat Exchanger for Boiler Systems

Carbon Steel Spiral Finned Tube Heat Exchanger in Heat Recovery of Boiler Ecomizer

General introduction

Spiral finned tubes are widely used in heat recovery of boiler economizer, air preheater, and waste heat boiler, as well as heat exchange equipment in chemical industry, pressure vessel and other fields. The capacity of units used in boilers has also increased from small to large, and their applications are increasing day by day. At present, many professional manufacturers in China can produce high frequency resistance welding, brazing spiral finned tubes, and the production equipment and technology of finned tubes have been developed, designed and manufactured from importation, digestion and absorption to self-development. The quality has reached the requirements of advanced foreign standards.

Advantages of using finned tubes:

1. the heat transfer area is increased in the effective space to improve the heat transfer effect.

2. Reduce the occupancy space of heat transfer surface and reduce its volume, especially for fast-loading boilers.

3. Reduce the equipment cost and improve the safety of equipment.

4. Due to the decrease of water side pressure drop, the operation cost is reduced.

5. The stiffness of finned tubes are increased, and the seismic resistance of the tube is improved.

Manufacturing method

Spiral finned tubes can be manufactured by various ways. At present, there are several main manufacturing methods for finned tubes used in heat exchangers such as boilers and pressure vessels.

High frequency resistance welding spiral finned tube

High frequency resistance welding spiral finned tube is kind of high frequency current imported into the welded parts. By using the resistance heat generated by the current through the contact surface of the welded joints and adjacent areas, the welded contact surface can reach the plastic state of melting or semi-melting, then appropriate pressure is applied to the welded contact surface, to complete welding work of finned tubes.

Brazed spiral finned tube

Brazing spiral finned tube is a kind of metal filler with a melting point lower than that of the welded part, and then heating the brazing temperature. When the welded part is not melting, the solder melting well wets and brazes, and forms the brazing joint depending on expansion and dispersion of the contact point of the welded part, thus completing the welding of the spiral finned tube.

Integral spiral finned tube

Integral spiral finned tube is formed by extrusion and tie of thick-walled tube(billet tube) under the condition of medium frequency continuous heating.It is known as the latest method of manufacturing finned tube in domestic market. It is developed by a domestic company and the researched and developed integral finned tube as well as the self-manufactured integral finned tube manufacturine equipment have been applied for patents.

Service life

High frequency resistance welding of spiral finned tube is to apply pressure while melting at the contact of two metal surfaces. The welding rate is better. The corrosion resistance of welded metal is more than twice that of brazing, and the service life of the finned tubes can be greatly improved. However, due to improper welding, long-term use is prone to weld cracking, which makes the fins and tubes detached, thus affecting their heat transfer efficiency, so finned tubes have to be replaced.

Integral spiral finned tubes do not have the problem of welding fins, so there is no need to worry about corrosion and cracking of fins, so the heat transfer efficiency will not be reduced. Moreover, because the surface hardness of integral spiral finned tube increases, the wear resistance of the finned tube is increased, and the root structure characteristics of the fins are convenient for heat transfer, the service life of integral spiral finned tubes is equal to that of the raw material of finned tubes, at least 2-3 times of that of high frequency resistance welding and brazing spiral finned tubes.

Economical efficiency

Brazing spiral finned tubes require a third kind of material-brazing filler metal. When brazing, the fins need to undergo cold winding, spraying solder, sintering and other major processes, so the manufacturing cost is high. High frequency resistance welding spiral finned tubes do not need a third material. The fin is formed by one-time welding, so the cost is relatively low. The winding end and termination end of high frequency resistance welding and brazing spiral finned tubes, should be fixed by manual welding method, then good for welding production.

Integral sprial finned tubes are made of thick-walled tubes by extrusion and rolling without the need of a second material. It eliminates the winding and welding of high frequency resistance welding fins, and high production efficiency and low cost. In addition, because the fin root of integral spiral finned tube is a small R smooth transition, it is convenient for heat transfer.