Finned tubes are divided into integral finned tubes, welded finned tubes, high-frequency welded finned tubes and mechanically connected finned tubes. The whole finned tube is made of casting, machining or rolling, and the fin is integrated with the pipe, such as the economizer of the low pressure boiler is the finned tube which is made by the whole casting.
This type of finned tube has no contact thermal resistance, high strength, heat shock and mechanical vibration, heat transfer, mechanical and thermal expansion performance are better, but the high manufacturing cost is suitable for low finned tubes with a fin ratio of less than 5. Welded fin tube is made by brazing or inert gas protection welding process, different materials of fins and tubes welded together, finned tube manufacturing simple, with good heat transfer and mechanical properties, widely used in industry.
Because the residue in the weld is not conducive to heat transfer, the welding quality must be guaranteed. High-frequency welded finned tube is the use of high-frequency generator generated by high-frequency electrical induction, so that the pipe surface and fins contact to produce high temperature and partial melting, and then through pressure to make the fin and pipe into one.
The connection process has no flux, no solder, simple manufacture, excellent performance, the most industrial applications of a process. Mechanical connection around the chip tube is poor, mainly the existence of contact thermal resistance, especially in the operation of the flake fin tension with the increase of temperature and rapid decline, so that contact thermal resistance also increased rapidly. Welding chip Heat Transfer performance is the best. The plate performance is also good, because the fin tight sleeve and tube surface after the surface hot-dip galvanizing. The heat transfer performance of bimetallic rolling is similar to that of the inlay type, which is then rolled out of the fins after the suit.