Brazed spiral finned tubes

Brazed spiral finned tubes are expensive, so an alternative method is often used, where the wrapped steel tube is placed in a zinc bath for overall hot-dip galvanizing. Although the overall hot-dip galvanizing solution does not necessarily penetrate well into the tiny gap between the fins and the steel tube, a complete galvanized layer is formed on the outer surface of the fins and the outer surface of the steel tube. Using the overall hot-dip galvanized spiral finned tube, because of the limitation of the thickness of the galvanized layer (when the galvanized layer is thick, the zinc layer is poorly firm and easy to fall off), coupled with the fact that it is impossible for the zinc solution to penetrate all the way into the gap, the bonding rate between the fins and the steel pipe is still not high. In addition, the heat transfer coefficient of zinc is smaller than that of steel (about 78% of steel), so the heat transfer capacity is low. Zinc is highly susceptible to corrosion in acids and alkalis, sulfides, therefore, the use of galvanized spiral finned tubes is not suitable for the production of air preheaters (recovery of boiler flue gas waste heat).

Finned tubes can be broadly classified into the following categories according to the shape of the fins.
1). Square finned tube (Square finned tube).
2). Circular finned tube
3). Spiral finned tube (spiral finned tube).
4). Longitudinal Finned Tube
5). corrugated finned tube
6). Spiral Serrated Finned Tube (Helical Serrated Finned Tubes)
7). Needle Finned Tubes
8). Integral plate finned tubes (plate fins).
9). Inner finned tube (inner finned tube). And so on.