China 304 316L Welded Stainless Steel Pipe Tube for Heat Exchanger

304 316L Welded Stainless Steel Pipe and Tube for Heat Exchanger

The finned tube is to improve the heat exchange efficiency, usually by adding fins on the surface of the heat exchange tube to increase the external surface area (or internal surface area) of the heat exchange tube, so as to achieve the purpose of improving the heat exchange efficiency, such a change Heat pipe.
classification
1. Divided by fin structure characteristics
According to the shape and structure of the fin, the finned tube can be divided into the following types: square finned tube, spiral finned tube, longitudinal finned tube, etc., spiral serrated Finned tubes (Helical Serrated Finned Tubes), inner finned tubes (inner finned tube) ,
2. According to whether the fin material of the finned tube is the same as the material of the tube body, it can be divided into a single metal finned tube and a bimetallic composite finned tube.
3. According to different processing techniques of finned tubes, finned tubes can be divided into: rolled finned tubes (extruded fin tubes), welded and formed finned tubes, roll-formed finned tubes, and packaged finned tubes.
Main performance requirements
As a heat exchange element, finned tubes work for a long period of time under high-temperature flue gas conditions. For example, the finned tubes for boiler heat exchangers have a harsh environment, high temperature and high pressure, and are in a corrosive atmosphere. This requires finned tubes to have high performance index.
1) Anti-corrosion performance (Anti-corrosion)
2) Anti-wear performance
3) Low contact resistance (lower contact resistance)
4) High stability (Higher Stability)
5) Anti-ashing ability
Fin tube production technology status
A set of fins
The set fin process is to process a batch of individual fins with a punch in advance, and then use manual or mechanical methods to set the fins on the outer surface of the pipe by interference at a certain pitch height (wing pitch). It is the earliest applied method for processing finned tubes. Due to the simple process of the kit, the technical requirements are not high, the equipment used is cheap, and it is easy to maintain, so many factories are still using it. This process is a labor-intensive process plan, suitable for the capital and technical conditions of general small factories or township enterprises.
Sets made by manual methods are called manual sets. It uses tools to rely on human power to press the fins one by one. In this method, the fins have limited pressing force, so the interference of the suit is small, and the fins are easy to loosen. The mechanical set of fins is carried out on a fin set machine. Since the fin pressing force is based on mechanical impact force or liquid pressure, the pressing force is large, so a larger interference amount can be used. The bonding strength between the fin and the tube is high, and it is not easy to loosen. The productivity of the mechanically driven set machine is high, but the noise is high, the safety is poor, and the working conditions of the workers are not good. Although the above problems do not exist in the hydraulic transmission, the equipment is more expensive, the technical requirements of the maintenance personnel are higher, and the productivity is also lower.
B mosaic spiral fin
Inlaid spiral finned tube is a spiral groove with a certain width and depth pre-processed on the steel pipe, and then the steel belt is embedded on the steel pipe on the lathe. During the winding process, due to a certain pre-tightening force, the steel belt will be tightly tightened in the spiral groove, thus ensuring a certain contact area between the steel belt and the steel pipe. In order to prevent the springback of the steel belt, both ends of the steel belt are welded to the steel pipe. In order to facilitate inlaying, there should be a certain side clearance between the steel strip and the spiral groove. If the backlash is too small and the interference is formed, the inlay process is difficult to proceed smoothly. In addition, the wound steel belt will always rebound to a certain extent, and as a result, the steel belt and the bottom surface of the spiral groove cannot be well joined. Inlaid fins can be carried out on general equipment, the cost is not high, but the process is complex and the production efficiency is low.
C brazed spiral finned tube
The brazed spiral finned tube is processed in two steps. First, the steel strip plane is perpendicular to the axis of the pipe and wound on the outer surface of the pipe in a spiral manner, and the two ends of the steel strip are welded to the steel pipe to fix, and then to eliminate the gap between the steel strip and the steel pipe, the method of brazing Weld the steel strip and steel pipe together. This method is expensive because of its cost, so another method is often used, that is, the tube with the steel strip wrapped in it is placed in a zinc bath for overall hot-dip galvanizing instead. Using integral hot-dip galvanizing Although the plating solution may not penetrate well into the very small gap between the fin and the steel pipe, a complete galvanized layer is formed on the outer surface of the fin and the outer surface of the steel pipe. The spiral finned tube with integral hot-dip galvanizing is limited by the thickness of the galvanized layer (when the galvanized layer is thick, the zinc layer is poorly solid and easy to fall off), and the zinc liquid cannot penetrate into the gap completely. The combination rate of steel pipes 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 extremely susceptible to corrosion in acids, alkalis, and sulfides. Therefore, the use of galvanized spiral finned tubes is not suitable for making air preheaters (recovery of boiler flue gas waste heat).
D high frequency welding spiral fin
High-frequency high-frequency welding spiral finned tube is one of the most widely used spiral finned tubes. It is now widely used in electric power, metallurgy, cement industry preheat recovery and petrochemical industry. High-frequency welding spiral finned tube is While the steel tape is wound around the steel tube, the skin effect and proximity effect of the high-frequency current are used to heat the outer surface of the steel tape and the steel tube until the plastic state or melting, and the welding is completed under a certain pressure of the wound steel tape. This high-frequency welding is actually a solid-phase welding. Compared with inlaying, brazing (or integral hot-dip galvanizing) and other methods, it is more advanced in terms of product quality (high welding rate of fins, up to 95%), productivity, and degree of automation .
E three-roller diagonal rolling integral spiral finned tube
The production principle of the three-roller cross-rolled integral spiral finned tube is shown in Figure 1.8. The smooth tube is lined with a mandrel, driven by the rotation of the roller blade, and the seamless steel tube passes through the cavity formed by the rolling groove and the core head. Fins are machined on the outer surface. The finned tube produced by this method is an organic whole because of the base tube and the outer fin, so there is no problem of contact thermal resistance loss, and it has a higher heat transfer efficiency. Compared with the welding method, the three-roll oblique rolling method has the advantages of high production efficiency, low raw material consumption, and high heat exchange rate of the finned tube.
At present, the three-roller cross-rolled integral spiral finned tube technology has been successfully applied to single-finned tubes or composite finned tubes with copper and aluminum fins, or steel low-finned tubes; steel integral finned tubes are currently available Low-fin tubes are more common in the market, and integral high-fin tubes are mostly made of aluminum, copper, etc., and are generally cold rolled. In view of the high frequency welding finned tube and non-ferrous metal integrally rolled finned tube on the market, it is easier to find, and the integrally rolled finned tube (steel) has fewer finned tubes.
Application :
It is extensively applied in hot air heating , drying , cooling , heumidifying and so on .