Finned tube is a heat exchange element. Finned tubes are almost always used in air-cooled exchangers to compensate for the low air-side heat-transfer coefficient. Finned tube manufacturer in China, In order to improve the heat exchange efficiency, the outer surface area (or inner surface area) of the heat exchange tube is generally increased by adding fins on the surface of the heat exchange tube, thereby achieving the purpose of improving heat exchange efficiency. finned tube is kind of heat exchange tube.
Finned tube main catalog
1. Main performance requirements of finned tubes
2. Fin tube production technology status
3. Classification of finned tubes
Main performance requirements of finned tubes
As a heat exchange component, the finned tube works for a long time under high temperature flue gas conditions. For example, the fin tube of the boiler heat exchanger has a harsh environment, high temperature and high pressure and is in a corrosive atmosphere, which requires high performance of the finned tube. index.
1), Anti-corrosion performance
2), Wear resistance (Anti-wear)
3), Low heat contact resistance
4), High Stability heat transfer capacity
5), anti-ashing ability
Current status of fin tube production technology
1),Plate fin tube
Stamped fins can be manufactured in almost any shape or size. This style of fin is commonly referred to as "Square Fin" or "Plate Fin". Although any shape is possible, square and round are the norm.
The finned tube process is to pre-process a batch of individual fins by punching, and then manually or mechanically, according to a certain height (wing distance), the fins are placed on the outer surface of the tube by interference. It is the earliest method of processing finned tubes. Due to the simple process and low technical requirements, the equipment used is inexpensive and easy to maintain, so many factories are still in use. This process is a labor-intensive process solution suitable for the capital and technical conditions of small or medium-sized enterprises.
The manual method is called a manual suit. It uses tools to rely on human strength to push the fins one by one. In this method, since the pressing force of the fin is limited, the interference of the set is small, and the fin is prone to looseness.
The mechanical set fins are made on a fin set machine. Since the fin press-in is caused by mechanical impact or liquid pressure, the press-in force is large, so that a large interference can be used. The joint strength between the fin and the tube is high and it is not easy to loosen. The mechanical transmission set machine has high productivity, but the noise is high, the safety is poor, and the labor conditions of the workers are not good. Although the above problems are not present in the hydraulic transmission, the equipment is more expensive, the technical requirements for the maintenance personnel are higher, and the productivity is lower.
2),Embedded spiral fin tube
The embedded spiral finned tube is a spiral groove of a certain width and depth pre-machined on the steel pipe, and then the steel strip is embedded on the steel pipe on the lathe. During the winding process, due to a certain pre-tightening force, the steel strip will be tightly placed in the spiral groove, thereby ensuring a certain contact area between the steel strip and the steel tube. In order to prevent the steel strip from rebounding, both ends of the steel strip are welded to the steel pipe. In order to facilitate the setting, there should be a certain backlash between the steel strip and the spiral groove. If the backlash is too small and an interference is formed, the inlaying process is difficult to proceed smoothly. In addition, the entangled steel strip always has a certain rebound, which results in a poor joint between the steel strip and the spiral groove bottom surface. Inlaid fins can be carried out on general-purpose equipment at a low cost, but the process is complicated and the production efficiency is low.
Brazed Finned Tubes are commonly used in applications with metal temperatures up to 380° C, and with special coating, 800° C.
The processing of the brazed spiral finned tube is carried out in two steps. Firstly, the steel strip plane is wound on the outer surface of the pipe in a spiral manner perpendicular to the axis of the pipe, and the two ends of the steel strip are welded to the steel pipe for fixing, and then the gap between the steel strip and the steel pipe is eliminated, and the brazing method is used. The steel strip and the steel tube are welded together.
Because of its high cost, this method is often used in another way, in which the tube wrapped with steel strip is placed in a zinc bath for integral hot-dip galvanizing instead. The use of integral hot-dip galvanizing, although the plating solution does not see a good gap between the fin and the steel pipe, but 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 weak and easy to fall off), and the zinc liquid cannot penetrate into the gap completely, so the fins and The joint 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 highly susceptible to corrosion in acids, alkalis and sulfides. Therefore, galvanized spiral finned tubes are not suitable for the production of air preheaters (recovery of boiler flue gas waste heat).
High-frequency high-frequency welding spiral finned tube is one of the most widely used spiral finned tubes. It is widely used in waste heat recovery in electric power, metallurgy, cement industry and petrochemical industry. High-frequency welding spiral finned tube is a steel strip wound steel pipe
The skin effect and the proximity effect of the high-frequency current are used to heat the outer surface of the steel strip and the steel pipe until plastic state or melting, and the welding is completed under a certain pressure of winding the steel strip. This high frequency welding is a solid phase welding. Compared with inlaying, brazing (or integral hot-dip galvanizing), it is more advanced in terms of product quality (high fin weldability, up to 95%), productivity and automation. .
5),Three-roller cross-rolling integral spiral finned tube
The production principle of the three-roller-rolled monolithic spiral finned tube is as follows: a mandrel is lined in the light pipe, and the seamless steel pipe is processed on the outer surface of the cavity formed by the groove and the core through the rotation of the roll blade. Finned. The finned tube produced by this method has an organic whole due to the base tube and the outer fin, so there is no problem of contact thermal resistance loss, and the heat transfer efficiency is high. Compared with the welding method, the three-roll cross-rolling method has the advantages of high production efficiency, low consumption of raw materials, and high heat exchange rate of the produced finned tubes.
At present, the three-roller-rolled monolithic spiral finned tube technology has been successfully applied to single-fin tube or composite finned tube with copper or aluminum fins, or steel low-fin tube; steel integral finned tube is currently The market is often seen as a low-fin tube, and the overall high-fin tube is made of aluminum or copper, which is usually cold-rolled.
Laser welded finned tubes are used in civil fireplaces, industrial boilers, etc., using German technology, domestically emerging, but in Europe for more than a decade, the advantage is that the contact thermal resistance is zero, compared with high-frequency welding winged Larger, lighter weight, assembled heat exchangers are compact, more energy efficient and environmentally friendly, meeting national emission requirements.
Classification of finned tubes
There are many types of finned tubes, and new varieties are constantly emerging. In general, it can be classified according to the following aspects:
1, according to processing technology classification
1), Extruded fin tube;
2), Welded molded finned tube (high frequency welded finned tube, submerged arc welded finned tube);
3), Roll formed finned tube;
4), Plate finned tubes;
5), Cast Iron finned tubes;
7), Embedded finned tube.
Classified by fin shape
1), Square finned tube;
2), Round finned tube;
3), Spiral finned tube;
5), Corrugated finned tube;
6), Helical Serrated Finned Tubes;
7), Nail finned tube, studded pipe or Pin tube, needle finned tube;
8), Integral plate finned tube (plate fin);
9), Inner finned tube.
3. According to whether the fin material of the finned tube is the same as the material of the base tube, it can be divided into:
2), Bimetallic finned tube
Single metal finned tube classified by material
1), Copper finned tube;
2), Aluminum finned tube;
3), Carbon steel finned tube;
4), Stainless steel finned tube;
5), Cast iron (cast steel) finned tube; and so on.
Bimetallic finned tube classified by material
1), Carbon steel finned tube with aluminum fin, copper fin;
2), Stainless steel finned tube with aluminum fin, copper fin;
3), Carbon steel finned tube with carbon steel fin;
4), Stainless steel finned tube with carbon steel fin;
5), Stainless steel finned tube with Stainless steel fin;
6), Cast iron (cast steel) finned tube;
7), Copper finned tube with copper fin;and so on.
Classified by fin tube usage
1), Finned tubes for air conditioning;
2), Air-cooled finned tube;
3), Boiler: finned tube used for water wall, economizer and air preheater respectively;
4), Finned tube for industrial waste heat recovery;
5), Other special purpose finned tubes; and so on.