Aluminum fin tube for oil cooler

Performance requirements 

As heat exchange elements, aluminum fin tube for oil cooler work under high-temperature flue gas conditions for a long time. For example, the finned tubes used in boiler heat exchangers are used in harsh environments, with high temperature, high pressure and corrosive atmospheres. This requires that the finned tubes should have very high performance indicators.

1. Anti-corrosion performance

2. Anti-wear performance

3. Low contact resistance

4. High stability

5. Anti-ashing ability

Production status

Fin set

The fin set process is to use a punch press to process a batch of single fins in advance, and then use manual or mechanical methods to fit the fins on the outer surface of the tube according to a certain pitch (wing pitch) by interference fit. It is the earliest method of processing fin tubes. Because the set process is simple, the technical requirements are not high, the equipment used is cheap, and it is easy to maintain, so many factories still use it. This process is a labor-intensive process solution, suitable for the capital and technical conditions of general small factories or township enterprises.

The manual method of fitting is called manual fitting. It is to press the fins one by one with the help of tools and human power. Because the pressing force of the fins is limited, the interference of the set is small, and the fins are prone to loosening.

Mechanical fin fitting is carried out on the fin fitting machine. Since the fins are pressed in by mechanical impact force or liquid pressure, the pressing force is large, so a larger interference fit can be used. The bonding strength between the fins and the tube is high and not easy to loosen. The mechanical transmission assembly machine has high productivity, but it is noisy, has poor safety, and poor working conditions for workers. Although the hydraulic transmission does not have the above problems, the equipment is expensive, the technical requirements for the maintenance personnel are high, and its productivity is also lower.

Inlaid spiral fins

The inlaid spiral aluminum fin tube for oil cooler is a spiral groove of a certain width and depth pre-processed on the steel pipe, and then the steel strip is inlaid on the steel pipe on the lathe. During the winding process, due to a certain pre-tightening force, the steel strip will be tightly tightened in the spiral groove, thereby ensuring a certain contact area between the steel strip and the steel pipe. In order to prevent the steel strip from rebounding and falling off, the two ends of the steel strip should be welded to the steel pipe. In order to facilitate inlaying, there should be a certain side gap between the steel strip and the spiral groove. If the side gap is too small and an interference is formed, the inlay process will be difficult to proceed smoothly. In addition, the wound steel strip will always have a certain rebound, resulting in the steel strip and the bottom surface of the spiral groove not being well joined. Inlaid fins can be carried out on general equipment, the cost is not high, but the process is complicated and the production efficiency is low.

Brazed spiral fin tubes

The processing of brazed spiral fin tubes is carried out in two steps. First, the plane of the steel strip is perpendicular to the axis of the tube and is wound on the outer surface of the tube in a spiral manner, and the two ends of the steel strip are welded to the steel tube to fix it. Then, in order to eliminate the gap at the contact point between the steel strip and the steel tube, the steel strip and the steel tube are welded together by brazing.

This method is expensive, so another method is often used, that is, the tube wrapped with the steel strip is placed in a zinc liquid tank for overall hot-dip galvanizing. Although the overall hot-dip galvanizing solution may not be able to penetrate the extremely small gap between the fin and the steel tube well, a complete galvanized layer is formed on the outer surface of the fin and the outer surface of the steel tube. The spiral fin tube using overall hot-dip galvanizing is limited by the thickness of the galvanized layer (when the galvanized layer is thick, the zinc layer is poor in firmness and easy to fall off), and the zinc liquid cannot penetrate into the gap completely, so the bonding rate between the fin and the steel tube 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 very susceptible to corrosion in acids, alkalis and sulfides. Therefore, galvanized spiral fin tubes are not suitable for making air preheaters (recovering waste heat from boiler flue gas).

High-frequency welded spiral fins

High-frequency welded spiral fin tubes are one of the most widely used spiral fin tubes. They are now widely used in waste heat recovery in the power, metallurgy, cement industries, and petrochemical industries. High-frequency welded spiral fin tubes are made by using the skin effect and proximity effect of high-frequency current while the steel strip is wrapped around the steel pipe to heat the outer surface of the steel strip and the steel pipe until they are plastic or melted, and the welding is completed under a certain pressure of the wrapped steel strip. This high-frequency welding is actually a solid phase welding. Compared with methods such as inlaying, brazing (or overall hot-dip galvanizing), it is more advanced in terms of product quality (the welding rate of the fins is high, up to 95%), productivity and degree of automation.

Product Categories

There are many types of fin tubes, and new types are constantly emerging. Generally speaking, they can be classified according to the following aspects:

1. Classification by processing technology

(1) Extruded fin tubes;

(2) Welded fin tubes (high-frequency welded fin tubes, submerged arc welded fin tubes);

(3) Rolled fin tubes;

(4) Set-formed fin tubes;

(5) Cast fin tubes;

(6) Tension-wound fin tubes;

(7) Laminated tubes.

2. Classification by fin shape

(1) Square finned tube;

(2) Circular finned tube;

(3) Spiral finned tube;

(4) Longitudinal finned tube;

(5) Corrugated finned tube;

(6) Helical serrated finned tube;

(7) Needle finned tube;

(8) Integral plate finned tube (plate fin);

(9) Inner finned tube. Etc.

3. According to whether the fin material of the fin tube is the same as the base tube material, it can be divided into:

(1) Single metal fin tube

(2) Bimetallic composite fin tube

4. Classification of single metal fin tube by material

(1) Copper fin tube;

(2) Aluminum fin tube;

(3) Carbon steel fin tube;

(4) Stainless steel fin tube;

(5) Cast iron (cast steel) fin tube; etc.

5. Classification by use

(1) Fin tube for air conditioning;

(2) Fin tube for air cooling;

(3) Boiler: fin tubes used for water wall, economizer, air preheater respectively;

(4) Fin tube for industrial waste heat recovery;

(5) Fin tube for other special purposes; etc.