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What’s right about laser welded finned tube working principle?

Laser welded finned tube

Laser welding spiral finned tube is processed by laser welding machine.

Stainless steel laser welded spiral finned tube

In traditional spiral finned tubes, high frequency welding, resistance welding and other techniques are used to attach stainless steel fins to the steel tube. Laser welding finned tube, the welding process has its shortcomings that cannot be overcome.

The laser welding  finned tube has a fully automatic welding process, which saves labor costs; secondly, the laser welding fins are firm and strong, and the high tensile strength test is qualified; laser welding has higher efficiency advantages.

Laser welding machine is the most advanced laser welded  finned tube laser welding equipment. Because the welding process is fully automatic and mechanical, the scientific and technological content and quality of laser welded finned tubes are superior to traditional cooling tubes.

Laser welding principle

Laser welding is a welding method that irradiates a high-intensity laser beam onto the surface of a metal, and through the interaction of the laser and the metal, the metal absorbs the laser light into heat and melts the metal to form a cooling crystal.

Stainless steel laser welded finned tube:

  1. High degree of automation, the automatic fin laser welding machine can complete welding at one time, and the synchronous winding enables the welding depth of the fin feet and the tube to be realized.

        2 Laser welding, high firmness and high binding force. Laser welding is a metallurgical combination with a welding strength greater than 600MPa.

  1. The laser welding machine has high precision, which can weld 8-meter-long laser welded finned tubes with an accuracy of 0.05mm.
  2. Laser welding can greatly improve the heat transfer coefficient.
  3. The length of the laser welding fin section is less than or equal to 2.5 mm, and the heat dissipation area is increased by nearly 50% compared with the high-frequency welded tube (the distance is greater than or equal to 4.5 mm), which greatly reduces the material of the tube and can also reduce the volume of the heat exchanger Variety.

Why use aluminum fins for stainless steel laser welded finned tubes?

According to the application and operation of heat exchange, there are various materials. Common are aluminum, alloys, copper, brass, nickel, titanium, stainless steel, carbon steel, etc., among which aluminum and alloys are the most commonly used.

The basic performance of laser welded finned tube heat exchange should have good welding ability and forming ability, high mechanical strength, good corrosion resistance and thermal conductivity. Nonetheless, aluminum and alloys are ductile, and their tensile strength increases at lower temperatures. They are widely used all over the world, especially in terms of low temperature and compact heat exchange.

 

Murphy finned tubes factory workshop
Murphy carbon steel high frequency fin tube HVAC A 1 scaled

 

Let’s take a look at the characteristics of aluminum

  1. Low density

Through alloying and heat treatment, the structure of building steel can be achieved. It is suitable for all kinds of transportation, especially small vehicles, reducing weight and consumption.

  1. Good corrosion resistance

Under harsh conditions, aluminum oxides are non-toxic. Using aluminum for heat exchange, there is no need to worry that oxides will damage the air or liquid inside after a long time.

  1. Good thermal conductivity,

Especially suitable for heat sink, heat transfer evaporator and condenser.

  1. High yield and die-cut resistance.

It is easy to process and shape.

As a professional laser welded finned tube manufacturer, our leading product is aluminum laser welded finned tube. If you are interested, please contact us for more information.

Fin tube ratio is affected by fin height, fin thickness and fin spacing

When the root of the fin is exposed on the bare base tube, if heat is transferred from the inside to the outside, the heat will be transferred from the root of the fin along the height of the fin. It is also continuously transferred to the surrounding fluid through convective heat transfer. As a result, the fin temperature gradually decreases along the height. 

This also shows that the difference between the fin temperature and the ambient fluid temperature is gradually decreasing, and the change in heat per unit is shrinking. Therefore, the effect of fin surface area on enhanced heat transfer is decreasing. The higher the fins, the smaller the contribution of the increased area to heat exchange.

Fin height

In general, for high-frequency laser welded  finned tubes used in engineering projects, the fin efficiency is about 0.8 when the fin height is 15 mm. When the fin height is 20mm, the fin efficiency drops to 0.7. Based on this, the optimal height is 15 mm. If the fin height exceeds 20mm, the fin efficiency will be very poor, so it is generally not used. However, for the aluminum fins on the air cooler, since the thermal conductivity of aluminum is much better than that of carbon steel, the height of 22-25mm is always used.

How will the fin pitch affect the fin ratio?

Usually a smaller pitch can effectively increase the fin ratio. When considering the nature of flowing gas and ash deposition, the following factors should be noted.

  1. Severe heavy ash deposition

Such as the exhaust gas of electric furnaces and converters in steel plants and industrial pit furnaces, the ash content is high. If finned tubes are used for heat exchange, it is recommended to use larger fin spacing. For example, if the pitch is greater than 10mm, you need to increase air emissions and choose a blower.

  1. For occasions with little ash, but also pay attention.

Taking the exhaust of factory boilers and industrial boilers as an example, a fin pitch of 8mm is suitable, but it should be designed to have self-blowing capability.

  1. No dust or light dust.

For example, the exhaust of natural gas burning equipment or air cooler, the fin spacing can be 4-6mm. For the aluminum air cooler, 3mm is also selected as the fin pitch.

Fin thickness

The choice of heat sink thickness depends on the corrosion and wear of the fluid gas. Normally, thicker heat sinks will be used in severely corroded sites.

How to improve the production efficiency of laser welded finned tubes and reduce production costs: The production efficiency of finned tubes is still very low at present, and there is much room for improvement. As long as the development is good, the production cost will be greatly reduced. There are many factors that affect the production efficiency of finned tubes, mainly including the following factors:

  1. Impedance matching problem: We all know that the electron tube is a voltage amplifying element, the output impedance is very high, and the contact welding is a current heating welding process, which requires a low-impedance power supply. Therefore, the impedance of the two does not match and it is difficult to output more Large electric power. Only by changing the ratio of the tank circuit and adjusting the relative position of the contacts properly can a large output be obtained.
  2. Reduce the standby time: the tube must provide a basic power consumption to work, that is to say, whether you are soldering or not, this part of the power must be consumed, so reducing the standby time will save power and thus reduce production costs. The actual standby time in the production process of finned tubes is more than 50%, and the power loss in this part cannot be ignored. The use of high-performance equipment will greatly reduce the standby time, resulting in higher efficiency and lower cost. Automatic loading, automatic unloading, pneumatic clamping of steel pipe, high production efficiency.

  3. Reduce the probability of breaking the band: For the same strip steel, the welding structure affects the probability of breaking the band. At present, there are three types of welding structures: spring structure, hydraulic series spring structure and pneumatic structure. The first two principles are the same, mainly relying on the pressure of the spring to achieve the forging force. 

When the pipe jumps, the spring is also used to buffer, because the elastic potential energy E=-KX2 means that the elastic potential energy is proportional to the square of the displacement. When the displacement changes by 5 mm, the change of upset energy is 25 times, so it is easy to break the steel strip, and the pressure roller is more likely to be damaged. However, there is no spring in the pneumatic structure, which mainly relies on the pressure of the gas to achieve the forging force. When the pipe jumps, it is buffered by the air pressure. When the displacement changes by 5 mm, because the length of the cylinder is 125 mm, the variation is only 4%.

Advantages of laser welded finned tube:

  1. Thin and continuous wet seam
  2. Small heat affected zone
  3. Short heating time
  4. The tube and fins have only slight microstructure changes
  5. High heat forms seams
  6. High welding speed
  7. Laser welding is carried out in a protective atmosphere, so the weld is free of impurities

Laser welded finned tube application

  • Power plant
  • Chemical industry
  • Heat recovery plant
  • Thermal Industry

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