Spiral finned tube consists of a base tube and spiral fins. The manufacturing process of spiral finned tube is usually to wrap the fin material around the base tube and weld the two into one by high frequency welding. As a result, the contact heat resistance between the base tube and the spiral fins is relatively small.
The spiral finned tube, as one of the typical structures with extended surface, has the following characteristics.
1.Increase the heat exchange area outside the tube, improve the heat transfer efficiency. The spiral finned tube extends the heat transfer area outside the light tube, so its convection heat transfer surface consists of two parts: the extended surface and the light tube surface. In the case of the same volume, its heat transfer area for the light tube of several times, thus significantly improving the heat transfer capacity of the outside of the tube and heat transfer efficiency of the heat exchanger.
2.Compact structure. Spiral fin tube bundle increases the heat transfer area per unit volume, so compared with the light tube bundle, in the case of the same heat transfer, the number of fin tube bundle tube row is relatively small, can reduce the volume of the heat exchanger, thus making the structure compact, metal consumption is reduced.
3.Enhanced heat transfer conditions. Spiral finned tubes cause the flow boundary layer to separate and develop periodically through their external curved structural channels, thinning the thickness of the boundary layer and shortening the length of the laminar flow boundary layer. These contribute to the destruction of the laminar bottom layer of the boundary layer, thus playing a role in enhancing heat transfer.
4.Reduce the resistance of fluid flow outside the tube, save operating costs. In the case of the same gas flow rate on the fin side, the resistance of each row of spiral fin tube bundle is greater than the resistance of each row of light tube, but the heat transfer area of each row of fin tube bundle increases a lot compared with that of light tube bundle, and the number of rows of tube bundle can be reduced in the case of the same heat transfer, making the total resistance of the heating surface reduced. At the same time, due to the spiral fin tube heat transfer capacity is greatly improved, under the condition of ensuring the heat transfer capacity, can also be appropriately reduced fin side fluid speed, and flow resistance is usually proportional to the square of the speed, thus reducing the fluid speed can reduce the resistance of the heating surface, saving operating costs.
5.Reduce the wear and tear of the heating surface In boilers burning solid fuels, the ash-containing airflow in the flow through the heating surface, impact and cutting the heat transfer surface will cause wear and tear of the heating surface, and the amount of wear and fluid speed is proportional to the third square. Due to the improvement of heat transfer capacity of spiral fin tube bundle, the speed of fluid outside the tube can be reduced. Thus, the wear and tear of the heating surface is greatly reduced.
At the same time, the structural characteristics of the spiral finned tube can make the fluid flowing through the spiral finned tube to a certain extent to form a flow condition that is conducive to reducing wear. Thus, the wear caused by the impact and cutting of solid ash particles on the heated surface is weakened. It is due to the above-mentioned advantages of the spiral finned tube bundle. The heat exchanger equipment with compact structure, low metal consumption, and low operating cost are the benefits of using it as a heat exchanger element. Therefore, it is widely used in boiler economizer, heat pipe air preheater, convection evaporation heating surface and waste heat recovery equipment in metallurgy and chemical industry.