Fin tube heat exchanger refers to the use of finned tubes as the main heat transfer element of the heat exchanger, when the medium heat transfer state for oil - oil, water - water, gas - gas and so on heat exchange occasions, often do not need to add fins, because the heat transfer coefficient inside and outside the tube on both sides are about the same, the processing of fins does not make any sense, but affect the flow of the medium, for heat transfer is not good. Of course, standing in the perspective of strengthening heat transfer, for how to improve the total heat transfer coefficient of the finned tube heat exchanger is also worthy of reference.

When the difference between the heat transfer film coefficient inside and outside the tube is large, finned tubes should be used to increase the contact area on the side where the heat transfer coefficient is insufficient to compensate for the lack of heat transfer capacity. Therefore, when designing a finned tube heat exchanger, the fins are added on the side of the poorer heat transfer coefficient. If the steam heats the air, the heat transfer capacity of the air is very low, the fins should be processed, as the processing of fins inside the tube is more difficult, then the fins are processed outside the tube. Of course, the air can only flow outside the tube, but also in line with the design principles of "high-temperature and high-pressure media, the tube outside the low-temperature and low-pressure media".

There is also a heat exchanger, the use of corrugated tubes or wave section tube, so both sides have increased the contact area, but also played a role in disturbing the flow, so the heat exchanger tube is suitable for oil - oil, water - water, gas - gas and so on the heat exchange occasions.

How to improve the total heat transfer coefficient of the finned tube heat exchanger?

First, reduce the cross-sectional area of the windward side to increase the flow rate of air and improve the mass flow rate of air. Or set up a wind baffle in the air pathway, folded plate to promote the degree of air turbulence, usually used in the finned tube heat exchanger on the tube process structure.

Second, the use of reasonable finning ratio. Most manufacturers of finned tubes using specifications are relatively arbitrary, are selected according to experience. The correct method should calculate the difference between the heat transfer coefficient inside and outside the tube. The general heat transfer coefficient difference should be controlled between 4:6 is more reasonable.

Third, deep excavation of the heat transfer capacity of the medium inside the tube. According to the calculation formula of heat transfer coefficient. When the heat transfer capacity of one side is increased, there is also an impact on the total heat transfer coefficient. Therefore, under the condition that the pressure loss in the tube is allowed, the flow rate should be increased as much as possible to improve the heat transfer capacity of the medium in the tube.

Fourth, eliminate contact heat resistance. The processing quality of the finned tube has a relatively large impact on the heat transfer coefficient. Certain contact poor finned tube its heat transfer capacity is low, it can be said that a price is worth a penny.

Fifth, Metal thermal resistance. The use of different base tubes whose thermal conductivity is completely different. Commonly used metal material thermal conductivity, copper is better than aluminum, aluminum is better than carbon steel, carbon steel is better than alloy steel, stainless steel heat transfer capacity is very low.

There is also the thickness of the wall of the tube for the heat transfer coefficient is also relatively large, foreign research data show that when the wall thickness of the tube is below 0.4, for the same 2mm material, the difference in heat transfer coefficient reaches 30%, unproven. In the process of use, dirt for the finned tube heat exchanger heat transfer capacity of the most serious impact, data show that 1mm of oil, equivalent to 50mm of steel plate metal thermal resistance.