Fin tube due to the characteristics of the structure, easy to become a "safe haven" for dirt, especially when the flue gas ash content is large, low flue gas flow rate, or dew point corrosion occurs, will form a large scale of dirt thermal resistance.

When the fouling thermal resistance in the total heat transfer thermal resistance of too large a proportion, will make the design of heat exchanger calculations lose meaning. Because the dirt thermal resistance is estimated and selected, and the other thermal resistance is calculated through a variety of formulas and correlations to see, when the estimated dirt thermal resistance to a certain extent, will make the other thermal resistance of the calculation is meaningless.

In addition, the fouling thermal resistance is too large, will make the finned tube heat exchanger area increases, increasing the operation of the equipment and investment costs. If the equipment in the initial operation stage of good heat transfer performance, but after a period of operation found that the heat transfer effect is reduced, the main reason is likely due to the accumulation of ash and fouling caused by.

In the design phase, it is recommended to set a range of values for tolerable fouling thermal resistance, for example, 20% of the total heat transfer thermal resistance. If the fouling thermal resistance exceeds this value, the designer should take appropriate measures to control it.

The technical countermeasures that can be taken :

1. increase the flow rate of the fluid so that the fluid has greater self-blowing ash capacity.

2. Adjust the fin structure, such as increasing the fin spacing and tube spacing, or use other fins that are not easy to accumulate ash, such as H-type fins, nail head tube fins, etc.

3. install soot blowing devices, using a strong active means of descaling.

4. Choose another suitable finned tube that is not easy to accumulate ash.