YUHONG GROUP - Fin tube selection principles

In the heat exchanger, many times the size of the heat transfer coefficient of the fluid on both sides of the heat transfer is not balanced, usually we will add fins on the side of the heat transfer coefficient is small. The structure of finned tube heat exchanger is basically the same as that of general shell and tube heat exchanger, except that the finned tube replaces the light tube as the heat transfer surface. This makes its structure more compact and increases the heat transfer area, which can strengthen the heat transfer.

If there is a large difference between the heat transfer coefficients of the two sides of the tube, fins should be added to the side with the smaller heat transfer coefficient.

For example:

1: boiler economiser, water goes inside the tube, flue gas flows outside the tube, fins should be used on the flue gas side.

2: Air cooler, tube goes liquid, tube outside the flow of air, fins should be added to the air side.

3: Steam generator, inside the tube is boiling water, outside the tube goes flue gas, fins should be added on the flue gas side.

It should be noted that in the design, the side with the small heat transfer coefficient should be placed outside the tube as far as possible to facilitate the addition of fins.

The heat transfer coefficient of both sides of the tube is very small, in order to strengthen the heat transfer, fins should be added on both sides at the same time, or if there are structural difficulties, both sides can be left unfinned. In this case, if only on one side with fins, the increase in heat transfer will not have a significant effect.

For example:

1: Traditional tube air preheater, the tube goes to the air, the tube goes to the flue gas. Because it is gas-to-gas heat transfer, both sides of the heat transfer coefficient is very low, the tube with fins and very difficult, you have to use the light tube.

2: heat pipe air preheater, although still flue gas heating air, but because the flue gas and air are flowing outside the tube, so the flue gas side and the air side of the finned tube can be easily used, so that the heat transfer greatly increased.

If the heat transfer coefficient is large on both sides of the tube, there is no need for finned tubes.

For example:

1: For a water/water heat exchanger, when heating cold water with hot water, the heat transfer coefficients are sufficiently high on both sides, and there is no need to use finned tubes. However, in order to further enhance heat transfer, threaded tubes or corrugated tubes may be used instead of light tubes.

2: A power plant condenser with condensation of water vapour outside the tube and water going inside the tube. The heat transfer coefficients are high on both sides, and finned tubes are not normally required.