It is also related to the flow velocity of the fluid and the shape of the solid surface

It is also related to the flow velocity of the fluid and the shape of the solid surface

The function of installing fins can also be illustrated with the following more vivid example: at the entry and exit point of a border port, assuming that the port of Party A has ten inspection ports, which can release 5000 people per hour, while the port of Party B only has one ticket inspection port, and the process is very slow, only 50 people can be released per hour. In this way, the second party becomes a bottleneck for passengers to clear customs, preventing the first party's "ability" from being fully utilized. The most effective way to increase the clearance flow is to open several inspection ports on the side of Party B. This is the same principle as adding fins. After understanding the principle and function of finned tubes, when choosing finned tubes, there are several principles: (1) If the heat transfer coefficients on both sides of the tube differ greatly, fins should be installed on the side with lower heat transfer coefficients. Example 1: Boiler economizer, with water flowing inside the pipe and smoke flowing outside the pipe, fins should be used on the smoke side. Example 2: Air cooler, with liquid flowing inside the tube and air flowing outside the tube, fins should be added on the air side. Example 3: In a steam generator, there is boiling water inside the tube, and smoke flows outside the tube. Fins should be added to the smoke side. It should be noted that during design, the side with a low heat transfer coefficient should be placed outside the tube as much as possible to facilitate the installation of fins. (2) If the heat transfer coefficient on both sides of the pipe is very small, in order to enhance heat transfer, fins should be installed on both sides simultaneously. If there are structural difficulties, fins can be omitted on both sides. In this case, adding fins only on one side will not have a significant effect on increasing heat transfer. Example 1: Traditional tubular air preheaters use air inside the pipes and smoke outside the pipes. Because it is gas to gas heat transfer, the heat transfer coefficients on both sides are very low, and it is difficult to add fins inside the tube, so we have to use the entire tube. Example 2: A heat pipe air preheater, although still heated by flue gas, can conveniently use finned tubes on both the flue gas and air sides due to the flow of both flue gas and air outside the tube, greatly increasing heat transfer. (3) If the heat transfer coefficients on both sides of the tube are large, it is not necessary to use finned tubes. Example 1: When using hot water to heat cold water in a water/water heat exchanger, if the heat transfer coefficients on both sides are high enough, there is no need to use finned tubes. But in order to further enhance heat transfer, threaded pipes or corrugated pipes can be used instead of light pipes. Example 2: The condenser of a power plant is a condensation of water vapor outside the pipe, while water flows inside the pipe. The heat transfer coefficients on both sides are very high, and in general, finned tubes are not needed.

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