How to choose the distance between fin tubes and fin pitch
In general, the distance between fin tubes and fin pitchs mainly affected fin ratio. The ratio of the fin and the heat transfer coefficient of the film has high relations. If the difference of heat transfer coefficient between the inner and outer membrane of the tube is large, such as the steam heating air, should be chosen to be larger fin tube. When one side of the medium is in the case of phase change, the difference of heat transfer coefficient is large, such as the exchange of cold and hot air, when the hot air is reduced to dew point, can be used to heat exchanger. In the absence of phase change of air and air heat exchange, or water and water heat exchange, usually with a bare tube is more suitable. Of course, can also be used for low fin tube, because at this time belong to the weak to heat coefficient, strengthen the side of which is a certain effect. However, a large wing of the ratio is not obvious, and the best contact area at the same time, can be used in the pipe or groove.
Fin spacing is mainly considered ash, dust, easy to clean, and other factors. At the same time, in strict compliance with the requirements of equipment of pressure drop. The spacing between the tube and the tube is not too large, the general > 1mm is more suitable for the tube. In the process of heat transfer, the air flow through the fin and tube heat exchanger, the main is the two sides of the fin and the heat exchange. Only a small amount of radiation heat transfer in the middle part of the two finned tube is not obvious. This site is easy to penetrate because of the absence of a fin, without resistance. In the process of air heating, the heat air which has not been changed to the middle of the air and the heat air through the fin has been formed and has reduced the effect of heat transfer. The distance between the tube and the fin tube is more important than that of the fin tube.
The tube arrangement of the fin tube heat exchanger should be arranged as far as possible. After the first row of the hot air, in the second row of resistance, there is a certain rebound in the wind, so the entire fin tube 360. So, should avoid an isosceles triangle, try not to use the square array, unless there are special requirements.
The pressure drop in the design is a very important parameter, which has a great relationship with the arrangement of the fin tube. The ratio of the narrow gap to the surface of the air flow is calculated.