Three key points of spiral duct fan system design

The advantages of spiral duct are that the installation significantly reduces the connection points between pipes, so that the leakage at the joint of pipe fittings is minimized. The length of typical spiral duct is 3 ~ 6m, while that of typical rectangular duct is only 1 ~ 1.5m. Moreover, only one pipe connector is needed to connect two spiral air ducts, while a completely independent double flange system is often required for the connection of traditional rectangular air duct Unification. Next, Shuanghua heavy industry will talk about the design guide of air duct system.

1. The air duct should be arranged as straight line as possible.

This requirement is the most important criterion for the layout of any duct system. The linear air duct system has the lowest energy consumption and initial investment. From the point of view of energy saving, air always "hopes" to go straight, which will reduce energy consumption. From the cost point of view, the cost of straight pipe section is much less than that of various elbows and other pipe fittings. Therefore, when arranging the plane direction of an air duct system, we should try our best to minimize the number of people turning.

2. Use standard length straight pipe section to minimize the number of various reducers and joints.

The cost of straight and standard length air ducts is relatively low because of their low processing cost. Standard length straight air ducts can be made on white moving production line according to standard width steel sheet coil. And any Section of non-standard length rectangular duct, technically speaking, can be used as accessories, because they can not be made of standard coil. Spiral circular duct can be made into any length. The standard length of oval duct depends entirely on the processing standard of metalworking plant. Some designers always think that in the plane design of an air duct system, reducing the cross-section size of the duct frequently seems to reduce the investment. It's not. As shown in Fig. 5-l, if the length of each straight pipe section is reduced by using four reducing pipes, it is better to increase the length of standard straight pipe section, and reduce the rod changing pipe to one. On the contrary, the initial investment and operation energy consumption cost of the latter can be reduced.

3. Spiral round air duct is recommended as long as the installation space is allowed.

Higher wind speeds are allowed for circular ducts. According to the recommendation of American Society of heating, refrigeration and air conditioning engineers, the wind speed of a medium-sized VAV air conditioning system can reach 20 m / s, while that of a large-scale variable air conditioning system can be as high as 30 m / s. For rectangular duct, the allowable wind speed is generally low. If the wind speed is too high, it will easily cause resonance of flat duct wall and produce noise, especially low-frequency noise which will be transmitted to the room. The investment can be saved by using circular duct and higher air supply speed. First of all, compared with the similar rectangular duct system, the circular duct system can save 15% - 30% steel sheet. For example, for the same transportation of 17000m3 / h air, according to the requirements of noise control, the wind speed of circular air duct is 19m / s, and that of rectangular duct is 10m / s. The comparison of steel plate consumption between them is shown in Table 5-1.

It can be seen from the table that 37% steel sheet can be saved by using circular air duct.

Secondly, the installation cost of circular duct is lower than that of rectangular duct. This is because the rigidity of the circular air duct is good, the prefabricated pipe section can be longer, and the workload of field installation is relatively less. The production and connection of circular air duct are more strict than rectangular duct, the air leakage rate is about 1%, while the air leakage rate of rectangular air duct is sometimes as high as 10%, or even higher. In order to prevent air leakage, it is necessary to spend a lot of manpower to detect and seal each rectangular air duct.

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