What are the roles of axial fans and centrifugal fans in mechanical ventilation

The difference between centrifugal fan and axial fan at startup:
The operating power of the centrifugal fan increases with the increase of the air volume, so the air door of the centrifugal fan should be fully closed when it is started, and then gradually opened to avoid the excessive current of the fan and the burning of the motor.
The operating power of the axial flow fan decreases with the increase of the air volume, so when the axial flow fan is started, the damper must be fully opened, and then gradually closed to the required air volume value.

The role of axial fans and centrifugal fans in mechanical ventilation:
1. Due to the large difference between air temperature and grain temperature, the first ventilation time should be selected during the day to reduce the gap between grain temperature and air temperature and reduce the occurrence of condensation. In the future, the ventilation should be carried out at night as much as possible, because this ventilation is mainly for cooling. At night, the atmospheric humidity is relatively high and the temperature is relatively low, which reduces water loss and makes full use of the low temperature at night to improve the cooling effect. .
2. In the initial stage of ventilation with centrifugal fans, condensation on doors and windows, walls, and even slight condensation on the surface of the grain may occur. Just stop the fan, open the windows, turn on the axial fan, and turn the grain surface if necessary to remove the hot and humid air in the warehouse. Just outside the warehouse. However, if the axial flow fan is used for slow ventilation, there will be no condensation, only the middle and upper grain temperature will rise slowly, and the grain temperature will drop steadily as the ventilation continues.
3. When the axial flow fan is used for slow-speed ventilation, because the air volume of the axial flow fan is small, and the grain is a poor conductor of heat, it is easy to ventilate some parts slowly at the initial stage of the ventilation. As the ventilation continues, the grain temperature of the whole warehouse will gradually balance.
4. The advantages of slow-speed ventilation with axial fans: good cooling effect; low unit energy consumption, which is especially important today when energy saving is advocated; ventilation timing is easy to grasp and condensation is not easy to occur; no separate fan is required, which is convenient and flexible. Disadvantages: Due to the small air volume, the ventilation time is long; the precipitation effect is not obvious, and the axial flow fan is not suitable for ventilation in high moisture areas.