The role of axial fans and centrifugal fans in mechanical ventilation

Summary:1 . Due to the large difference between air temperature and grain temperature, the first ventilation time should be sele...

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 early 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, turn the grain surface if necessary, and remove the hot and humid air from the bin. can. However, if the axial flow fan is used for slow ventilation, there will be no condensation, and only the middle and upper grain temperature will rise slowly. As the ventilation continues, the grain temperature will drop steadily.
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 ventilation. As the ventilation continues, the grain temperature of the whole warehouse will gradually balance.
4. Grain for slow ventilation must be cleaned by a vibrating screen, and the grain entering the warehouse must be cleaned in time to clean the impurity area caused by automatic classification, otherwise it is easy to cause uneven local ventilation.
5. Energy consumption calculation: No. 14 warehouse uses an axial fan to ventilate for 50 days, an average of 15 hours a day, sharing 750 hours, an average of 0.4% drop in moisture, an average drop in grain temperature of 23.1 degrees, unit energy consumption: 0.027kw.h /t.℃. The No. 28 warehouse has been ventilated for 6 days and 126 hours in total. The moisture content dropped by 1.0%, the temperature dropped by 20.3 degrees, and the unit energy consumption was 0.038kw.h/t.℃.
6. The advantages of slow-speed ventilation with axial flow 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 high-moisture grains are not suitable for ventilation with axial fans.
7. The advantages of centrifugal fans: obvious cooling and precipitation effects, short ventilation time; disadvantages: high energy consumption per unit; poor ventilation timing is prone to condensation.
8 . Conclusion: In the ventilation for the purpose of cooling, the axial fan is used for safe, efficient and energy-saving slow ventilation; the centrifugal fan is used for the ventilation for the purpose of precipitation.