The Role Of Axial Fans And Centrifugal Fans in Mechanical Ventilation

1. Due to the large difference between the air temperature and the grain temperature, the first ventilation time should be selected in the daytime to reduce the gap between the grain temperature and the air temperature and reduce the occurrence of condensation. The future 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 low, which not only reduces water loss, but also makes full use of the low temperature at night, improving the cooling effect .

2. In the early stage of ventilation with a centrifugal fan, there may be condensation on the doors, windows, walls, and even slight condensation on the surface grain surface. Just stop the fan, open the window, turn on the axial flow 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, condensation will not occur, and only the grain temperature in the middle and upper layers will rise slowly, and the grain temperature will drop steadily as the ventilation continues.

3. When using an axial flow fan for slow ventilation, due to the small air volume of the axial flow fan and the fact that grain is a poor conductor of heat, some parts tend to be ventilated slowly at the initial stage of ventilation. As the ventilation continues, the grain temperature of the whole warehouse will gradually balance .

4. The grain that needs to be ventilated at a slow speed must be cleaned by a vibrating sieve, and the grain that enters the warehouse must be cleaned of the impurity area caused by automatic grading in time, otherwise it will easily cause local uneven ventilation.

5. Calculation of energy consumption: No. 14 storehouse has been ventilated by axial fans for 50 days, an average of 15 hours a day, and 750 hours in total. The average moisture content has dropped by 0.4%, and the grain temperature has dropped by an average of 23.1 degrees. The unit energy consumption is: 0.027kw .h/t.℃. Warehouse No. 28 was ventilated for 6 days in total and took 126 hours. The moisture content dropped by an average of 1.0%, the temperature dropped by an average of 20.3 degrees, and the unit energy consumption was: 0.038kw.h/t.℃.

6. The advantages of slow ventilation with axial flow fans: good cooling effect; low unit energy consumption, which is especially important in today's energy-saving advocacy; ventilation timing is easy to grasp, and condensation is not easy; no separate fan is needed, 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 of high-moisture grains.

7. 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 flow fan is used for safe, efficient and energy-saving slow ventilation; in the ventilation for the purpose of precipitation, the centrifugal fan is used.