The role of axial flow fan and centrifugal fan in mechanical ventilation

Because of the large difference between air temperature and grain temperature, ventilation time should be chosen in daytime to reduce the difference between grain temperature and air temperature and reduce the occurrence of dewing. In the future, the ventilation should be carried out at night as far as possible, because this ventilation is mainly for cooling, the air humidity is relatively high and the temperature is low at night, so that the water loss is reduced and the low temperature at night is fully utilized, the cooling effect is improved. 2 in the early stage of ventilation with centrifugal fan, there may be dew on doors, windows and walls, even slight dew on the surface of grain, if the fan is stopped, the window is opened, the axial fan is opened, and if necessary, the grain surface is turned over, the hot and humid air in the bin can be discharged outside the bin. The slow-speed ventilation with axial fan will not appear the phenomenon of condensation, only a slow rise in the upper layer of grain temperature, with the continued ventilation of grain temperature will fall steadily. When using axial fan for slow-speed ventilation, because of the small air volume of axial fan and the bad heat conductor of grain, it is easy to have slow ventilation in individual parts in the early stage of ventilation, as the ventilation continues, the temperature of the whole grain bin will gradually equalize. 4 slow-speed ventilation of the grain must go through the vibrating screen cleaning, and the grain into the bin must be timely clean the impurities caused by the automatic grading area, otherwise easy to cause uneven local ventilation.

5 calculation of energy consumption: the axial flow fan used in No. 14 bin has been ventilated for 50 days, with an average of 15 hours per day and a total of 750 hours. The average water content has decreased by 0.4% , the average grain temperature has decreased by 23.1 degrees, and the unit energy consumption is 0.027 kw. H/T. C. 28 storehouse has been ventilated for 6 days and used for 126 hours. The average water content has decreased by 1.0% , the average temperature has decreased by 20.3 degrees, and the unit energy consumption is 0.038 kw. H/T. C. 6 advantages of slow-speed ventilation with axial flow fan: good cooling effect; low energy consumption per unit, especially important in advocating energy saving today; easy to grasp the timing of ventilation, not easy to appear condensation; no need to be equipped with a separate fan, convenient and flexible. Disadvantages: due to small air volume, ventilation time is long; precipitation effect is not obvious, high-moisture grain is not suitable for axial fan ventilation. 7 advantages of centrifugal fan: cooling, precipitation effect is obvious, ventilation time is short; disadvantages: high unit energy consumption;. Conclusion: axial flow fan is safe, efficient and energy-saving for slow-speed ventilation, and centrifugal fan is used for precipitation ventilation.