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The role of axial fans and centrifugal fans in mechanical ventilation

- Jul 06, 2018 -

1.Due to the large difference between temperature and grain temperature, the first ventilation time should be selected during the day to reduce the gap between grain temperature and temperature and reduce the occurrence of condensation. The ventilation should be selected at night as much as possible, because the ventilation is mainly based on cooling, the atmospheric humidity is relatively high at night, and the temperature is low, which reduces the water loss, and makes full use of the low temperature at night to improve the cooling effect. .


2.When the centrifugal fan is used for ventilation, there may be condensation on the doors and windows, walls, and even the surface of the grain. Just stop the fan, open the window, open the axial fan, and if necessary, turn the grain surface to remove the hot and humid air in the warehouse. It can be outside. When the axial fan is used for slow ventilation, there will be no condensation. Only the middle and upper grain temperature will rise slowly. As the ventilation continues, the grain temperature will drop steadily.


3.When using axial flow fan for slow ventilation, the air volume of the axial flow fan is small, and the grain is a poor conductor of heat. In the initial stage of ventilation, the ventilation of individual parts is slow, and the grain temperature will gradually balance as the ventilation continues.

4.The food that is slowly ventilated must be cleaned by vibrating screen, and the grain that enters the bin must be cleaned in time to the impurity zone caused by automatic classification, otherwise it will easily cause local ventilation unevenness.


5.Energy consumption calculation: The total flow of the axial fan of No. 14 warehouse is 50 days, with an average of 15 hours per day, sharing 750 hours, the average moisture is reduced by 0.4%, the grain temperature is reduced by 23.1 degrees, and the unit energy consumption is 0.027kw. h/t.°C. The warehouse No. 28 was ventilated for 6 days, sharing 126 hours, the water was reduced by 1.0% on average, the temperature was reduced by 20.3 degrees, and the unit energy consumption was 0.038kw.h/t.°C.


6.Advantages of slow-flow ventilation by axial flow fan: good cooling effect; low energy consumption per unit is especially important in today's energy-saving promotion; ventilation timing is easy to grasp, condensation is not easy to occur; Disadvantages: Because the air volume is small, the ventilation time is long; the precipitation effect is not obvious, and the high water content grain should not be ventilated by the axial flow fan.


7.Advantages of centrifugal fan: The effect of cooling and precipitation is obvious, and the ventilation time is short; Disadvantages: high energy consumption per unit; poor timing of ventilation 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; the centrifugal fan is used in the ventilation for the purpose of precipitation.