The role of centrifugal fans and axial fans in mechanical ventilation

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 dew. The future ventilation should be carried out at night as far as possible, because the ventilation is mainly 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, and improves the cooling effect.

2. In the early stage of ventilation with centrifugal fan, there may be dew condensation on doors and Windows, walls, and even slight dew condensation on the surface grain surface. As long as the fan is stopped, the window is opened, the axial flow fan is opened, and the grain surface is turned over if necessary to remove the hot and humid air from the warehouse. When the axial fan is used for slow ventilation, there will be no condensation phenomenon, and only the grain temperature in the middle and upper layer will rise slowly, and the grain temperature will decline steadily as the ventilation continues.

3. When the axial fan is used for slow ventilation, due to the small air volume of the axial fan and the poor conductor of heat, slow ventilation of individual parts is easy to occur in the early stage of ventilation, and the temperature of the whole warehouse grain will gradually balance as the ventilation continues.

4. The food for slow ventilation must be cleaned by the vibration screen, and the food into the warehouse must be cleaned in time by the impurities caused by the automatic classification, otherwise it is easy to cause uneven local ventilation.

5. Calculation of energy consumption: The axial fan in Warehouse 14 has been ventilated for 50 days for an average of 15 hours a day and shared for 750 hours. The average moisture has been reduced by 0.4%, the average grain temperature has been reduced by 23.1 degrees, and the unit energy consumption is 0.027kw.h/t. C. No. 28 warehouse has been ventilated for 6 days and 126 hours. The average moisture decreased by 1.0%, the average temperature decreased by 20.3 degrees, and the unit energy consumption was 0.038kw.h/t. C.

6. The advantages of slow ventilation with axial fan: good cooling effect; Low unit energy consumption is particularly important in advocating energy conservation today; Ventilation time is easy to grasp, not easy to appear condensation; No separate fan, convenient and flexible. Disadvantages: Due to small air volume, long ventilation time; The effect of precipitation is not obvious, and the high moisture grain should not be ventilated by axial fan.