Due to the large difference between air temperature and grain temperature, the 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. .
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, and turn the grain surface if necessary to remove the hot and humid air from the bin. Outside. However, the slow-speed ventilation with an axial fan will not cause condensation, but only a slow rise in the grain temperature in the middle and upper layers, and the grain temperature will drop steadily as the ventilation continues.
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. 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.
The advantages of slow-speed ventilation with axial fans are good cooling effect; low unit energy consumption, which is particularly important 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. However, due to the small air volume, the ventilation time is long; the precipitation effect is not obvious, and the high-moisture grains should not be ventilated with axial fans.
The advantages of centrifugal fans are that the cooling and precipitation effects are obvious, and the ventilation time is short; in the ventilation for the purpose of cooling, the axial fan is used for safe, efficient and energy-saving slow ventilation; the centrifugal is used in the ventilation for the purpose of precipitation Type fan.