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The role of axial and centrifugal fans in mechanical ventilation
1. Due to the large difference between the temperature and the grain temperature, the first ventilation time should be selected during the day to reduce the gap between the grain temperature and the temperature and reduce the occurrence of condensation. In the future, the ventilation will be carried out at night as far as possible, because this ventilation is mainly based on cooling, and the atmospheric humidity is relatively high and the temperature is low at night, which reduces the water loss and makes full use of the low temperature at night to improve the cooling effect.
2. At the initial stage of ventilation with centrifugal fan, condensation on doors and windows, walls and even slight condensation on the surface grain surface may occur. As long as the fan is stopped, the window is opened, the axial flow fan is turned on, the grain surface is turned over if necessary, and the hot and humid air in the warehouse is removed from the warehouse. However, condensation will not occur if axial flow fan is used for slow ventilation, and only the middle and upper grain temperature will rise slowly. As the ventilation continues, the grain temperature will drop steadily.
3. When the axial flow fan is used for slow ventilation, due to the small air volume of the axial flow fan and the poor conductor of heat, the slow ventilation of individual parts is easy to occur at the initial stage of ventilation, and the grain temperature of the whole warehouse will gradually balance as the ventilation continues.
4. The grain for slow ventilation must be cleaned by the 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.
5. Calculation of energy consumption: warehouse 14 is ventilated with axial flow fan for a total of 50 days, with an average of 15 hours per day and 750 hours of sharing. The average water content is reduced by 0.4, the average grain temperature is reduced by 23.1 degrees, and the unit energy consumption is 0.027kw.h/t.℃. Warehouse 28 has been ventilated for 6 days and shared 126 hours. The water content has dropped by 1.0 on average, the temperature has dropped by 20.3 degrees on average, and the unit energy consumption is 0.038kw.h/t.℃.
6. The advantages of slow ventilation with axial flow fan: the cooling effect is good; the unit energy consumption is low, which is particularly important today when energy saving is advocated; the ventilation time is easy to grasp and condensation is not easy to occur; it is not necessary to equip a fan separately, which is convenient and flexible. Disadvantages: due to the small air volume, long ventilation time; precipitation effect is not obvious, high moisture grain should not be ventilated with axial fan.
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