The role of axial fans and tunnel fans in mechanical ventilation
1. Due to the large difference between air temperature and grain temperature, the first ventilation time should be selected in the daytime to reduce the gap between grain temperature and temperature and reduce the occurrence of dew. After the ventilation as far as possible in the evening, because the ventilation is mainly cooling, the night humidity is relatively high, the temperature is low, which reduces the water loss, and make full use of the low temperature at night, improve the cooling effect. 2. In the early stage of ventilation with tunnel fan, condensation on doors, Windows and walls may occur, and even slight condensation on the surface grain surface. As long as you stop the fan, open the window, open the axial flow fan, turn over the grain surface when necessary, and remove the hot and humid air in the warehouse from the outside of the warehouse, you can. When the axial fan is used for slow ventilation, there will be no condensation phenomenon, only the middle and upper grain temperature will rise slowly, and the grain temperature will decline steadily as the ventilation continues. 3, the advantages of slow ventilation with axial fan: good cooling effect; Low unit energy consumption, in the advocacy of energy saving today is particularly important; Ventilation time is easy to master, 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, high moisture grain should not be ventilated by axial fan. 4. When the axial fan is used for slow ventilation, because the air volume of the axial fan is small and the grain is a bad 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 with the continuation of ventilation. 5, slow ventilation of food must be cleaned by vibration screen, and into the warehouse of food must be timely clean automatic classification caused by impurities, otherwise easy to cause local uneven ventilation. 8. Calculation of energy consumption: Axial fan was used to ventilate No. 14 warehouse for 50 days, 15 hours a day on average, 750 hours shared. Water content decreased by 0.4% on average, grain temperature decreased by 23.1 degrees on average, and unit energy consumption was 0.027kw.h/t. C. No. 28 warehouse has been ventilated for 6 days and 126 hours. The average water content and temperature decreased by 1.0% and 20.3 degrees respectively, and the unit energy consumption was 0.038kw.h/t. C.