The Difference And Fuction Between Centrifugal Fan And Axial Fan
Centrifugal fan and axial fan main difference is:
1, the centrifugal fan changes the flow direction of the medium in the duct, but the axial fan does not change the flow direction of the medium in the duct;
2, the former installation is more complicated, the former motor and fan are usually driven by the belt to rotate the wheel connected, which is generally within the fan motor;
3, the former is often installed in the air-conditioning unit at the exit, the boiler drum, induced draft fan, and so on. The latter is often installed in the duct, or duct outlet front.
In addition there are oblique flow (mixed flow) fan,
And it’s air pressure coefficient is bigger than the axial fan, and it’s flow coefficient is bigger than the centrifugal fan. Fill the gap between the axial fan and centrifugal fan. At the same time with the installation of simple and convenient features. Francis (or Axial Flow) fans combine axial and axial flow Centrifugal fan Although it looks more like atraditional axial fan. The curved plate-shaped blade welded to the conical steel hub. By changing impeller The angle of the vanes in the upstream inlet shell changes the flow rate. The enclosure may have an open access, but more often it has a right-angled shape that allows the motor to be placed outside the pipe. The excretion shell slowly expands to slow the flow of air or gas and convert kinetic energy to useful static pressure.
Two types of role
Axial flow fan and centrifugal fan in the role of mechanical ventilation
1 Due to the large difference between air temperature and food temperature, the first ventilation time should be chosen during the day to reduce the gap between food temperature and air temperature and reduce the occurrence of condensation. Ventilation after the election as far as possible in the evening, because the ventilation is based on cooling, atmospheric humidity is relatively high at night, the temperature islower, thus reducing the water loss, but also make full use of the evening's cold and improve the cooling effect .
2 Centrifugal fan ventilation early may appear windows and doors, wall condensation, and even the surface of the grain surface of a slight condensation, just stop the fan, open the window, open the axial fan, if necessary, flip the grain surface, the warehouse hot and humid airexclude
warehouse Outside can. The use of axial flow fan for slow ventilation will not appear condensation phenomenon , only the middle and upper grain temperature rise slowly, with ventilation continue to grain temperature will decline steadily.
3 with axial flow fan slow ventilation, due to the axial fan Air volume Small, another food isBad conductor of heat, Ventilation early prone to slow ventilation of individual parts, with ventilation continue to be full
grain temperature will gradually balance.
4 slow retreat of the food must be cleaned through the vibration sieve, and the food into the warehouse must be promptly cleaned of impurities caused by automatic grading, or easily lead to uneven local ventilation.
5 Energy consumption calculation: The accumulative ventilation of No.14 warehouse with axial fan for 50 days, averagely 15 hours per day and 750 hours of common use,the average water temperature dropped by 0.4% and the grain temperature dropped by 23.1 degrees on average. The unit energy consumption was 0.027kw. h / t. °C. 28 positions accumulated ventilation for 6 days, a totalof 126 hours, an average drop of 1.0%water, the average temperature dropped 20.3 degrees, the unit energy consumption is: 0.038kw.h / t. °C.
6 Advantages of slow ventilating with axial fan: Good cooling effect; Unit
energy consumption is low, advocating energy saving is especially important today; Ventilation timing easy to grasp, not prone to dew; Do not have separate fan, convenient and flexible. Disadvantages: Due to the small amount of air, ventilation for a long time; precipitation effect is not obvious, high moisture grain should not be ventilated with axial fan.
7 Centrifugal fan advantages: cooling, precipitation effect is obvious, ventilation time is short; Disadvantages: high energy consumption unit;
ventilation timing is not easy to control condensation.
8 Conclusion: In the purpose of cooling for the purpose of cooling, the application of axial fan for safe, efficient, energy-saving slow ventilation; in the purpose of precipitation for the application of centrifugal fan ventilation.