Peripheral knowledge of PPH equipment: common sense of fans (4)

Second, the belt pulley optional
The optional pulley is mainly calculated according to the following formula:
Motor speed / fan speed = fan pulley / motor pulley (diameter is pitch diameter, the same below) Currently, there are two main options: ordinary V-belt and high-efficiency narrow V-belt. High-efficiency narrow V-belt is mainly suitable for motors with high power . Outer diameter of pulley = pitch diameter + 2ha.
The ha value of type A is 3.5; type B is 5; type C is 6.
  Proceed as follows:
1. First calculate the transmission ratio i=motor speed/fan speed.
2. Calculate the diameter and number of slots of the pulley on the motor side according to the motor power.
3. The pulley diameter of the fan can be calculated by multiplying the diameter of the pulley by the transmission ratio.

Third, the fan law
When a fan is installed in the system, there will be regular changes in performance due to system changes, which follow certain regular changes, which we call the fan law.
Simply put, it mainly has the following points:
1. The air volume is proportional to the rotational speed Q1/Q2=N1/N2
2. The square of pressure and rotational speed is proportional to P1/P2=(N1/N2)
3. Shaft power is proportional to the cube of rotational speed Pw1/Pw2=(N1/N2)
When the altitude is different, the air density is also different. When calculating the Q and Pt of the fan, it is also different, mainly because the pressure difference is different, mainly because the air density is proportional to the pressure. If the air density in Tibet is 0.8, the pressure ratio to the standard atmospheric pressure area is also 0.8:1, and the standard in Tibet is 1600Pa for 2000Pa.