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Blower

Published on November 2016 | Categories: Documents | Downloads: 29 | Comments: 0
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Blower: cap. 85 000 cub.m/hr, peller: dia. = 1800 mm, tip width = 255 mm (from item master: 19061) Pulley (spv item master: 36771 & 36772) - motor side = 280 mm pitch dia, 290 mm OD - blower side = 560 mm pitch dia, , 572 mm OD Motor: chimney blower#1 = 110 kW, Chimney blower#2 = 90 kW Actual speed (checking by condition monitoring dept.) - Chimney blower#1 = motor : 1493 RPM, blower : 734 RPM - Chimney bower#2: motor : 1487 RPM, blower : 731 RPM

Fan affinity law : Affinity laws can be used to calculate volume capacity, head or power consumption - when speed or rpm, and wheel diameters are changed
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The Affinity Laws of centrifugal pumps or fans can be used to express the influence on volume capacity, head (pressure) or power consumption of a pump or fan due to 1. change in speed of wheel - revolutions per minute (rpm) 2. geometrically similarity - change in impeller diameter Note that the affinity laws for pumps are not identical with fans.

Fan Affinity Laws
Volume Capacity

The volume capacity of a centrifugal fan can be expressed like q1 / q2 = (n1 / n2)(d1 / d2)3 (1) where q = volume flow capacity (m3/s, gpm, cfm, ..) n = wheel velocity - revolution per minute - (rpm) d = wheel diameter
Head or Pressure

The head or pressure of a centrifugal fan can be expressed like dp1 / dp2 = (n1 / n2)2 (d1 / d2)2 (2) where

dp = head or pressure (m, ft, Pa, psi, ..)
Power

The power consumption of a centrifugal fan can be expressed as P1 / P2 = (n1 / n2)3 (d1 / d2)5 (3) where P = power (W, bhp, ..)
Changing the Wheel Velocity

If the wheel diameter is constant - change in fan wheel velocity can simplify the affinity laws to
Volume Capacity

q1 / q2 = (n1 / n2) (1a)
Head or Pressure

dp1 / dp2 = (n1 / n2)2 (2a)
Power

P1 / P2 = (n1 / n2)3 (3a)

Note! If the speed of a fan is increased with 10%
  

the volume flow increases with 10% the head increases with 21% the power increases with 33 %

If the volume flow capacity of an existing system is increased with 10% the power supply is increased with 33%. The electrical motor and power supply may need an upgrade.
Fan Affinity Laws Calculator - Changing Wheel Velocity

Replace the default values with the actual values. The calculator is generic and can be used with all common units as long as the use is consistent.
100

q1 - volume capacity - (m3/s, gpm, cfm, ..) dp1 - head or pressure (m, ft, Pa, psi, ..) P1 - power (W, bhp) n1 - initial wheel velocity (rpm) n2 - final wheel velocity (rpm)

100

5

1750

3500

Changing the Impeller Diameter

If wheel velocity is constant a change in impeller diameter can simplify the affinity laws to
Volume Capacity

q1 / q2 = (d1 / d2)3 (1b)
Head or Pressure

dp1 / dp2 = (d1 / d2)2 (2b)
Power

P1 / P2 = (d1 / d2)5 (3b)

Fan Affinity Laws Calculator - Changing Wheel Diameter

Replace the default values with the actual values. The calculator is generic and can be used with all common units as long as the use is consistent.
100

q1 - volume capacity - (m3/s, gpm, cfm, ..) dp1 - head or pressure (m, ft, Pa, psi, ..)

100

5

P1 - power (W, bhp) d1 - initial wheel diameter (m, in, ft ...) d2 - final wheel diameter (m, in, ft ..)

8

6

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