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Save 88.8% in Energy Cost with the Pump Affinity Law
The Pump Affinity Law states:
1. The change in flow is proportional to the change in speed
2. The change in head is proportional to the square of the change in speed
3. The change in energy use is proportional to the cube of the change in speed
The Mathematical Expression is:
New Flow = Old Flow x (new speed/old speed)
New Head = Old Head x (new speed/old speed)2
New Energy Use = Old Energy Used x (new speed/old speed)3
The first affinity law: Flow is proportional to speed. Half (1/2) the speed would be 1/2 the flow (50%
less).
The second affinity law: Head changes by the square of the speed change. 1/2 the speed would be
(1/2)2 or 1/4 the head; with 1/2 the speed a pump previously generating 40 ft. head would now
generate 10 ft. head (75% less).
The third affinity law: Energy use changes by the cube of the speed change. 1/2 the motor speed
would be (1/2)3 or 1/8 the energy requirement; with 1/2 the speed a pump that previously used 2000
kW would now use 250 kW (87.5% less).
Using the Pump Affinity Law, you can cut your RPM's in half, circulate half the water, but only use
1/8th the energy. By doubling the run time at half speed, you will filter the same gallons as before,
but consume only 1/4th the energy, that's a 75% savings.
If the pump is slowed to 1/3rd the original rotational speed, you will get 1/3rd the flow. If the pump is
run 3 times longer to maintain the same turn over gallonage, the energy consumed will be 1/9th of
what is consumed at the higher speed, or 88.8% less energy.
Source: www.gpspool.com