Phone: 440-684-0601
Fax: 440-684-0656
Toll Free: 800-468-5404
|
|
Hughes-Primeau Controls celebrates the life and work of Henry G. Hughes
1933-2006
|
Hughes-Primeau Controls combines 135+ years of selling engineered heat tracing systems with over 50 years of experience from Thermon.
No other company in Ohio, Western Pennsylvania, or West Virginia
can match our heat tracing solutions, inventory, nor expertise.
 A Drug Free Workplace |
Laws of Affinity Calculation Guide
The Affinity Laws:
The turbo machine affinity laws are common used for pumps and fans to calculate capacity, head and power consumption when changing speed or wheels diameters.
The Affinity Laws of a centrifugal pump or fan express the effect on capacity, head and power consumption of a pump or fan due to:
different speed - revolutions per minute (rpm)
geometrically similarity - impeller diameter
Changing the Pump or Fan Speed (rpm)
Changing the speed (rpm, rev/min) of the pump or fan:
Capacity
Q1 / Q2 = N1 / N2 (1)
Head
H1 / H2 = (N1 / N2)2 (2)
Power
P1 / P2 = (N1 / N2)3 (3)
where
Q = capacity
H = head
P = power
N = speed
If the speed increase with 10%
the volume increase 10% the head increase 21%
the power increase 33 %
Note! This mean that if we want to increase the volume flow in an existing system with 10% we have to increase the power with 33%. In general the motor and the power supply must be changed.
Changing the Impeller Diameter
Changing the impeller diameter:
Capacity
Q1 / Q2 = D1 / D2 (4)
Head
H1 / H2 = (D1 / D2)2 (5)
Power
P1 / P2 = (D1 / D2)3 (6)
where
D = impeller diameter
Example - Pump Affinity Laws
Pump Speed Changed (Impeller Size Constant):
The initial flow is 100 GPM, the initial head is 100 ft, the initial power is 5 bhp, the initial speed is 1750 rpm and the final speed 3500 rpm.
The final flow capacity can be calculated by transforming (1):
Q2 = Q1 N2 / N1 = (100 GPM) (3500 rpm) / (1750 rpm) = 200 GPM
The final head can be calculated by transforming (2):
H2 = H1 (N2 / N1)2 = (100 ft) ((3500 rpm) / (1750 rpm))2 = 400 ft
The final power consumption can be calculated by transforming (3):
P2 = P1 (N2 / N1)3 = (5 bhp) ((3500 rpm) / (1750 rpm))3 = 40 bph
Pump Impeller Diameter Changed (Pump Speed Constant)
The impeller diameter is changed from 8" (inch) to 6" (inch).
The final flow capacity can be calculated by transforming (4):
Q2 = Q1 D2 / D1 = ( 100 GPM) (6") / (8") = 75 GPM
The final head can be calculated by transforming (5):
H2 = H1 (D2 / D1)2 = (100 ft) ((6") / ( 8"))2 = 56,25 ft
The final power consumption can be calculated by transforming (6):
P2 = P1 (D2 / D1)3 = (5 bhp) ((6") / ( 8"))3 = 2,1 bph
