Question

4. (25 pt) Assuming that a system using a pump at 3500 rpm operates at 225 gpm and loss, how much would the pump rotational speed have to be reduced to reu 100 gpm? What would the head loss be at the new flow rate? mp at 3500 rpm operates at 225 gpm and 150 ft head speed have to be reduced to reduce the flow rate to

Need some help with a Thermal Fluid Design problem. Thanks!

Answer 1

Using Pump Affinity laws,

With Impeller Diameter held constant,

0

Q = Flow Rate

N = Shaft Speed

=> 225 GPM/100 GPM = 3500 RPM/ N₂ RPM

N₂ = 3500*100/225 = 1555.56 RPM

With Impeller Diameter held constant,

$\frac{H_1}{H_2} = (\frac{N_1}{N_2})^2$

=> 150 ft/H₂ ft = (3500 RPM/155.56 RPM)²

H₂ = 150 ft/2.25² = 29.63 ft