4.35 A Bell & Gossett Series 80SC 4 4 9 model pump is delivering 400...

4.35 A Bell & Gossett Series 80SC 4 × 4 × 9½ model pump is delivering 400 gpm while operating at 1750 rpm with an impeller diameter of 8½ in. The pump’s impeller is now changed to an 8-in. diameter size, and its operational speed is adjusted to 1150 rpm using a variable speed drive.

a. Using the affinity laws, determine the capacity, head, input power, and efficiency of the pump operating under these new conditions.

b. Using the new capacity calculated from the affinity laws, compare your answers calculated in part

(a) to the actual values read from the Series 80-SC 4 × 4 × 9½ model pump curves operating at 1150 rpm with an 8-in.

impeller.

c. Comment on the validity of the affinity laws for this application.