Question

elt.I.39.24 Chandler Williams: Attempt 1 Question 39 (5 points) Scenario: A pump with a 6 in impeller diameter delivers 53 gpm at a head 21 ft when operating at 1150 rpm. What would be the required impeller size (D) for a comparable model to operate at the same rpm but produce a head of 50 ft.? 7.4 in 8.0 in 8.6 in 9.3 in Question 40 (5 points) Scenario: a pump operating at 1800 rpm delivers 180 gpm at a 80 ft head. If the same pump L T JUN 20 A

Answer 1

Here 2 things are given (i) proto type (ii) Model for Prototype Impeller Diameter (D_p) = 6 in Discharge (Q_p) = 53 gpm Head (H_p) = 21 ft Speed of Pump(N_p) = 1150 rpm for Model Impeller Diameter (B_m) ? Head (H_am) = 50 ft Speed of pump (N_m) = 1150 rmp therefore Velocity of pump alpha squareroot Head u alpha squareroot H u = pi D N/60 where D = Diameter N = Speed in rpm squareroot H alpha DN implies D alpha squareroot H/N implies DB/squareroot H = constant - (A) Apply Equation (a) prototype & Model implies D_p N_p/squareroot H_p = D_m N_m/squareroot H_m implies 6 times 1150/squareroot 21 = D_m times 1150/squareroot 50 implies D_M = 6/squareroot 21 times squareroot 50 D_m = 9.258 in D_m TildeEqual 9.3 in So option (iv) is is correct Diameter o model impeller D_m = 9.3 in