1544 A centrifugal pump discharges 300 gpm against a head of

15.44 A centrifugal pump discharges 300 gpm against a head of 55 ft when the speed is 1500 rpm. The diameter of the impeller is 15.5 in. and the brake horsepower is 6.0. (a) Determine the efficiency of the pump. (b) What should be the speed of a geomet- rically similar pump of 15 in. diameter running at a capacity of 400 gpm?

Solution

Solution:-

Given

Q = 300 gpm

H = 55 feet

Speed = 1500 rpm

Braking horse power = 6

(1) efficiency = Q *H/(3960 * Braking horse power )

                       = 300 * 55 /(3960 *6 )

                       = 0.69

% of efficiency of the pump = 69 %   Answer

Specific speed = n * (Q)/H^0.75

                          = 1500 * (300)/55^0.75

                        =   1286.4

(2) Solution :-

Given Q₂ = 400 gpm

    Speed of pump = specific speed * 55^0.75/(400)

Speed of pump = 1286.4 * 55^0.75/(400)

                           = 1299 rpm   Answer