Question

A pump delivers water at 50Cbetween reservoirs differing in elevation by 30[m]. The 0.25[m]diameter commercial steel pipe between the reservoirs is 800[m] in total length with a dis-charge side length of 712[m]. Total minor losses for the system contribute a k coefficient equal to 8. The pump characteristic curve is represented by the equation (in SI units):

HP= 35.5 + 165Q−4820Q^2.

1. Compute the match point for the system (operating head and discharge). Provide a graph clearly indicating the match point, as well as a table listing at least ten com-puted values for the pump characteristic curve and system curve. Show one example calculation.

2. If the pump is installed 4.0[m] above the water surface of the lower reservoir, compute the available NPSH

3. If the pump has a required NPSH of 8.0[m], discuss whether cavitation will be a concern and why. Clearly state any assumptions you need to make.

4. Compute the maximum safe elevation that the pump may be placed above the water surface elevation of the lower reservoir.

5. The pump, with its characteristic curve described in the problem statement was operating at a maximum speed of 1500 rpm. Suppose the pump speed was decreased to1200 rpm. Determine the new match point of the system, and calculate the operating head and discharge.

6. Repeat the previous question if pump speed increased to 1800 rpm.

7. Compute the dimensionless specific speeds for the match points from parts (1) and (6).

Answer 1

Temp. 50C sol leng th)-- 2-三88m_ ( suction-pipe (delievaoy pipe length) ( Diameter) Commextial sheel pipa D 025 m Relative Roughne 0.25 = 30 그 D 2 IT X0.25 20. 3720 2x 9.0 Suppose ISug m 31s

Re U- FReE .oi5u68 So ok head HsStatic head (Suctio 0.25 2x9.C1 10.31 1.2.2 NPSH achuat Cavitation-dsstil_-occur heae. BeQune NPSH.一available. D-Les--than-that. our

Nİ H, .60gms 800x 32.653 1500 34 Non dimensio al 1500 4lO.ous&Xlooo) g.3x 32.553 IsO,113