Problem 7.4 operating Point Given: The 10.4 inch diameter pump shown, with 1760

Question

Problem 7.4 operating Point Given: The 10.4 inch diameter pump shown, with 1760 revolution per minute angular velocity, pumps water through a piping system with a 65 foot static head Model 4010 1760 RPM Curve No.756 Min mp, Dia, 7.70 aCO CM & FM Series Sizes 5 x 4 x10 NPSH, ft 600 65% 10.40 in 0.00 in 100 so im... 9.00 in 80 in 8.00 in 7.70 in 30 bhp 125 bhp Curves based on clear wrer 20 bhp with specific gravity of l 0 375 000 Flow, gal/min Problems 7.3 and 7.4 and a constant system curve coefficient C. The operating point is 500 gpm, and the pipe/pump system connects two reservoirs. Required: (a) What is the value of Ci? (b) Power costs S0.13/kw-hour. What is the monthly cost of the losses (minor plus pipe friction together) of the system?

Explanation / Answer

The head is related to Q by the eqn H =kQ2+H0

Where   Ho is the head at zero Q ( intercept on the left Y axis)

It means K is a constant, termed system curve coeff ( Cl)

lFitting the observed points, take Q =1000, H =84, H-H0 = -34, K = -3.4 10-5

at the given flow pt (500), calculate 1*10-5 = reqd system curve coeff. at given condn.

B) The loss is K Q2 where Q is in gal/mt, found to be a loss of about 2 ft? due to friction etc.

Calculate power loss due to this friction head and find the KW, multiply by mothly usage and get the figure. Seems to be large.

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