Chapter 6, Problem 6.2DP

It is desired to design a pump-piping system to keep a 1-million-gallon capacity water tank filled. The plan is to use a modi?ed (in size and speed) version of the model 1206 centrifugal pump manufactured by Taco Inc., Cranston, Rhode Island. Test data have been provided to us by Taco Inc. for a small model of this pump: D = 5.45 in, $\Omega =\text{176}0\text{r}/\text{min}$ , tested with water at 20°C:

Q, gal/min	0	5	10	15	20	25	30	35	40	45	50	55	60
H, ft	28	28	29	29	28	28	27	26	25	23	21	18	15
Efficiency, %	0	13	25	35	44	48	51	53	54	55	53	50	45

The tank is to be filled daily with rather chilly (10°C) groundwater from an aquifer, which is 0.8 mi from the tank and 150 ft lower than the tank. Estimated daily water use is 1.5 million gal/day. Filling time should not exceed 8 h per day. The piping system should have four “butter?y” valves with variable openings (see Fig. 6.19), 10 elbows of various angles, and galvanized iron pipe of a size to be selected in the design. The design should be economical—both in capital costs and operating expense. Taco Inc. has provided the following cost estimates for system components:

Pump and motor	$3500 plus $1500 per inch of impeller size
Pump speed	Between 900 and 1800 r/min
Valves	$300 + $200 per inch of pipe size
Elbows	$50 plus $50 per inch of pipe size
Pipes	$1 per inch of diameter per foot of length
Electricity cost	10 Ȼ per kilowatt-hour

Your design task is to select an economical pipe size and pump impeller size and speed for this task, using the pump test data in nondimensional form (see Prob. P5.61) as design data. Write a brief report (five to six pages) showing your calculations and graphs.