Consider the water distribution system given in Figure Example 8.1. Assume the pump efficiency of 0.70.

a. Determine the primary pump size (in hp) and the valve settings to balance the system.

b. Determine primary and secondary pump sizes as well as the new valve settings for the optimal primary/secondary distribution system

c. Estimate the total energy cost savings from the retrofit from existing system to the optimal distribution system. Assume that the system is operated 6,000 hours per year, that the cost of energy is $0.10/kWh, and that the efficiency of all pump motors is 90 percent.

Figure Example 8.1

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Boiler efficiency (percent) 85 88.989 75 70 85 85 -80 75 Flue gas O (percent) Natural gas no. 2 no. 5 11 10 9 B 7 6 5 3 0 5.8 13 7.0 8 E B 180 9 460 Percent total a 10 8 10 1 11 Flue gas CO (percent) 450 SI: temperature 9 11 12 1 1 12 10 100C 150C 200 H 250C 100 andsc 100 11 11.9 13 14 15 -- 12 13 14 15 16 L L