7. A chilled-water air-conditioning system is to be designed for a four-story office complex, as outlined in Fig. P1-7. Each story requires a chilled-water flow rate of 18,000 lbm/h. All water flow velocities are to be maintained at less than 5 ft/s. A single-size pipe is used for the ver-

tical supply and return pipes, and a single-size pipe is used on each floor. Each floor has 100 ft of pipe and two valves, one check and one gate. The pressure drop across the air-handling unit on each floor is 50 psi, and the pressure drop across the chiller is 100 psi. Neglecting the losses of any elbows or tees, specify the following:

(a) Supply and return pipe size (schedule 80)

(b) Floor pipe size (schedule 80)

(c) ΔP required for the pump

(d) Pump power requirements for η = 0.55

(e) Verification that the flow rate on each floor is 18,000 lbm/h.

Evaluate all properties at 60°F. Be sure to state all assumptions made in the calculations.

C AHU 1 12'

AHU 2 12'

AHU 3 12'

P AHU 4 300'

FIGURE P1-7