C1
Pipe size is 1-1/4" SCH 40 steel pipe
The pressure measurement at the inlet pipe is 1 psig (= 2.3 ft wg.)
The chiller has a pump, model CH4-40.
The water temperature is 12°C.
The atmospheric pressure at the site of installation is 32.3 ft wg.
From the steel pipe data table (Section 3), the cross sectional area of the 1-1/4"
pipe is 965 mm
2
= 0.0104 ft
2
.
Therefore, the water velocity at the inlet pipe = 2.674/0.0104 = 257.12 ft/min.
= 4.28 ft/sec.
At 12°C (53.6°F), the vapour pressure of water is 0.48 ft wg.
Entering equation 2:
NPSHA = 32.2 +2.3 + (4.28
2
/2*32.17) - 0.48 = 33.7 ft.
From the pump curve, we find that NPSHR = 0.9 m = 2.95 ft.
0.9
4.54
Again, we find that there is no problem of cavitation in this example since
NPSHR < NPSHA.
Section 5 Page 85
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