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A pump can lift water at a discharge of 0.15 m3 /s to a head of 25 m. The critical cavitation number (σc) for the pump is found to be 0.144. The pump is to be installed at a location where the barometric pressure is 9.8 m of water and the vapour pressure of water is 0.30 of water. The intake pipe friction loss is 0.40 m. Using the minimum value of NPSH (Net Positive Suction Head), the maximum allowable elevation above the sump water surface at which the pump can be located is
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- 9.80 m
- 6.20 m
- 5.50 m
- none of the above
Correct Option: C
| σc = | ||
| H |
| ⇒ 0.144 = | ||
| 25 |
∴ NPSH = 3.6 m
NPSH = Hatm - hv - hs - h2
Patm = Hatm = 9.8 m of water
Pv = Hv = 0.3 m of water
h2 = 0.4
⇒ 3.6 = 9.8 – 0.3 – hs – 0.4
⇒ hs = 5.5 m
