PUMPS

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PUMPS

• NPSH based on pressure unit.

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Formula for NPSH available

• General
• Zsurface Zpump - ?HL (Patm Pvap ) / ?
• 9.81 kN/m3 or 62.4 lb/ft3
• English unit
• Zsurface Zpump - ?HL (Patm Pvap ) x 2.31
  / sg
• Patm Pvap in psi.

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Review water properties

• Specfic gravity gt sg
• sgwater 1 sgmercury 1
• Specific weight gt ? ?.g
• ?water 62.4 lb/ft3 or 9.81 kN/m3
• Mass density gt ? mass / Volume
• ?water 1.94 lb/ft2s-4 or 1000 kg/m3
• g 32.2 ft/s2 or 9.81 m/s2

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Problem 1(a)

• What is NPSH available for below condition.
• Atmosphere pressure is 101.32 kN/m3
• Vapour pressure is 176.5 N/m2 at 15.6oC.
• Head friction 2 m
• Minor Losses 0
• Static head -3 m.

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Problem 1(b)

• if NPSH minimum is 3 m, does the NPSH available
  meet the requirement.?

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Problem 2

• What is NPSH available for below condition.
• Hot water at 200oF vapor pressure is 11.53 psia
• Specific gravity the hot water is 0.965
• Atmospheric pressure 14.7 psia at sea level.
• Head friction 8ft
• Minor Losses 0
• Static head -10 ft.

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PUMPS

• Pump Efficiency

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S.I. Unit

• Eff Water(hydraulic) Power x 100
• Electrical(brake) Power
• Water Power H x Q x ?
• Electrical Power Water Power x 100
• Eff.

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Problem 1(a)

• Based on the data on the chart, determine water
  power, electrical power.
• Water Power 9.81(0.020m3/s)(6.7m)
• 1.3 kW
• Electrical Power 1.3 / (53/100) 2.5 kW

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Problem 1(b)

• Each day 600m3 of water is pumped to a tank 10m
  above. Pump and water surface from reservoir is
  at same elevation. The work hour for the pump is
  6hrs. Calculate the power required to do this.
  What is the efficiency if power supplied is 3.5
  kW.
• Q V/t 600/(6hrsx3600s) 0.028 m3/s
• Water Power 9.81 (0.028 m3/s) (10m) 2.74 kW
• Eff 2.74 x 100 / 3.5 78

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English Unit

• Eff Water(hydraulic) HP x 100
• Electrical(brake) HP
• Water HP H (ft) x Q (cfs) x sg / 550
• Water HP H (ft) x Q (gpm) x sg/3960
• Electrical Power (kW) Electrical HP x 0.7457

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Problem 2(a)

• Based on the chart data, determine water HP,
  electrical HP, electrical kW.
• Water HP (320gpm)(22ft)/3960
• 1.8 HP
• Electrical HP 1.8 / (53/100) 3.35 HP
• Electrical Power 3.35 x 0.7457 2.5 kW

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Problem 2(b)

• Determine the electric power requirement of a
  pump pumping 5000 gpm to a height of 30ft if the
  overall efficiency is 80 .
• Water HP 62.4(5000gpm)(30ft) / 3960 37.9 HP
• Electrical HP 37.9 / 0.8 47.38
• Electrical Power 47.38 x0.7457 35.33 kW