12. Flow Analysis

The pressure drop and the pumping power required for a pipe carrying water at ambient temperature in a horizontal pipe is considered in this write-up.
  From Darcy-Weisbach’s formula
Pressure drop = hf =
   fl W2
   2 g d
Exercise
  f = friction factor = 0.02
  l = length of pipe = 1.000m
  V = mass flow rate = 10 tonne / hr = 10x1,000 /3,600 = 2.78kh / sec
  p = density of fluid (water) = 1,000 kg / cu m
  Wl = flow rate = V / p = 2.78 / 1,000 = 0.00278 cu m / sec
  Use NPS 4 Sechedule 80 pipe – Ø 114.3 x 8.6 mm
  d = pipe inside diameter = 114.3 = 2x8.6 = 97.1 mm = 0.0971 m
  AF = pipe flow area = π (114.3 – 2x8.6)2 / (4 x 106 )7405 x 10-6 sq m
  g = gravitational constant = 9.80665 m / sec2
  W = velocity of flow = Wl/AF = 0.00278 / (7405 x 10-6)= 0.375 m/sec
hf =
   fl W2 0.02 x 1,000 x 0.3752 = 1.5m
   2 g d 2 x 9.80665 x 0.0971
HP =
   hf p W AF = 1.5 x 1,000 x 0.375 x 7405 x 10-6 = 0.06 HP
   75 75
Assuming a pump efficiency of 80% HP required = 0.06/0.8 = 0.0.08 Use 0.1 HP Pump
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