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Dec 7th, 2016
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  1.  
  2.  
  3. Flow rate Q = 200 gal/min = 0.4456 ft3/s
  4.  
  5. Inlet pipe cross-section Ain = pi/4 * Din2 = 3.14/4 * (4/12)2 = 0.0872 ft2
  6.  
  7. Discharge pipe cross-section Aout = pi/4 * Dout2 = 3.14/4 * (3/12)2 = 0.0491 ft2
  8.  
  9. Velocity in inlet pipe V1 = Q / Ain = 0.4456 / 0.0872 = 5.11 ft/s
  10.  
  11. Velocity in discharge pipe V2 = Q / Aout = 0.4456 / 0.0491 = 9.08 ft/s
  12.  
  13. For water at 70F, kinematic viscosity, neu = 1.052*10-5 ft2/s
  14.  
  15. Reynolds number in inlet pipe Re1 = V1*Din / neu = 5.11*(4/12) / (1.052*10-5) = 161917
  16.  
  17. Reynolds number in discharge pipe Re2 = V2*Dout / neu = 9.08*(3/12) / (1.052*10-5) = 215779
  18.  
  19. For commercial steel pipe, roughness e = 0.00015 ft
  20.  
  21. In inlet pipe, relative roughness e/Din = 0.00015 / (4/12) = 0.00045
  22.  
  23. In discharge pipe, relative roughness e/Dout = 0.00015 / (3/12) = 0.0006
  24.  
  25. From Moody diagram, for Re1 = 161917 and e/Din = 0.00045, we get friction factor f1 = 0.019
  26.  
  27. From Moody diagram, for Re2 = 215779 and e/Dout = 0.0006, we get friction factor f2 = 0.0193
  28.  
  29. For threaded 90 deg elbow, loss coeff K = 1.5
  30.  
  31. For rounded pipe entrance, K = 0.04
  32.  
  33. For pipe exit, K = 1
  34.  
  35. Total inlet pipe length L1 = 10 + 14 = 24 ft
  36.  
  37. Total discharge pipe length L2 = 14 + 20 + 14 + 14 + (6 - (22-20)/2) = 67 ft
  38.  
  39. Head at inlet of pump = [15 + V12 / (2g)] - (0.04 + 1.5 + f1*L1/Din) V12 / (2g)
  40.  
  41. Head at inlet of pump = 15 - (0.04 + 1.5 + 0.019*24/(4/12) - 1) 5.112 / (2*32.2)
  42.  
  43. Head at inlet of pump = 14.226 ft
  44.  
  45. Pressure at inlet of pump = 14.226*rho = 14.226*62.4 = 887.72 lb/ft2 = 6.16 psi (gage)....Ans (b)
  46.  
  47. For the discharge line, 14.226 + Hp - (3*1.5 + 15 + 1 + f2*L2 / Dout)*V22 / (2g) - 22 + 6 = 0 + V22 / (2g)
  48.  
  49. 14.226 + Hp - (3*1.5 + 15 + 1 + f2*L2 / Dout - 1)*V22 / (2g) - 22 + 6 = 0
  50.  
  51. 14.226 + Hp - (3*1.5 + 15 + 1 + 0.0193*67 / (3/12) - 1)*9.082 / (2*32.2) - 22 + 6 = 0
  52.  
  53. Hp = 33.36 ft............Ans (a)
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