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Pipe Flow/Friction Factor Calculations I: (S.I. units)
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Calculation of Head Loss, hL, or Frictional Pressure Drop, DPf,
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for given flow rate, Q, pipe diam., D, pipe length, L,
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pipe roughness, e, and fluid properties, r & m.
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Written by: Harlan Bengtson
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1. Determine Friction Factor, f, assuming completely turbulent flow [f = 1.14 + 2 log10(D/e)-2]
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InputsCalculations
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Pipe Diameter, D 1600mmPipe Diameter, D 1.6000m
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Pipe Roughness, ε0.15mmFriction Factor, f 0.01182
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Pipe Length, L66mCross-Sect. Area, A 2.0106m2
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Pipe Flow Rate, Q3.500m3/sAve. Velocity, V 1.7m/s
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Fluid Density, ρ1000kg/m3 Reynolds number, Re 2,142,470
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Fluid Viscosity, μ0.0013N-s/m2
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2. Check on whether the given flow is "completely turbulent flow"
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(Calculate f with the transition region equation and see if differs from the one calculated above.)
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 f = {-2*log10[((e/D)/3.7)+(2.51/(Re*(f1/2))]}-2
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Transition Region Friction Factor, f:f =0.0127
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Repeat calc of f using new value of f:f =0.0126
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Repeat again if necessary:f =0.0126
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3. Calculate hL and DPf, using the final value for f calculated in step 2
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 (hL = f(L/D)(V2/2g) and DPf = rghL)the Darcy Weisbach equation 
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Frictional Head Loss, hL 0.081m
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Frictional Pressure
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 Drop, DPf 790N/m2
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Frictional Pressure
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 Drop, DPf 0.79kN/m2
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http://upload.wikimedia.org/wikipedia/commons/8/80/Moody_diagram.jpg
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References
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1. Source for pipe roughness values - http://www.efunda.com/formulae/fluids/roughness.cfm
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2. Munson, B. R., Young, D. F., & Okiishi, T. H., Fundamentals of Fluid Mechanics, 4th Ed., New York: John Wiley and Sons, Inc, 2002.
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3. Darcy Weisbach equation history - http://biosystems.okstate.edu/darcy/DarcyWeisbach/Darcy-WeisbachHistory.htm
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http://www.brighthub.com/engineering/civil/articles/84765.aspx
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Read more: http://www.brighthub.com/engineering/civil/articles/84765.aspx#ixzz1OK4uPCo0