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Calculating Frictional Pressure Loss in a Pipeline

In engineering, fluid flow and programming is a big deal. A thorough understanding of fluid flow fundamentals is a requirement for any mechanical engineer. Whether you are sizing a pump for a pipeline, designing a heat exchanger, or trying to alleviate bottlenecks in pipeline gathering systems, fluid flow shows up in many cases in our profession. I want to demonstrate a step-by-step procedure to calculate frictional pressure losses in a pipeline for single-phase incompressible flow using a hand calculation. Then I will demonstrate how to code this in excel VBA so the process is repeatable for different cases.

The sample code is presented below:

 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 'Gives the pressure gradient in psi/ft in a pipeline 'Uses Oil and Gas Units Function PressureLossgradbbl(Q, D, SG, u, e)           'Q: flow rate, bbl/day     'D: pipeline diameter, in     'SG: specific gravity     'u: viscosity, sp     'e: roughness, in           g = 32.2     A = WorksheetFunction.Pi() / 4 * D ^ 2           Re = Reynoldsbbl(SG, Q, D, u)     f = FrictionFactor(Re, e, D)           'Darcy Weasback Equation in psi/ft     PressureLossgradbbl = 0.433 * SG * (0.00105) * f * (1 / D) * ((Q / A) ^ 2) / (2 * g)   End Function '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 'Reynolds number for pipeline flow Function Reynoldsbbl(SG, Q, D, u)           'SG: Specific Gravity     'Q: Flow rate,(bbl/day)     'D: Diameter, in     'u: viscosity, cp           Reynoldsbbl = 92.35 * (SG * Q) / (D * u) End Function '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 'Friction Factor Function FrictionFactor(Re, e, D)     'Re: Reynolds Number     'e: roughness, in           'laminar flow or turbulent('Swamee Jain Friction Factor)?     If Re < 2100 Then         FrictionFactor = 64 / Re     Else         A = e / (3.7 * D)         b = 5.74 / (Re ^ 0.9)           FrictionFactor = 0.25 / (WorksheetFunction.Log10(A + b) ^ 2)           End If   End Function

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