Calculate pressure loss for single phase gas pipelines using the Darcy Weisbach version of the Moody Diagram.
`fdl = 64/(Re) `
`1/(√fdo) = -2 log10(r/3.7 + 2.51 / (Re √(fdo))) `
`1/(√fdm) = -2 log10(r/3.7 + 2.825 / (Re √(fdm))) `
where :
fdl = Hagen-Poiseuille laminar flow equation Darcy friction factor
fdo = original Colebrook White equation Darcy friction factor
fdm = modified Colebrook White equation Darcy friction factor
Re = Reynolds number
r = relative roughness
For low Reynolds numbers Re < 2000, the fluid flow is laminar and the Darcy friction factor should be calculated using the Hagen-Poiseuille laminar flow equation. For high Reynolds numbers Re > 4000, the fluid flow is turbulent and the Darcy friction factor should be calculated using one of the turbulent flow equations. In the transition region 2000 < Re < 4000, the flow is unstable and the friction loss cannot be reliably calculated. The minor loss K factor is used to account for pipeline fittings such as bends, tees, valves etc..
The calculators use the Darcy-Weisbach version of the Moody diagram. The Fanning transmission factor combined with the Fanning equation is commonly used for gas flow. The results for the Darcy and Fanning equations are identical provided that the correct friction factor is used.
`ff = (fd) / 4 `
`tf = 1 / (√ff)= 2 / (√fd) `
where :
fd = Darcy friction factor
ff = Fanning friction factor
tf = Fanning transmission factor
The gas specific gravity is the ratio of gas density over the density of dry air at base temperature and pressure. The compressibility factor is assumed to equal 1 at the base conditions. The gas specific gravity is proportional to the gas molar mass.
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