checalc.com guide linesize.html

Step by Step procedure to do Line sizing and pressure drop calculation for single phase of fluid flowing through a pipe.

Criterion for Line size selection is generally pressure drop expressed as ?P per 100 feet or meters of pipe. In certainservices, velocity is used as governing principle.

Step 1

Calculate Fluid Velocity

Estimate an initial pipe diameter (D) and calculate Velocity (V) of fluid flowing through pipe using following equation :

V = M / (? * (?D/4) )

where,

M, Fluid mass flowrate

?, Density of fluid flowing through pipe

Step 2

Determine Reynold's Number

Reynold's number (Re) is calculated using following equation :

Re = D * V * ? / ?

where,

?, Viscosity of fluid flowing through pipe

Step 3

Determine Friction Factor

For Reynold's Number

Step 4

Calculate Pressure Drop

Pressure Drop (?P) is calculated based on Darcy-Weisbach equation :

where,

L, Pipe Length

Step 5

Check Pressure Drop

Check whether pressure drop is within allowable limits, if it is higher than the allowable pressure drop increase the pipediameter and repeat from step 1.

References1. Darcy friction factor formulae at Wikipedia2. Darcy Weisbach equation at Wikipedia

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Calculation Spreadsheet

Pipe internal diameter for 6" Sch40 pipe is 154.051 mm.

Calculate Fluid Velocity

V = 1.753 m/s

Determine Reynold's Number

Re = 22,958

Determine Friction Factor

Flow regime is Turbulent, Re > 4000. Solving Colebrook-White equation iteratively, after 6 iterations f value does notchange

Fuel Oil having density 850 Kg/m and viscosity of 10 cP is being pumped through a 1 Km long 6", Sch 40 pipe atthe rate of 100,000 Kg/h. What is the pressure loss through pipe ? Pipe roughness is 0.045 mm.

Example

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f = 0.0257

Calculate Pressure Drop

Using Darcy-Weisbach equation, pressure drop is

?P = 2.18 bar

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