Pipe pressure drop calculator – two phase

This is a sample of the Pipe pressure drop calculator. To access the working calculator, please sign up for free membership trial.

The output of this calculator is the pressure drop per unit length given in bar/km. This output figure must be multiplied by the equivalent length of the pipe to calculate the total pressure drop across length of the pipe. The total equivalent length of the pipe is obtained by adding the equivalent lengths of all the fittings to the straight pipe length.


For two phase flow the calculator given below calculates the pressure drop per unit length of the pipe based on the Lockhart-Martinelli Method. For prediction of the two phase flow regime various methods can be used.

WL - Liquid Mass flow kg/h
ρL - Density of liquid kg/m3
µL - Viscosity of liquid cP
WG - Vapour Mass flow kg/h
ρG - Density of vapour phase kg/m3
µG - Viscosity of vapour phase cP
M - Molecular weight of vapour phase gm/gmoles
z - Compressibility factor of vapour phase
Cp/Cv ratio for vapour phase
e - Effective roughness of the pipe mm
d - Nominal diameter of the pipe inches
sch - pipe schedule
Fluid (mixture) velocity m/s
Fluid (mixture) density kg/m3
Fluid (mixture) Reynolds Number
Pressure loss bar/km

This calculator gives value of pressure drop per unit length of a straight line. But usually pipes are accompanied by bends, fittings, valves etc. Use EnggCyclopedia’s K-factor calculator to obtain pressure drop across fittings in a line.

For a single phase flow case through a pipe, use EnggCyclopedia's single phase pressure drop calculator.


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