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INPUT   DATA

♥ EXAMPLE Of Input/Output

Title

Pipe inside diameter		in.
Liquid flow rate		lb/hr
Liquid density		lb/ft3
Gas flow rate		lb/hr
Gas density		lb/ft3

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OUTPUT   VARIABLES   &   GRAPHS

Variables	Values	Units
♦  Liquid velocity		ft/s
♦  Gas velocity		ft/s
♦  Froude number (liquid phase)
♦  Froude number (gas phase)
♦  Flow condition

2-Phase Vertical Downflow

Two phase flow situations are encountered in many chemical process plants, and downward pipe flow is also common. The dimensionless number, Froude number (the ratio of inertial force to gravitational force), is used for predicting two-phase conditions. If the liquid Froude number if less than 0.31, the line is self-venting and therefore no vibration problems are expected. In the region 0.31 to 1.0 pulsation flow occurs which usually lead to line vibrations. If the liquid Froude exceeds 1.0 the frictional forces offsets gravitational force and thus requires no pressure gradient in the vertical downflow liquid. The relevant equations are given below:

where
     V = flow velocity
     W = flowrate
     D = pipe inside diameter
     A = pipe cross-sectional area = πD²/4
     ρ = density
     N_Fr = Froude number
     Subsript: l = liquid phase, g = gas phase

Tips

    ◊ Use link EXAMPLE Of Input/Output  to demo data entry expectations and results; you may edit & use it as starting point

BIBLIOGRAPHY

• Coker, AK; Fortran Programs For Chemical Process Design, Analysis & Simulation; Gulf Publ. Co, Houston, 1995.
• Chopey, NP; Handbook of Chemical Engineering Calculations; McGraw Hill, New York, 2003.