Pipe Pressure Drop

This window is used to select the pressure drop correlation method and to enter data for friction factor, flow efficiency, etc.

Usage

To display this window, push the Pressure Drop Method button from the Pipe Main Window.

Pressure Drop Correlation

PRO/II provides numerous pressure drop correlation methods to cover a wide range of piping situations. They are:

Beggs-Brill-Moody : This is the default PRO/II method, and is the recommended method for most systems, especially single phase systems.

Beggs-Brill-Moody High Velocity: A good correlation for all pipe lines, esspecially at high velocity.

Beggs-Brill-Moody-Palmer : This method uses the same correlations as above and also includes the Palmer modification to account for liquid holdup, based on experimental data for uphill and downhill lines.

Dukler-Eaton-Flanigan : This hybrid correlation is for gas condensate systems that are mainly gas.

Olimens : Used for gas condensate systems which uses the Eaton correlation to calculate liquid holdup and Moody diagrams for friction factor.

Mukherjee-Brill : Used for gas condensate systems. This method must be used with care due to its discontinuities. Use at least 2 pipe segments to avoid failures due to changing flow regimes.

Gray : Recommended for vertical gas condensate systems. It should not be used for horizontal lines.

Hagedorn-Brown : This method is also recommended for vertical pipelines, and should not be used for horizontal pipes.

For a detailed discussion on these methods, see the Pipe section in the PRO/II Reference Manual.

Estimated Pressure Drop

By default PRO/II assumes a value of zero for the estimated pressure drop through the entire length of the pipe. An accurate estimate often reduces computing time.

Convergence Tolerance

Supplies a relative convergence tolerance value for the calculated pressure drop per pipe segment, between each successive iteration. By default, PRO/II uses a one percent tolerance.

Flow Efficiency

This parameter is used for linear adjustment of the calculated pressure drop to match actual conditions. For given flow conditions, decreasing this value causes an increase in the calculated pressure drop. The value may be greater than 100 percent. It is recommended that data for roughness or Moody friction factor be provided for accurate calibration of results.

Moody Friction Factor

PRO/II usually calculates the friction factor from pipe roughness and Reynolds number using the modified Colebrook-White equations. You can supply a value for this field if desired.

Acceleration Term

Check this option to include the acceleration pressure gradient. Under certain high velocity or high pressure conditions, the Beggs and Brill acceleration term becomes unrealistically large and dominates the equation. Dropping the term often results in a better answer in these cases.

Note that instead of entering a value for flow efficiency and friction factor, they may be referenced using the Define system relative to any available unit operation or stream parameter calculated elsewhere in the simulation.