button on the toolbar.Pipe - Technical Information
The pipe unit operation calculates single (liquid or gas) or mixed phase pressure drops through piping between unit operations. It can also determine the line size required for a given maximum pressure drop or minimum outlet pressure.
The pipe unit can be used to simulate one line, one fitting, or both a line and a fitting. When both a line and fitting are used, PRO/II assumes that the fitting follows the line in the direction of fluid flow and that the fitting and pipe have the same diameter. Configurations involving a fitting followed by a line require two pipe units. To model a fitting by itself the line length must be zero. By default, the pipe unit simulates one line.
Calculation Method
PRO/II contains numerous pressure drop correlation methods to cover a wide range of piping situations. These include single-phase, multi-phase, and gas condensate systems in horizontal, vertical, uphill and downhill configurations. The default correlation is Beggs-Brill method with the Moody friction factor. If the friction factor is not supplied, PRO/II calculates the value using the iterative Colebrook-White equation, with an initial value calculated from the explicit Jain equation. See the PRO/II Reference Manual for more details on these correlations.
The pipe unit operation uses transport properties including vapor and/or liquid viscosities and liquid surface tension. It is important that you specify the required methods for computing these transport properties in the appropriate thermodynamic data entry windows. These windows can be accessed by pushing the button on the toolbar.
Rigorous heat transfer may be considered during the calculations, where heat may be added to the pipe over its length (representing a furnace), or lost to the ambient surroundings, allowing the fluid to cool as it flows down the pipe. All heat transfer occurs in the line portion only, and the duty of the fitting is zero. By default, no heat transfer is considered in the calculations. See Pipe Heat Transfer for more details.
A backward calculation option is also available, where you can define the desired conditions exiting from the pipe, and the entering conditions are computed.
To perform the line sizing calculations (by specifying the required maximum pressure drop or minimum outlet pressure), you may provide a set of standard pipe sizes for the calculations. PRO/II then selects the most appropriate size from this set to meet your specification. If no sizes are given, a default list of sizes are used. See Pipe Line Sizing for more details.
Feeds and Products
The pipe unit can have any number of feed streams. Product streams may be vapor, liquid, or mixed phase. Additional products may remove decant water and solids separately. If the feed has a pressure drop less than one psi (or equivalent), the products are set to the inlet pressure. In the case of a zero rate feed, the products will have zero rates.
The pipe unit can perform both VLE and rigorous VLLE calculations, with the resultant product split into the appropriate phases if desired.
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