Importing PIPE-FLO® Compressible 2007 Files in PIPE-FLO® Advantage
PIPE-FLO Advantage 17 adds the ability to import and open PIPE-FLO Compressible 2007 files. Because of the differences between the original file format and the new Advantage format, the imported design data should be evaluated closely prior to relying on calculated results.
In addition, some system configurations may prevent calculations in Advantage and will require changes before the compressible analysis can be performed.
Importing Fluid Zones
In PIPE-FLO Compressible 2007, the properties of the System Fluid can be calculated using a Fluid Table or directly entered as a Custom Fluid. For a Table Fluid, only the selection of a gas is required to determine the Molecular Weight (Relative Molecular Mass) and the entry of the Total Temperature to calculate the Viscosity and Specific Heat Ratio from the Fluid Table. For a Custom Fluid, the use only has to enter values for the Total Temperature, Molecular Weight, Viscosity, and Specific Heat Ratio. For both types, the gas density was calculated after the static pressures were calculated from the compressible analysis.
In PIPE-FLO Advantage, using a Fluid Table to define the Fluid Zone requires the entry of both the Total Temperature and Total Pressure to calculate the remaining fluid properties. For a Custom Fluid, all fluid properties must be user-entered, including Total Pressure and density. Because the System Fluid in PIPE-FLO Compressible does not contain a pressure or density, they must be populated during the import. For a Fluid Table, the pressure is calculated from the set pressures in Pressure Sources and control valves in a pressure control mode of operation, using settings in all the lineups. For a Custom System Fluid, the pressure is set to "1.0", regardless of units used, and the density is calculated using the Ideal Gas Law.
An Import Log File is generated documenting the changes made and saved in a .txt file format.
Table Fluid Import
Custom Fluid Property Import
Adjusting Fluid Zone Properties After Import
After importing the PIPE-FLO Compressible file into PIPE-FLO Advantage, the Fluid Zone properties may need to be adjusted to proceed with a compressible analysis. The key parameter to adjust is the density of the gas. Because an incompressible analysis is performed prior to any compressible calculations, a high Fluid Zone density may result in erroneous choked flow conditions somewhere in the model. Entering a lower density either directly (for a Custom Fluid) or by entering a lower average total pressure that calculates a lower density (for a Table Fluid), may result in reasonably accurate results. Determining a typical pressure or density to enter may require an iterative process.
Imported System Configurations Requiring Changes
In PIPE-FLO Advantage, the compressible analysis cannot be performed when all of the attached pipes to a Node have an assumed flow direction either entering or leaving the node. When this configuration is detected, a Level 0 ID 228 will be thrown stating "The node does not have an inlet and an outlet. Reverse flow direction on one attached pipe." All affected nodes will be highlighted in red and the incompressible analysis will result in the reversal of at least one of the pipes involved.
This configuration may be easy to detect but difficult to find in very large models. Turning off all the text for all the devices in the Device View Options may make it easier to find the node(s) when the model is calculated.