Q: What medium is ΣPipe written in, and what are the system requirements?
A:ΣPipe is a C# Windows application written in Visual Studio 2010 and XNA Game Studio 4.0 - it is primarily targeted at Windows 7 (or higher). It requires XNA Game Studio Redistributable 4.0 for handling of 3D objects. If necessary, this prerequisite must be downloaded from the Microsoft website as part of the installation process.
Q: How are pressure drop and critical flow calculated?
A: In general, the methods used for pressure drop are those found in Chemical Engineering Vol 1 by Coulson and Richardson. Single-phase pressure drop is evaluated via friction-factor expressions plus velocity head pressure loss factors. Two-phase pressure drop is determined via Lockhart-Martinelli expressions. For gas-phase critical flow situations, sonic velocity (at prevailing conditions) is monitored for each fluid type. Flow is assumed to be limited to the sonic maximum (ie no supersonic conditions are predicted).
Q: How is heat transfer calculated?
A: For single-phase flow, turbulent heat transfer coefficients are evaluated using the Dittus-Boelter correlation and laminar coefficients are calculated via the Hausen equation (Perry 6th Ed Eq 10-49). For boiling heat transfer the Shah correlation (ASHRAE Trans Vol 82, No 2, pp 66-86 1976) is used. For condensing heat transfer the methods outlined in HEDH Section 2.6, Rev 1996 (eg the Kosky and Staub expression for annular flow, AIChEJ 17, 5, 1037-1043, 1971) are applied.
Q: What changes when the solver resolution setting is changed?
A: Solver resolution is essentially a way of adjusting the number of "slices" used in the calculation. Bends, orifices and venturi's have fixed "nodes" or slices, but straight pipes can be calculated with many or few internal slices. If the solver is set to its lowest resolution, straight pipe sections will have nodes at each end plus internal nodes at a 100 x pipe ID distance (ie for most situations, only inlet and outlet nodes). As solver resolution is increased, this maximum node spacing changes to 10 x pipe ID, 3 x pipe ID and (finally) to 1 x pipe ID at the highest setting.
Q: What is the value of the pipe roughness factor?
A:Each material type has a surface roughness built in. By right-clicking on a 3D item and selecting "Properties" you can view the roughness factor (along with various other properties such as density, thermal conductivity etc). You can also modify default materials or define new ones with user-specified roughness factors.
Q: What is the file storage format and is it compatible with AutoCAD and/or MicroStation?
A: SigmaPipe files are not currently compatible with AutoCAD/MicroStation, but such a connection is possible in future (if there is sufficient interest). Current storage format uses simple text files - these files may also be opened with Notepad or Excel. Data format is "open" and deliberately positioned for possible creation of AutoCAD/MicroStation translators.
Q: How rigorously does ΣPipe treat pure steam/water systems?
A: ΣPipe uses the full ASME97 steam table set of equations, and is capable of describing (pure) steam-water systems across the range 0-800 °C and 0-500 bar (including critical and supercritical conditions).
Q: Process Boxes and Tubes have a "Pipe Exposure Fraction" - what precisely is this?
A: This is the portion of the pipe circumference that is exposed to process box/tube conditions. If the pipe is to be fully exposed (such that heat transfer occurs all the way round the circumference) then the exposure fraction should be set to 1.0. If, on the other hand, if only 40% of the pipe inside the box is to be exposed to box conditions, then the exposure fraction should be 0.4. The other 60% is treated as adiabatic (no heat transfer at all). The net effect of setting the pipe exposure fraction to 0.4 is to multiply heat transfer to/from the pipe by 0.4. (Note: if a pipe section is partially inside and partially outside a process box/tube, the solver will automatically cut the pipe into two sections at the box/tube boundary. The discussion above only applies to the pipe section that is physically inside the box/tube.)