Pipe Flow Expert User Guide
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Introduction 13 Pipe Flow Expert Software Overview Pipeline systems range from very simple ones with a single pipe to very large and complex networks with hundreds of interconnecting pipes. They may be as simple as a single pipe carrying water from one reservoir to another reservoir, or they may be more complex with many pipelines interconnecting to distribute fluid over a large area, or they could fall somewhere in-between such as a system that transfers a chemical from a supply container to various process points. The pipelines may vary in size and nature and will usually involve changes in elevation from one point to another. These pipeline systems may include reservoirs, pressurized tanks, pumps, valves, flow control devices, heat exchangers and other components that affect flow in the pipelines. The pipeline system is modeled by drawing the join points and the connecting pipes on a drawing pane. Horizontal, vertical or sloping lines can be used to connect one node to another node. The physical data describing the system is entered by the user and typically includes: The internal size, internal roughness and length of each connecting pipe The elevation of each join point (node) The In-flow and the Out-flow at each join point (if applicable) The elevation, liquid level and surface pressure data for each tank The performance data for each pump Data input boxes are located at the left hand side of the drawing pane. These input boxes will display the data for the currently selected node or pipe and may be used to amend the current data. The data for a node, pipe, pump, etc. can be amended at any point during the design process. Once the design has been completed, the system can be analyzed and the flow and pressure results can be calculated. For liquid systems, the pressure losses within the system are calculated using friction factors obtained from the Colebrook-White equation, and the pressure loss due to friction in each pipe is obtained from the Darcy-Weisbach equation. For gas systems, the pressure losses are calculated using a compressible isothermal flow equations such as the General Flow Equation. An initial approximate solution is obtained using Linear Theory methods and an iterative approach that adjusts the flow rates until an approximate pressure balance is achieved. The solution is then converged to an accurate solution using sophisticated matrix techniques and other iterative algorithms. Pipe Flow Expert defines the elements of the pipeline system in a series of mathematical equations. Pipe systems can produce a highly non-linear set of equations that are difficult to solve. The Pipe Flow Expert software uses the Newton method and other proprietary algorithms to solve the equations, to determine the flow rate and pressure loss in each pipe that provides a balanced solution. The results of the flow rates for each pipe, the fluid velocities for each pipe, Reynolds numbers, friction factors, friction pressure losses for each pipe, fittings pressure losses, pressure at join points (nodes), HGLs (hydraulic grade line), pump operating points and more can be viewed on the results drawing and on the results grid. |