Pipe Flow Expert User Guide
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- Điều hướng trang này:
- The General Fundamental Isothermal Flow Equation
- Figure 99 Compressible Flow Calculation Options 198 Pipe Flow Expert User Guide
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Working with Compressible Fluids 197 Using Compressible Flow Equations There are a number of different equations that can be used to calculate flow rate and pressure loss in a compressible gas system and the type of design and user preference often determines which equation they use to calculate the results. Pipe Flow Expert allows for the selection of a specific compressible isothermal flow equation from a list that includes: General Fundamental Isothermal Flow Equation Complete Isothermal Flow Equation AGA Isothermal Flow Equation Panhandle A Isothermal Flow Equation Panhandle B Isothermal Flow Equation IGT Isothermal Flow Equation Weymouth Isothermal Flow Equation The General Fundamental Isothermal Flow Equation (sometimes known as just the General Flow equation or the Fundamental Flow equation) provides perhaps the most universal method for calculating isothermal flow rates, however it relies on the inclusion of an accurate friction factor. The Pipe Flow Expert software provides such a friction factor by calculating this using the Colebrook- White equation. For complex interconnected pipe systems the General Flow equation will often provide the best overall calculation result, however this approach is only made possible by the advanced software algorithms and the power of computer calculation. The preferred method of calculation can be selected from the Calculations Tab in Configuration Options. Figure 99 Compressible Flow Calculation Options 198 Pipe Flow Expert User Guide The calculations can incorporate the Ideal Gas Law, a custom Compressibility Factor (applied to the whole network) or the CNGA Compressibility Factor that is calculated for each pipe based on the pressures at the start and end of each pipe. The Compressible Flow Calculation Engine will automatically take account of pressure changes within the pipe network and will automatically adjust the density properties of the gas as appropriate when performing the gas flow rate and pressure loss calculations. The equations used in the calculations currently assume isothermal flow where there is no change in temperature. If the pipe system contains a compressor, component or valve that either significantly increase the gas pressure or significantly reduces the gas pressure then an additional fluid zone should be defined to specify the density properties of the gas at the required temperature condition. Pipe Flow Expert will automatically account for changes in pressure within the system, however the user must define fluid properties and gas data for the operating temperature within the pipe system (or within each part of the pipe network if zone of different temperature exist). When a user clicks to ‘Calculate’ a compressible gas system , if the calculation engine method of solution is not set to ‘Compressible Gas Flow’ then the software will prompt the user to ask if they wish to automatically switch to the Compressible Flow Calculation Engine (which is recommended). If the user chooses not to switch to the Compressible Flow Calculation Engine then they can continue to solve their system using the standard Non-Compressible Calculation Engine, which uses the Darcy-Weisbach equation that assumes a constant density and viscosity for the gas as defined in the fluid data. tải về 4.95 Mb. Chia sẻ với bạn bè của bạn:
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