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AFT Blog

Welcome to the Applied Flow Technology Blog where you will find the latest news and training on how to use AFT Fathom, AFT Arrow, AFT IMpulse, AFT xStream and other AFT software products.
Applied Flow Technology

Is This Valve Choked?

Under sub-sonic gas flow conditions, loss models can use the familiar K, Cv or resistance curve methods. At choked flow, however, the dynamics of compressible flow require a different method to characterize the loss, which AFT Arrow users will see as the optional 'CdA' input value on the valve and other junctions specifications window. The product of coefficient of discharge and effective flow area under choked conditions, AFT Arrow can directly calculate the CdA for some cases, such as at the discharge from a pipe. For other components, such as valves, determining these values is most commonly done through flow testing....
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Applied Flow Technology

Preferred Fluid Database for Optimization

Whenever possible, use AFT Standard fluids when performing optimization because they are much faster. Final optimization runs can be performed with more detailed fluid models such ASME Steam or Chempak.
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Applied Flow Technology

Displaying the Fluid Name in Chempak Excel Add-in

If you are using multiple fluids in the same Excel Add-In worksheet, you display which fluid or fluid alias is used in an Excel cell by using the "Fluid" or "FluidAlias" function.
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Applied Flow Technology

Adjusting Ambient Pressure

We're not talking about literally adjusting atmospheric pressure here, rather, the ambient reference pressure used in AFT software. The default value is 1 standard atmosphere, but can be changed as desired. Open System Properties either from the Analysis menu or by double clicking the System Properties check box in the status bar, and select the System Data tab. Enter the desired value in the 'Atmospheric Pressure' field and select the appropriate pressure unit in the adjacent unit drop down box. Gauge pressures, NPSHA and cavitation calculations will reflect this specified atmospheric pressure. Note that this does not change the value of...
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Applied Flow Technology

Calculating Results in Pipes and Junctions Not in Service

AFT flow modeling software allows you to easily change system line-up by closing junctions and pipes. How you take a portion of a system out of service affects what calculated results are available in output. Let's take the case where we have a valve, pipe, heat exchanger, pipe and valve in sequence. To close one of the valves we can either open its specifications window, select the Optional tab and check 'Special Condition / Closed' or simply click the valve junction to select it then click the Special Condition button on the toolbar. A red "X" will appear next to the...
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Applied Flow Technology

Right Clicking (or left clicking if you're a 'lefty' like the author)

Right clicking a pipe or junction in Workspace is a quick way to display a summary of input data for the object, but is only one of three options available when right clicking - Right click only - opens the 'Inspection window' displaying a summary of the object's input data[shift]+right click - lists missing, required input information[ctl]+right click - display output information.
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Applied Flow Technology

Applying a Default Unit System

AFT software supports ISO and English units and provides a variety of ways to select the units to be used. For example, in the Output window you can change units 'on the fly' for a specific parameter by double clicking an output column header and selecting the desired unit from the Change Units window. To globally change the unit system, go to the Options menu and select Parameter and Units Preferences. Select the Unit Preferences tab, choose the Default Unit System then click the Apply Default Units button. This will both apply the default units for the selected unit system and...
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