AFT Blog
Filters and screens impose a pressure drop that varies with flow rate. The variation is non-linear, but manufacturers will often provide only one data point for pressure loss at the design flow rate. Using a single point, or constant pressure drop, can produce significant inaccuracies in your model. With this in mind, AFT offers the “Fill As Quadratic” option for entering loss data. Using only a single point, “Fill As Quadratic” will create two additional points for you. This first is simply 0,0; zero flow produces zero pressure drop. The second point is 2 x Flow and 4 x Pressure Drop....
You can jump from junction to junction or from pipe to pipe by pressing F5 while in a specifications window.
Using “Specified Heat Rate In Constants” for the thermal model of heat exchangers can often cause problems in system models. The reason why is because this thermal model type causes the heat exchanger to act like an “assigned heat input” junction as does an assigned flow junction does for providing constant flow rates. Another problem is that this thermal model can cause unrealistic temperature changes across a heat exchanger. When the heat rate is specified and the mass flow rate and heat capacity are calculated based on the system solution, the temperature change will be whatever is required to maintain the...
The zoom select tool is a quick way to zoom into an area of interest. If you click the zoom select tool and draw your selection box the selected area will expand to fit the selection box. The drawn selection box will expand to fit your Workspace so that the magnification will will vary according to the size of the selection box and the area of the model selected. Alternatively you can always have zoom select zoom to 100% by clicking the zoom select tool then holding the shift key down while you draw the selection box and release the mouse...
You probably already know that you can quickly view a summary of the input data for any object in your model with the Inspection Window. Simply place the cursor over a pipe or junction and 'right click' your mouse ('left click' for you lefties). Think how handy it would be if you could also see a summary of output information on the Workspace. You can and it's as easily done as viewing the Inspection Window by holding the 'ctl' key down as you right click. P.S. - In case you didn't already know, holding the 'shift' key down while right clicking...
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...
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...