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Modeling a Centrifugal Fan, Compressor, or Blower

by Engineered Software, Inc.

When you are modeling a compressible system in PIPE-FLO Professional, it is often necessary to simulate the effects of a fan, compressor, or blower.  The way to model this is to install a Pressure Gain Device (in PIPE-FLO® Professional Version 12 and above), and enter the device’s characteristic curve data in the “Curve Data” window.  The following example details this procedure:

Let's say you have the system as shown in Figure 1.  There is a centrifugal fan supplying air to 5 user points.  Let's assume, for this model, that you want to see flow rates in pounds per hour and pressure in psi g.

Figure 1. Air Supply System

To model the fan’s performance data, you need to use a Pressure Gain Device and the manufacturer's  performance curve for this particular fan shown in Figure 2.

Figure 2. Centrifugal Fan Performance Curve Data

From this curve, you can pick off data points with flow units of SCFM, and head units of Inches of Water.  In PIPE-FLO Professional, the data points that you specify for your fan curve can be entered in whatever units you choose, and they do not necessarily have to match your System units. You man have to change the System units in order to display a flow rate in lb/hr and head in psi. This can be done by going to the menu bar in System/Units and changing the flow rate type from Volume to Mass.  Once that is done, go back and right click on the Pressure Gain Device and select enter curve data. You will see the Curve Data window. Here, you can set your Flow units to scfm and Head units to in H2O, and enter the manufacturer’s fan curve data as shown in Figure 3.

Figure 3. Fan Curve Data entered into PIPE-FLO

After clicking OK, and pressing the calculate button, you will see the calculated system with the fan curve with flows and pressures in the system units you originally specified, even though you entered more conventional units for your fan curve data.  The calculated system is shown in Figure 4. If desired, you may still access your entered data from the “Curve Data” window by right clicking on the device and selecting enter curve data or through the device's Property Grid under the Curve field by selecting the  button.

Figure 4. Calculated PIPE-FLO System with Fan Curve

After calculating a model with compressible fluids in PIPE-FLO Professional, the results should be evaluated to ensure they meet the Darcy Limits. This can be done using the DataLink feature in version 12 and above and the X-Link feature in version 2009 and before. For more information, see: