Introduction
The Auto-Size Pump feature in FluidFlow enables engineers to automatically determine the required duty point for a pump based on the hydraulic demands of the system. This eliminates guesswork, ensures optimal pump selection, and improves accuracy when modeling real-world performance.
By leveraging Auto-Size, users can size pumps to meet target flow rates and system requirements, then quickly select a matching pump model from the database for verification.
When to Use Auto-Size Pump
Use Auto-Size when:
You're in the preliminary design phase and don't yet know the pump model or curve.
You know the required system flow rate but need to determine the pump head (using the Size for Flow model).
You know the required pressure rise but need to calculate the flow rate (using the Size for Pressure Rise model).
You want to replace artificial flow constraints (e.g., known flow nodes) with a realistic pump that drives the system.
You need to match a pump selection to a calculated duty point.
Step-by-Step Guide
The steps are taken directly from our Loom training video.
Start with a Completed Model
Ensure all input parameters are correct before inserting a pump.
Figure 1. Completed model before pump insertion.
Insert a Centrifugal Pump
From the Boosters tab, place a Centrifugal Pump between the known flow inlet boundary and the first tee junction
Figure 2. Pump inserted into the system.
Adjust Suction and Discharge Piping
After insertion, FluidFlow splits the pipe automatically.
Reset discharge length to 30 m and suction length to 3 m (same diameter).
Figure 3. Adjusted pipe lengths.
Enable Auto-Size Mode
In the pump’s Input Editor, switch on Auto-Size.
Set Sizing Model to Size for Flow and enter a target flow of 50 m³/h.
Figure 4. Auto-Size pump settings.
Replace the Inlet Boundary Node
Remove the known flow component—it constrains the model.
Add a Known Pressure component (0 m elevation, 1 atm).
Figure 5. Known Pressure node inputs.
Recalculate the Model
Verify the flow distribution remains at approximately 10 m³/h per branch.
Figure 6. Post-calculation results.
Review the Duty Point
The pump results tab displays the calculated pressure rise (59,195 Pa ≈ 6 m fluid head).
Figure 7. Duty point results.
Select a Pump from the Database
Turn off Auto-Size mode.
Go to Tools → Equipment Performance → Pump Performance.
Search for pumps matching flow and head near their Best Efficiency Point (BEP).
Figure 8. Performance Viewer dialog.
Apply Selected Pump & Recalculate
Load the chosen pump model into the pump component.
Recalculate to confirm performance matches system needs.
Figure 9. Flow results with the selected pump.
Confirm Performance
This approach models the actual system with a real pump curve instead of artificial flow nodes.
Best Practices
Always remove fixed flow boundaries before sizing a pump based on design flow to avoid over-constraint.
Check that pipe lengths and diameters are correct after inserting boosters.
Select pumps operating near their BEP for optimal efficiency and lifespan.
Conclusion
The Auto-Size Pump feature in FluidFlow streamlines pump selection, improves accuracy, and ensures the hydraulic model reflects real-world performance.
Mastering Auto-Size Pump ensures you select the right pump the first time—reducing energy costs, preventing over-sizing, and optimizing system performance.