Introduction
Automatic Pipe Sizing in FluidFlow is a powerful tool that helps engineers optimize pipe diameters to achieve desired velocities and pressure drops. By selecting appropriate sizing criteria, users can eliminate high- or low-velocity warnings, improve hydraulic balance, and enhance system efficiency.
When to Use Auto-Size Pipes
Use Auto-Size Pipes when:
You need preliminary pipe sizes
You need to eliminate high or low velocity warnings in your system
You want to optimize pipe sizes based on economic velocity considerations
You need pipe sizes that meet specific target velocity or pressure gradient criteria for process requirements
You want to balance flow distribution in a complex network
Sizing Criteria Options
Three available criteria:
Economic Velocity – Calculated by FluidFlow using density, installed cost, power cost, and other data.
By Velocity – Calculates pipe size to match a specified velocity.
By Pressure Gradient – Calculates pipe size to match a specified pressure loss per unit length.
Note: For By Velocity and By Pressure Gradient, users must provide the desired value.
To Access Economic Velocity Data: Go to Database menu → Pipe Sizing Data.
Step-by-Step Guide
This guide walks through a complete example from this Loom tutorial video, using economic velocity to size pipes and correct velocity warnings.
Control Flow Before Sizing
Ensure balanced flow distribution to each destination before applying pipe sizing.
Replace all pressure boundaries with Known Flow components to control flow to each destination.
Set each Known Flow to the desired value (e.g., 10 m³/h) using multi-select.
At least one Known Pressure or Reservoir must be present for the solver to run.
In this example: Replace the inlet with a Known Pressure of 1.5 atm.
Check Initial Calculation and Warnings
Run the solver to identify velocity warnings and verify flow distribution.
Confirm that flow to each Known Flow component meets the specified value.
Note any high or low velocity warnings that need addressing.
Apply Sizing by Economic Velocity
Use economic velocity to determine optimal pipe sizes. This is the default setting for the pipe material in the model.
Multi-select pipes that need sizing.
Display Economic Size on the flowsheet for better visibility and analysis.
Replace existing pipe sizes with standard sizes closest to the calculated economic size.
Recalculate and Verify
Confirm that velocity warnings are eliminated.
Check that the model still meets flow requirements.
Verify that pipe velocities now fall within acceptable ranges.
Address Tee Junction Warnings
Resolve any warnings related to tee junctions
For Idelchik tee relationship outside allowable range warnings:
Option 1: Ignore the warnings if K values appear reasonable.
Option 2: Change the tee definition method (e.g., Crane) to resolve warnings.
In this example, switching to the Crane method eliminates these warnings.
Final Verification
Ensure the complete model meets all hydraulic requirements.
Confirm pipes are sized appropriately without velocity warnings.
Check that pressure drops are within acceptable limits.
Best Practices
Always maintain at least one pressure reference point in the model.
Use multi-select to efficiently apply changes to multiple pipes or components.
Match standard pipe sizes as closely as possible to calculated economic sizes.
Verify K values for tee junctions before deciding to ignore warnings.
Recalculate the model after any pipe size changes to check for new velocity issues.
FAQs
Q: Can I use Automatic Pipe Sizing with mixed materials?
A: Yes, but each material has its own economic velocity values.
Q: Is economic velocity always the best option?
A: Not necessarily—By Velocity or By Pressure Gradient may be better for specialized systems.
Q: Will replacing pipe sizes affect network balance?
A: Yes, so always recalculate and check flows after changes.
Conclusion
Automatic Pipe Sizing in FluidFlow streamlines the pipe sizing process, eliminates velocity warnings, and ensures optimal hydraulic performance across the system.
Leveraging on Auto-Size Pipes ensures your designs achieve the perfect balance between flow requirements, velocity and pressure drop constraints, and cost-effectiveness—resulting in more efficient and reliable fluid systems.