Calculator Inputs
Example Data Table
| Scenario | Flow (m³/h) | Length (m) | Diameter (mm) | Inlet Pressure (kPa) | Total Drop (kPa) | Outlet Pressure (kPa) |
|---|---|---|---|---|---|---|
| Cooling water line | 18 | 90 | 80 | 280 | 29.152 | 250.848 |
| Process transfer line | 32 | 180 | 150 | 450 | 68.800 | 381.200 |
| Plant header segment | 55 | 320 | 250 | 900 | 98.962 | 801.038 |
These rows illustrate typical engineering use. Actual pressure results depend on fluid properties, roughness, minor losses, and elevation profile.
Formula Used
The calculator uses the Darcy-Weisbach framework for steady liquid flow in a closed pipe. It combines friction loss, minor losses, elevation effects, and an optional safety allowance.
A = πD² / 4
V = Q / A
Re = (ρVD) / μ
Laminar: f = 64 / Re
Turbulent estimate: f = 0.25 / [log10((ε / 3.7D) + (5.74 / Re^0.9))]²
ΔPmajor = f(L / D)(ρV² / 2)
ΔPminor = K(ρV² / 2)
ΔPstatic = ρgΔz
ΔPtotal = (ΔPmajor + ΔPminor + ΔPstatic) × (1 + Safety % / 100)
Pout = Pin - ΔPtotal
Positive elevation means the outlet is higher than the inlet, which adds required pressure. Negative elevation creates a static gain that can reduce total loss.
How to Use This Calculator
Enter the known pipe and fluid values first. Use a material preset for roughness and a fluid preset for density and viscosity when a quick estimate is acceptable.
Add the total minor loss coefficient for fittings, valves, entrances, and exits. If you do not know every fitting separately, use an engineering estimate for the whole line.
Set elevation change as positive when the outlet is above the inlet. Enter a safety margin if you want extra design conservatism for uncertainty.
Press the calculate button to show the result block above the form. You can then export the result table to CSV or PDF.
Frequently Asked Questions
1. What does this calculator estimate?
It estimates velocity, Reynolds number, friction factor, pressure losses, head loss, and outlet pressure for steady incompressible flow through a pipe segment.
2. Which pressure-loss method is used?
It uses the Darcy-Weisbach approach for major losses and a K-value method for minor losses. This combination is common in engineering design and troubleshooting.
3. When is the Swamee-Jain friction estimate applied?
It is applied for non-laminar flow to estimate turbulent friction factor from Reynolds number, diameter, and pipe roughness without iterative chart reading.
4. Can I use this tool for gases?
This page is intended for incompressible liquids. Gas systems need compressibility corrections, density changes along the line, and sometimes choking or sonic-flow checks.
5. Why can the outlet pressure rise or fall strongly?
Longer pipes, smaller diameters, rougher walls, higher viscosity, high fitting losses, and uphill elevation all increase pressure drop. Downhill elevation can reduce it.
6. What is the minor loss coefficient K?
K is a dimensionless factor that represents fittings and local disturbances such as elbows, tees, valves, contractions, expansions, entrances, and exits.
7. How should I choose roughness?
Use a material preset for a quick estimate, then replace it with measured or specification-based roughness when detailed design accuracy is needed.
8. Why add a safety margin?
A safety margin helps cover uncertainty in fitting counts, aging, fouling, property variation, and expected operating changes before final equipment selection.