Pipe Flow Calculator

Pipe Flow Rate Calculator

Calculate volumetric flow rate and velocity

Calculation Results:

Gallons Per Minute (GPM) 0.00

Cubic Feet per Second (CFS) 0.00

Liters Per Minute (L/min) 0.00

Cross-Sectional Area (sq in) 0.00

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Understanding Pipe Flow and Volumetric Rate

The Pipe Flow Rate Calculator is an essential tool for engineers, plumbers, and HVAC technicians. It determines the volume of fluid passing through a pipe based on its internal diameter and the speed (velocity) at which the fluid is moving. Understanding these dynamics is critical for sizing pumps, determining pressure drops, and ensuring efficient fluid transport systems.

The Flow Rate Formula

The fundamental equation used in this calculator is the Continuity Equation for incompressible fluids:

Q = A × v

Where:

• Q is the volumetric flow rate.
• A is the cross-sectional area of the pipe ($\pi \times r^2$).
• v is the flow velocity.

Practical Example

Suppose you have a 4-inch (internal diameter) PVC pipe with water flowing at a velocity of 8 feet per second (fps). How many gallons per minute (GPM) is moving through the system?

1. Calculate Area: Radius = 2 inches. Area = $\pi \times 2^2 \approx 12.566$ square inches.
2. Convert Velocity: 8 feet per second = 96 inches per second.
3. Volume per Second: $12.566 \times 96 = 1,206.33$ cubic inches per second.
4. Convert to GPM: Multiply by 60 (seconds to minutes) and divide by 231 (cubic inches in a gallon).
5. Result: $\approx 313.3$ GPM.

Key Considerations in Pipe Design

When using a pipe flow calculator, keep these engineering principles in mind:

• Velocity Limits: In domestic water systems, velocity is usually kept between 4 and 8 fps to prevent pipe erosion and water hammer noise.
• Internal Diameter (ID): Always use the internal diameter, not the nominal pipe size. For example, a Schedule 40 2-inch pipe has an ID of 2.067 inches, while Schedule 80 has an ID of 1.939 inches.
• Laminar vs. Turbulent Flow: Higher velocities usually lead to turbulent flow, which increases friction loss (pressure drop).

function calculatePipeFlow() { var diameter = parseFloat(document.getElementById('pipeDiameter').value); var velocity = parseFloat(document.getElementById('flowVelocity').value); if (isNaN(diameter) || isNaN(velocity) || diameter <= 0 || velocity <= 0) { alert("Please enter valid positive numbers for diameter and velocity."); return; } // Calculation Logic // Area in square inches var radius = diameter / 2; var areaSqIn = Math.PI * Math.pow(radius, 2); // Flow in cubic feet per second (CFS) // Area in sq ft = areaSqIn / 144 var areaSqFt = areaSqIn / 144; var cfs = areaSqFt * velocity; // Gallons Per Minute (GPM) // 1 CFS is approx 448.831 GPM var gpm = cfs * 448.831; // Liters Per Minute (L/min) // 1 Gallon is 3.78541 Liters var lpm = gpm * 3.78541; // Update DOM document.getElementById('gpmResult').innerHTML = gpm.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}); document.getElementById('cfsResult').innerHTML = cfs.toLocaleString(undefined, {minimumFractionDigits: 4, maximumFractionDigits: 4}); document.getElementById('lpmResult').innerHTML = lpm.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}); document.getElementById('areaResult').innerHTML = areaSqIn.toLocaleString(undefined, {minimumFractionDigits: 3, maximumFractionDigits: 3}); document.getElementById('resultsArea').style.display = 'block'; }