Pipe Diameter Pressure Flow Rate Calculator

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Pipe Diameter & Flow Rate Calculator

Calculation Results:

Flow Velocity: 0 m/s

Flow Rate (m³/h): 0 m³/h

Flow Rate (L/min): 0 L/min

Cross-Sectional Area: 0 m²

Understanding Pipe Flow and Pressure Drop

Calculating the relationship between pipe diameter, pressure drop, and flow rate is essential for hydraulic engineering, plumbing, and industrial fluid transport. This calculator utilizes the Darcy-Weisbach equation principle to estimate how much fluid will pass through a pipe based on the energy lost through friction.

Key Variables Explained

  • Internal Diameter: The actual inside width of the pipe where the fluid flows. Smaller diameters increase velocity but also increase resistance.
  • Pressure Drop: The difference in pressure between the start and end of the pipe section. This "driving force" overcomes friction.
  • Friction Factor: A dimensionless value representing the pipe's internal roughness. Smooth PVC pipes have lower factors (~0.015-0.02) compared to rusted iron pipes (~0.04).
  • Fluid Density: The mass per unit volume. Water is typically 1000 kg/m³, while oils are usually lighter.

The Math Behind the Calculation

The calculation is based on the Darcy-Weisbach formula for head loss, converted to find velocity ($v$):

v = √((2 * ΔP * D) / (f * L * ρ))

Where:

  • ΔP: Pressure Drop (Pascals)
  • D: Diameter (meters)
  • f: Friction Factor
  • L: Pipe Length (meters)
  • ρ: Density (kg/m³)

Practical Examples

Scenario Diameter Pressure Drop Resulting Flow
Residential Water Line 25 mm 0.2 bar (10m) ~1.4 m/s
Industrial Cooling 100 mm 0.5 bar (20m) ~3.5 m/s
function calculatePipeFlow() { // Inputs var d_mm = parseFloat(document.getElementById("pipeDiameter").value); var l_m = parseFloat(document.getElementById("pipeLength").value); var p_bar = parseFloat(document.getElementById("pressureDrop").value); var f = parseFloat(document.getElementById("frictionFactor").value); var rho = parseFloat(document.getElementById("fluidDensity").value); // Validation if (isNaN(d_mm) || isNaN(l_m) || isNaN(p_bar) || isNaN(f) || isNaN(rho) || d_mm <= 0 || l_m <= 0 || p_bar <= 0 || f <= 0 || rho <= 0) { alert("Please enter valid positive numbers for all fields."); return; } // Convert units var d_m = d_mm / 1000; // mm to m var p_pa = p_bar * 100000; // bar to Pascals // Calculation (Darcy-Weisbach rearrangement) // v = sqrt((2 * deltaP * D) / (f * L * rho)) var velocity = Math.sqrt((2 * p_pa * d_m) / (f * l_m * rho)); // Cross-sectional Area var area = Math.PI * Math.pow((d_m / 2), 2); // Flow Rate Q = v * A var flowRateM3s = velocity * area; var flowRateM3h = flowRateM3s * 3600; var flowRateLmin = flowRateM3s * 1000 * 60; // Output Results document.getElementById("resVelocity").innerText = velocity.toFixed(3); document.getElementById("resFlowM3").innerText = flowRateM3h.toFixed(2); document.getElementById("resFlowL").innerText = flowRateLmin.toFixed(2); document.getElementById("resArea").innerText = area.toFixed(6); // Show results section document.getElementById("resultsArea").style.display = "block"; }

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