Pipe Pressure Drop Calculator

This Pipe Pressure Drop Calculator determines frictional pressure loss in straight pipes for Newtonian fluids using the Darcy-Weisbach equation. It calculates Reynolds number, friction factor, and pressure drop for both laminar and turbulent flow regimes. Essential for engineers designing piping systems and selecting pumps.

Pipe Pressure Drop / Diameter Calculator

Pipe Pressure Drop / Diameter Calculator

Pressure Drop
Pipe Diameter

How the Pipe Pressure Drop / Diameter Calculator Works

This calculator helps you either:

  1. Calculate the frictional pressure loss (ΔP) in a pipe when the pipe diameter is known.
  2. Determine the required pipe diameter to achieve a target pressure drop.

1. Pressure Drop Mode

When calculating the pressure drop, the calculator uses the Darcy-Weisbach equation:

ΔP = f × (L / D) × (ρ × v² / 2)

  • ΔP = pressure drop (Pa, also displayed in bar and psi)
  • f = Darcy friction factor (dimensionless)
  • L = pipe length
  • D = internal diameter of the pipe
  • ρ = fluid density
  • v = average flow velocity (calculated from flow rate and pipe cross-sectional area)
Key Calculation Steps:

1. Flow Velocity (v):

A = π × (D / 2)2
v = Q / A

Where Q is the volumetric flow rate.

2. Reynolds Number (Re):

Re = (ρ × v × D) / μ

Where μ (mu) is the dynamic viscosity of the fluid.

  • Re < 2300: Laminar Flow
  • 2300 ≤ Re ≤ 4000: Transitional Flow (treated as turbulent for safety)
  • Re > 4000: Turbulent Flow

3. Friction Factor (f):

  • Laminar Flow (Re < 2300): f = 64 / Re
  • Turbulent Flow (Re > 4000): Uses Colebrook-White approximation accounting for Reynolds number and pipe roughness (ε / D)

4. Pressure Drop (ΔP): Calculated with the Darcy-Weisbach formula and automatically displayed in bar and psi.

2. Pipe Diameter Mode

When calculating the required pipe diameter, the calculator determines the diameter needed to achieve a specified pressure drop for a given flow rate, fluid properties, and pipe length.

  • Pipe diameter results are automatically displayed in mm, inches, and feet.
  • Input fields dynamically adjust so only relevant parameters are visible, and the main variable label changes to “Allowable Pressure Drop”.

Calculation Principle: The calculator reverses the Darcy-Weisbach relationship to estimate the pipe diameter that satisfies the target ΔP, given the flow rate, density, viscosity, pipe length, and roughness.

Results

  • Pressure Drop Mode: Provides ΔP in multiple units, plus flow velocity, Reynolds number, and friction factor.
  • Diameter Mode: Provides pipe diameter in multiple units suitable for engineering design.

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