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💧 Tube Pressure Drop Calculator

Calculate pressure drop inside heat exchanger tubes using Darcy-Weisbach equation.

Inputs

Darcy friction factor. Typical turbulent flow ~0.02

Results

Pressure Drop (ΔP)
0.00 psi
Head Loss (h_f)
0.00
ft

Pressure Drop Profile

P₁P₂Length (L)

Calculator Description

Pressure drop inside a pipe is the energy lost to friction and minor losses as fluid flows through piping or heat-exchanger tubes. It is a key factor setting pump head, pipe diameter and operating cost.

What this calculator finds

Given length L, inside diameter D, velocity v, fluid density ρ and the Darcy friction factor f, it computes the pressure drop ΔP (or head loss h_f) inside the tube — chiefly used for heat-exchanger tube design.

Why it matters

  • Sizing required pump/compressor head and power
  • Optimizing pipe diameter and velocity (energy vs capital cost)
  • Evaluating tube-side pressure loss in heat exchangers

Formula

Darcy-Weisbach Equation

The pressure drop is proportional to the friction factor f, the length-to-diameter ratio L/D, and the dynamic pressure (ρv²/2). Head loss h_f is the same relation divided by g.

ΔP=f LD ρv22\Delta P = f\,\dfrac{L}{D}\,\dfrac{\rho v^{2}}{2}
hf=f LD v22gh_f = f\,\dfrac{L}{D}\,\dfrac{v^{2}}{2g}
  • ΔP — Pressure drop [Pa]
  • h_f — Head loss [m]
  • f — Darcy friction factor (dimensionless)
  • L, D — Length and inside diameter [m]
  • v, ρ — Velocity [m/s] and density [kg/m³]
  • g — Gravitational acceleration (≈ 9.81 m/s²)

How the formula works

  • f is set by Reynolds number (Re = ρvD/μ) and roughness; it grows with turbulence.
  • Drop scales with v² → doubling velocity quadruples the loss.
  • A smaller D raises both L/D and dynamic pressure, sharply increasing loss.

Worked example

For water (ρ = 1000 kg/m³) flowing at 2 m/s in a 50 mm ID, 10 m long tube with f = 0.02: ΔP = 0.02 × (10/0.05) × (1000×2²/2) = 0.02 × 200 × 2000 = 8000 Pa = 8 kPa, with head loss h_f ≈ 0.82 m.

Useful Tips

Practical tips

  • Obtain f from the Moody chart or Colebrook–White equation (fully developed turbulent flow).
  • Add minor losses (elbows, valves) as equivalent length Le to L.
  • Pick diameter within an economic velocity range (water ≈ 1–3 m/s) for balanced cost.

Limitations & cautions

  • Valid for single-phase Newtonian fully developed flow; in laminar flow f = 64/Re.
  • For non-Newtonian, multiphase or strongly compressible flow, use dedicated correlations.