PIPING PRESSURE DROP

Piping Pressure Drop – Frictional Pressure Loss (Re = 2,100 – 10⁶)

This section calculates the frictional pressure loss for internal pipe flow in the transitional and turbulent range (Reynolds number between 2,100 and 10⁶). It uses the inputs below to estimate how much pressure is lost due to wall friction as fluid moves through the pipe.

Inputs Used

• Viscosity (μ) (cp) – Dynamic viscosity of the fluid
• Flow Rate (W) (lb/hr) – Mass flow rate through the pipe
• Density (ρ) (lb/ft³) – Fluid density
• Internal Pipe Diameter (d) (inch) – Inside diameter of the pipe

How the Pressure Loss Is Calculated

1. Convert flow to velocity: The mass flow rate and density are used to obtain volumetric flow, then divided by the pipe’s cross-sectional area to find the average velocity.
2. Compute Reynolds number: Reynolds number is calculated from density, velocity, diameter, and viscosity to ensure the flow is within the stated range.
3. Determine friction factor (f): A standard turbulent/transitional correlation is applied to estimate the friction factor.
4. Calculate frictional pressure loss (ΔP): Pressure drop is estimated using the Darcy–Weisbach relationship:
   ΔP = f · (L/d) · (ρv²/2)

Outputs

• Frictional Pressure Loss (ΔP) is reported as psi per 100 ft of pipe (psi/100 ft).
• An equivalent length of pipe may also be shown, representing the length of straight pipe that would create the same pressure loss.

Interpretation

• Higher flow rate (W) increases velocity and raises pressure loss.
• Higher viscosity (μ) increases resistance and raises pressure loss.
• Smaller diameter (d) sharply increases loss due to higher velocity and friction effects.
• Higher density (ρ) increases dynamic pressure and typically increases loss.

Use this tool to compare piping options and confirm that pressure losses stay within system limits.