Compressed Air Pressure Drop Nomograph

Overview

Engineering reference data for Compressed Air Pressure Drop Nomograph in fluid mechanics.

Key Formulas

Reynolds Number

$Re = \frac{\rho v D}{\mu}$

Ratio of inertial to viscous forces — determines flow regime.

Bernoulli's Equation

$P + \frac{1}{2}\rho v^2 + \rho g h = \text{const}$

Conservation of energy for steady, inviscid, incompressible flow.

Continuity Equation

$A_1 v_1 = A_2 v_2$

Conservation of mass for incompressible flow.

Darcy-Weisbach

$\Delta P = f \frac{L}{D} \frac{\rho v^2}{2}$

Pressure drop due to friction in a pipe.

Variables

Symbol	Description	Unit
$Re$	Reynolds number	—
$\rho$	Fluid density	kg/m³
$v$	Flow velocity	m/s
$D$	Characteristic dimension	m
$\mu$	Dynamic viscosity	Pa·s
$P$	Pressure	Pa
$f$	Darcy friction factor	—

Example Calculation

Using the parameters from the original example:

Parameter	Value
Pipeline Length	100 m
Air Flow	500 l/s
Inside Diameter	100 mm
Working Pressure	9 bar (gauge)
Pressure Drop	0.07 bar

This illustrates how the nomograph connects multiple variables to determine the pressure loss in a compressed air system.

How to Use the Nomograph

The nomograph allows you to estimate pressure drop visually. Follow these steps:

1. First Line: Draw a straight line from the pipeline length scale through the air flow volume scale to the first reference line.
2. Second Line: From that intersection point, draw a line through the pipe inside diameter scale to the second reference line.
3. Final Line: Draw a line from the working pressure scale, through the point on the second reference line, to the pressure drop scale. The value at the intersection is the estimated pressure drop.

This method provides a quick graphical solution without complex calculations.

References

• Original Source