# Pressure Drop

The difference in pressure between two points, usually caused by friction resistance in the pipe, but moisture can also affect it.

## Formula

A relationship for turbulent flow in commercial steel pipes is:

\(\Delta P = \frac{Q^{1.8} \mu^{0.2}}{C \cdot d^{4.8} \cdot \rho}\)

Where:

\(\Delta P\) = pressure loss due to friction, psi per 100' of pipe

\(\mathrm{C}\) = 20,000 for rough carbon steel pipe and 23,000 for smooth tubes.

\(Q\) = flow rate, lb/hr

\(\mu\) (Greek symbol mu) = Viscosity, cp

\(\rho\) (Greek symbol rho) = density of the fluid, lb/ft^{3}

\(d\) = the internal pipe diameter, In