# Pressure Loss

Written by Matt Milbury on . Posted in Pump

Pressure loss, abbreviated as $$\Delta P$$, also called pressure drop, is the difference in pressure between two points, usually caused by friction resistance in the pipe, but moisture can also affect it.

## Pressure Loss formula

$$\large{ P_l = \mu \; \left( \frac{ l_p }{ d_h } \right) \; \left( \rho\;\frac{ v^2 }{ 2 } \right) }$$
Symbol English Metric
$$\large{ P_l }$$ = pressure loss $$\large{\frac{lbf}{in^2}}$$ $$\large{Pa}$$
$$\large{ \rho }$$   (Greek symbol rho) = density $$\large{\frac{lbm}{ft^3}}$$ $$\large{\frac{kg}{m^3}}$$
$$\large{ \mu }$$  (Greek symbol mu) = friction coefficient $$\large{ dimensionless }$$
$$\large{ d_h }$$ = hydraulic diameter $$\large{ ft }$$ $$\large{ m }$$
$$\large{ l }$$ = lenght of pipe $$\large{ ft }$$ $$\large{ m }$$
$$\large{ v }$$ = velocity of fluid  $$\large{\frac{ft}{sec}}$$ $$\large{\frac{m}{s}}$$

Tags: Pressure Equations