# Friction Loss

on . Posted in Classical Mechanics

Friction loss, abbreviated as FL, is how much loss of flow through a pipe is due to the viscosity, the measure of the internal friction/resistance to the flow of a liquid near the surface of the pipe.

## Friction loss formula

$$\large{ FL = f \; \frac{ l }{ d } \; \frac{ v^2 }{ 2 \; g } }$$
Symbol English Metric
$$\large{ FL }$$ = friction loss  $$\large{ lbf }$$ $$\large{ N }$$
$$\large{ f }$$ = friction factor $$\large{ dimensionless }$$
$$\large{ d }$$ = inside diameter of pipe $$\large{ in }$$  $$\large{ mm }$$
$$\large{ l }$$ = length of pipe $$\large{ ft }$$  $$\large{ m }$$
$$\large{ g }$$ = standard gravity  $$\large{\frac{ft}{sec^2}}$$     $$\large{\frac{m}{s^2}}$$
$$\large{ v }$$ = velocity of fluid  $$\large{\frac{ft}{sec}}$$   $$\large{\frac{m}{s}}$$

## Friction loss formula

$$\large{ FL = C \; \left( \frac{ Q }{ 100 } \right)^2 \; \frac{ l }{ 100 } }$$
Symbol English Metric
$$\large{ FL }$$ = friction loss  $$\large{ lbf }$$ $$\large{ N }$$
$$\large{ Q }$$ = flow rate $$\large{\frac{ft^3}{sec}}$$ $$\large{\frac{m^3}{s}}$$
$$\large{ C }$$ = friction loss coefficient  $$\large{ dimensionless }$$
$$\large{ l }$$ = length of pipe $$\large{ ft }$$  $$\large{ m }$$