A horizontal pipe with a diameter of 90 mm conveys water at 30 L/s with a pressure drop of 60 kPa per 20 meters of pipeline. Calculate the value of the coefficient of friction, f, using the Darcy formula.

The diameter $D$ is $90 \text{ mm}$, which is $0.090 \text{ m}$.
The flow rate $Q$ is $30 \text{ L/s}$, which is $30 \times 10^{-3} \text{ m}^3/\text{s}$.
The pressure drop $\Delta P$ is $60 \text{ kPa}$, which is $60 \times 10^3 \text{ Pa}$.
The length of the pipeline $L$ is $20 \text{ m}$.
The density of water $\rho$ is approximately $1000 \text{ kg/m}^3$.
The acceleration due to gravity $g$ is approximately $9.81 \text{ m/s}^2$.

The area $A$ of a circular pipe is given by $A = \frac{\pi D^2}{4}$.

The velocity $V$ is given by $V = \frac{Q}{A}$.

The head loss $h_f$ is related to the pressure drop $\Delta P$ by $h_f = \frac{\Delta P}{\rho g}$.

The Darcy-Weisbach formula for head loss is $h_f = f \frac{L}{D} \frac{V^2}{2g}$.
Rearranging to solve for $f$:

Substitute the calculated values:

The value of the coefficient of friction is $\textbf{0.0243}$.