Hazen-Williams Coefficient

Hazen-Williams coefficient, abbreviated as C, also called Hazen-Williams friction coefficient or, Hazen-Williams roughness coefficient, a dimensionless number, is used in the Hazen-Williams Equation.  The coefficient is used in fluid dynamics to calculate the resistance of water flow in a pipe network.  The lower the coefficient, the smoother the pipe is.  The higher the coefficient, the less fluid flow is restricted.  By using pipe materials with improved flow characteristics, energy costs for pumping can be reduced or smaller pipes can be used.

The Hazen-Williams coefficient represents the internal roughness of the pipe, taking into account factors such as pipe material, age, and condition.  It is used to incorporate the effect of pipe roughness on the flow characteristics.  The higher the coefficient, the smoother the pipe surface, resulting in a higher flow rate for a given pressure drop.  The Hazen-Williams coefficient varies depending on the pipe material, and it is typically determined through empirical testing.  The coefficient values for different pipe materials are usually available in engineering references and design manuals.

It's important to note that the Hazen-Williams equation is an empirical approximation and is most accurate for steady, uniform flow conditions in water supply systems.  For more complex or non-uniform flow situations, other equations, such as the Darcy-Weisbach equation, may be more appropriate.

Note that the Hazen-Williams Coefficient is '''not''' the same as the Darcy-Weibach-Colebrook friction factor, f.  These are not in any way related to each other.