2022 Volume 27 Issue 2 Pages 43-49
There are two types of mean flow velocity formulas for pipes, the Darcy-Weisbach equation and the Hazen-Williams equation. In the process of deriving the Hazen-Williams equation from the Darcy-Weisbach equation, it was clarified that the friction loss coefficient f is expressed by the exponential function of f ＝ aRe-b. Next, the Hazen-Williams equation C was obtained by eliminating the effect of the Reynolds number Re. It was confirmed that only the constant a remained in the equation C and there was almost no influence of water temperature and viscosity, and the meanings of the constants a and b were considered. When designing the pipeline, the influence of the relative roughness k/D on the inner surface of the pipe was evaluated using the Colebrook equation in order to set the transition section in which both the effects of viscosity and roughness are effective as the design range. The relationship between these hydraulic constants f, C, Re and k/D was verified by the Moody chart, and hydraulic issues were raised in the design.
