| Fig. 95. |
§ 84. Practical Calculations on the Flow of Water in Pipes.—In the following explanations it will be assumed that the pipe is of so great a length that only the loss of head in friction against the surface of the pipe needs to be considered. In general it is one of the four quantities d, i, v or Q which requires to be determined. For since the loss of head h is given by the relation h = il, this need not be separately considered.
There are then three equations (see eq. 4, § 72, and 9a, § 76) for the solution of such problems as arise:—
ζ = α (1 + 1/12d);
(1)
where α = 0.005 for new and = 0.01 for incrusted pipes.
ζv2 / 2g = 1⁄4di.
(2)
Q = 1⁄4πd2v.
(3)