. Principles and practice of plumbing . s back to e,the wetted perimeter will be reduced to inches, or aboutone-half the length of the combined perimeters of the four1-inch pipes, while the sectional area remains Friction varies almost as the square of the velocityand is entirely independent of press-ure. That is, if the velocity of flowof water in a pipe is doubled, thefrictional resistance will be quad-rupled, while if the initial velocity isreduced to one-half, the frictional re-sistance will be decreased to one-quarter, regardless ■ of the intensityPig. 70 of pressure in
. Principles and practice of plumbing . s back to e,the wetted perimeter will be reduced to inches, or aboutone-half the length of the combined perimeters of the four1-inch pipes, while the sectional area remains Friction varies almost as the square of the velocityand is entirely independent of press-ure. That is, if the velocity of flowof water in a pipe is doubled, thefrictional resistance will be quad-rupled, while if the initial velocity isreduced to one-half, the frictional re-sistance will be decreased to one-quarter, regardless ■ of the intensityPig. 70 of pressure in the pipe. wettea Perimeter of Pipes Loss of head due to frictiou in pipes can be determined by the formula: Ivli = f , in which h = loss of head in feet, f = coefficient for size and rough- ness of pipe, 1 = length of pipe in feet, v = velocity in feet per second,d ^= diameter of pipe in feet, g = acceleration due to gravity. The value of coefficient / for different sizes of pipesTABLE XXXVI. Values of Coefficient /- (MEKRIMAN). Diameterof Pipe in Velocity of Feet per Second Ft. In. 1 2 3 4 6 10 15 .05 Vs .047 .041 .037 .034 .031 .029 .028 .1 114 .038 .032 .030 .028 .026 .024 .023 .25 3 .032 .028 .026 .025 .024 .022 .021 .5 6 .028 .026 .025 .023 .022 .021 ,019 .75 9 .026 .025 .024 .022 .021 .019 .018 1. 12 .025 ,024 .023 .022 .020 .018 .017 Digitized by Microsoft® Principles and Practice of Plumbing lil and with different velocities of flow can be found in TableXXXVI. Example—What is the loss of head due to friction in a 3-inch pipe 600feet long, if the mean velocity of flow is 4 feet per second? Solution—From the taljle it is found that the value of / for a 3-inch pipewith a velocity of 4 feet per second is .025; then, substituting given values inthe formula: 600 X 16 h = .025 X = 15 feet.—Answer. .25 X Table XXXVII gives the loss of head in pounds persquare inch for each 100 feet of length in different sizes ofclean pipes discharging given quantities of w
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