Incidence of the pressure on roughness coefficient C of Hazen-Williams

Abstract

The objective of this research was to evaluate the incidence of pressure in the friction coefficient C used in the Hazen-Williams expression, as an argument to define the diameters to reduce costs in installations using pressurized plastic pipes. For this purpose, 10 test pressures were evaluated, using 88 m polyethylene hose, two glycerin manometers, a medium flow sprinkler and a three-inch centrifugal turbine pump. The load losses were evaluated with each pressure in triplicate, with the appropriate altimetric correction of the surface, and the respective flows produced in the sprinkler. With the experimental information obtained the coefficient C was calculated, using the expression of Hazen-Williams cleared for this coefficient. With the load data and the C value, a regression model was established, determining its goodness through the respective coefficient of determination (r2). When verifying the results it was possible to establish that the coefficient C is affected by the pressure by means of a quadratic type relation, increasing as the load increases; and maintaining more or less the same loss of energy at each of the test pressures. This result allowed to conclude that for smooth pipes such as plastic, it is possible to consider coefficient C values above 150 indicated for plastic; which consequently reduces the costs of pressurized piping systems.