Assessment of Friction Losses and Friction Factor in Polypropylene Pipes

Recently, polypropylene (PPR) pipes have been increasingly used to replace galvanized iron pipes in most water transmission systems due to their ease of installation and perceived health safety. Also, PPR has engineering features that do not deteriorate over time. Despite the good properties of these pipes, there is a lack of in-depth studies on calculating the friction factor and friction losses within them. The present study calculates the friction losses in PPR pipes and the variables that influence them, whether they are associated with the pipes themselves or the internal flow properties. The experimental work was conducted using three diameters of PPR pipes: 0.0131 m, 0.01675 m, and 0.021 m, with four lengths for each diameter: 3 m, 10 m, 20 m, and 30 m. For each model, nine discharges were studied, and the head loss, for each run, was measured using pressure sensors. The number of experiments conducted was 108, and for comparison purposes, 36 experiments were conducted on a galvanized iron pipe with a diameter of 0.0171 m and the same length as the PPR pipes. The results showed that the internal surface of the PPR pipes was very smooth, with an internal roughness height of approximately 0.00001mm. The friction losses increased with flow velocity in a nonlinear relationship and pipe length in a linear relationship, where the rate of increase in friction losses was 9.75 times when the pipe length increased from 3 to 30m. The friction losses decreased with the pipe diameter in a linear relationship, with a 40% decrease observed when the pipe diameter increased from 0.0131 m to 0.01675 m for a 30 m long pipe and a flow velocity of 1.53 m/s. The percentage of losses decreased by 55% when the diameter increased from 0.0131 m to 0.021 m. Regarding low flow velocity, 0.380 m/s, the decrease was very small compared to high velocities, as the percentage of decrease does not exceed 17% when the diameter increases from 0.0131m to 0.021m. The results also showed that the friction losses in PPR pipes were approximately 20% lower than those in galvanized iron pipes.