Abstract
The paper presents results of investigation of the local resistance coefficient ζ in welded polypropylene T-junctions with the internal diameter 13.2 mm. The investigations were performed on an independently constructed test rig. The scope of investigations encompassed the T-junctions, which were (1) properly warmed up and properly pressed, (2) poorly warmed up and poorly pressed, or (3) excessively warmed up and excessively pressed. The local resistance coefficients ζ determined by measurements according to the standard PN-EN 1267:2012(Designation of the Polish Standard) were compared to those determined with use of the nomograms recommended for designing water supply systems and installations. Real values of the coefficients ζ, obtained in measurements were significantly higher than those read from the nomograms. The local resistance coefficients ζ in welded polypropylene T-junctions depend on water flow velocity and the manufacturing precision of a T-junction joint.
Highlights
Fittings, including bends, elbows, T-junctions, diffusers, confusors, and cutting valves, are essential elements of any hydraulic system
Equations (13)–(21) and the nomogram shown in Figure 8 can be used to design of water supply installations made of polypropylene and to determine real values of the resistance coefficient ζ relative to the assumed manufacturing precision of a T-junction with an internal diameter 13.2 mm
The comparison of the mean values of the local resistance coefficient ζ determined from the measurements of properly warmed up and properly pressed T-junctions with the respective values for poorly warmed up and poorly pressed T-junctions (ζ4p, ζ5p, ζ6p ) and excessively warmed up and excessively pressed T-junctions (ζ7p, ζ8p, ζ9p ) allowed us to state that for the through-run water flow, the value of ζ4p increased by 45%, ζ7p by 70.1%, in the divergent water flow ζ5p increased by 21.7%
Summary
Fittings, including bends, elbows, T-junctions, diffusers, confusors, and cutting valves, are essential elements of any hydraulic system. The liquid flow through fittings connecting pipelines is more complicated than that through straight sections [1]. The pressure losses associated with the fittings are caused by disturbances in liquid flow which occur during changes in its direction or sudden or gradual changes in the cross-section or shape of the pipeline. Investigations of water flow through fittings have tremendous significance in understanding and improving their flow capacity and minimizing hydraulic losses. It is well known that viscous incompressible liquids [3] and compressible gases [4] moving through fittings are characterized by flow splitting [5,6,7], occurrence of secondary flows [1,8,9,10], and Dean vortexes, and, in general, by high instability [8,9,11,12]
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