Minor pressure losses for different connections of PP-R and PEX/Al/PEX installation pipes

This paper presents results of laboratory and numerical research concerning determination of water flow resistance through three types of two-way connection of polymer installation pipes: PP-R 20x3.4 mm and PEX/Al/PEX 16x2.0 mm. The following fittings were applied: the direct connection, pipe union and coupler, allowing to test six measurement variants. The laboratory measurements of pressure loss for the tested pipes connections were performed for variable Reynolds number, from approx. 5000 to 50000. The numerical modeling allowing to assess the distributions of velocity of flow and turbulence intensity were performed using FLUENT, Ansys Inc. modelling software. The relations between determined values of minor pressure loss and coefficients of local pressure losses and type of pipes connection, direction of flow as well as the value of Reynolds number were observed. The applied nonparametric statistics, combined with multi comparison, showed that in most cases of analyzed connections, besides the pipe union, the observed differences in pressure losses for various directions of flows are statistically significant for p = 0.05.