Flow of Dilute Polymer Solutions Through Curved Pipes : 2nd Report, Pressure Loss in 360°Bends

Abstract

Experiments on flows of water and dilute aqueous solutions of polyethylene oxide are carried out in the Reynolds number range of 10³ to 5× 10⁴. Concentration of polymer solutions is varied from 1ppm to 100ppm. The ratios of curvature radius to pipe radius, R/a, are 18.7, 34.3 and 47.3. Measured pressure distributions along a bend axis are classified in three types by their patterns. Flow property of each pattern is clarified by using the method of flow visualization. Drag reduction in a bend flow is smaller than that in a straight pipe flow. Pressure loss coefficients are correlated with the Reynolds number, the ratio of radius R/a and the Weissenberg number. The empirical formulas presented for the bend loss coefficient are useful from an engineering viewpoint.