(296f) Drag Reduction and Degradation of Diutan Biopolymer Solutions during Turbulent Flow in a 4.6 Mm ID x 200 L/D Smooth Pipe
AIChE Annual Meeting
2019
2019 AIChE Annual Meeting
Engineering Sciences and Fundamentals
Turbulent and Reactive Flows and Flow Characterization
Tuesday, November 12, 2019 - 9:15am to 9:30am
The Diutan biopolymer, of MW ~ 4.0E6, is a double-helix, with contour length Lc ~ 4.5 um, chain diameter Dch ~ 1.8 nm and aspect ratio Lc/Dch ~ 2600. Aqueous Diutan solutions of concentrations C from 1 to 100 wppm exhibited Type B drag reduction, characteristic of extended macromolecules, yielding turbulent flow segments roughly parallel to, but displaced upwards from, the Prandtl-Karman law, the more so with increasing concentration. At fixed Reâf = 2500, flow enhancements relative to solvent S' = [(1/âf)p - (1/âf)n]Reâf increased almost linearly with increasing concentration, providing intrinsic flow enhancement [Sâ] = Limcâ0[Sâ/c] = 0.10±0.02.
The experiments were also able to detect turbulent flow-induced Diutan degradation, that has not previously been reported. Degradation was visible as a slight downward dip of the overall P-K friction factor data at the highest flowrates and also as a slight dip of downstream relative to upstream points in each data cluster. These yielded a quantitative Diutan "degradation modulus" (kdeg/Tw) = 0.0035 +/- 0.0005 (1/Pa s), which is ~ 1/3 of previously known moduli for conventional vinyl-backbone polymers, such as PEO W309 MW 11E6 (kdeg/Tw) = 0.011 +/- 0.002 and PAMH B1120 MW 18E6 (kdeg/Tw) = 0.012 +/- 0.001. The foregoing show the Diutan biopolymer to be ~ 3 times more resistant to degradation than the PEOs and PAMHs commonly used for turbulent drag reduction.