Advanced Turbulent Drag Reducing and Flocculating Materials Based on Polysaccharides

Singh, R. P.

doi:10.1007/978-1-4899-0502-4_24

Cited by 62 publications

(38 citation statements)

References 18 publications

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“…Later on, the investigations on their flocculation ability yield the same pattern, i.e. the graft copolymers having fewer and longer grafted chains are found to be more effective flocculants [6]. Among the grafted guar gum, xanthan gum, carboxy methyl cellulose, starch, amylase and amylopectin, it has been found that grafted amylopectin is the most efficient flocculant [5][6][7] Starch consists of linear amylose (molecular weight 10,000-60,000) and branched amylopectin (Mw = 50,000-10 7 g mol -1 ).…”

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confidence: 92%

“…Among all the polysaccharides, grafted amylopectin [6][7][8] has been found to have best flocculation. Graft copolymers are characterized [6] by viscometry, IR, NMR, thermal analysis, morphological study and XRD. Recently the proof of grafting has been given by enzyme hydrolysis [7].…”

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confidence: 99%

“…Among the grafted guar gum, xanthan gum, carboxy methyl cellulose, starch, amylase and amylopectin, it has been found that grafted amylopectin is the most efficient flocculant [5][6][7] Starch consists of linear amylose (molecular weight 10,000-60,000) and branched amylopectin (Mw = 50,000-10 7 g mol -1 ). Among all the polysaccharides, grafted amylopectin [6][7][8] has been found to have best flocculation. Graft copolymers are characterized [6] by viscometry, IR, NMR, thermal analysis, morphological study and XRD.…”

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confidence: 99%

“…Their shear stability and drag reduction efficiency have been extensively studied [3,6]. Most polysaccharides are purified before use [3].…”

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confidence: 99%

“…As mentioned earlier, the grafted polysaccharides are less prone to biological attack [8]. The standard jar test and settling tests were followed for measurement of flocculation and settling characteristics [5][6][7]. First the effectiveness as flocculant was measured in synthetic effluents of kaolin, PbNO 3 and coal.…”

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Res Dev Material Sciapproachability to the particles in colloidal suspensions increases. There is an optimum degree of hydrolysis where grafted chains get straightened but have some degree of flexibility. Beyond the optimum level, the grafted chains lose their flexibility and behave like a rigid rod. The flocculation efficiency of the above graft copolymers is found to be much higher than that of commercial polyacrylamide-based flocculants because of their greater degree of branching and higher molecular weight [10][11][12][13].

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confidence: 92%

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confidence: 99%

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confidence: 99%

“…Their shear stability and drag reduction efficiency have been extensively studied [3,6]. Most polysaccharides are purified before use [3].…”

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confidence: 99%

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confidence: 99%

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Drag Reduction

Singh

2004

Encyclopedia of Polymer Science and Technology

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Turbulent drag reduction in fluid flow by additives has been an exotic field of research ever since its reported discovery in 1949. Various technical applications have been envisaged both for polymeric and surfactant drag reduction. Some successful applications include increased flow of oil and other fluids through pipelines, improved fire fighting and irrigation, improved flow in storm sewers, and flow augmentation by drag reducers in pipeline transport of sediments and slurries. Other possible applications include district heating circuits, industrial and agricultural sprays, and slow‐release fertilizers and pesticides. However, the mechanism of drag reduction still eludes exact explanation mainly because of the inability to characterize polymers, surfactants, and their interactions at molecular or micellar levels in turbulent flows. The main features of polymeric and surfactant homogeneous and heterogeneous drag reduction have been investigated by two‐component laser‐Doppler velocity meter in fully developed, well‐mixed, low concentration (1–2 ppm) drag‐reducing channel flows. Advances in computer technology have led to improved accuracies and reliability of experimental techniques and made possible direct numerical simulation of drag‐reducing turbulent flows. The role of extensional viscosity and elasticity of drag reducers is being keenly debated for the origin of drag reduction in theoretical and experimental investigations. A better understanding is emerging. Some synergistic effects have been observed in combining passive drag‐reducing devices such as riblets with polymers surfactants. Similar observations have been made in combination with microbubbles. This article provides an overview of the latest salient developments in materials, mechanisms, and applications in the field of polymeric drag reduction of various forms and geometries.

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