SynopsisAn extensive study on the turbulent drag reduction caused by the various mixtures of polyacrylamide, purified guargum, xanthangum, and their graft copolymers has been conducted at low concentrations and Re = 14,000 using a turbulent flow rheometer. It has been found in most of the cases that the drag reduction caused by mixtures shows a positive deviation from the linearly additive straight line. This effect is more prominent when the drag reduction caused by both the constituents differ appreciably. In most of the cases, the drag reduction caused by the mixtures is higher than the DR caused by either of the constituent polymers; however, the drag reduction caused by the mixture is less than the sum of the drag reduction caused by both the constituents at their respective concentration in the mixture. I t has also been noticed that there is no evidence of synergism in these mixtures at low concentrations.

Abstract:The shear stability of drag reducing polymer-polymer and polymer-fibre mixtures has been studied at a Reynolds number of 14,000 using a turbulent flow rheometer. The ratio of the drag reduction at a particular pass number to the initial drag reduction has been determined for the mixtures at various pass numbers and compositions in order to determine the effect of composition on the shear stability of the mixtures.It has been found in both cases that when there is a drastic difference in the shear stabilities of the constituents of the mixtures, the incorporation of a small amount of the less shear stable drag reducing agent reduces the shear stability drastically. On the other hand, when the shear stability of the constituents are of the same order, there is only a proportional change in the shear stability of the mixtures on addition of one component to the other. A correlation between the decay coefficient of the mixture (RM), the decay coefficients of the constituents (R 1 and R2) and the weight fractions of the mixture components (W 1 and W2) is suggested. An efficacious method for preparing asbestos fibre stock suspensions is also described.

SynopsisThe turbulent drag reduction studies by asbestos fiber mixtures with purified guargum, p m e d xanthangum, and their graft copolymers have been conducted at low concentration and Re 14OOO using turbulent flow rheometer designed by Hoyt. A methd for making stock suspension of asbestos fibers is also suggested which givea better drag reduction. It has been found from the present studies that purified guargum-asbestos fiber mixtures give positive synergiatic effect even at low concentration and synergism in drag reduction may be caused by a mixture when its constituents are rigid. A simple mixture rule equation having interaction parameter may be used for the prediction of drag reduction by the mixture.

If you would like to write for this, or any other Emerald publication, then please use our Emerald for Authors service information about how to choose which publication to write for and submission guidelines are available for all. Please visit www.emeraldinsight.com/authors for more information. About Emerald www.emeraldinsight.comEmerald is a global publisher linking research and practice to the benefit of society. The company manages a portfolio of more than 290 journals and over 2,350 books and book series volumes, as well as providing an extensive range of online products and additional customer resources and services.Emerald is both COUNTER 4 and TRANSFER compliant. The organization is a partner of the Committee on Publication Ethics (COPE) and also works with Portico and the LOCKSS initiative for digital archive preservation.Abstract A modelling approach of gas solid flow, considering different physical phenomenon such as fluid turbulence, particle turbulence and interparticle collision effects are presented. The approach is based on the two-fluid model formulation where both phases are treated as continuum. This implies that the gas phase as well as the particle phase are weighted by their separate volumetric fractions. According to the experimental results and numerical simulations, the inter-particle collision possesses a significant influence of turbulence level on particle transport properties in gas solid turbulent flow even for dispersed phase volume fraction (a , 0.01). Comparisons in predictions have been depicted with inclusion of interparticle collision effect in the equation of particle turbulent kinetic energy and with exclusion of this effect. Experimental research has been conducted in a thermal power plant depicting higher erosion resistance of noncircular square sectioned coal pipe bends in comparison with those with circular cross section, the salient features of the experimental work are presented in this paper. Experiments have been conducted to determine, pressure drop in straight and curved portions of conduits conveying air coal mixtures in a thermal power plant. Validation of this experimental data with numerical predictions have been presented.

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