The turbulent flow characteristics of model fibre suspensions

Bobkowicz, A. J.; Gauvin, W. H.

doi:10.1002/cjce.5450430210

Cited by 45 publications

(17 citation statements)

References 5 publications

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“…The third region is called the fully turbulent region. In this region the friction factor is not decreasing as rapidly with increasing Reynolds number as a pure fluid and in many cases the friction factor is increasing with Reynolds number, The data of investigators using synthetic fiber drag reducing additives (Bobkowicz and Gauvin, 1965; Kerekes and Douglas, 1972) follow the same trends on plots of this type.…”

Section: Solid-liquid Suspensionsmentioning

confidence: 72%

“…In addition, several authors (Bobkowicz and Gauvin, 1965;Hoyt, 1972;Vaseleski, 1973;Zandi, 1967) have claimed that nonfibrous solid-liquid suspension pipe flow pressure drop measurements of earlier authors indicated drag reduction. Those earlier papers which have been so described are the water suspensions of sand used by Blatch ( 1906), of emery used by Maude and Whitemore (1958), and of thoria used by Thomas (1962) and by Eissenberg ( 1964).…”

Section: Solid-liquid Suspensionsmentioning

confidence: 99%

“…tion factor is essentially that of the suspending Newtonian fluid. Bobkowicz and Gauvin (1965) studied the effects of suspensions of drag reducing nylon fibers of various sizes and shapes. They observed that drag reduction increased with the aspect ratio ( l / d ) of the fibers at a fixed concentration.…”

Section: Effect Of Particle Shapementioning

confidence: 99%

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Polyethylene vs. stainless steel impellers for crystallization processes

1973

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The importance of controlling the crystal size distribution of the product from an industrial crystallizer has long been recognized. To do this, some control over the nucleation and growth rates of crystals must be maintained. The crystal growth rate can be influenced by varying degrees of agitation, supersaturation, and temperature. However, these variables also have a major effect on the nucleation rate, so that it is seldom possible to change one of these quantities without simultaneously changing the other. It is the purpose of this note to discuss one means of substantially influencing the nucleation rate without affecting the growth rate.The role of crystal impacts in determining the nucleation rates was established by Clontz and McCabe (1971) and Johnson et al. (1972). Ottens and deJong (1972) have presented data to indicate that the major source of nucleation in an industrial crystallizer is at the impel'er , if there is internal mixing, or at the pump, if the mixing in the crystallizer is accomplished by external recycle Johnson et a]. (1972) also show that when a single crystal is impacted by a polyethylene rod, whose face is parallel to the crystal face being impacted, no new crystals are Kenerated. This can be contrasted to the generous number of crystals produced by impact with a metal rod. Their system was magnesium sulfate heptahydrate.On the basis of these reports an experimental plan to investigate the influence of the material of construction of the impeller in a stirred tank crystallizer was formulated. The crystallizer was a cylindrical Pyrex battery jar 15.25 cm in diameter and filled to a depth ol' 17.15 cm Three equally spaced plexiglass baffles extending to within 3 cm of the bottom were attached to the crystallizer. A fitted plexiglass cover was constructed to accommodate the impeller shaft, a thermometer which could be read to O.l"C, and seed crystal insertion. The entire apparatus was placed in a constant temperature bath. The impellers used were 5.1 cm in diameter, three bladed, with a square pitch, and located 9 cm from the bottom of the crystallizer.In all of the experiments of this series, the impeller speed was held at 700 rev./min., a value which kept the seed crystal adequately suspended. The size of the seed crystals was held essentially constant at about 5 mm x 2 mm x 2 mm; when deviations from this size occurred the results were erratic. Supersaturation was kept at 2°C and the temperature at about 33 to 35°C. A typical run went as follows: A solution of MgS04.7H20 was prepared, filtered, and placed in the crystallizer. The saturation temperature of the solution was determined by refractive index and the temperature of the solution was adjusted to 2°C above saturation. A seed crystal of the appropriate size and shape, and which had been recrystallized below 48.2"C to ensure the pure heptahydrate form, was inserted into the crystallizer and cured for 16 minutes with agitation. Shorter curing times gave excessively high crystal counts. Agitation was discontinued and the solut...

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Section: Solid-liquid Suspensionsmentioning

confidence: 72%

Section: Solid-liquid Suspensionsmentioning

confidence: 99%

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Polyethylene vs. stainless steel impellers for crystallization processes

1973

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“…On the basis of their observations, they attributed the lower head losses for the fiber suspensions to a modification of the turbulent momentum transfer mechanism by the fiber or fiber network. Bobkowicz and Gauvin [8] reported turbulence measurements for fiber suspensions based on a dispersion technique and found an increase in radial diffusivity and radial turbulence intensity. They postulated that the increase in radial turbulence was more than offset by a decrease in the axial turbulence, which caused the observed drag reduction.…”

Section: Literature Reviewmentioning

confidence: 98%

“…The flow of fibers has been investigated with particular emphasis on how fiber dimensions affect turbulent drag reduction [4,5]. Intensive research for a long time has yet to uncover the hydrodynamics and mechanisms of turbulent pulp suspension flow in closed conduit.…”

Section: Literature Reviewmentioning

confidence: 99%

The Effect of Varying Fiber Characteristics on the Simultaneous Measurement of Heat and Momentum Transfer to Flowing Fiber Suspensions

Kazi

Duffy

Chen

2014

Journal of Heat Transfer

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Heat transfer and pressure loss measurements were obtained simultaneously for a range of wood pulp fiber suspensions flowing in a pipeline. Data were obtained over a selected range of flow rates and temperatures from a specially built flow loop. It was found that the magnitude of the heat transfer coefficient was above water at equivalent experimental conditions and at very low fiber concentrations, but progressively decreased until it was below water at slightly higher concentrations. Similar trends were obtained for the pressure drop measurements obtained simultaneously, showing good correspondence between the two sets of data. It was found that both heat and momentum transfer are affected in a closely similar way by varying fiber properties, such as fiber length, fiber flexibility, fiber chemical and mechanical treatment, the variation of fibers from different parts of the tree, as well as the different pulping methods used to liberate the fibers from the wood structure. Drag reduction increased and heat transfer coefficient decreased with increasing fiber flexibility as found by previous workers.

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In‐line jet mixing of liquid‐pulp‐fiber suspensions: Effect of fiber properties, flow regime, and jet penetration

et al. 2012

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Mixing effectiveness was determined experimentally for side jet injection into pipe flow for water and pulp suspensions for a range of fiber mass concentrations (0-3.0%), mainstream velocities (0.5-5.0 m/s), and side-stream velocities (1.0-12.7 m/s). The mixing quality was measured in cross-sectional planes along the pipe using electrical resistance tomography and quantified by a modified mixing index, derived from the coefficient of variation of conductivity. Mixing depended strongly on the flow regime and jet penetration. For turbulent flow, the criteria for in-line jet mixing in water are applicable to the mixing in suspensions, with small differences likely due to differences in fiber network strength and influences of fiber-turbulence interactions in modifying turbulent structures in the bulk. When a suspension flows as a plug, however, the mixing differs greatly from that in water, depending on the fiber network strength in the core of the pipe.

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The turbulent flow characteristics of model fibre suspensions

Cited by 45 publications

References 5 publications

Polyethylene vs. stainless steel impellers for crystallization processes

Polyethylene vs. stainless steel impellers for crystallization processes

The Effect of Varying Fiber Characteristics on the Simultaneous Measurement of Heat and Momentum Transfer to Flowing Fiber Suspensions

In‐line jet mixing of liquid‐pulp‐fiber suspensions: Effect of fiber properties, flow regime, and jet penetration

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