Flow conditions in the grooves of a Low-Consistency refiner

Wittberg, Lisa Prahl; Björkman, Magnus; Khokhar, Gohar T.; Mohlin, Ulla Britt; Dahlkild, Anders

doi:10.3183/npprj-2012-27-02-p173-183

Cited by 13 publications

(21 citation statements)

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“…Due to its high importance in the paper-making industry, the eucalyptus pulp is considered in the present study. 1 The present results are also compared with those of softwood pulp in rotating and non-rotating grooves obtained by the Newtonian model proposed in Wittberg et al 11 Finally, the effect of variation in the groove geometry is investigated on the rotational motion of eucalyptus pulp within the rotating and non-rotating grooves.…”

Section: Introductionmentioning

confidence: 71%

Investigation of pulp flow helicity in rotating and non-rotating grooves

Jouybari

Engberg

Persson

et al. 2021

Proceedings of the Institution of Mechanical Engineers, Part E:

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Numerical simulation of pulp flow in rotating and non-rotating grooves is carried out to investigate the effect of pulp rheological properties and groove geometry on the rotational motion of the pulp flow. The eucalyptus pulp suspension is considered as a working fluid in the present study whose apparent viscosity correlation is available from the experimental measurements reported in the literature. The simulations are carried out with OpenFoam for different values of pulp material, fiber concentrations, and groove cross-section. Helicity is introduced to measure the turnover rate of pulp flow in the groove due to the importance of such motion on the final properties of the pulp flow. A measurement of helicity magnitude and its distribution along the groove revealed that a change in the pulp material would significantly affect the flow structures within the groove. Further investigation on the effects of fiber concentration, c, showed that this parameter does not have a significant effect on the averaged helicity magnitude for c = 2.0 and 2.5, whereas the helicity distribution over the groove cross-section changes clearly for c = 1.5. The results showed that the helicity level is negligible for almost half of the cavity cross-section in the non-rotating groove simulations, which can be considered as a shortcoming of the original geometry of the groove. Therefore, a smaller cross-section for the groove is considered through which an enhancement in the helicity magnitude is observed.

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Section: Introductionmentioning

confidence: 71%

Investigation of pulp flow helicity in rotating and non-rotating grooves

Jouybari

Engberg

Persson

et al. 2021

Proceedings of the Institution of Mechanical Engineers, Part E:

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“…Earlier work has shown that there is internal recirculation in LC refiners that depend on the differential pressure over the refiner (Wittberg et al 2012). At high flow through the refiner, the outlet pressure was much lower, in the Braviken trial even lower than the feed pressure.…”

Section: Resultsmentioning

confidence: 96%

Effect of flow recirculation on pulp quality and energy efficiency in low consistency refining of mechanical pulp

Sandberg

Berg

2015

Nordic Pulp &Amp; Paper Research Journal

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SUMMARY:The effect of pulp flow recirculation on energy efficiency and pulp properties development in low consistency refining of TMP has been studied. Trials were made with TwinFlo 58 refiners in two mills in Sweden. The refiners were operated at constant specific refining energy but different flow conditions. No effect of recirculation was seen on refining energy efficiency, pulp quality or fibre wall delamination /internal fibrillation. At high degree of recirculation though, a somewhat larger fibre length reduction was seen. This means that a large degree of recirculation can be used to attain a high specific energy in one stage low consistency refining, without significant negative effects on fibre properties. If a high specific energy input is desirable, it is more cost effective to install one large refiner with recirculation compared to several small without recirculation in series. When recirculation was increased by means of increased flow through the refiner, the outlet pressure dropped. The lower pressure drop over the refiner probably decreased the internal recirculation between rotor and stator, which could explain the observation that there was little effect on fibre development by recirculation. This means that at certain conditions the distribution in fibre treatment might not increase so much when the outer recirculation is increased, since the internal recirculation might be reduced simultaneously. ADDRESSES OF THE AUTHORS: Christer Sandberg

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“…The case where

G > 0

is of interest because it represents a close geometrical similarity to that found in an LC refiner. Wittberg et al and Khohkar simulated a three‐dimensional cavity with an imposed pressure gradient along the cavity axis. The formation of multiple primary vortices under

T / W

ratios of

1.5

was observed, as in the case of

G = 0

above.…”

Section: Introductionmentioning

confidence: 99%

“…These studies have focused on high-speed photography and describe the flow field qualitatively. [28,[33][34][35] For very dilute suspensions, Fox et al [36,37] reports found that the suspension flows inward in the stationary and outward in the moving cavities (see Figure 5). Minor recirculation currents, called secondary and tertiary flows, have also been observed.…”

Section: Introductionmentioning

confidence: 99%

Turbulent couette flow between corrugated walls: The case with motion of one wall perpendicular to the corrugation cavities

et al. 2014

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In this work, we numerically examine the two dimensional flow of a Newtonian fluid in the gap formed between two opposing cavities. The fluid is driven by the motion of the upper cavity and the case considered represents a simplified version of the geometry found in Low Consistency (LC) refiners. Numerical studies were conducted in which we characterized the effect of gap size on the flow field. Then, we examine material transport between the cavities by introducing a passive scalar to represent the motion of tracer particles. A large number of unsteady simulations were conducted over the range of velocities and gap sizes. Over the range of parameters studied, we identify two characteristic flow fields, defined as either steady or unsteady.

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Flow conditions in the grooves of a Low-Consistency refiner

Cited by 13 publications

References 0 publications

Investigation of pulp flow helicity in rotating and non-rotating grooves

Investigation of pulp flow helicity in rotating and non-rotating grooves

Effect of flow recirculation on pulp quality and energy efficiency in low consistency refining of mechanical pulp

Turbulent couette flow between corrugated walls: The case with motion of one wall perpendicular to the corrugation cavities

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