Particle mixing and solids flowability in granular beds stirred by paddle-type blades

Malhotra, Karun; Mujumdar, Arun S.

doi:10.1016/0032-5910(90)80150-w

Cited by 24 publications

(12 citation statements)

References 4 publications

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“…into powder mixing. Thus, Malhotra and Mujumdar 1990 viewed a cylindrical stirred system through one end wall and interpreted their findings in relation to particle motion in the vicinity of the blade. In 1995, McCarthy et al developed a theory of the powder behavior in rotary drums.…”

Section: Introductionmentioning

confidence: 98%

Motion in a particle bed agitated by a single blade

2000

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Section: Introductionmentioning

confidence: 98%

Motion in a particle bed agitated by a single blade

2000

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“…These studies found the existence of particle recirculation patterns that move with the blade. Horizontal cylindrical mixer studies were performed by Malhotra et al,7–9 Laurent et al,10 Jones et al11 and Bridgwater et al12 The studies by Malhotra focused on two‐dimensional geometries and provide information on mixing kinetics and heat transfer coefficients for agitated dryers. Laurent et al10 found that flows in this geometry are periodic in nature, whereas Jones et al11 observed slower mixing when the fill level was increased.…”

Section: Introductionmentioning

confidence: 99%

Discrete element simulation of free flowing grains in a four‐bladed mixer

2009

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Numerical simulations of granular flow in a cylindrical vessel agitated by a fourblade impeller were performed using the discrete element method. Velocity, density, and stress profiles within the mixer displayed a periodic behavior with a fluctuation frequency equal to that of the blade rotation. Blade orientation was found to affect flow patterns and mixing kinetics. For an obtuse blade pitch orientation, a threedimensional recirculation zone develops in-front of the blade due to formation of heaps where the blades are present. This flow pattern promotes vertical and radial mixing. No recirculation zone was observed when the blade orientation was changed to an acute blade pitch. The system's frictional characteristics are shown to strongly influence the granular behavior within the mixer. At low friction coefficients, the 3-D recirculation in front of the obtuse blade is not present reducing convective mixing. Higher friction coefficients lead to an increase in granular temperature which is associated with an increase in diffusive mixing. Normal and shear stresses were found to vary with mixer height with maximum values near the bottom plate. Additionally, a strong dependence between the magnitude of the shear stresses and the friction coefficient of the particles was found. The stress tensor characteristics indicate that the granular flow in our simulations occurs in the quasi-static regime. At the same time, the averaged pressure was found to vary linearly with bed height and could be predicted by a simple hydrostatic approximation. V

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“…Various interesting comparisons can be carried out at this end. First, t th,DEM can be compared with the time constant of real mechanical mixing (see also Bridgewater, [33] Malhotra et al, [34] and Malhotra and Mujumdar [35] ), denoted by t mech in Table 3. To derive t mech , separate DEM simulations have been conducted under otherwise the same conditions as previously, though without heat transfer.…”

Section: Time Constants and Their Comparisonmentioning

confidence: 99%

Modeling of Contact Dryers

2007

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Contact drying of stagnant or agitated beds can be reliably described by the penetration model under vacuum or inert conditions. However, the penetration model has disadvantages in the consideration of granular mechanics and statistics due its continuous nature. The fact that such disadvantages can be avoided by discrete approaches is illustrated by application of the discrete element method to the problem of heating of particles in a rotary drum. Important limiting cases are treated, along with conditions for equivalence between continuous and discrete model. Time constants and scaling aspects are addressed and opportunities of combined product and process engineering are pointed out.

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Particle mixing and solids flowability in granular beds stirred by paddle-type blades

Cited by 24 publications

References 4 publications

Motion in a particle bed agitated by a single blade

Motion in a particle bed agitated by a single blade

Discrete element simulation of free flowing grains in a four‐bladed mixer

Modeling of Contact Dryers

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