Motion of solid particles

Kelsall, D.F, A Study of the Motion of Solid Particle.s in a Hydraulic Cyclone. Trans. Inst. Chem. Engrs. 30 (1952), pp. 87-108. 

Metastable elements of the structure (both solid particles and micropores) are eventually stabilized because of the motion of solid particles. 

Heat Transfer to the Wall A number of investigations of heat-transfer coefficients at the wall in fluidized beds have been reported, and in all cases the values found for h, were considerably larger than those for an empty tube at the same fluid velocity. Presumably this is because the motion of solid particles near the wall tends to prevent the development of a slow-moving layer or film of gas, and the heat-carrying capacity of the particles themselves as they move between the center and the wall of the reactor is significant. 

ABRASIVE EROSION - Erosive wear caused by the relative motion of solid particles which are entrained in a fluid, moving nearly parallel to a solid surface. 

Kelsall DF. A study of the motion of solid particles in a hydraulic cyclone. Trans Inst Chem Eng 30 87-104, 1952. 

The problems posed by the motion of solid particles or a moving bed of particles in countercurrent adsorption processes have led to a number of different operational configurations. In a gas-fluidized multistage countercurrent adsorber, there are multiple sieve-tray plates in a vertical column. The adsorbent particles are fluidized by the gas stream to be cleaned entering through the perforations in the sieve tray. The fluidization level is not very vigorous. 

Huang, P. Y., Feng, J., Hu, H. H., Joseph, D. D. (1997), Direct simulation of the motion of solid particles in Couette and Poiseuille flows of viscoelastic fluids , J Fluid Mech, 343, 73-94. 

Fluidized-bed catalytic reactors. In fluidized-bed reactors, solid material in the form of fine particles is held in suspension by the upward flow of the reacting fluid. The effect of the rapid motion of the particles is good heat transfer and temperature uniformity. This prevents the formation of the hot spots that can occur with fixed-bed reactors. 

Static This is a dense bed of solids in which each particle rests upon another at essentially the settled bulk density of the solids phase. Specifically, there is no relative motion among solids particles (Fig. 12-26). 

Filtration frequently is accompanied by hindered or free gravitational sedimentation of solid particles. The directions of action of gravity force and filtrate motion may be cocurrent, countercurrent or cross current, depending on the orientation of the... 

Many engineering operations involve the separation of solid particles from fluids, in which the motion of the particles is a result of a gravitational (or other potential) force. To illustrate this, consider a spherical solid particle with diameter d and density ps, surrounded by a fluid of density p and viscosity /z, which is released and begins to fall (in the x = — z direction) under the influence of gravity. A momentum balance on the particle is simply T,FX = max, where the forces include gravity acting on the solid (T g), the buoyant force due to the fluid (Fb), and the drag exerted by the fluid (FD). The inertial term involves the product of the acceleration (ax = dVx/dt) and the mass (m). The mass that is accelerated includes that of the solid (ms) as well as the virtual mass (m() of the fluid that is displaced by the body as it accelerates. It can be shown that the latter is equal to one-half of the total mass of the displaced fluid, i.e., mf = jms(p/ps). Thus the momentum balance becomes... 

Both Fig. 37 and Fig. 39 show solid particles highly dispersed as a dilute phase in the oscillating fluid, either gas or liquid, without evidence of any bubbles. When a packed bed of solid particles was subjected to the action of an oscillating liquid, however, only the upstroke portion of the periodic fluid motion was capable of dispersing the solid particles against the action of gravity, while during downstroke they fell back onto the distributor plate. 

Because of the unavoidable tendency of granular solids to become triboelectrically charged when handled, it is no surprise that electrostatic phenomena are often quite pronounced in fluidized and spouted beds. The vigorous motion of fluidized particles—with constant particle-particle and particle-wall contacts—guarantees that electrical charging will take place. Electrostatic adhesion and cohesion, observed and recorded in the very earliest experimental investigations of fluidization, were immediately identified as experimental nuisances to be overcome. Somewhat later, the hazardous nature of electrostatics came to be appreciated. 

C. Modeling the Motion and Collision Dynamics of Solid Particles in Gas-Liquid-Solid Fluidization... 

The prime difficulty of modeling two-phase gas-solid flow is the interphase coupling, which deals with the effects of gas flow on the motion of solids and vice versa. Elgobashi (1991) proposed a classification for gas-solid suspensions based on the solid volume fraction es, which is shown in Fig. 2. When the solid volume fraction is very low, say es< 10-6, the presence of particles has a negligible effect on the gas flow, but their motion is influenced by the gas flow for sufficiently small inertia. This is called one-way coupling. In this case, the gas flow is treated as a pure fluid and the motion of particle phase is mainly controlled by the hydrodynamical forces (e.g., drag force, buoyancy force, and so... 

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