Particle transport processes

The previous investigations of hard particle transport processes during laser beam dispersing have shown, that the high speed microfocus radioscopy system is a usable arrangement to observe and analyse the movements, velocities and accelerations of particles inside the molten bath. That possibility was, until now, not given by conventional techniques of process... 

If the tracer is composed of the same species as that of the solid host, then the diffusion coefficient is named the tracer self-diffusion coefficient, where DA is the tracer self-diffusion coefficient. It is necessary to clarify that self-diffusion is a particle transport process that takes place in the absence of a chemical potential gradient [13]. This process is described, as explained later, by following the molecular trajectories of a large number of molecules, and determining their mean square displacement (MSD). 

Imadakm, A.O. and Sahimi, M. Computer simulation of particles transport processes in flow through porous media, Chem. Eng. Sci., 46, 1977, 1991. 

These functions can be measured and used in both conceptual and empirical studies on coagulation and other particle transport processes. 

The friction coefficient is a quantity fundamental to most particle transport processes. The Stokes law form. / = 3jt fidp, holds for a rigid sphere that moves through a fluid at constant velocity with a Reynolds number. dpUjv, much less than unity. Here U is the velocity, and V is the kinematic viscosity. The particle must be many diameters away from any surfaces and much larger than the mean free path of the gas molecules, ip, which is about 0.065 jum at 25°C. 

Three particle transport processes that bring about interparticle contacts are considered here Brownian diffusion (thermal effects), fluid shear (flow effects), and differential settling (gravity effects). Following Smoluchowski s approach, the appropriate individual transport coefficients for these three processes arc as... 

The solid phase could be a reactant, product, or catalyst. In general the decision on the choice of the particle size rests on an analysis of the extra-and intra-particle transport processes and chemical reaction. For solid-catalyzed reactions, an important consideration in the choice of the particle size is the desire to utilize the catalyst particle most effectively. This would require choosing a particle size such that the generalized Thiele modulus < gen, representing the ratio of characteristic intraparticle diffusion and reaction times, has a value smaller than 0.4 see Fig. 13. Such an effectiveness factor-Thiele modulus analysis may suggest particle sizes too small for use in packed bed operation. The choice is then either to consider fluidized bed operation, or to used shaped catalysts (e.g., spoked wheels, grooved cylinders, star-shaped extrudates, four-leafed clover, etc.). Another commonly used procedure for overcoming the problem of diffu-sional limitations is to have nonuniform distribution of active components (e.g., precious metals) within the catalyst particle. 

Sediment traps cannot resolve the influence of lateral particle transport processes. At best, these... 

These functions can be measured and used in both conceptual and empirical studies of coagulation and other particle transport processes. They are particularly useful in expressing data obtained with particle counters that directly determine the number of particles in each of many size intervals. 

ETi, is removed by extrinsic processes, such as nose blowing. For the other regions, clearance of inhaled material is competitive between particle transport processes (such as macrophage uptake and ciliary action) to the gastro-intestinal tract and to lymph nodes and absorption into blood. 

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