Wall particles

The density functional approach of Refs. 91, 92 introduces a correction to the wall-particle direct correlation function resulting from the HNCl approximation (see Eqs. (32)-(34)). A correction to Eq. (34) reads (we drop the species label because the model is one-component)... 

Logtenberg, S. A., Nijemeisland, M., and Dixon, A. G., Computational fluid dynamics simulations of fluid flow and heat transfer at the wall-particle contact points in a fixed-bed reactor, Chem. Eng. Sci. 54, 2433-2439 (1999). 

To compare molecular theoretical and molecular dynamics results, we have chosen the same wall-particle potential but have used the 6 - oo fluid particle potential. Equation 14, Instead of the truncated 6-12 LJ potential. This Is done because the molecular theory Is developed In terms of attractive particles with hard sphere cores. The parameter fi n Equation 8 Is chosen so that the density of the bulk fluid In equilibrium with the pore fluid Is the same, n a = 0.5925, as that In the MD simulations. 

Nwp = Nusselt number for wall-particle heat transfer... 

The wall-particle Nwp represents the heat transfer process between the wall and a contacting particle. For gas-solid systems, where thermal resistance of the gas gap dominates,... 

We can see that for these conditions, the temperature fields inside the wall particles are far from symmetric. Significant temperature incursions appear inside the spheres, and the influence of the wall is strong. The spheres are hotter close to the tube wall than on the side facing the center of the segment. The interior particles appear to be more symmetrical in temperature. It is noticeable that the particles are considerably lower in temperature than the surrounding... 

PET flakes have different crystallinities. The wall particles are oriented and crystallized, while the flakes from the neck and bottom of non-heat-set bottles are amorphous and require crystallization to prevent sintering before they can be subjected to SSP. Separating the thick amorphous PET flakes before SSP to circumvent the sticking risk and to improve the uniformity of the product has also been suggested [122], However, this may only be commercially acceptable if the separated flakes can be used in a final application. 

Spinning disk. A new method was developed by Professor Robert E. Sparks at Washington University in St. Louis. This method relies upon a spinning disk and the simultaneous motion of core material and wall material exiting from that disk in droplet form (11). The capsules and particles of wall material are collected below the disk. The capsules are separated from the wall particles (chaff) by a sizing operation ... 

Figure 7.6 Possible arrangement for a thin-walled particle microelectrophoresis cell...

Figure 7.25 Alignment of anisometric particles in the slip-cast layer is possible due to the capillary forces acting normal to the mold wall. Particles will tend to follow the mold contours.

Plischke and Henderson (PH) [102] compared the inhomogeneous OZ equation (14), combined with the WLMB equation (15) which is required for closure, with the HAB equation (16) assuming the same closure. They applied these equations to a single component Lennard-Jones fluid near a hard wall and noted that these two wall-particle OZ equations are fundamentally different. 

FIG. 6 Schematic representation of the experimental tracking device for the investigation of wall- particle interactions. 

Fig. 6. A field of T7 heads obtained from a cryoelectron micrograph of a complete tail-deletion (genes 11 and 12) mutant. Empty capsids appear as thin-walled particles. Full capsids exhibit the characteristic 2.5-nm spacing of densely packed DNA duplexes in motifs that vary according to viewing direction. The concentric ring motif is discemable in the views along the axis that passes through the connector-core vertex that is in the center of the particle.

To address this, Liem, Brown, and Clarke ° simulated in excess of 40,000 particles interacting via a Weeks-Chandler-Andersen (WCA) potential. While the x and z directions were treated normally, the y direction was divided into three regions two atomistic walls separated by a fluid region. The walls consisted of three hexagonally close-packed layers of particles. The wall atoms interacted with the fluid particles and with each other through the same WCA potential used for the fluid-fluid interactions. Additionally, each wall particle felt a harmonic potential centered at its triangular lattice site. This setup allowed heat transfer from the fluid to the wall while allowing the wall to remain crystalline. The momenta of the wall particles were rescaled to keep the total... 

When simulating the trajectories of dispersed phase particles, appropriate boundary conditions need to be specified. Inlet or outlet boundary conditions require no special attention. At impermeable walls, however, it is necessary to represent collisions between particles and wall. Particles can reflect from the wall via elastic or inelastic collisions. Suitable coefficients of restitution representing the fraction of momentum retained by a particle after a collision need to be specified at all the wall boundaries. In some cases, particles may stick to the wall or may remain very close to the wall after they collide with the wall. Special boundary conditions need to be developed to model these situations (see, for example, the schematic shown in Fig. 4.5). 

Figure 2 illustrates the kinds of particles made in this study. Here, polystyrene nanoparticles (170-nm diameter) were prepared in an ethanol cosolvent and spray-dried to produce large thin-walled particles with a wall thickness of approximately 400 nm, or 3 layers of nanoparticles. The study showed that such particles aerosolize effectively from a small inhaler and redisperse into nanoparticles once in solution. Nanoparticle aggregates were made with a variety of different materials and through many different spraydrying conditions, suggesting that these large porous nanoparticle systems are robust and functional as aerosols. 

Density profiles are the central quantity of interest in computer simulation studies of interfacial systems. They describe the correlation between atom positions in the liquid and the interface or surface . Density profiles play a similarly important role in the characterization of interfaces as the radial distribution functions do in bulk liquids. In integral equation theories this analogy becomes apparent when formalisms that have been established for liquid mixtures are employed. Results for interfacial properties are obtained in the simultaneous limit of infinitesimally small particle concentration and infinite radius for one species, the wall particle (e.g., Ref. 125-129). Of course, this limit can only be taken for a smooth surface that does not contain any lateral structure. Among others, this is one reason why, up to now, integral equation theories have not been able to move successfully towards realistic models of the double layer. 

Silva and Nerba [39] also used the two-fluid approach and presented a mathematical model of drying in cyclone. Slip condition of particles on the wall, particles-wall heat transfer, and particles shrinkage were considered. The mathematical model considered a steady state, incompressible, two-dimensional, axisymmetric, turbulent gas-solids flow. The gravity force effect on the particles was neglected. The particles assumed to be spherical and distributed in a layer of uniform concentration... 

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