Effective particle diameter

The often expressed intuitive belief that small particles are more difficult to remove From a ga.s than laige ones is usually not correct. The particles most difficult to collect are those in the size range corresponding to the transition from diffusional to inertial deposition, usually between 0.1 and 1 iim. The transition may be strongly influenced by direct interception (finite particle diameter effect) depending on the dimensions of the system. 

Particle diameter effect on the particle settling velocity... 

Fig. 5. The effect of ultrasonic irradiation on the surface morphology and particle size ofNi powder. Initial particle diameters (a) before ultrasound were i 160 fim-, (b) after ultrasound, fim. High velocity interparticle coUisions caused by ultrasonic irradiation of slurries are responsible for the smoothing...

In Figure 13 the relation between the intrinsic coercivity and the particle diameter dis given. The figure is based on a described model (35). The maximum is found around the critical particle diameter. In general the particle diameter and size is not very well defined. For the multidomain particles (d > ) the is smaller than the intrinsic anisotropy field of the particle. Nucleation effects cause a decrease in as the increases. This behavior is... 

A commercial bacterial cellulose product (CeUulon) was recently introduced by Weyerhaeuser (12). The fiber is produced by an aerobic fermentation of glucose from com symp in an agitated fermentor (13,14). Because of a small particle diameter (10 P-m), it has a surface area 300 times greater than normal wood cellulose, and gives a smooth mouthfeel to formulations in which it is included. CeUulon has an unusual level of water binding and works with other viscosity builders to improve their effectiveness. It is anticipated that it wiU achieve GRAS status, and is neutral in sensory quaUty microcrystaUine ceUulose has similar attributes. 

The effects of flow nonuniformities, in particular, can be severe in gas systems when the ratio of bed-to-particle diameters is small in liquid systems when viscous fingering occurs as a result of large viscosity gradients in the adsorption bed when very small particles (<50 Im) are used, such as in high performance liqmd chromatography systems and in large-diameter beds. A lower bound of the axial... 

The major purpose of ambient particulate sampling is to obtain mass concentration and chemical composition data, preferably as a function of particle diameter. This information is valuable for a variety of problems effects on human health, identification of particulate matter sources, understanding of atmospheric haze, and particle removal processes. 

The authors also investigated the effect of solvent composition on the retention of a series of solutes including a dispersion of silica smoke (mean particle diameter 0.002 pm). The silica smoke was used to simulate a solute of very large molecular size... 

Katz et al. [1] also examined the effect of particle diameter on resistance to mass transfer constant (C). They employed columns packed with 3.2 im, 4.4 p,m, 7.8 pm, and 17.5 pm, and obtained HETP curves for the solute benzyl acetate in 4.3%w/w of ethyl acetate in n-heptane on each column. The data were curve fitted to the Van Deemter equation and the values for the A, B and C terms for all four columns extracted. A graph relating the value of the (C) term with the square of the particle diameter is shown in Figure 8. 

The function f(k ) is shown plotted against the thermodynamic capacity ratio in Figure 1. It is seen that for peaks having capacity ratios greater than about 2, the magnitude of (k ) has only a small effect on the optimum particle diameter because the efficiency required to effect the separation tends to a constant value for strongly retained peaks. From equation (1) it is seen that the optimum particle diameter varies as the square root of the solute diffusivity and the solvent viscosity. As, in... 

Figure 1. The Effect of Solute Capacity Ratio on the Magnitude of the Optimum Particle Diameter...

The optimum particle diameter will decrease as the reciprocal of the available pressure and, thus, pressure will have a very significant effect on the magnitude of (dp(opt)). As already stated, the higher the pressure, the smaller the particle diameter,... 

It is seen that the optimum velocity is inversely proportional to the optimum particle diameter and it would be possible to insert the expression for the optimum particle diameter into equation (2) to provide an explicit expression for the optimum velocity. The result would, however, be algebraically cumbersome and it is easier to consider the effects separately. The optimum velocity is inversely... 

The effective use of column volume overload for preparative separations was experimentally demonstrated by Scott and Kucera [1]. These authors used a column 25 cm long, 4.6 mm I.D. packed with Partisil silica gel 10 mm particle diameter and employed n-heptane as the mobile phase. The total mass of sample injected was kept constant at 176 mg, 8 mg and 0.3 mg of benzene, naphthalene and anthracene, respectively, but the sample volumes used which contained the same mixture of solutes were 1 pi, 1 ml, 2 ml and 3 ml. The chromatograms of each separation are... 

To allow for the effect of roughness one can use the results of empirical tests in ducts that have been artificially roughened with particles glued on the surface. This approach allows roughness levels to be determined as a function of the particle diameter k. The following friction factor equation has been derived for large Reynolds numbers ... 

---