Effect of size distribution

Minimum Fluidizing Velocity U,nj, the minimum fluidizing velocity, is frequently used in fluid-bed calculations and in quantifying one of the particle properties. This parameter is best measured in small-scale equipment at ambient conditions. The correlation by Wen audYu [A.l.Ch.E.j., 610-612 (1966)] given below can then be used to back calculate d. This gives a particle size that takes into account effects of size distribution and sphericity. The correlation can then be used to estimate U, at process conditions, if U,nj cannot be determined experimentally, use the expression below directly. 

Comparison of Eq. (184) with Eq. (183) shows the effect of size distribution for the case of fast chemical reaction with simultaneous diffusion. This serves to emphasize the error that may arise when one applies uniform-drop-size assumptions to drop populations. Quantitatively the error is small, because 1 — is small in comparison with the second term in the brackets [i.e., kL (kD)112). Consequently, Eq. (184) and Eq. (183) actually give about the same result. In general, the total average mass-transfer rate in the disperser has been evaluated in this model as a function of the following parameters ... 

The moment equations of the size distribution should be used to characterize bubble populations by evaluating such quantities as cumulative number density, cumulative interfacial area, cumulative volume, interrelationships among the various mean sizes of the population, and the effects of size distribution on the various transfer fluxes involved. If one now assumes that the particle-size distribution depends on only one internal coordinate a, the typical size of a population of spherical particles, the analytical solution is considerably simplified. One can define the th moment // of the particle-size distribution by... 

Although they are a relatively small volume product—approximately 75,000 tons produced in 1949 (126)—interest in asphalt emulsion has continued at a high level. Abraham (6) has reviewed the patent literature relative to the types of emulsifying agents used, while commercial practice has been discussed by Day (16). The most common emulsifiers are sodium or potassium soaps of tall oil, abietic acid, or Vinsol resin, or colloidal clays such as bentonite for adhesive base emulsions. Lyttleton and Traxler (53) studied the flow properties of asphalt emulsions, and Traxler (122) has investigated the effect of size distribution of the dispersed particles on emulsion viscosity. A decrease in particle size uniformity was found to be accompanied by a decrease in consistency because particles of various size assume a more loosely packed condition than do those of the same size. 

In a study of acrylonitrile synthesis in a 0.5-m x 9-m reactor. Pell and Jordan [21] found a steady increase in conversion as the fines concentration was increased from 23% to 44%. The effect was more pronounced at a velocity of 0.38 m/sec than at 0.66 m/sec, and the optimum fines concentration was about 40%. A strong effect of size distribution was also demonstrated in the ozone decomposition tests of Sun and Grace [16]. For the same average particle size (60 /rm), a wide PSD gave significantly higher conversion than a narrow PSD, as shown in Figure 9.13. The study covered... 

The effect of size distribution in ELM systems has been studied. Tereraoto et al. (98) studied the effect of globule size distribution on copper extraction. Their results indicated that the Sauter mean diameter was sufficient to characterize the membrane size and it was not necessary to use the size distribution. Hanna and Larson (99) studied the influence of ELM preparation on the Internal droplet size distribution. They demonstrated the Internal phase surface area can affect extraction rate with a copper extraction system. 

The effects of size distribution and of the presence of suspending agents on dissolution of different lots of prednisolone ac te (both commercial and formulated) were investigated by Howard et al. (57J8). The observed lot-to-Iot variations in the dissolution rate were related to the percentage of line particles in the distribution furthermore, the presence of hydroxypropylmethylceltulosc and sodium carboxymethylccllulose was found to reduce the dissolution rate in some lots. 

Hergt R, Andra W, d Ambly C G, Hilger I, Kaiser W A, Richter U and Schmidt H-G (1998) Physical limits of hyperthermia using magnetite fine particles, IEEE Trans Magn 34 3745-3754. Hergt R, Dutz S and ROder M (2008) Effects of size distribution on hysteresis losses of magnetic nanoparticles for hyperthermia, J Phys Condens Matter 20 1-12. 

The mesoscale model is of significant importance in catalyst design, since it could be used to investigate the effect of size, distribution, and amount of microporous crystal particles in the catalyst pellet on the overall catalytic performance. For convenience, as Eq. (3) in microscale model, another internal effective factor is defined to quantify catalytic performance of the pellet ... 

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