Settling criterion

Porosity constitutes a important criterion in a description based on straining. Porosity is determined by the formula V /Vc, in which V c is the total or apparent volume limitated by the filter wall and is the free volume between the particles. The porosity of a filter layer changes as a function of the operation time of the filters. The grains become thicker because of the adherence of material removed from the water, whether by straining or by some other fixative mechanism of particles on the filtering sand. Simultaneously the interstices between the grains diminish in size. This effect assists the filtration process, in particular for slow sand filters, where a deposit is formed as a skin or layer of slime that has settled on the... 

The Archimedes number contains parameters that characterize the properties of the heterogeneous system and the criterion establishing the type of settling. The criterion of separation essentially establishes the separating capacity of a sedimentation machine. The product of these criteria is ... 

For purposes of this survey an important distinction must be made between a commonly used criterion of instability and the sense in which the term is used here. A stable dispersion is not necessarily one which will not settle, because the only disturbance involved in settling is motion of translation of the parti-... 

Perhaps the best rheological stability criterion is the volume occupied by the sediment per unit volume of original dispersion. A flocculated dispersion settles rapidly to a high sediment volume, while a deflocculated one settles slowly to a low volume, as shown in Figure 8. Of course, the ultimate volume depends on the concentration of the dispersion and in order to give a criterion of more fundamental interest the concept of relative sediment volume RSV may... 

The extrapolation of this ratio to m2 = 0 is shown in Figure 17.2. The curve in Figure 17.2 should have a horizontal limiting slope. If an experimental curve does not have a horizontal limiting slope, the data have not been obtained in sufficiently dilute solution to show Henry s-law behavior. Very few data are available that satisfy this rigorous criterion [1]. We frequently settle for a condition in which the plot of 2/ 2 has a clear linear extrapolation to m2 = 0, as opposed to a continuing curvature that makes an extrapolation impossible. 

In other cases, one may elect to use the best case scenario and make plans based on the left bound within the p-box. Which criterion one might use is outside the scope of probability bounds analysis. However, it should be emphasized that the possibilities within the bounds are not equivalent. And the analyst should not pick any answer from within these bounds. We recall the case of the engineers who designed Kansai International Airport on an island constructed with fill in a harbor near Kobe, Japan. They were reportedly told by geologists that the island would settle between 19 and 25 feet. They chose to plan for 19-foot subsidence, supposedly because planning for 25 feet would have been prohibitively expensive. One needs not be a student of Greek tragedy to anticipate the fate of such hubris. 

An extreme in sediment volume was usedt as a criterion for the effective cancellation of interparticle attraction by the continuous phase. Nylon-6,6 dispersions consisting of 1.0 g of solid in 10 ml of /2-propanol-thiodiethanol mixtures of various compositions were allowed to settle to sedimentation equilibrium. Listed here are the equilibrium sediment volumes, the volume/volume compositions, and the surface tensions of the media ... 

Practical flotation processes, however, take place under conditions of turbulence. Turbulent flow, as opposed to laminar flow (see Section 6.1), is characterized by rapid, almost random, fluctuations in flow velocity. Turbulence helps keep the solid particles suspended, helps disperse the injected air phase into bubbles, and helps induce particle-bubble collisions and attachments. With regard to the role of turbulence in mineral flotation, a rule of thumb for suspension stability is the one-second criterion which states that the particles in a suspension are sufficiently well dispersed for flotation if individual particles do not remain settled at the bottom of the flotation vessel for longer than one second [53]. 

Solids suspension involves producing the required distribution of solids in the tank and is essentially a physical phenomenon. The criterion is normally a physical description of the degree of uniformity required in the suspension. A key variable for solids suspension is the settling velocity of the solids. This is usually measured by timing the fall velocity of individual solid particles in a defined depth of... 

Visibly clean is not an acceptable cleaning criterion. A detailed, sequential cleaning procedure is advisable, for surfaces inside and outside laboratory chemical hoods and ventilated weighing enclosures. If settling of powder occurs on the floor, this indicates that material is escaping and that additional administrative and personal protective controls are warranted when using chemical fume hoods for subdivision applications. 

The fact and the approximate temperature being settled so, the exact determination may best bo carried out with a dilato-meter, the change—frequently considerable —in volume accompanying the conversion serving as criterion. The instrument in its latest form suited for use with a very small amount of material, consists of a capillary a (Fig. 8), fused on to a reservoir B that can be filled from c. After c is sealed off and the apparatus is pumped out through a, the liquid n, e. g. petroleum, is allowed to enter. If the... 

Newton s-law proportionality factor, 32.174ft-lb/lbj-s hf Total friction loss in fluid, J/kg or ft-lb /lb K Criterion for settling, defined by Eq. (7.45), dimensionless... 

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