Presence of solid particles

The most direct test of the tensile strength hypothesis would be to compare the value of Tq calculated from the closure point of the isotherm by Equation (3.61) with the tensile strength of the bulk liquid determined directly. Unfortunately, experimental measurement of the tensile strength is extremely difficult because of the part played by adventitious factors such as the presence of solid particles and dissolved gases, so that the values in the literature vary widely (between 9 and 270 bar for water at 298 K, for example). 

Impingement and erosion-corrosion forms of attack will usually be intensified by the presence of solid particles in the fluid. Variations of the jet test have been proposed to take this effect into account. ... 

The results reported for beds of small particles (1 mm diameter and less) are in substantial agreement on the fact that the presence of solid particles tends to decrease the gas holdup and, as a consequence, the gas residencetime. This fact may also support the observations of gas absorption rate by Massimilla et al. (Section V,E,1) if it is assumed that a decrease of absorption rate caused by a decrease of residence time outweighs the increase of absorption rate caused by increase of mass-transfer coefficient arising from the increase in bubble Reynolds number. These results on gas holdup are in... 

The works of Fukuma et al. [23], Morooka et al. [24] and Clark [25] has indicated that the presence of solid particles in the reactor favours the transition to the heterogeneous flow regime. A critical solid hold-up exists, beyond which the coalescence of bubbles is more frequent. This critical value is higher with smaller particles. Clark [25], studied operation at pressure above 100 bar, and inferred that... 

In the simplest emulsions just described, the linal separation is into two liquid phases upon deslahilizalinn. The majority of emulsions tire of this kind, but in some cases the emulsion is divided into more Ilian two phases. One ubvious reason lor such a behavior is the presence of it material thal does not dissolve in the oil or the water. One such case is Ihe presence of solid particles, which is common in emulsions lor food, pharmaceuticals, and cosmetics. Another less trivial reason is that the surfactant associates w ith the water and/or Ihe oil to form a colloidal structure that spontaneously separates from the two liquid phases. This colloidal structure may be an isotropic liquid or may he a. semisnlid phase, a liquid crystal, with long-range order. 

The nature of dispersion. The effect which the solid packing has on the flow pattern within a tubular reactor can sometimes be of sufficient magnitude to cause significant departures from plug flow conditions. The presence of solid particles in a tube causes elements of flowing gas to become displaced randomly and therefore produces a mixing effect. An eddy diffusion coefficient can be ascribed to this mixing effect and becomes superimposed on the transport processes which normally occur in unpacked tubes—either a molecular diffusion process at fairly low Reynolds... 

I want you now to follow me in this point,-that whenever a substance burns, as the iron filings burnt in the flame of gunpowder, without assuming the vaporous state (whether it becomes liquid or remains solid), it becomes exceedingly luminous. I have here taken three or four examples apart from the candle, on purpose to illustrate this point to you because what I have to say is applicable to all substances, whether they burn or whether they do not burn,-that they are exceedingly bright if they retain their solid state, and that it is to this presence of solid particles in the candle-flame that it owes its brilliancy. 

On the resistance constitution of the equipment system, the major conclusions that can be drawn from the investigation are (1) Where millets or rapeseeds are the material to be processed, the power for the operation of the impinging stream contactor is mainly (>80%) consumed in the acceleration of particles (2) The pressure loss due to the impingement between the opposing streams is independent of the presence of solid particles. 

The structure of the interfacial layers in food colloids can be quite complex as these are usually comprised of mixtures of a variety of surfactants and all are probably at least partly adsorbed at interfaces which even individually, can form complex adsorption layers. The layers can be viscoelastic. Phospholipids form multi-lamellar structures at the interface and proteins, such as casein, can adsorb in a variety of conformations [78]. Lecithins not only adsorb also at interfaces, but can affect the conformations of adsorbed casein. The situation in food emulsions can be complicated further by the additional presence of solid particles. For example, the fat droplets in homogenized milk are surrounded by a membrane that contains phospholipid, protein and semi-solid casein micelles [78,816], Similarly, the oil droplets in mayonnaise are partly coated with granular particles formed from the phospho and lipo-protein components of egg yolk [78]. Finally, the phospholipids can also interact with proteins and lecithins to form independent vesicles [78], thus creating an additional dispersed phase. 

Mei scattering can be a severe interference, although also only for resonance fluorescence. The presence of solid particles can completely eliminate the possibility of using an optical method. For smaller particle densities, however, one may overcome particle problems with optical and processing tricks. Each case must be examined individually. 

The major contributors to radiation are soot, carbon dioxide, water vapor, inorganic particulates and other intermediate products whose concentrations depend upon the particular fuel. The presence of solid particles such as ash and carbonaceous material affects the radiation heat transport as they are continuous emitters, absorbers, and scatterers of radiation. Carbonaceous particles tend to be large relative to the wavelength of radiation and have surfaces with high absorptivity. 

In the presence of some coagulated soles it is possible to produce stable foams in which there are no surfactants [89]. Usually it is assumed [83] that the presence of solid particles in foams leads to delay of drainage because the Pateau borders become narrower, their walls become rougher and the particles form local caps. An analogous delay of drainage results from emulsion drops that enter the Plateau borders [90]. However, as pointed out in [84], the influence of solid particles on foam drainage rate should not be considered synonymously. 

In this Section instability of asymmetric films is explained by decrease in the surfactant adsorption. Another reason for this instability can be the presence of solid particles at the water-oil interface. Such a heterogeneous defoaming is created when a foam is broken down by the antifoam drops that contain solid hydrophobic particles. The mechanism of action of such types of antifoams will be discussed in Section 9.4. 

It is not known how the presence of solid particles affects the fluid dynamic regime in an agitated vessel hence, it is necessary to assume that solid-liquid systems behave similarly to one-liquid-phase systems as described in Section II. Obviously this assumption will be best for systems in which the solids are small, are not very different in density from the liquid, are present in low concentration, and do not affect the Newtonian characteristics of the liquid. 

To this author s knowledge, no data on three-phase stirred columns are available. Preliminary observations indicate that the axial dispersion in the gas phase is considerably reduced by the presence of solid particles. Under certain conditions, even for a very low L/dc (where L is the length and dc the diameter of the stirred column) the gas phase may move essentially in plug flow. 

Massimilla et al.79 found that the presence of solid particles reduced the gas-liquid mass-transfer rate in a bubble-column. This was explained as being due to the higher rate of bubble coalescence and. consequently, a lower gas liquid interfacial area obtained in the presence of solids. They also found that the absorption rate increased with an increase in the nominal liquid velocity and a decrease in particle size. 

A further complicating fact is that the presence of solid particles in general is now recognised as having a detrimental effect on the life of rolling-element bearings . Thus the improvements reported by Popinceanu et al, Scott and Blackwell, and Kuhnell and Stecki differ from the usual effect of solid particles, and must represent some specific property of molybdenum disulphide. 

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