Mixing process property changes

At pressures and temperatures above the critical point, where liquid and vapour phases become indistinguishable, supercritical fluids (SCFs) exhibit very different properties to those of the liquids or gases at ambient. Particle formation in SCFs occurs as a result of a rapid increase in supersaturation, either by means of expansion or by antisolvent mixing processes. Thus Chang and Randolph (1989) demonstrated that small ([Pg.60]

The conventional scale-up criteria scale-up with constant stirrer speed , scale-up with constant tip speed and scale-up with constant specific energy input are all based on the assumption that only one mixing process is limiting. If, for example, the specific energy input is kept constant with scale-up, the same micromixing behaviour could be expected on different scales. The mesomixing time, however, will change with scale-up as a result, the kinetic rates and particle properties will be different and scale-up will fail. 

The initial plastic state of the fresh concrete subsequent to the mixing process, where properties such as the air content, density and workability are normally measured by relevant standard tests, and utilized as a means of control of production. The magnitude of these properties is affected by the addition of water-reducing admixtures, either intentionally or as a side effect, which could result not only in a change in the characteristics in the plastic state, but could also be reflected in changed properties in the hardened state. 

In addition, for each of the major downstream processing units (FCC, hydrocracker, motor and BTX reformers), the preprocessor generates a set of feed property balance rows. It is through these rows and the corresponding feed property change activities that the unit performance can respond to changes in crude mix and distillation cutpoint as well as changes in properties or proportion of feed from other process units. 

Most food biopolymers have limited miscibility on a molecular level and form multicomponent, heterophase and nonequilibrium dispersed systems. A thermodynamic approach is applicable for studying structure-property relationships in formulated foods since their structures are based on nonspecific interactions between components and such thermodynamically based operations as mixing of components, changing temperature and/or pH, underlies processing conditions. 

All of the important heat effects are illnstratedby this relatively simple chemical-manu-factnring process. In contrast to sensible heat effects, which are characterized by temperatnre changes, the heat effects of chemical reaction, phase transition, and the formationand separation of solntions are determined from experimental measnrements made at constant temperatnre. In this chapter we apply thermodynamics to the evalnation of most of the heat effects that accompany physical and chemical operations. However, the heat effects of mixing processes, which depend on the thermodynamic properties of mixtnres, are treated in Chap. 12. 

The relations between excess properties and property changes of mixing (Sec. 12.3) facilitate discnssionof the molecular phenomena which give rise to observed excess-property behavior. An essential coimectionis provided by Eq. (12.33), which asserts the identity of and AH. Tims we focus on the mixing process (and hence on for explainingthe behavior of. ... 

In a mixture of ideal gases the sound velocity and consequently the resonant frequencies of a resonator depend on the effective specific heat ratio and the average molecular mass of the mixture. Chemical reaction and mixing processes, for example, are normally accompanied with a change of these properties. Therefore, such dynamic processes can be monitored by a repeated measurement of the shift of one of the eigenfrequencies of the resonator as a function of time. 

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