Bulk gas/liquid

To trace the bulk gas-liquid (and gas-solid if depression was the case) coexistence line, the coexistence p-T relation for U fluid in the literature [7,8] was used to evaluate corresponding chemical potentials. Thus obtained combinations of T-fi were used as inputs to the simulations. A few to several hundred millions of elemental GCMC steps (movement, insertion or deletion) were conducted for each condition. 

If, on the other hand, the substrates are sufficiently attractive, one notices from the plots in Fig. 4.7 that F (T, pb) may either vary continuously or discontinuously depending on whether the (bulk) isochoric path is super-or subcritical, respectively, with regard to the critical point of the confined fluid. Hence, discontinuities in the plots in Fig. 4.7 indicate capillary condensation (evaporation) in the model pore prior to condensation in the bulk, which would, of course, occur at bulk gas-liquid coexistence, i.e., at T - Tzb) /Tzb = 0. 

Notice also that, at temperatures higher than that corresponding to capillary condensation, F (T. pb) increases with decreasing T. Tliis is indicative of a regime where one would observe growth of a wetting film, which at a mean-field level, manifests itself as an increase in overall density of an otherwise homogeneous low-density phase adsorbed all across the slit pore. For temperatures lower than that at which capillary condensation sets in, F (pb) turns out to be nearly independent of T the lower T becomes. This reflects that, when sufficiently close to bulk gas-liquid coexistence, the pore is com-... 

The calculation of the profile is similar to that of the bulk gas-liquid interface, discussed in Chapter 2. We consider the case where [Pg.118]

Effective interfacial gas-liquid mass transfer must occur in gas-liquid and gas-liquid-liquid systems. In an unsparged tank, gas-liquid mass transfer occurs primarily through the bulk gas-liquid surface unless extreme vortex formation occurs. If a sparger is used, gas-liquid mass transfer occurs through the surface as well as through the surface area associated with the dispersed gas... 

Figure Bl.22.8. Sum-frequency generation (SFG) spectra in the C N stretching region from the air/aqueous acetonitrile interfaces of two solutions with different concentrations. The solid curve is the IR transmission spectrum of neat bulk CH CN, provided here for reference. The polar acetonitrile molecules adopt a specific orientation in the air/water interface with a tilt angle that changes with changing concentration, from 40° from the surface nonnal in dilute solutions (molar fractions less than 0.07) to 70° at higher concentrations. This change is manifested here by the shift in the C N stretching frequency seen by SFG [ ]. SFG is one of the very few teclnhques capable of probing liquid/gas, liquid/liquid, and even liquid/solid interfaces.

The noble gases are mostly unreactive. In some instances, they act mostly as a place holder to fill a cavity. For dynamical studies of the bulk gas phase or liquid-phase noble gases, hard-sphere or soft-sphere models work rather well. 

For systems in which the solute concentrations in the gas and hquid phases are dilute, the rate of transfer may be expressed by equations which predic t that the rate of mass transfer is proportional to the difference between the bulk concentration and the concentration at the gas-liquid interface. Thus... 

Equihbrium concentrations which tend to develop at solid-liquid, gas-liquid, or hquid-liquid interfaces are displaced or changed by molecular and turbulent diffusion between biilk fluid and fluid adjacent to the interface. Bulk motion (Taylor diffusion) aids in this mass-transfer mechanism also. 

Expressions of this type can be written for both gas and liquid films in which the absorption coefficients are the gas- and liquid-film coefficients, respectively. The driving force across the gas film is given by the difference between the actual partial pressure of the soluble gas and that at the interface, v/hile the driving force across the liquid film is given by the difference between the concentration of the soluble gas at the interface and that in the main bulk of liquid. 

A non-ideal MSMPR model was developed to account for the gas-liquid mass transfer resistance (Yagi, 1986). The reactor is divided into two regions the level of supersaturation in the gas-liquid interfacial region (region I) is higher than that in the main body of bulk liquid (region II), as shown in Figure 8.12. 

Carbon dioxide gas diluted with nitrogen is passed continuously across the surface of an agitated aqueous lime solution. Clouds of crystals first appear just beneath the gas-liquid interface, although soon disperse into the bulk liquid phase. This indicates that crystallization occurs predominantly at the gas-liquid interface due to the localized high supersaturation produced by the mass transfer limited chemical reaction. The transient mean size of crystals obtained as a function of agitation rate is shown in Figure 8.16. 

Molar transformation of oxygen is proportional to the concentration gradient of oxygen at the gas-liquid interface and oxygen dissolved in the bulk liquid phase ... 

The rate of CO transport from the bulk gas into the gas and liquid films is as follows ... 

The gaseous components must be transferred from the bulk gaseous phase to the bulk liquid phase. The components are transferred to the gas-liquid interface by convection and diffusion in the gas and from the interface by diffusion and convection in the liquid. 

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