Wetting models comparison

Becker D, Rigassi T, Bauer-Brandl A. Effectiveness of binders in wet granulation comparison using model formulations of different tabletability. Drug Dev Ind Pharm 1997 23(8) 791—808. 

As described by the Wenzel wetting model, the increase of surface roughness should lead to a certain increase of contact angle (CA) values. To verify this statement, we investigated three different kinds of commonly used thin films known to be very different in grain size and, therefore, in surface roughness. Figure 3 shows the comparison of a 50 nm Au film, an 800 nm native oxidized titanium film (TiO") and an 800 nm wet chemically oxidized titanium film (TiO ) on a polished silicon substrate. 

Figure 2 Comparison of measured wet deposition of ammonium at Rothamsted, England with model estimates by Asman et al for regions whieh assume ehanges in emissions are only due to differenees in animal numbers. (Taken from Sutton et al ).

Fig. 6 Comparison of results of the AF model solved with and without streamflow trend for wet and dry years, expressed as years above and below the mean water residence time in the reservoir (0.25 years)...

Plates of glass, PTFE, dolomite and marble were used. Dolomite and marble were chosen because they represent minerals found in oil reservoirs. Glass and PTFE were investigated because they represent high and low surface energy solids respectively and are good model systems for data comparisons. Liquid/solid wetting cycles were obtained for each of the solids in the liquids listed in Table III. 

Of the 30 lakes that were cored 9 reached geochemical background concentrations and had current concentrations and/or fluxes that are decreasing to present. Five additional lakes that did not reach geochemical background were included for comparison to current wet deposition. Linear models of recovery were estimated on the most recent decreasing trend of concentration and/or flux and by ignoring episodic or short term increases in fluxes or concentrations (Fig. 1). 

In an attempt to test the surface renewal theory of gas absorption, Danckwerts and Kennedy measured the transient rate of absorption of carbon dioxide into various solutions by means of a rotating drum which carried a film of liquid through the gas. Results so obtained were compared with those for absorption in a packed column and it was shown that exposure times of at least one second were required to give a strict comparison this was longer than could be obtained with the rotating drum. Roberts and Danckwerts therefore used a wetted-wall column to extend the times of contact up to 1.3 s. The column was carefully designed to eliminate entry and exit effects and the formation of ripples. The experimental results and conclusions are reported by Danckwerts, Kennedy, and Roberts110 who showed that they could be used, on the basis of the penetration theory model, to predict the performance of a packed column to within about 10 per cent. 

Our developed model was applied to simulate drying process of wet sand in a pneumatic dryer. The numerical solutions were compared with the results of independent numerical and experimental investigations. These comparisons are quite encouraging. 

Fig. 7. Comparison of mean particle size obtained in a wet milling of a-alumina (cm = 0.2) with the results of a population balance model.

Fig. 11.14. Comparison between measured TPR patterns for Fe2C>3 and calculated TPR peaks for Fe304 —>Fe metal reduction step, using the three-dimensional nucleation model according to Avrami-Erofeev at 0.2 K/min. Calculated dotted line (a) dry series, (b) wet series, E = 172...

In the whole range of our experimental conditions, maleic acid has no measurable volatility and we hoped so to obtain more accurate information on the wetting efficiency as well as to check the model in a much more constrained situation. Moreover the direct comparison of this reaction with the very similar hydrogenation of alphamethylstyrene (the volatility of the reactant excepted) which we experienced previously, could directly put into sight the role of dry or badly irrigated catalyst particles. 

Taking into account the very limited number of experimental results for unforced wetting of liquid metals, no detailed comparison with model prediction is... 

Figures 1 and 4 show the water flood matches to the water-wet and oil-wet lab model curves, respectively. The carbon dioxide flooding runs in the lab model were then matched by computer simulation. In the simulations, as in the lab model, the carbon dioxide slug was followed by waterflooding to an assumed economically limiting water cut of 98%, and the enhanced oil recovery was calculated as the difference between the ultimate total recovery at this point and that of a water flood starting from initial oil saturation and continued until a 98% water cut was reached. Secondary carbon dioxide floods started from the same initial oil saturation, while tertiary carbon dioxide floods started with the condition at the 98% water cut point in the simple water flood. Since the foam or emulsion tests involved a 1 1 ratio of water and carbon dioxide, comparisons are shown only for the case of 1 1 WAG operation vs foam.

A remarkable difference in the Pt spectra of oxide- and carbon-supported platinum is especially clear for the 2.5-nm sample the fuel cell material shows much less intensity at the bulk resonance position (1.138 G/kHz). A similar difference is shown by the spectrum for the 2.0-nm sample. In terms of the NMR layer model, this comparison means that the healing length is larger in the carbon-supported material. It is not clear whether this result is related to the conducting nature of the carrier or to the presence of the electrolyte comparisons between wet and dry samples are needed. 

For this reason Williams and Clapper developed a mathematical equation on the basis of a simple physical model, describing the relation between the reflection density Dr and the transmission density Dj. Practice, however, has shown that for a more exact description empirical reflection curves must be measured. From these empirical curves the transformed reflection density g(Dn) can be obtained. This transformation is effected from a multitude of comparisons with patient samples (the concentration of which should be distributed over the entire range of measurement) by means of wet chemistry methods. 

Theoretical isotherms obtained using DFT method rival the accuracy of model isotherms constructed from molecular simulation, as shown in the comparison in Fig. 12 for N2 adsorption results in model graphitic slit pores at 77 K [22]. Tlie DFT model correctly predicts the capillary condensation pressure, the most prominent feature of the subcritical isotherm, relative to the exact computer simulation results shown in Fig. 11. DFT also provides a good description of the secondary structure of the mesopore isotherm (e.g., H = 42.9 A in Fig. 12), in which capillary condensation may be preceded by one or more wetting transitions. 

Fig. 17. (a) Schematic of vapor-liquid equilibrium in a wetted pore used in the Kelvin equation model [2]. (b) Comparison of PSD results obtained using the BJH Kelvin equation model to interpret the PSDs of two mesoporous MCM-41 structures, C16 (circles) and C12 (squares) [130]. The open and filled symbols denote PSD results obtained from the adsorption and desorption branches of the isotherm, respectively. 

The chemical environment of adsorbed paramagnetic ions [Cu(II), Fe(III), Mn(II)] has been studied by comparison of ESR (electron spin resonance) spectra of wet adsorbents treated with solutions of salts of these metals on the one hand and of some model compounds vide Section G) on the other. For instance, clustering or surface precipitation can be verified as the sorption mechanism. 

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